use crate::{
    humanize_token_count, prompts::PromptBuilder, AssistantPanel, AssistantPanelEvent,
    CharOperation, LineDiff, LineOperation, ModelSelector, StreamingDiff,
};
use anyhow::{anyhow, Context as _, Result};
use client::{telemetry::Telemetry, ErrorExt};
use collections::{hash_map, HashMap, HashSet, VecDeque};
use editor::{
    actions::{MoveDown, MoveUp, SelectAll},
    display_map::{
        BlockContext, BlockDisposition, BlockProperties, BlockStyle, CustomBlockId, RenderBlock,
        ToDisplayPoint,
    },
    Anchor, AnchorRangeExt, Editor, EditorElement, EditorEvent, EditorMode, EditorStyle,
    ExcerptRange, GutterDimensions, MultiBuffer, MultiBufferSnapshot, ToOffset, ToPoint,
};
use feature_flags::{FeatureFlagAppExt as _, ZedPro};
use fs::Fs;
use futures::{
    channel::mpsc,
    future::{BoxFuture, LocalBoxFuture},
    stream::{self, BoxStream},
    SinkExt, Stream, StreamExt,
};
use gpui::{
    anchored, deferred, point, AppContext, ClickEvent, EventEmitter, FocusHandle, FocusableView,
    FontWeight, Global, HighlightStyle, Model, ModelContext, Subscription, Task, TextStyle,
    UpdateGlobal, View, ViewContext, WeakView, WindowContext,
};
use language::{Buffer, IndentKind, Point, TransactionId};
use language_model::{
    LanguageModelRegistry, LanguageModelRequest, LanguageModelRequestMessage, Role,
};
use multi_buffer::MultiBufferRow;
use parking_lot::Mutex;
use rope::Rope;
use settings::Settings;
use smol::future::FutureExt;
use std::{
    future::{self, Future},
    mem,
    ops::{Range, RangeInclusive},
    pin::Pin,
    sync::Arc,
    task::{self, Poll},
    time::{Duration, Instant},
};
use theme::ThemeSettings;
use ui::{prelude::*, CheckboxWithLabel, IconButtonShape, Popover, Tooltip};
use util::{RangeExt, ResultExt};
use workspace::{notifications::NotificationId, Toast, Workspace};

pub fn init(
    fs: Arc<dyn Fs>,
    prompt_builder: Arc<PromptBuilder>,
    telemetry: Arc<Telemetry>,
    cx: &mut AppContext,
) {
    cx.set_global(InlineAssistant::new(fs, prompt_builder, telemetry));
    cx.observe_new_views(|_, cx| {
        let workspace = cx.view().clone();
        InlineAssistant::update_global(cx, |inline_assistant, cx| {
            inline_assistant.register_workspace(&workspace, cx)
        })
    })
    .detach();
}

const PROMPT_HISTORY_MAX_LEN: usize = 20;

pub struct InlineAssistant {
    next_assist_id: InlineAssistId,
    next_assist_group_id: InlineAssistGroupId,
    assists: HashMap<InlineAssistId, InlineAssist>,
    assists_by_editor: HashMap<WeakView<Editor>, EditorInlineAssists>,
    assist_groups: HashMap<InlineAssistGroupId, InlineAssistGroup>,
    assist_observations:
        HashMap<InlineAssistId, (async_watch::Sender<()>, async_watch::Receiver<()>)>,
    confirmed_assists: HashMap<InlineAssistId, Model<Codegen>>,
    prompt_history: VecDeque<String>,
    prompt_builder: Arc<PromptBuilder>,
    telemetry: Option<Arc<Telemetry>>,
    fs: Arc<dyn Fs>,
}

impl Global for InlineAssistant {}

impl InlineAssistant {
    pub fn new(
        fs: Arc<dyn Fs>,
        prompt_builder: Arc<PromptBuilder>,
        telemetry: Arc<Telemetry>,
    ) -> Self {
        Self {
            next_assist_id: InlineAssistId::default(),
            next_assist_group_id: InlineAssistGroupId::default(),
            assists: HashMap::default(),
            assists_by_editor: HashMap::default(),
            assist_groups: HashMap::default(),
            assist_observations: HashMap::default(),
            confirmed_assists: HashMap::default(),
            prompt_history: VecDeque::default(),
            prompt_builder,
            telemetry: Some(telemetry),
            fs,
        }
    }

    pub fn register_workspace(&mut self, workspace: &View<Workspace>, cx: &mut WindowContext) {
        cx.subscribe(workspace, |_, event, cx| {
            Self::update_global(cx, |this, cx| this.handle_workspace_event(event, cx));
        })
        .detach();
    }

    fn handle_workspace_event(&mut self, event: &workspace::Event, cx: &mut WindowContext) {
        // When the user manually saves an editor, automatically accepts all finished transformations.
        if let workspace::Event::UserSavedItem { item, .. } = event {
            if let Some(editor) = item.upgrade().and_then(|item| item.act_as::<Editor>(cx)) {
                if let Some(editor_assists) = self.assists_by_editor.get(&editor.downgrade()) {
                    for assist_id in editor_assists.assist_ids.clone() {
                        let assist = &self.assists[&assist_id];
                        if let CodegenStatus::Done = &assist.codegen.read(cx).status {
                            self.finish_assist(assist_id, false, cx)
                        }
                    }
                }
            }
        }
    }

    pub fn assist(
        &mut self,
        editor: &View<Editor>,
        workspace: Option<WeakView<Workspace>>,
        assistant_panel: Option<&View<AssistantPanel>>,
        initial_prompt: Option<String>,
        cx: &mut WindowContext,
    ) {
        let snapshot = editor.read(cx).buffer().read(cx).snapshot(cx);
        struct CodegenRange {
            transform_range: Range<Point>,
            selection_ranges: Vec<Range<Point>>,
            focus_assist: bool,
        }

        let newest_selection_range = editor.read(cx).selections.newest::<Point>(cx).range();
        let mut codegen_ranges: Vec<CodegenRange> = Vec::new();

        let selection_ranges = snapshot
            .split_ranges(editor.read(cx).selections.disjoint_anchor_ranges())
            .map(|range| range.to_point(&snapshot))
            .collect::<Vec<Range<Point>>>();

        for selection_range in selection_ranges {
            let selection_is_newest = newest_selection_range.contains_inclusive(&selection_range);
            let mut transform_range = selection_range.start..selection_range.end;

            // Expand the transform range to start/end of lines.
            // If a non-empty selection ends at the start of the last line, clip at the end of the penultimate line.
            transform_range.start.column = 0;
            if transform_range.end.column == 0 && transform_range.end > transform_range.start {
                transform_range.end.row -= 1;
            }
            transform_range.end.column = snapshot.line_len(MultiBufferRow(transform_range.end.row));
            let selection_range =
                selection_range.start..selection_range.end.min(transform_range.end);

            // If we intersect the previous transform range,
            if let Some(CodegenRange {
                transform_range: prev_transform_range,
                selection_ranges,
                focus_assist,
            }) = codegen_ranges.last_mut()
            {
                if transform_range.start <= prev_transform_range.end {
                    prev_transform_range.end = transform_range.end;
                    selection_ranges.push(selection_range);
                    *focus_assist |= selection_is_newest;
                    continue;
                }
            }

            codegen_ranges.push(CodegenRange {
                transform_range,
                selection_ranges: vec![selection_range],
                focus_assist: selection_is_newest,
            })
        }

        let assist_group_id = self.next_assist_group_id.post_inc();
        let prompt_buffer =
            cx.new_model(|cx| Buffer::local(initial_prompt.unwrap_or_default(), cx));
        let prompt_buffer = cx.new_model(|cx| MultiBuffer::singleton(prompt_buffer, cx));
        let mut assists = Vec::new();
        let mut assist_to_focus = None;

        for CodegenRange {
            transform_range,
            selection_ranges,
            focus_assist,
        } in codegen_ranges
        {
            let transform_range = snapshot.anchor_before(transform_range.start)
                ..snapshot.anchor_after(transform_range.end);
            let selection_ranges = selection_ranges
                .iter()
                .map(|range| snapshot.anchor_before(range.start)..snapshot.anchor_after(range.end))
                .collect::<Vec<_>>();

            let codegen = cx.new_model(|cx| {
                Codegen::new(
                    editor.read(cx).buffer().clone(),
                    transform_range.clone(),
                    selection_ranges,
                    None,
                    self.telemetry.clone(),
                    self.prompt_builder.clone(),
                    cx,
                )
            });

            let assist_id = self.next_assist_id.post_inc();
            let gutter_dimensions = Arc::new(Mutex::new(GutterDimensions::default()));
            let prompt_editor = cx.new_view(|cx| {
                PromptEditor::new(
                    assist_id,
                    gutter_dimensions.clone(),
                    self.prompt_history.clone(),
                    prompt_buffer.clone(),
                    codegen.clone(),
                    editor,
                    assistant_panel,
                    workspace.clone(),
                    self.fs.clone(),
                    cx,
                )
            });

            if focus_assist {
                assist_to_focus = Some(assist_id);
            }

            let [prompt_block_id, end_block_id] =
                self.insert_assist_blocks(editor, &transform_range, &prompt_editor, cx);

            assists.push((
                assist_id,
                transform_range,
                prompt_editor,
                prompt_block_id,
                end_block_id,
            ));
        }

        let editor_assists = self
            .assists_by_editor
            .entry(editor.downgrade())
            .or_insert_with(|| EditorInlineAssists::new(&editor, cx));
        let mut assist_group = InlineAssistGroup::new();
        for (assist_id, range, prompt_editor, prompt_block_id, end_block_id) in assists {
            self.assists.insert(
                assist_id,
                InlineAssist::new(
                    assist_id,
                    assist_group_id,
                    assistant_panel.is_some(),
                    editor,
                    &prompt_editor,
                    prompt_block_id,
                    end_block_id,
                    range,
                    prompt_editor.read(cx).codegen.clone(),
                    workspace.clone(),
                    cx,
                ),
            );
            assist_group.assist_ids.push(assist_id);
            editor_assists.assist_ids.push(assist_id);
        }
        self.assist_groups.insert(assist_group_id, assist_group);

        if let Some(assist_id) = assist_to_focus {
            self.focus_assist(assist_id, cx);
        }
    }

    #[allow(clippy::too_many_arguments)]
    pub fn suggest_assist(
        &mut self,
        editor: &View<Editor>,
        mut range: Range<Anchor>,
        initial_prompt: String,
        initial_transaction_id: Option<TransactionId>,
        workspace: Option<WeakView<Workspace>>,
        assistant_panel: Option<&View<AssistantPanel>>,
        cx: &mut WindowContext,
    ) -> InlineAssistId {
        let assist_group_id = self.next_assist_group_id.post_inc();
        let prompt_buffer = cx.new_model(|cx| Buffer::local(&initial_prompt, cx));
        let prompt_buffer = cx.new_model(|cx| MultiBuffer::singleton(prompt_buffer, cx));

        let assist_id = self.next_assist_id.post_inc();

        let buffer = editor.read(cx).buffer().clone();
        {
            let snapshot = buffer.read(cx).read(cx);
            range.start = range.start.bias_left(&snapshot);
            range.end = range.end.bias_right(&snapshot);
        }

        let codegen = cx.new_model(|cx| {
            Codegen::new(
                editor.read(cx).buffer().clone(),
                range.clone(),
                vec![range.clone()],
                initial_transaction_id,
                self.telemetry.clone(),
                self.prompt_builder.clone(),
                cx,
            )
        });

        let gutter_dimensions = Arc::new(Mutex::new(GutterDimensions::default()));
        let prompt_editor = cx.new_view(|cx| {
            PromptEditor::new(
                assist_id,
                gutter_dimensions.clone(),
                self.prompt_history.clone(),
                prompt_buffer.clone(),
                codegen.clone(),
                editor,
                assistant_panel,
                workspace.clone(),
                self.fs.clone(),
                cx,
            )
        });

        let [prompt_block_id, end_block_id] =
            self.insert_assist_blocks(editor, &range, &prompt_editor, cx);

        let editor_assists = self
            .assists_by_editor
            .entry(editor.downgrade())
            .or_insert_with(|| EditorInlineAssists::new(&editor, cx));

        let mut assist_group = InlineAssistGroup::new();
        self.assists.insert(
            assist_id,
            InlineAssist::new(
                assist_id,
                assist_group_id,
                assistant_panel.is_some(),
                editor,
                &prompt_editor,
                prompt_block_id,
                end_block_id,
                range,
                prompt_editor.read(cx).codegen.clone(),
                workspace.clone(),
                cx,
            ),
        );
        assist_group.assist_ids.push(assist_id);
        editor_assists.assist_ids.push(assist_id);
        self.assist_groups.insert(assist_group_id, assist_group);
        assist_id
    }

    fn insert_assist_blocks(
        &self,
        editor: &View<Editor>,
        range: &Range<Anchor>,
        prompt_editor: &View<PromptEditor>,
        cx: &mut WindowContext,
    ) -> [CustomBlockId; 2] {
        let prompt_editor_height = prompt_editor.update(cx, |prompt_editor, cx| {
            prompt_editor
                .editor
                .update(cx, |editor, cx| editor.max_point(cx).row().0 + 1 + 2)
        });
        let assist_blocks = vec![
            BlockProperties {
                style: BlockStyle::Sticky,
                position: range.start,
                height: prompt_editor_height,
                render: build_assist_editor_renderer(prompt_editor),
                disposition: BlockDisposition::Above,
                priority: 0,
            },
            BlockProperties {
                style: BlockStyle::Sticky,
                position: range.end,
                height: 0,
                render: Box::new(|cx| {
                    v_flex()
                        .h_full()
                        .w_full()
                        .border_t_1()
                        .border_color(cx.theme().status().info_border)
                        .into_any_element()
                }),
                disposition: BlockDisposition::Below,
                priority: 0,
            },
        ];

        editor.update(cx, |editor, cx| {
            let block_ids = editor.insert_blocks(assist_blocks, None, cx);
            [block_ids[0], block_ids[1]]
        })
    }

    fn handle_prompt_editor_focus_in(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let assist = &self.assists[&assist_id];
        let Some(decorations) = assist.decorations.as_ref() else {
            return;
        };
        let assist_group = self.assist_groups.get_mut(&assist.group_id).unwrap();
        let editor_assists = self.assists_by_editor.get_mut(&assist.editor).unwrap();

        assist_group.active_assist_id = Some(assist_id);
        if assist_group.linked {
            for assist_id in &assist_group.assist_ids {
                if let Some(decorations) = self.assists[assist_id].decorations.as_ref() {
                    decorations.prompt_editor.update(cx, |prompt_editor, cx| {
                        prompt_editor.set_show_cursor_when_unfocused(true, cx)
                    });
                }
            }
        }

        assist
            .editor
            .update(cx, |editor, cx| {
                let scroll_top = editor.scroll_position(cx).y;
                let scroll_bottom = scroll_top + editor.visible_line_count().unwrap_or(0.);
                let prompt_row = editor
                    .row_for_block(decorations.prompt_block_id, cx)
                    .unwrap()
                    .0 as f32;

                if (scroll_top..scroll_bottom).contains(&prompt_row) {
                    editor_assists.scroll_lock = Some(InlineAssistScrollLock {
                        assist_id,
                        distance_from_top: prompt_row - scroll_top,
                    });
                } else {
                    editor_assists.scroll_lock = None;
                }
            })
            .ok();
    }

    fn handle_prompt_editor_focus_out(
        &mut self,
        assist_id: InlineAssistId,
        cx: &mut WindowContext,
    ) {
        let assist = &self.assists[&assist_id];
        let assist_group = self.assist_groups.get_mut(&assist.group_id).unwrap();
        if assist_group.active_assist_id == Some(assist_id) {
            assist_group.active_assist_id = None;
            if assist_group.linked {
                for assist_id in &assist_group.assist_ids {
                    if let Some(decorations) = self.assists[assist_id].decorations.as_ref() {
                        decorations.prompt_editor.update(cx, |prompt_editor, cx| {
                            prompt_editor.set_show_cursor_when_unfocused(false, cx)
                        });
                    }
                }
            }
        }
    }

    fn handle_prompt_editor_event(
        &mut self,
        prompt_editor: View<PromptEditor>,
        event: &PromptEditorEvent,
        cx: &mut WindowContext,
    ) {
        let assist_id = prompt_editor.read(cx).id;
        match event {
            PromptEditorEvent::StartRequested => {
                self.start_assist(assist_id, cx);
            }
            PromptEditorEvent::StopRequested => {
                self.stop_assist(assist_id, cx);
            }
            PromptEditorEvent::ConfirmRequested => {
                self.finish_assist(assist_id, false, cx);
            }
            PromptEditorEvent::CancelRequested => {
                self.finish_assist(assist_id, true, cx);
            }
            PromptEditorEvent::DismissRequested => {
                self.dismiss_assist(assist_id, cx);
            }
        }
    }

    fn handle_editor_newline(&mut self, editor: View<Editor>, cx: &mut WindowContext) {
        let Some(editor_assists) = self.assists_by_editor.get(&editor.downgrade()) else {
            return;
        };

        let editor = editor.read(cx);
        if editor.selections.count() == 1 {
            let selection = editor.selections.newest::<usize>(cx);
            let buffer = editor.buffer().read(cx).snapshot(cx);
            for assist_id in &editor_assists.assist_ids {
                let assist = &self.assists[assist_id];
                let assist_range = assist.range.to_offset(&buffer);
                if assist_range.contains(&selection.start) && assist_range.contains(&selection.end)
                {
                    if matches!(assist.codegen.read(cx).status, CodegenStatus::Pending) {
                        self.dismiss_assist(*assist_id, cx);
                    } else {
                        self.finish_assist(*assist_id, false, cx);
                    }

                    return;
                }
            }
        }

        cx.propagate();
    }

    fn handle_editor_cancel(&mut self, editor: View<Editor>, cx: &mut WindowContext) {
        let Some(editor_assists) = self.assists_by_editor.get(&editor.downgrade()) else {
            return;
        };

        let editor = editor.read(cx);
        if editor.selections.count() == 1 {
            let selection = editor.selections.newest::<usize>(cx);
            let buffer = editor.buffer().read(cx).snapshot(cx);
            let mut closest_assist_fallback = None;
            for assist_id in &editor_assists.assist_ids {
                let assist = &self.assists[assist_id];
                let assist_range = assist.range.to_offset(&buffer);
                if assist.decorations.is_some() {
                    if assist_range.contains(&selection.start)
                        && assist_range.contains(&selection.end)
                    {
                        self.focus_assist(*assist_id, cx);
                        return;
                    } else {
                        let distance_from_selection = assist_range
                            .start
                            .abs_diff(selection.start)
                            .min(assist_range.start.abs_diff(selection.end))
                            + assist_range
                                .end
                                .abs_diff(selection.start)
                                .min(assist_range.end.abs_diff(selection.end));
                        match closest_assist_fallback {
                            Some((_, old_distance)) => {
                                if distance_from_selection < old_distance {
                                    closest_assist_fallback =
                                        Some((assist_id, distance_from_selection));
                                }
                            }
                            None => {
                                closest_assist_fallback = Some((assist_id, distance_from_selection))
                            }
                        }
                    }
                }
            }

            if let Some((&assist_id, _)) = closest_assist_fallback {
                self.focus_assist(assist_id, cx);
            }
        }

        cx.propagate();
    }

    fn handle_editor_release(&mut self, editor: WeakView<Editor>, cx: &mut WindowContext) {
        if let Some(editor_assists) = self.assists_by_editor.get_mut(&editor) {
            for assist_id in editor_assists.assist_ids.clone() {
                self.finish_assist(assist_id, true, cx);
            }
        }
    }

    fn handle_editor_change(&mut self, editor: View<Editor>, cx: &mut WindowContext) {
        let Some(editor_assists) = self.assists_by_editor.get(&editor.downgrade()) else {
            return;
        };
        let Some(scroll_lock) = editor_assists.scroll_lock.as_ref() else {
            return;
        };
        let assist = &self.assists[&scroll_lock.assist_id];
        let Some(decorations) = assist.decorations.as_ref() else {
            return;
        };

        editor.update(cx, |editor, cx| {
            let scroll_position = editor.scroll_position(cx);
            let target_scroll_top = editor
                .row_for_block(decorations.prompt_block_id, cx)
                .unwrap()
                .0 as f32
                - scroll_lock.distance_from_top;
            if target_scroll_top != scroll_position.y {
                editor.set_scroll_position(point(scroll_position.x, target_scroll_top), cx);
            }
        });
    }

    fn handle_editor_event(
        &mut self,
        editor: View<Editor>,
        event: &EditorEvent,
        cx: &mut WindowContext,
    ) {
        let Some(editor_assists) = self.assists_by_editor.get_mut(&editor.downgrade()) else {
            return;
        };

        match event {
            EditorEvent::Edited { transaction_id } => {
                let buffer = editor.read(cx).buffer().read(cx);
                let edited_ranges =
                    buffer.edited_ranges_for_transaction::<usize>(*transaction_id, cx);
                let snapshot = buffer.snapshot(cx);

                for assist_id in editor_assists.assist_ids.clone() {
                    let assist = &self.assists[&assist_id];
                    if matches!(
                        assist.codegen.read(cx).status,
                        CodegenStatus::Error(_) | CodegenStatus::Done
                    ) {
                        let assist_range = assist.range.to_offset(&snapshot);
                        if edited_ranges
                            .iter()
                            .any(|range| range.overlaps(&assist_range))
                        {
                            self.finish_assist(assist_id, false, cx);
                        }
                    }
                }
            }
            EditorEvent::ScrollPositionChanged { .. } => {
                if let Some(scroll_lock) = editor_assists.scroll_lock.as_ref() {
                    let assist = &self.assists[&scroll_lock.assist_id];
                    if let Some(decorations) = assist.decorations.as_ref() {
                        let distance_from_top = editor.update(cx, |editor, cx| {
                            let scroll_top = editor.scroll_position(cx).y;
                            let prompt_row = editor
                                .row_for_block(decorations.prompt_block_id, cx)
                                .unwrap()
                                .0 as f32;
                            prompt_row - scroll_top
                        });

                        if distance_from_top != scroll_lock.distance_from_top {
                            editor_assists.scroll_lock = None;
                        }
                    }
                }
            }
            EditorEvent::SelectionsChanged { .. } => {
                for assist_id in editor_assists.assist_ids.clone() {
                    let assist = &self.assists[&assist_id];
                    if let Some(decorations) = assist.decorations.as_ref() {
                        if decorations.prompt_editor.focus_handle(cx).is_focused(cx) {
                            return;
                        }
                    }
                }

                editor_assists.scroll_lock = None;
            }
            _ => {}
        }
    }

    pub fn finish_assist(&mut self, assist_id: InlineAssistId, undo: bool, cx: &mut WindowContext) {
        if let Some(assist) = self.assists.get(&assist_id) {
            let assist_group_id = assist.group_id;
            if self.assist_groups[&assist_group_id].linked {
                for assist_id in self.unlink_assist_group(assist_group_id, cx) {
                    self.finish_assist(assist_id, undo, cx);
                }
                return;
            }
        }

        self.dismiss_assist(assist_id, cx);

        if let Some(assist) = self.assists.remove(&assist_id) {
            if let hash_map::Entry::Occupied(mut entry) = self.assist_groups.entry(assist.group_id)
            {
                entry.get_mut().assist_ids.retain(|id| *id != assist_id);
                if entry.get().assist_ids.is_empty() {
                    entry.remove();
                }
            }

            if let hash_map::Entry::Occupied(mut entry) =
                self.assists_by_editor.entry(assist.editor.clone())
            {
                entry.get_mut().assist_ids.retain(|id| *id != assist_id);
                if entry.get().assist_ids.is_empty() {
                    entry.remove();
                    if let Some(editor) = assist.editor.upgrade() {
                        self.update_editor_highlights(&editor, cx);
                    }
                } else {
                    entry.get().highlight_updates.send(()).ok();
                }
            }

            if undo {
                assist.codegen.update(cx, |codegen, cx| codegen.undo(cx));
            } else {
                self.confirmed_assists.insert(assist_id, assist.codegen);
            }
        }

        // Remove the assist from the status updates map
        self.assist_observations.remove(&assist_id);
    }

    pub fn undo_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) -> bool {
        let Some(codegen) = self.confirmed_assists.remove(&assist_id) else {
            return false;
        };
        codegen.update(cx, |this, cx| this.undo(cx));
        true
    }

    fn dismiss_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) -> bool {
        let Some(assist) = self.assists.get_mut(&assist_id) else {
            return false;
        };
        let Some(editor) = assist.editor.upgrade() else {
            return false;
        };
        let Some(decorations) = assist.decorations.take() else {
            return false;
        };

        editor.update(cx, |editor, cx| {
            let mut to_remove = decorations.removed_line_block_ids;
            to_remove.insert(decorations.prompt_block_id);
            to_remove.insert(decorations.end_block_id);
            editor.remove_blocks(to_remove, None, cx);
        });

        if decorations
            .prompt_editor
            .focus_handle(cx)
            .contains_focused(cx)
        {
            self.focus_next_assist(assist_id, cx);
        }

        if let Some(editor_assists) = self.assists_by_editor.get_mut(&editor.downgrade()) {
            if editor_assists
                .scroll_lock
                .as_ref()
                .map_or(false, |lock| lock.assist_id == assist_id)
            {
                editor_assists.scroll_lock = None;
            }
            editor_assists.highlight_updates.send(()).ok();
        }

        true
    }

    fn focus_next_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let Some(assist) = self.assists.get(&assist_id) else {
            return;
        };

        let assist_group = &self.assist_groups[&assist.group_id];
        let assist_ix = assist_group
            .assist_ids
            .iter()
            .position(|id| *id == assist_id)
            .unwrap();
        let assist_ids = assist_group
            .assist_ids
            .iter()
            .skip(assist_ix + 1)
            .chain(assist_group.assist_ids.iter().take(assist_ix));

        for assist_id in assist_ids {
            let assist = &self.assists[assist_id];
            if assist.decorations.is_some() {
                self.focus_assist(*assist_id, cx);
                return;
            }
        }

        assist.editor.update(cx, |editor, cx| editor.focus(cx)).ok();
    }

    fn focus_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let Some(assist) = self.assists.get(&assist_id) else {
            return;
        };

        if let Some(decorations) = assist.decorations.as_ref() {
            decorations.prompt_editor.update(cx, |prompt_editor, cx| {
                prompt_editor.editor.update(cx, |editor, cx| {
                    editor.focus(cx);
                    editor.select_all(&SelectAll, cx);
                })
            });
        }

        self.scroll_to_assist(assist_id, cx);
    }

    pub fn scroll_to_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let Some(assist) = self.assists.get(&assist_id) else {
            return;
        };
        let Some(editor) = assist.editor.upgrade() else {
            return;
        };

        let position = assist.range.start;
        editor.update(cx, |editor, cx| {
            editor.change_selections(None, cx, |selections| {
                selections.select_anchor_ranges([position..position])
            });

            let mut scroll_target_top;
            let mut scroll_target_bottom;
            if let Some(decorations) = assist.decorations.as_ref() {
                scroll_target_top = editor
                    .row_for_block(decorations.prompt_block_id, cx)
                    .unwrap()
                    .0 as f32;
                scroll_target_bottom = editor
                    .row_for_block(decorations.end_block_id, cx)
                    .unwrap()
                    .0 as f32;
            } else {
                let snapshot = editor.snapshot(cx);
                let start_row = assist
                    .range
                    .start
                    .to_display_point(&snapshot.display_snapshot)
                    .row();
                scroll_target_top = start_row.0 as f32;
                scroll_target_bottom = scroll_target_top + 1.;
            }
            scroll_target_top -= editor.vertical_scroll_margin() as f32;
            scroll_target_bottom += editor.vertical_scroll_margin() as f32;

            let height_in_lines = editor.visible_line_count().unwrap_or(0.);
            let scroll_top = editor.scroll_position(cx).y;
            let scroll_bottom = scroll_top + height_in_lines;

            if scroll_target_top < scroll_top {
                editor.set_scroll_position(point(0., scroll_target_top), cx);
            } else if scroll_target_bottom > scroll_bottom {
                if (scroll_target_bottom - scroll_target_top) <= height_in_lines {
                    editor
                        .set_scroll_position(point(0., scroll_target_bottom - height_in_lines), cx);
                } else {
                    editor.set_scroll_position(point(0., scroll_target_top), cx);
                }
            }
        });
    }

    fn unlink_assist_group(
        &mut self,
        assist_group_id: InlineAssistGroupId,
        cx: &mut WindowContext,
    ) -> Vec<InlineAssistId> {
        let assist_group = self.assist_groups.get_mut(&assist_group_id).unwrap();
        assist_group.linked = false;
        for assist_id in &assist_group.assist_ids {
            let assist = self.assists.get_mut(assist_id).unwrap();
            if let Some(editor_decorations) = assist.decorations.as_ref() {
                editor_decorations
                    .prompt_editor
                    .update(cx, |prompt_editor, cx| prompt_editor.unlink(cx));
            }
        }
        assist_group.assist_ids.clone()
    }

    pub fn start_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let assist = if let Some(assist) = self.assists.get_mut(&assist_id) {
            assist
        } else {
            return;
        };

        let assist_group_id = assist.group_id;
        if self.assist_groups[&assist_group_id].linked {
            for assist_id in self.unlink_assist_group(assist_group_id, cx) {
                self.start_assist(assist_id, cx);
            }
            return;
        }

        let Some(user_prompt) = assist.user_prompt(cx) else {
            return;
        };

        self.prompt_history.retain(|prompt| *prompt != user_prompt);
        self.prompt_history.push_back(user_prompt.clone());
        if self.prompt_history.len() > PROMPT_HISTORY_MAX_LEN {
            self.prompt_history.pop_front();
        }

        let assistant_panel_context = assist.assistant_panel_context(cx);

        assist
            .codegen
            .update(cx, |codegen, cx| {
                codegen.start(user_prompt, assistant_panel_context, cx)
            })
            .log_err();

        if let Some((tx, _)) = self.assist_observations.get(&assist_id) {
            tx.send(()).ok();
        }
    }

    pub fn stop_assist(&mut self, assist_id: InlineAssistId, cx: &mut WindowContext) {
        let assist = if let Some(assist) = self.assists.get_mut(&assist_id) {
            assist
        } else {
            return;
        };

        assist.codegen.update(cx, |codegen, cx| codegen.stop(cx));

        if let Some((tx, _)) = self.assist_observations.get(&assist_id) {
            tx.send(()).ok();
        }
    }

    pub fn assist_status(&self, assist_id: InlineAssistId, cx: &AppContext) -> InlineAssistStatus {
        if let Some(assist) = self.assists.get(&assist_id) {
            match &assist.codegen.read(cx).status {
                CodegenStatus::Idle => InlineAssistStatus::Idle,
                CodegenStatus::Pending => InlineAssistStatus::Pending,
                CodegenStatus::Done => InlineAssistStatus::Done,
                CodegenStatus::Error(_) => InlineAssistStatus::Error,
            }
        } else if self.confirmed_assists.contains_key(&assist_id) {
            InlineAssistStatus::Confirmed
        } else {
            InlineAssistStatus::Canceled
        }
    }

    fn update_editor_highlights(&self, editor: &View<Editor>, cx: &mut WindowContext) {
        let mut gutter_pending_ranges = Vec::new();
        let mut gutter_transformed_ranges = Vec::new();
        let mut foreground_ranges = Vec::new();
        let mut inserted_row_ranges = Vec::new();
        let empty_assist_ids = Vec::new();
        let assist_ids = self
            .assists_by_editor
            .get(&editor.downgrade())
            .map_or(&empty_assist_ids, |editor_assists| {
                &editor_assists.assist_ids
            });

        for assist_id in assist_ids {
            if let Some(assist) = self.assists.get(assist_id) {
                let codegen = assist.codegen.read(cx);
                let buffer = codegen.buffer.read(cx).read(cx);
                foreground_ranges.extend(codegen.last_equal_ranges().iter().cloned());

                let pending_range =
                    codegen.edit_position.unwrap_or(assist.range.start)..assist.range.end;
                if pending_range.end.to_offset(&buffer) > pending_range.start.to_offset(&buffer) {
                    gutter_pending_ranges.push(pending_range);
                }

                if let Some(edit_position) = codegen.edit_position {
                    let edited_range = assist.range.start..edit_position;
                    if edited_range.end.to_offset(&buffer) > edited_range.start.to_offset(&buffer) {
                        gutter_transformed_ranges.push(edited_range);
                    }
                }

                if assist.decorations.is_some() {
                    inserted_row_ranges.extend(codegen.diff.inserted_row_ranges.iter().cloned());
                }
            }
        }

        let snapshot = editor.read(cx).buffer().read(cx).snapshot(cx);
        merge_ranges(&mut foreground_ranges, &snapshot);
        merge_ranges(&mut gutter_pending_ranges, &snapshot);
        merge_ranges(&mut gutter_transformed_ranges, &snapshot);
        editor.update(cx, |editor, cx| {
            enum GutterPendingRange {}
            if gutter_pending_ranges.is_empty() {
                editor.clear_gutter_highlights::<GutterPendingRange>(cx);
            } else {
                editor.highlight_gutter::<GutterPendingRange>(
                    &gutter_pending_ranges,
                    |cx| cx.theme().status().info_background,
                    cx,
                )
            }

            enum GutterTransformedRange {}
            if gutter_transformed_ranges.is_empty() {
                editor.clear_gutter_highlights::<GutterTransformedRange>(cx);
            } else {
                editor.highlight_gutter::<GutterTransformedRange>(
                    &gutter_transformed_ranges,
                    |cx| cx.theme().status().info,
                    cx,
                )
            }

            if foreground_ranges.is_empty() {
                editor.clear_highlights::<InlineAssist>(cx);
            } else {
                editor.highlight_text::<InlineAssist>(
                    foreground_ranges,
                    HighlightStyle {
                        fade_out: Some(0.6),
                        ..Default::default()
                    },
                    cx,
                );
            }

            editor.clear_row_highlights::<InlineAssist>();
            for row_range in inserted_row_ranges {
                editor.highlight_rows::<InlineAssist>(
                    row_range,
                    Some(cx.theme().status().info_background),
                    false,
                    cx,
                );
            }
        });
    }

    fn update_editor_blocks(
        &mut self,
        editor: &View<Editor>,
        assist_id: InlineAssistId,
        cx: &mut WindowContext,
    ) {
        let Some(assist) = self.assists.get_mut(&assist_id) else {
            return;
        };
        let Some(decorations) = assist.decorations.as_mut() else {
            return;
        };

        let codegen = assist.codegen.read(cx);
        let old_snapshot = codegen.snapshot.clone();
        let old_buffer = codegen.old_buffer.clone();
        let deleted_row_ranges = codegen.diff.deleted_row_ranges.clone();

        editor.update(cx, |editor, cx| {
            let old_blocks = mem::take(&mut decorations.removed_line_block_ids);
            editor.remove_blocks(old_blocks, None, cx);

            let mut new_blocks = Vec::new();
            for (new_row, old_row_range) in deleted_row_ranges {
                let (_, buffer_start) = old_snapshot
                    .point_to_buffer_offset(Point::new(*old_row_range.start(), 0))
                    .unwrap();
                let (_, buffer_end) = old_snapshot
                    .point_to_buffer_offset(Point::new(
                        *old_row_range.end(),
                        old_snapshot.line_len(MultiBufferRow(*old_row_range.end())),
                    ))
                    .unwrap();

                let deleted_lines_editor = cx.new_view(|cx| {
                    let multi_buffer = cx.new_model(|_| {
                        MultiBuffer::without_headers(0, language::Capability::ReadOnly)
                    });
                    multi_buffer.update(cx, |multi_buffer, cx| {
                        multi_buffer.push_excerpts(
                            old_buffer.clone(),
                            Some(ExcerptRange {
                                context: buffer_start..buffer_end,
                                primary: None,
                            }),
                            cx,
                        );
                    });

                    enum DeletedLines {}
                    let mut editor = Editor::for_multibuffer(multi_buffer, None, true, cx);
                    editor.set_soft_wrap_mode(language::language_settings::SoftWrap::None, cx);
                    editor.set_show_wrap_guides(false, cx);
                    editor.set_show_gutter(false, cx);
                    editor.scroll_manager.set_forbid_vertical_scroll(true);
                    editor.set_read_only(true);
                    editor.highlight_rows::<DeletedLines>(
                        Anchor::min()..=Anchor::max(),
                        Some(cx.theme().status().deleted_background),
                        false,
                        cx,
                    );
                    editor
                });

                let height =
                    deleted_lines_editor.update(cx, |editor, cx| editor.max_point(cx).row().0 + 1);
                new_blocks.push(BlockProperties {
                    position: new_row,
                    height,
                    style: BlockStyle::Flex,
                    render: Box::new(move |cx| {
                        div()
                            .bg(cx.theme().status().deleted_background)
                            .size_full()
                            .h(height as f32 * cx.line_height())
                            .pl(cx.gutter_dimensions.full_width())
                            .child(deleted_lines_editor.clone())
                            .into_any_element()
                    }),
                    disposition: BlockDisposition::Above,
                    priority: 0,
                });
            }

            decorations.removed_line_block_ids = editor
                .insert_blocks(new_blocks, None, cx)
                .into_iter()
                .collect();
        })
    }

    pub fn observe_assist(&mut self, assist_id: InlineAssistId) -> async_watch::Receiver<()> {
        if let Some((_, rx)) = self.assist_observations.get(&assist_id) {
            rx.clone()
        } else {
            let (tx, rx) = async_watch::channel(());
            self.assist_observations.insert(assist_id, (tx, rx.clone()));
            rx
        }
    }
}

pub enum InlineAssistStatus {
    Idle,
    Pending,
    Done,
    Error,
    Confirmed,
    Canceled,
}

impl InlineAssistStatus {
    pub(crate) fn is_pending(&self) -> bool {
        matches!(self, Self::Pending)
    }
    pub(crate) fn is_confirmed(&self) -> bool {
        matches!(self, Self::Confirmed)
    }
    pub(crate) fn is_done(&self) -> bool {
        matches!(self, Self::Done)
    }
}

struct EditorInlineAssists {
    assist_ids: Vec<InlineAssistId>,
    scroll_lock: Option<InlineAssistScrollLock>,
    highlight_updates: async_watch::Sender<()>,
    _update_highlights: Task<Result<()>>,
    _subscriptions: Vec<gpui::Subscription>,
}

struct InlineAssistScrollLock {
    assist_id: InlineAssistId,
    distance_from_top: f32,
}

impl EditorInlineAssists {
    #[allow(clippy::too_many_arguments)]
    fn new(editor: &View<Editor>, cx: &mut WindowContext) -> Self {
        let (highlight_updates_tx, mut highlight_updates_rx) = async_watch::channel(());
        Self {
            assist_ids: Vec::new(),
            scroll_lock: None,
            highlight_updates: highlight_updates_tx,
            _update_highlights: cx.spawn(|mut cx| {
                let editor = editor.downgrade();
                async move {
                    while let Ok(()) = highlight_updates_rx.changed().await {
                        let editor = editor.upgrade().context("editor was dropped")?;
                        cx.update_global(|assistant: &mut InlineAssistant, cx| {
                            assistant.update_editor_highlights(&editor, cx);
                        })?;
                    }
                    Ok(())
                }
            }),
            _subscriptions: vec![
                cx.observe_release(editor, {
                    let editor = editor.downgrade();
                    |_, cx| {
                        InlineAssistant::update_global(cx, |this, cx| {
                            this.handle_editor_release(editor, cx);
                        })
                    }
                }),
                cx.observe(editor, move |editor, cx| {
                    InlineAssistant::update_global(cx, |this, cx| {
                        this.handle_editor_change(editor, cx)
                    })
                }),
                cx.subscribe(editor, move |editor, event, cx| {
                    InlineAssistant::update_global(cx, |this, cx| {
                        this.handle_editor_event(editor, event, cx)
                    })
                }),
                editor.update(cx, |editor, cx| {
                    let editor_handle = cx.view().downgrade();
                    editor.register_action(
                        move |_: &editor::actions::Newline, cx: &mut WindowContext| {
                            InlineAssistant::update_global(cx, |this, cx| {
                                if let Some(editor) = editor_handle.upgrade() {
                                    this.handle_editor_newline(editor, cx)
                                }
                            })
                        },
                    )
                }),
                editor.update(cx, |editor, cx| {
                    let editor_handle = cx.view().downgrade();
                    editor.register_action(
                        move |_: &editor::actions::Cancel, cx: &mut WindowContext| {
                            InlineAssistant::update_global(cx, |this, cx| {
                                if let Some(editor) = editor_handle.upgrade() {
                                    this.handle_editor_cancel(editor, cx)
                                }
                            })
                        },
                    )
                }),
            ],
        }
    }
}

struct InlineAssistGroup {
    assist_ids: Vec<InlineAssistId>,
    linked: bool,
    active_assist_id: Option<InlineAssistId>,
}

impl InlineAssistGroup {
    fn new() -> Self {
        Self {
            assist_ids: Vec::new(),
            linked: true,
            active_assist_id: None,
        }
    }
}

fn build_assist_editor_renderer(editor: &View<PromptEditor>) -> RenderBlock {
    let editor = editor.clone();
    Box::new(move |cx: &mut BlockContext| {
        *editor.read(cx).gutter_dimensions.lock() = *cx.gutter_dimensions;
        editor.clone().into_any_element()
    })
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum InitialInsertion {
    NewlineBefore,
    NewlineAfter,
}

#[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Hash)]
pub struct InlineAssistId(usize);

impl InlineAssistId {
    fn post_inc(&mut self) -> InlineAssistId {
        let id = *self;
        self.0 += 1;
        id
    }
}

#[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Hash)]
struct InlineAssistGroupId(usize);

impl InlineAssistGroupId {
    fn post_inc(&mut self) -> InlineAssistGroupId {
        let id = *self;
        self.0 += 1;
        id
    }
}

enum PromptEditorEvent {
    StartRequested,
    StopRequested,
    ConfirmRequested,
    CancelRequested,
    DismissRequested,
}

struct PromptEditor {
    id: InlineAssistId,
    fs: Arc<dyn Fs>,
    editor: View<Editor>,
    edited_since_done: bool,
    gutter_dimensions: Arc<Mutex<GutterDimensions>>,
    prompt_history: VecDeque<String>,
    prompt_history_ix: Option<usize>,
    pending_prompt: String,
    codegen: Model<Codegen>,
    _codegen_subscription: Subscription,
    editor_subscriptions: Vec<Subscription>,
    pending_token_count: Task<Result<()>>,
    token_counts: Option<TokenCounts>,
    _token_count_subscriptions: Vec<Subscription>,
    workspace: Option<WeakView<Workspace>>,
    show_rate_limit_notice: bool,
}

#[derive(Copy, Clone)]
pub struct TokenCounts {
    total: usize,
    assistant_panel: usize,
}

impl EventEmitter<PromptEditorEvent> for PromptEditor {}

impl Render for PromptEditor {
    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        let gutter_dimensions = *self.gutter_dimensions.lock();
        let status = &self.codegen.read(cx).status;
        let buttons = match status {
            CodegenStatus::Idle => {
                vec![
                    IconButton::new("cancel", IconName::Close)
                        .icon_color(Color::Muted)
                        .shape(IconButtonShape::Square)
                        .tooltip(|cx| Tooltip::for_action("Cancel Assist", &menu::Cancel, cx))
                        .on_click(
                            cx.listener(|_, _, cx| cx.emit(PromptEditorEvent::CancelRequested)),
                        ),
                    IconButton::new("start", IconName::SparkleAlt)
                        .icon_color(Color::Muted)
                        .shape(IconButtonShape::Square)
                        .tooltip(|cx| Tooltip::for_action("Transform", &menu::Confirm, cx))
                        .on_click(
                            cx.listener(|_, _, cx| cx.emit(PromptEditorEvent::StartRequested)),
                        ),
                ]
            }
            CodegenStatus::Pending => {
                vec![
                    IconButton::new("cancel", IconName::Close)
                        .icon_color(Color::Muted)
                        .shape(IconButtonShape::Square)
                        .tooltip(|cx| Tooltip::text("Cancel Assist", cx))
                        .on_click(
                            cx.listener(|_, _, cx| cx.emit(PromptEditorEvent::CancelRequested)),
                        ),
                    IconButton::new("stop", IconName::Stop)
                        .icon_color(Color::Error)
                        .shape(IconButtonShape::Square)
                        .tooltip(|cx| {
                            Tooltip::with_meta(
                                "Interrupt Transformation",
                                Some(&menu::Cancel),
                                "Changes won't be discarded",
                                cx,
                            )
                        })
                        .on_click(
                            cx.listener(|_, _, cx| cx.emit(PromptEditorEvent::StopRequested)),
                        ),
                ]
            }
            CodegenStatus::Error(_) | CodegenStatus::Done => {
                vec![
                    IconButton::new("cancel", IconName::Close)
                        .icon_color(Color::Muted)
                        .shape(IconButtonShape::Square)
                        .tooltip(|cx| Tooltip::for_action("Cancel Assist", &menu::Cancel, cx))
                        .on_click(
                            cx.listener(|_, _, cx| cx.emit(PromptEditorEvent::CancelRequested)),
                        ),
                    if self.edited_since_done || matches!(status, CodegenStatus::Error(_)) {
                        IconButton::new("restart", IconName::RotateCw)
                            .icon_color(Color::Info)
                            .shape(IconButtonShape::Square)
                            .tooltip(|cx| {
                                Tooltip::with_meta(
                                    "Restart Transformation",
                                    Some(&menu::Confirm),
                                    "Changes will be discarded",
                                    cx,
                                )
                            })
                            .on_click(cx.listener(|_, _, cx| {
                                cx.emit(PromptEditorEvent::StartRequested);
                            }))
                    } else {
                        IconButton::new("confirm", IconName::Check)
                            .icon_color(Color::Info)
                            .shape(IconButtonShape::Square)
                            .tooltip(|cx| Tooltip::for_action("Confirm Assist", &menu::Confirm, cx))
                            .on_click(cx.listener(|_, _, cx| {
                                cx.emit(PromptEditorEvent::ConfirmRequested);
                            }))
                    },
                ]
            }
        };

        h_flex()
            .bg(cx.theme().colors().editor_background)
            .border_y_1()
            .border_color(cx.theme().status().info_border)
            .size_full()
            .py(cx.line_height() / 2.)
            .on_action(cx.listener(Self::confirm))
            .on_action(cx.listener(Self::cancel))
            .on_action(cx.listener(Self::move_up))
            .on_action(cx.listener(Self::move_down))
            .child(
                h_flex()
                    .w(gutter_dimensions.full_width() + (gutter_dimensions.margin / 2.0))
                    .justify_center()
                    .gap_2()
                    .child(
                        ModelSelector::new(
                            self.fs.clone(),
                            IconButton::new("context", IconName::SlidersAlt)
                                .shape(IconButtonShape::Square)
                                .icon_size(IconSize::Small)
                                .icon_color(Color::Muted)
                                .tooltip(move |cx| {
                                    Tooltip::with_meta(
                                        format!(
                                            "Using {}",
                                            LanguageModelRegistry::read_global(cx)
                                                .active_model()
                                                .map(|model| model.name().0)
                                                .unwrap_or_else(|| "No model selected".into()),
                                        ),
                                        None,
                                        "Change Model",
                                        cx,
                                    )
                                }),
                        )
                        .with_info_text(
                            "Inline edits use context\n\
                            from the currently selected\n\
                            assistant panel tab.",
                        ),
                    )
                    .map(|el| {
                        let CodegenStatus::Error(error) = &self.codegen.read(cx).status else {
                            return el;
                        };

                        let error_message = SharedString::from(error.to_string());
                        if error.error_code() == proto::ErrorCode::RateLimitExceeded
                            && cx.has_flag::<ZedPro>()
                        {
                            el.child(
                                v_flex()
                                    .child(
                                        IconButton::new("rate-limit-error", IconName::XCircle)
                                            .selected(self.show_rate_limit_notice)
                                            .shape(IconButtonShape::Square)
                                            .icon_size(IconSize::Small)
                                            .on_click(cx.listener(Self::toggle_rate_limit_notice)),
                                    )
                                    .children(self.show_rate_limit_notice.then(|| {
                                        deferred(
                                            anchored()
                                                .position_mode(gpui::AnchoredPositionMode::Local)
                                                .position(point(px(0.), px(24.)))
                                                .anchor(gpui::AnchorCorner::TopLeft)
                                                .child(self.render_rate_limit_notice(cx)),
                                        )
                                    })),
                            )
                        } else {
                            el.child(
                                div()
                                    .id("error")
                                    .tooltip(move |cx| Tooltip::text(error_message.clone(), cx))
                                    .child(
                                        Icon::new(IconName::XCircle)
                                            .size(IconSize::Small)
                                            .color(Color::Error),
                                    ),
                            )
                        }
                    }),
            )
            .child(div().flex_1().child(self.render_prompt_editor(cx)))
            .child(
                h_flex()
                    .gap_2()
                    .pr_6()
                    .children(self.render_token_count(cx))
                    .children(buttons),
            )
    }
}

impl FocusableView for PromptEditor {
    fn focus_handle(&self, cx: &AppContext) -> FocusHandle {
        self.editor.focus_handle(cx)
    }
}

impl PromptEditor {
    const MAX_LINES: u8 = 8;

    #[allow(clippy::too_many_arguments)]
    fn new(
        id: InlineAssistId,
        gutter_dimensions: Arc<Mutex<GutterDimensions>>,
        prompt_history: VecDeque<String>,
        prompt_buffer: Model<MultiBuffer>,
        codegen: Model<Codegen>,
        parent_editor: &View<Editor>,
        assistant_panel: Option<&View<AssistantPanel>>,
        workspace: Option<WeakView<Workspace>>,
        fs: Arc<dyn Fs>,
        cx: &mut ViewContext<Self>,
    ) -> Self {
        let prompt_editor = cx.new_view(|cx| {
            let mut editor = Editor::new(
                EditorMode::AutoHeight {
                    max_lines: Self::MAX_LINES as usize,
                },
                prompt_buffer,
                None,
                false,
                cx,
            );
            editor.set_soft_wrap_mode(language::language_settings::SoftWrap::EditorWidth, cx);
            // Since the prompt editors for all inline assistants are linked,
            // always show the cursor (even when it isn't focused) because
            // typing in one will make what you typed appear in all of them.
            editor.set_show_cursor_when_unfocused(true, cx);
            editor.set_placeholder_text("Add a prompt…", cx);
            editor
        });

        let mut token_count_subscriptions = Vec::new();
        token_count_subscriptions
            .push(cx.subscribe(parent_editor, Self::handle_parent_editor_event));
        if let Some(assistant_panel) = assistant_panel {
            token_count_subscriptions
                .push(cx.subscribe(assistant_panel, Self::handle_assistant_panel_event));
        }

        let mut this = Self {
            id,
            editor: prompt_editor,
            edited_since_done: false,
            gutter_dimensions,
            prompt_history,
            prompt_history_ix: None,
            pending_prompt: String::new(),
            _codegen_subscription: cx.observe(&codegen, Self::handle_codegen_changed),
            editor_subscriptions: Vec::new(),
            codegen,
            fs,
            pending_token_count: Task::ready(Ok(())),
            token_counts: None,
            _token_count_subscriptions: token_count_subscriptions,
            workspace,
            show_rate_limit_notice: false,
        };
        this.count_tokens(cx);
        this.subscribe_to_editor(cx);
        this
    }

    fn subscribe_to_editor(&mut self, cx: &mut ViewContext<Self>) {
        self.editor_subscriptions.clear();
        self.editor_subscriptions
            .push(cx.subscribe(&self.editor, Self::handle_prompt_editor_events));
    }

    fn set_show_cursor_when_unfocused(
        &mut self,
        show_cursor_when_unfocused: bool,
        cx: &mut ViewContext<Self>,
    ) {
        self.editor.update(cx, |editor, cx| {
            editor.set_show_cursor_when_unfocused(show_cursor_when_unfocused, cx)
        });
    }

    fn unlink(&mut self, cx: &mut ViewContext<Self>) {
        let prompt = self.prompt(cx);
        let focus = self.editor.focus_handle(cx).contains_focused(cx);
        self.editor = cx.new_view(|cx| {
            let mut editor = Editor::auto_height(Self::MAX_LINES as usize, cx);
            editor.set_soft_wrap_mode(language::language_settings::SoftWrap::EditorWidth, cx);
            editor.set_placeholder_text("Add a prompt…", cx);
            editor.set_text(prompt, cx);
            if focus {
                editor.focus(cx);
            }
            editor
        });
        self.subscribe_to_editor(cx);
    }

    fn prompt(&self, cx: &AppContext) -> String {
        self.editor.read(cx).text(cx)
    }

    fn toggle_rate_limit_notice(&mut self, _: &ClickEvent, cx: &mut ViewContext<Self>) {
        self.show_rate_limit_notice = !self.show_rate_limit_notice;
        if self.show_rate_limit_notice {
            cx.focus_view(&self.editor);
        }
        cx.notify();
    }

    fn handle_parent_editor_event(
        &mut self,
        _: View<Editor>,
        event: &EditorEvent,
        cx: &mut ViewContext<Self>,
    ) {
        if let EditorEvent::BufferEdited { .. } = event {
            self.count_tokens(cx);
        }
    }

    fn handle_assistant_panel_event(
        &mut self,
        _: View<AssistantPanel>,
        event: &AssistantPanelEvent,
        cx: &mut ViewContext<Self>,
    ) {
        let AssistantPanelEvent::ContextEdited { .. } = event;
        self.count_tokens(cx);
    }

    fn count_tokens(&mut self, cx: &mut ViewContext<Self>) {
        let assist_id = self.id;
        self.pending_token_count = cx.spawn(|this, mut cx| async move {
            cx.background_executor().timer(Duration::from_secs(1)).await;
            let token_count = cx
                .update_global(|inline_assistant: &mut InlineAssistant, cx| {
                    let assist = inline_assistant
                        .assists
                        .get(&assist_id)
                        .context("assist not found")?;
                    anyhow::Ok(assist.count_tokens(cx))
                })??
                .await?;

            this.update(&mut cx, |this, cx| {
                this.token_counts = Some(token_count);
                cx.notify();
            })
        })
    }

    fn handle_prompt_editor_events(
        &mut self,
        _: View<Editor>,
        event: &EditorEvent,
        cx: &mut ViewContext<Self>,
    ) {
        match event {
            EditorEvent::Edited { .. } => {
                let prompt = self.editor.read(cx).text(cx);
                if self
                    .prompt_history_ix
                    .map_or(true, |ix| self.prompt_history[ix] != prompt)
                {
                    self.prompt_history_ix.take();
                    self.pending_prompt = prompt;
                }

                self.edited_since_done = true;
                cx.notify();
            }
            EditorEvent::BufferEdited => {
                self.count_tokens(cx);
            }
            EditorEvent::Blurred => {
                if self.show_rate_limit_notice {
                    self.show_rate_limit_notice = false;
                    cx.notify();
                }
            }
            _ => {}
        }
    }

    fn handle_codegen_changed(&mut self, _: Model<Codegen>, cx: &mut ViewContext<Self>) {
        match &self.codegen.read(cx).status {
            CodegenStatus::Idle => {
                self.editor
                    .update(cx, |editor, _| editor.set_read_only(false));
            }
            CodegenStatus::Pending => {
                self.editor
                    .update(cx, |editor, _| editor.set_read_only(true));
            }
            CodegenStatus::Done => {
                self.edited_since_done = false;
                self.editor
                    .update(cx, |editor, _| editor.set_read_only(false));
            }
            CodegenStatus::Error(error) => {
                if cx.has_flag::<ZedPro>()
                    && error.error_code() == proto::ErrorCode::RateLimitExceeded
                    && !dismissed_rate_limit_notice()
                {
                    self.show_rate_limit_notice = true;
                    cx.notify();
                }

                self.edited_since_done = false;
                self.editor
                    .update(cx, |editor, _| editor.set_read_only(false));
            }
        }
    }

    fn cancel(&mut self, _: &editor::actions::Cancel, cx: &mut ViewContext<Self>) {
        match &self.codegen.read(cx).status {
            CodegenStatus::Idle | CodegenStatus::Done | CodegenStatus::Error(_) => {
                cx.emit(PromptEditorEvent::CancelRequested);
            }
            CodegenStatus::Pending => {
                cx.emit(PromptEditorEvent::StopRequested);
            }
        }
    }

    fn confirm(&mut self, _: &menu::Confirm, cx: &mut ViewContext<Self>) {
        match &self.codegen.read(cx).status {
            CodegenStatus::Idle => {
                cx.emit(PromptEditorEvent::StartRequested);
            }
            CodegenStatus::Pending => {
                cx.emit(PromptEditorEvent::DismissRequested);
            }
            CodegenStatus::Done | CodegenStatus::Error(_) => {
                if self.edited_since_done {
                    cx.emit(PromptEditorEvent::StartRequested);
                } else {
                    cx.emit(PromptEditorEvent::ConfirmRequested);
                }
            }
        }
    }

    fn move_up(&mut self, _: &MoveUp, cx: &mut ViewContext<Self>) {
        if let Some(ix) = self.prompt_history_ix {
            if ix > 0 {
                self.prompt_history_ix = Some(ix - 1);
                let prompt = self.prompt_history[ix - 1].as_str();
                self.editor.update(cx, |editor, cx| {
                    editor.set_text(prompt, cx);
                    editor.move_to_beginning(&Default::default(), cx);
                });
            }
        } else if !self.prompt_history.is_empty() {
            self.prompt_history_ix = Some(self.prompt_history.len() - 1);
            let prompt = self.prompt_history[self.prompt_history.len() - 1].as_str();
            self.editor.update(cx, |editor, cx| {
                editor.set_text(prompt, cx);
                editor.move_to_beginning(&Default::default(), cx);
            });
        }
    }

    fn move_down(&mut self, _: &MoveDown, cx: &mut ViewContext<Self>) {
        if let Some(ix) = self.prompt_history_ix {
            if ix < self.prompt_history.len() - 1 {
                self.prompt_history_ix = Some(ix + 1);
                let prompt = self.prompt_history[ix + 1].as_str();
                self.editor.update(cx, |editor, cx| {
                    editor.set_text(prompt, cx);
                    editor.move_to_end(&Default::default(), cx)
                });
            } else {
                self.prompt_history_ix = None;
                let prompt = self.pending_prompt.as_str();
                self.editor.update(cx, |editor, cx| {
                    editor.set_text(prompt, cx);
                    editor.move_to_end(&Default::default(), cx)
                });
            }
        }
    }

    fn render_token_count(&self, cx: &mut ViewContext<Self>) -> Option<impl IntoElement> {
        let model = LanguageModelRegistry::read_global(cx).active_model()?;
        let token_counts = self.token_counts?;
        let max_token_count = model.max_token_count();

        let remaining_tokens = max_token_count as isize - token_counts.total as isize;
        let token_count_color = if remaining_tokens <= 0 {
            Color::Error
        } else if token_counts.total as f32 / max_token_count as f32 >= 0.8 {
            Color::Warning
        } else {
            Color::Muted
        };

        let mut token_count = h_flex()
            .id("token_count")
            .gap_0p5()
            .child(
                Label::new(humanize_token_count(token_counts.total))
                    .size(LabelSize::Small)
                    .color(token_count_color),
            )
            .child(Label::new("/").size(LabelSize::Small).color(Color::Muted))
            .child(
                Label::new(humanize_token_count(max_token_count))
                    .size(LabelSize::Small)
                    .color(Color::Muted),
            );
        if let Some(workspace) = self.workspace.clone() {
            token_count = token_count
                .tooltip(move |cx| {
                    Tooltip::with_meta(
                        format!(
                            "Tokens Used ({} from the Assistant Panel)",
                            humanize_token_count(token_counts.assistant_panel)
                        ),
                        None,
                        "Click to open the Assistant Panel",
                        cx,
                    )
                })
                .cursor_pointer()
                .on_mouse_down(gpui::MouseButton::Left, |_, cx| cx.stop_propagation())
                .on_click(move |_, cx| {
                    cx.stop_propagation();
                    workspace
                        .update(cx, |workspace, cx| {
                            workspace.focus_panel::<AssistantPanel>(cx)
                        })
                        .ok();
                });
        } else {
            token_count = token_count
                .cursor_default()
                .tooltip(|cx| Tooltip::text("Tokens used", cx));
        }

        Some(token_count)
    }

    fn render_prompt_editor(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        let settings = ThemeSettings::get_global(cx);
        let text_style = TextStyle {
            color: if self.editor.read(cx).read_only(cx) {
                cx.theme().colors().text_disabled
            } else {
                cx.theme().colors().text
            },
            font_family: settings.ui_font.family.clone(),
            font_features: settings.ui_font.features.clone(),
            font_fallbacks: settings.ui_font.fallbacks.clone(),
            font_size: rems(0.875).into(),
            font_weight: settings.ui_font.weight,
            line_height: relative(1.3),
            ..Default::default()
        };
        EditorElement::new(
            &self.editor,
            EditorStyle {
                background: cx.theme().colors().editor_background,
                local_player: cx.theme().players().local(),
                text: text_style,
                ..Default::default()
            },
        )
    }

    fn render_rate_limit_notice(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        Popover::new().child(
            v_flex()
                .occlude()
                .p_2()
                .child(
                    Label::new("Out of Tokens")
                        .size(LabelSize::Small)
                        .weight(FontWeight::BOLD),
                )
                .child(Label::new(
                    "Try Zed Pro for higher limits, a wider range of models, and more.",
                ))
                .child(
                    h_flex()
                        .justify_between()
                        .child(CheckboxWithLabel::new(
                            "dont-show-again",
                            Label::new("Don't show again"),
                            if dismissed_rate_limit_notice() {
                                ui::Selection::Selected
                            } else {
                                ui::Selection::Unselected
                            },
                            |selection, cx| {
                                let is_dismissed = match selection {
                                    ui::Selection::Unselected => false,
                                    ui::Selection::Indeterminate => return,
                                    ui::Selection::Selected => true,
                                };

                                set_rate_limit_notice_dismissed(is_dismissed, cx)
                            },
                        ))
                        .child(
                            h_flex()
                                .gap_2()
                                .child(
                                    Button::new("dismiss", "Dismiss")
                                        .style(ButtonStyle::Transparent)
                                        .on_click(cx.listener(Self::toggle_rate_limit_notice)),
                                )
                                .child(Button::new("more-info", "More Info").on_click(
                                    |_event, cx| {
                                        cx.dispatch_action(Box::new(
                                            zed_actions::OpenAccountSettings,
                                        ))
                                    },
                                )),
                        ),
                ),
        )
    }
}

const DISMISSED_RATE_LIMIT_NOTICE_KEY: &str = "dismissed-rate-limit-notice";

fn dismissed_rate_limit_notice() -> bool {
    db::kvp::KEY_VALUE_STORE
        .read_kvp(DISMISSED_RATE_LIMIT_NOTICE_KEY)
        .log_err()
        .map_or(false, |s| s.is_some())
}

fn set_rate_limit_notice_dismissed(is_dismissed: bool, cx: &mut AppContext) {
    db::write_and_log(cx, move || async move {
        if is_dismissed {
            db::kvp::KEY_VALUE_STORE
                .write_kvp(DISMISSED_RATE_LIMIT_NOTICE_KEY.into(), "1".into())
                .await
        } else {
            db::kvp::KEY_VALUE_STORE
                .delete_kvp(DISMISSED_RATE_LIMIT_NOTICE_KEY.into())
                .await
        }
    })
}

struct InlineAssist {
    group_id: InlineAssistGroupId,
    range: Range<Anchor>,
    editor: WeakView<Editor>,
    decorations: Option<InlineAssistDecorations>,
    codegen: Model<Codegen>,
    _subscriptions: Vec<Subscription>,
    workspace: Option<WeakView<Workspace>>,
    include_context: bool,
}

impl InlineAssist {
    #[allow(clippy::too_many_arguments)]
    fn new(
        assist_id: InlineAssistId,
        group_id: InlineAssistGroupId,
        include_context: bool,
        editor: &View<Editor>,
        prompt_editor: &View<PromptEditor>,
        prompt_block_id: CustomBlockId,
        end_block_id: CustomBlockId,
        range: Range<Anchor>,
        codegen: Model<Codegen>,
        workspace: Option<WeakView<Workspace>>,
        cx: &mut WindowContext,
    ) -> Self {
        let prompt_editor_focus_handle = prompt_editor.focus_handle(cx);
        InlineAssist {
            group_id,
            include_context,
            editor: editor.downgrade(),
            decorations: Some(InlineAssistDecorations {
                prompt_block_id,
                prompt_editor: prompt_editor.clone(),
                removed_line_block_ids: HashSet::default(),
                end_block_id,
            }),
            range,
            codegen: codegen.clone(),
            workspace: workspace.clone(),
            _subscriptions: vec![
                cx.on_focus_in(&prompt_editor_focus_handle, move |cx| {
                    InlineAssistant::update_global(cx, |this, cx| {
                        this.handle_prompt_editor_focus_in(assist_id, cx)
                    })
                }),
                cx.on_focus_out(&prompt_editor_focus_handle, move |_, cx| {
                    InlineAssistant::update_global(cx, |this, cx| {
                        this.handle_prompt_editor_focus_out(assist_id, cx)
                    })
                }),
                cx.subscribe(prompt_editor, |prompt_editor, event, cx| {
                    InlineAssistant::update_global(cx, |this, cx| {
                        this.handle_prompt_editor_event(prompt_editor, event, cx)
                    })
                }),
                cx.observe(&codegen, {
                    let editor = editor.downgrade();
                    move |_, cx| {
                        if let Some(editor) = editor.upgrade() {
                            InlineAssistant::update_global(cx, |this, cx| {
                                if let Some(editor_assists) =
                                    this.assists_by_editor.get(&editor.downgrade())
                                {
                                    editor_assists.highlight_updates.send(()).ok();
                                }

                                this.update_editor_blocks(&editor, assist_id, cx);
                            })
                        }
                    }
                }),
                cx.subscribe(&codegen, move |codegen, event, cx| {
                    InlineAssistant::update_global(cx, |this, cx| match event {
                        CodegenEvent::Undone => this.finish_assist(assist_id, false, cx),
                        CodegenEvent::Finished => {
                            let assist = if let Some(assist) = this.assists.get(&assist_id) {
                                assist
                            } else {
                                return;
                            };

                            if let CodegenStatus::Error(error) = &codegen.read(cx).status {
                                if assist.decorations.is_none() {
                                    if let Some(workspace) = assist
                                        .workspace
                                        .as_ref()
                                        .and_then(|workspace| workspace.upgrade())
                                    {
                                        let error = format!("Inline assistant error: {}", error);
                                        workspace.update(cx, |workspace, cx| {
                                            struct InlineAssistantError;

                                            let id =
                                                NotificationId::identified::<InlineAssistantError>(
                                                    assist_id.0,
                                                );

                                            workspace.show_toast(Toast::new(id, error), cx);
                                        })
                                    }
                                }
                            }

                            if assist.decorations.is_none() {
                                this.finish_assist(assist_id, false, cx);
                            } else if let Some(tx) = this.assist_observations.get(&assist_id) {
                                tx.0.send(()).ok();
                            }
                        }
                    })
                }),
            ],
        }
    }

    fn user_prompt(&self, cx: &AppContext) -> Option<String> {
        let decorations = self.decorations.as_ref()?;
        Some(decorations.prompt_editor.read(cx).prompt(cx))
    }

    fn assistant_panel_context(&self, cx: &WindowContext) -> Option<LanguageModelRequest> {
        if self.include_context {
            let workspace = self.workspace.as_ref()?;
            let workspace = workspace.upgrade()?.read(cx);
            let assistant_panel = workspace.panel::<AssistantPanel>(cx)?;
            Some(
                assistant_panel
                    .read(cx)
                    .active_context(cx)?
                    .read(cx)
                    .to_completion_request(cx),
            )
        } else {
            None
        }
    }

    pub fn count_tokens(&self, cx: &WindowContext) -> BoxFuture<'static, Result<TokenCounts>> {
        let Some(user_prompt) = self.user_prompt(cx) else {
            return future::ready(Err(anyhow!("no user prompt"))).boxed();
        };
        let assistant_panel_context = self.assistant_panel_context(cx);
        self.codegen
            .read(cx)
            .count_tokens(user_prompt, assistant_panel_context, cx)
    }
}

struct InlineAssistDecorations {
    prompt_block_id: CustomBlockId,
    prompt_editor: View<PromptEditor>,
    removed_line_block_ids: HashSet<CustomBlockId>,
    end_block_id: CustomBlockId,
}

#[derive(Debug)]
pub enum CodegenEvent {
    Finished,
    Undone,
}

pub struct Codegen {
    buffer: Model<MultiBuffer>,
    old_buffer: Model<Buffer>,
    snapshot: MultiBufferSnapshot,
    transform_range: Range<Anchor>,
    selected_ranges: Vec<Range<Anchor>>,
    edit_position: Option<Anchor>,
    last_equal_ranges: Vec<Range<Anchor>>,
    initial_transaction_id: Option<TransactionId>,
    transformation_transaction_id: Option<TransactionId>,
    status: CodegenStatus,
    generation: Task<()>,
    diff: Diff,
    telemetry: Option<Arc<Telemetry>>,
    _subscription: gpui::Subscription,
    prompt_builder: Arc<PromptBuilder>,
}

enum CodegenStatus {
    Idle,
    Pending,
    Done,
    Error(anyhow::Error),
}

#[derive(Default)]
struct Diff {
    deleted_row_ranges: Vec<(Anchor, RangeInclusive<u32>)>,
    inserted_row_ranges: Vec<RangeInclusive<Anchor>>,
}

impl Diff {
    fn is_empty(&self) -> bool {
        self.deleted_row_ranges.is_empty() && self.inserted_row_ranges.is_empty()
    }
}

impl EventEmitter<CodegenEvent> for Codegen {}

impl Codegen {
    pub fn new(
        buffer: Model<MultiBuffer>,
        transform_range: Range<Anchor>,
        selected_ranges: Vec<Range<Anchor>>,
        initial_transaction_id: Option<TransactionId>,
        telemetry: Option<Arc<Telemetry>>,
        builder: Arc<PromptBuilder>,
        cx: &mut ModelContext<Self>,
    ) -> Self {
        let snapshot = buffer.read(cx).snapshot(cx);

        let (old_buffer, _, _) = buffer
            .read(cx)
            .range_to_buffer_ranges(transform_range.clone(), cx)
            .pop()
            .unwrap();
        let old_buffer = cx.new_model(|cx| {
            let old_buffer = old_buffer.read(cx);
            let text = old_buffer.as_rope().clone();
            let line_ending = old_buffer.line_ending();
            let language = old_buffer.language().cloned();
            let language_registry = old_buffer.language_registry();

            let mut buffer = Buffer::local_normalized(text, line_ending, cx);
            buffer.set_language(language, cx);
            if let Some(language_registry) = language_registry {
                buffer.set_language_registry(language_registry)
            }
            buffer
        });

        Self {
            buffer: buffer.clone(),
            old_buffer,
            edit_position: None,
            snapshot,
            last_equal_ranges: Default::default(),
            transformation_transaction_id: None,
            status: CodegenStatus::Idle,
            generation: Task::ready(()),
            diff: Diff::default(),
            telemetry,
            _subscription: cx.subscribe(&buffer, Self::handle_buffer_event),
            initial_transaction_id,
            prompt_builder: builder,
            transform_range,
            selected_ranges,
        }
    }

    fn handle_buffer_event(
        &mut self,
        _buffer: Model<MultiBuffer>,
        event: &multi_buffer::Event,
        cx: &mut ModelContext<Self>,
    ) {
        if let multi_buffer::Event::TransactionUndone { transaction_id } = event {
            if self.transformation_transaction_id == Some(*transaction_id) {
                self.transformation_transaction_id = None;
                self.generation = Task::ready(());
                cx.emit(CodegenEvent::Undone);
            }
        }
    }

    pub fn last_equal_ranges(&self) -> &[Range<Anchor>] {
        &self.last_equal_ranges
    }

    pub fn count_tokens(
        &self,
        user_prompt: String,
        assistant_panel_context: Option<LanguageModelRequest>,
        cx: &AppContext,
    ) -> BoxFuture<'static, Result<TokenCounts>> {
        if let Some(model) = LanguageModelRegistry::read_global(cx).active_model() {
            let request = self.build_request(user_prompt, assistant_panel_context.clone(), cx);
            match request {
                Ok(request) => {
                    let total_count = model.count_tokens(request.clone(), cx);
                    let assistant_panel_count = assistant_panel_context
                        .map(|context| model.count_tokens(context, cx))
                        .unwrap_or_else(|| future::ready(Ok(0)).boxed());

                    async move {
                        Ok(TokenCounts {
                            total: total_count.await?,
                            assistant_panel: assistant_panel_count.await?,
                        })
                    }
                    .boxed()
                }
                Err(error) => futures::future::ready(Err(error)).boxed(),
            }
        } else {
            future::ready(Err(anyhow!("no active model"))).boxed()
        }
    }

    pub fn start(
        &mut self,
        user_prompt: String,
        assistant_panel_context: Option<LanguageModelRequest>,
        cx: &mut ModelContext<Self>,
    ) -> Result<()> {
        let model = LanguageModelRegistry::read_global(cx)
            .active_model()
            .context("no active model")?;

        if let Some(transformation_transaction_id) = self.transformation_transaction_id.take() {
            self.buffer.update(cx, |buffer, cx| {
                buffer.undo_transaction(transformation_transaction_id, cx);
            });
        }

        self.edit_position = Some(self.transform_range.start.bias_right(&self.snapshot));

        let telemetry_id = model.telemetry_id();
        let chunks: LocalBoxFuture<Result<BoxStream<Result<String>>>> =
            if user_prompt.trim().to_lowercase() == "delete" {
                async { Ok(stream::empty().boxed()) }.boxed_local()
            } else {
                let request = self.build_request(user_prompt, assistant_panel_context, cx)?;

                let chunks =
                    cx.spawn(|_, cx| async move { model.stream_completion(request, &cx).await });
                async move { Ok(chunks.await?.boxed()) }.boxed_local()
            };
        self.handle_stream(telemetry_id, self.transform_range.clone(), chunks, cx);
        Ok(())
    }

    fn build_request(
        &self,
        user_prompt: String,
        assistant_panel_context: Option<LanguageModelRequest>,
        cx: &AppContext,
    ) -> Result<LanguageModelRequest> {
        let buffer = self.buffer.read(cx).snapshot(cx);
        let language = buffer.language_at(self.transform_range.start);
        let language_name = if let Some(language) = language.as_ref() {
            if Arc::ptr_eq(language, &language::PLAIN_TEXT) {
                None
            } else {
                Some(language.name())
            }
        } else {
            None
        };

        // Higher Temperature increases the randomness of model outputs.
        // If Markdown or No Language is Known, increase the randomness for more creative output
        // If Code, decrease temperature to get more deterministic outputs
        let temperature = if let Some(language) = language_name.clone() {
            if language.as_ref() == "Markdown" {
                1.0
            } else {
                0.5
            }
        } else {
            1.0
        };

        let language_name = language_name.as_deref();
        let start = buffer.point_to_buffer_offset(self.transform_range.start);
        let end = buffer.point_to_buffer_offset(self.transform_range.end);
        let (transform_buffer, transform_range) = if let Some((start, end)) = start.zip(end) {
            let (start_buffer, start_buffer_offset) = start;
            let (end_buffer, end_buffer_offset) = end;
            if start_buffer.remote_id() == end_buffer.remote_id() {
                (start_buffer.clone(), start_buffer_offset..end_buffer_offset)
            } else {
                return Err(anyhow::anyhow!("invalid transformation range"));
            }
        } else {
            return Err(anyhow::anyhow!("invalid transformation range"));
        };

        let selected_ranges = self
            .selected_ranges
            .iter()
            .filter_map(|selected_range| {
                let start = buffer
                    .point_to_buffer_offset(selected_range.start)
                    .map(|(_, offset)| offset)?;
                let end = buffer
                    .point_to_buffer_offset(selected_range.end)
                    .map(|(_, offset)| offset)?;
                Some(start..end)
            })
            .collect::<Vec<_>>();

        let prompt = self
            .prompt_builder
            .generate_content_prompt(
                user_prompt,
                language_name,
                transform_buffer,
                transform_range,
                selected_ranges,
            )
            .map_err(|e| anyhow::anyhow!("Failed to generate content prompt: {}", e))?;

        let mut messages = Vec::new();
        if let Some(context_request) = assistant_panel_context {
            messages = context_request.messages;
        }

        messages.push(LanguageModelRequestMessage {
            role: Role::User,
            content: vec![prompt.into()],
        });

        Ok(LanguageModelRequest {
            messages,
            stop: vec!["|END|>".to_string()],
            temperature,
        })
    }

    pub fn handle_stream(
        &mut self,
        model_telemetry_id: String,
        edit_range: Range<Anchor>,
        stream: impl 'static + Future<Output = Result<BoxStream<'static, Result<String>>>>,
        cx: &mut ModelContext<Self>,
    ) {
        let snapshot = self.snapshot.clone();
        let selected_text = snapshot
            .text_for_range(edit_range.start..edit_range.end)
            .collect::<Rope>();

        let selection_start = edit_range.start.to_point(&snapshot);

        // Start with the indentation of the first line in the selection
        let mut suggested_line_indent = snapshot
            .suggested_indents(selection_start.row..=selection_start.row, cx)
            .into_values()
            .next()
            .unwrap_or_else(|| snapshot.indent_size_for_line(MultiBufferRow(selection_start.row)));

        // If the first line in the selection does not have indentation, check the following lines
        if suggested_line_indent.len == 0 && suggested_line_indent.kind == IndentKind::Space {
            for row in selection_start.row..=edit_range.end.to_point(&snapshot).row {
                let line_indent = snapshot.indent_size_for_line(MultiBufferRow(row));
                // Prefer tabs if a line in the selection uses tabs as indentation
                if line_indent.kind == IndentKind::Tab {
                    suggested_line_indent.kind = IndentKind::Tab;
                    break;
                }
            }
        }

        let telemetry = self.telemetry.clone();
        self.diff = Diff::default();
        self.status = CodegenStatus::Pending;
        let mut edit_start = edit_range.start.to_offset(&snapshot);
        self.generation = cx.spawn(|this, mut cx| {
            async move {
                let chunks = stream.await;
                let generate = async {
                    let (mut diff_tx, mut diff_rx) = mpsc::channel(1);
                    let diff: Task<anyhow::Result<()>> =
                        cx.background_executor().spawn(async move {
                            let mut response_latency = None;
                            let request_start = Instant::now();
                            let diff = async {
                                let chunks = StripInvalidSpans::new(chunks?);
                                futures::pin_mut!(chunks);
                                let mut diff = StreamingDiff::new(selected_text.to_string());
                                let mut line_diff = LineDiff::default();

                                while let Some(chunk) = chunks.next().await {
                                    if response_latency.is_none() {
                                        response_latency = Some(request_start.elapsed());
                                    }
                                    let chunk = chunk?;
                                    let char_ops = diff.push_new(&chunk);
                                    line_diff.push_char_operations(&char_ops, &selected_text);
                                    diff_tx
                                        .send((char_ops, line_diff.line_operations()))
                                        .await?;
                                }

                                let char_ops = diff.finish();
                                line_diff.push_char_operations(&char_ops, &selected_text);
                                line_diff.finish(&selected_text);
                                diff_tx
                                    .send((char_ops, line_diff.line_operations()))
                                    .await?;

                                anyhow::Ok(())
                            };

                            let result = diff.await;

                            let error_message =
                                result.as_ref().err().map(|error| error.to_string());
                            if let Some(telemetry) = telemetry {
                                telemetry.report_assistant_event(
                                    None,
                                    telemetry_events::AssistantKind::Inline,
                                    model_telemetry_id,
                                    response_latency,
                                    error_message,
                                );
                            }

                            result?;
                            Ok(())
                        });

                    while let Some((char_ops, line_diff)) = diff_rx.next().await {
                        this.update(&mut cx, |this, cx| {
                            this.last_equal_ranges.clear();

                            let transaction = this.buffer.update(cx, |buffer, cx| {
                                // Avoid grouping assistant edits with user edits.
                                buffer.finalize_last_transaction(cx);

                                buffer.start_transaction(cx);
                                buffer.edit(
                                    char_ops
                                        .into_iter()
                                        .filter_map(|operation| match operation {
                                            CharOperation::Insert { text } => {
                                                let edit_start = snapshot.anchor_after(edit_start);
                                                Some((edit_start..edit_start, text))
                                            }
                                            CharOperation::Delete { bytes } => {
                                                let edit_end = edit_start + bytes;
                                                let edit_range = snapshot.anchor_after(edit_start)
                                                    ..snapshot.anchor_before(edit_end);
                                                edit_start = edit_end;
                                                Some((edit_range, String::new()))
                                            }
                                            CharOperation::Keep { bytes } => {
                                                let edit_end = edit_start + bytes;
                                                let edit_range = snapshot.anchor_after(edit_start)
                                                    ..snapshot.anchor_before(edit_end);
                                                edit_start = edit_end;
                                                this.last_equal_ranges.push(edit_range);
                                                None
                                            }
                                        }),
                                    None,
                                    cx,
                                );
                                this.edit_position = Some(snapshot.anchor_after(edit_start));

                                buffer.end_transaction(cx)
                            });

                            if let Some(transaction) = transaction {
                                if let Some(first_transaction) = this.transformation_transaction_id
                                {
                                    // Group all assistant edits into the first transaction.
                                    this.buffer.update(cx, |buffer, cx| {
                                        buffer.merge_transactions(
                                            transaction,
                                            first_transaction,
                                            cx,
                                        )
                                    });
                                } else {
                                    this.transformation_transaction_id = Some(transaction);
                                    this.buffer.update(cx, |buffer, cx| {
                                        buffer.finalize_last_transaction(cx)
                                    });
                                }
                            }

                            this.update_diff(edit_range.clone(), line_diff, cx);

                            cx.notify();
                        })?;
                    }

                    diff.await?;

                    anyhow::Ok(())
                };

                let result = generate.await;
                this.update(&mut cx, |this, cx| {
                    this.last_equal_ranges.clear();
                    if let Err(error) = result {
                        this.status = CodegenStatus::Error(error);
                    } else {
                        this.status = CodegenStatus::Done;
                    }
                    cx.emit(CodegenEvent::Finished);
                    cx.notify();
                })
                .ok();
            }
        });
        cx.notify();
    }

    pub fn stop(&mut self, cx: &mut ModelContext<Self>) {
        self.last_equal_ranges.clear();
        if self.diff.is_empty() {
            self.status = CodegenStatus::Idle;
        } else {
            self.status = CodegenStatus::Done;
        }
        self.generation = Task::ready(());
        cx.emit(CodegenEvent::Finished);
        cx.notify();
    }

    pub fn undo(&mut self, cx: &mut ModelContext<Self>) {
        self.buffer.update(cx, |buffer, cx| {
            if let Some(transaction_id) = self.transformation_transaction_id.take() {
                buffer.undo_transaction(transaction_id, cx);
                buffer.refresh_preview(cx);
            }

            if let Some(transaction_id) = self.initial_transaction_id.take() {
                buffer.undo_transaction(transaction_id, cx);
                buffer.refresh_preview(cx);
            }
        });
    }

    fn update_diff(
        &mut self,
        edit_range: Range<Anchor>,
        line_operations: Vec<LineOperation>,
        cx: &mut ModelContext<Self>,
    ) {
        let old_snapshot = self.snapshot.clone();
        let old_range = edit_range.to_point(&old_snapshot);
        let new_snapshot = self.buffer.read(cx).snapshot(cx);
        let new_range = edit_range.to_point(&new_snapshot);

        let mut old_row = old_range.start.row;
        let mut new_row = new_range.start.row;

        self.diff.deleted_row_ranges.clear();
        self.diff.inserted_row_ranges.clear();
        for operation in line_operations {
            match operation {
                LineOperation::Keep { lines } => {
                    old_row += lines;
                    new_row += lines;
                }
                LineOperation::Delete { lines } => {
                    let old_end_row = old_row + lines - 1;
                    let new_row = new_snapshot.anchor_before(Point::new(new_row, 0));

                    if let Some((_, last_deleted_row_range)) =
                        self.diff.deleted_row_ranges.last_mut()
                    {
                        if *last_deleted_row_range.end() + 1 == old_row {
                            *last_deleted_row_range = *last_deleted_row_range.start()..=old_end_row;
                        } else {
                            self.diff
                                .deleted_row_ranges
                                .push((new_row, old_row..=old_end_row));
                        }
                    } else {
                        self.diff
                            .deleted_row_ranges
                            .push((new_row, old_row..=old_end_row));
                    }

                    old_row += lines;
                }
                LineOperation::Insert { lines } => {
                    let new_end_row = new_row + lines - 1;
                    let start = new_snapshot.anchor_before(Point::new(new_row, 0));
                    let end = new_snapshot.anchor_before(Point::new(
                        new_end_row,
                        new_snapshot.line_len(MultiBufferRow(new_end_row)),
                    ));
                    self.diff.inserted_row_ranges.push(start..=end);
                    new_row += lines;
                }
            }

            cx.notify();
        }
    }
}

struct StripInvalidSpans<T> {
    stream: T,
    stream_done: bool,
    buffer: String,
    first_line: bool,
    line_end: bool,
    starts_with_code_block: bool,
}

impl<T> StripInvalidSpans<T>
where
    T: Stream<Item = Result<String>>,
{
    fn new(stream: T) -> Self {
        Self {
            stream,
            stream_done: false,
            buffer: String::new(),
            first_line: true,
            line_end: false,
            starts_with_code_block: false,
        }
    }
}

impl<T> Stream for StripInvalidSpans<T>
where
    T: Stream<Item = Result<String>>,
{
    type Item = Result<String>;

    fn poll_next(self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<Option<Self::Item>> {
        const CODE_BLOCK_DELIMITER: &str = "```";
        const CURSOR_SPAN: &str = "<|CURSOR|>";

        let this = unsafe { self.get_unchecked_mut() };
        loop {
            if !this.stream_done {
                let mut stream = unsafe { Pin::new_unchecked(&mut this.stream) };
                match stream.as_mut().poll_next(cx) {
                    Poll::Ready(Some(Ok(chunk))) => {
                        this.buffer.push_str(&chunk);
                    }
                    Poll::Ready(Some(Err(error))) => return Poll::Ready(Some(Err(error))),
                    Poll::Ready(None) => {
                        this.stream_done = true;
                    }
                    Poll::Pending => return Poll::Pending,
                }
            }

            let mut chunk = String::new();
            let mut consumed = 0;
            if !this.buffer.is_empty() {
                let mut lines = this.buffer.split('\n').enumerate().peekable();
                while let Some((line_ix, line)) = lines.next() {
                    if line_ix > 0 {
                        this.first_line = false;
                    }

                    if this.first_line {
                        let trimmed_line = line.trim();
                        if lines.peek().is_some() {
                            if trimmed_line.starts_with(CODE_BLOCK_DELIMITER) {
                                consumed += line.len() + 1;
                                this.starts_with_code_block = true;
                                continue;
                            }
                        } else if trimmed_line.is_empty()
                            || prefixes(CODE_BLOCK_DELIMITER)
                                .any(|prefix| trimmed_line.starts_with(prefix))
                        {
                            break;
                        }
                    }

                    let line_without_cursor = line.replace(CURSOR_SPAN, "");
                    if lines.peek().is_some() {
                        if this.line_end {
                            chunk.push('\n');
                        }

                        chunk.push_str(&line_without_cursor);
                        this.line_end = true;
                        consumed += line.len() + 1;
                    } else if this.stream_done {
                        if !this.starts_with_code_block
                            || !line_without_cursor.trim().ends_with(CODE_BLOCK_DELIMITER)
                        {
                            if this.line_end {
                                chunk.push('\n');
                            }

                            chunk.push_str(&line);
                        }

                        consumed += line.len();
                    } else {
                        let trimmed_line = line.trim();
                        if trimmed_line.is_empty()
                            || prefixes(CURSOR_SPAN).any(|prefix| trimmed_line.ends_with(prefix))
                            || prefixes(CODE_BLOCK_DELIMITER)
                                .any(|prefix| trimmed_line.ends_with(prefix))
                        {
                            break;
                        } else {
                            if this.line_end {
                                chunk.push('\n');
                                this.line_end = false;
                            }

                            chunk.push_str(&line_without_cursor);
                            consumed += line.len();
                        }
                    }
                }
            }

            this.buffer = this.buffer.split_off(consumed);
            if !chunk.is_empty() {
                return Poll::Ready(Some(Ok(chunk)));
            } else if this.stream_done {
                return Poll::Ready(None);
            }
        }
    }
}

fn prefixes(text: &str) -> impl Iterator<Item = &str> {
    (0..text.len() - 1).map(|ix| &text[..ix + 1])
}

fn merge_ranges(ranges: &mut Vec<Range<Anchor>>, buffer: &MultiBufferSnapshot) {
    ranges.sort_unstable_by(|a, b| {
        a.start
            .cmp(&b.start, buffer)
            .then_with(|| b.end.cmp(&a.end, buffer))
    });

    let mut ix = 0;
    while ix + 1 < ranges.len() {
        let b = ranges[ix + 1].clone();
        let a = &mut ranges[ix];
        if a.end.cmp(&b.start, buffer).is_gt() {
            if a.end.cmp(&b.end, buffer).is_lt() {
                a.end = b.end;
            }
            ranges.remove(ix + 1);
        } else {
            ix += 1;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use futures::stream::{self};
    use serde::Serialize;

    #[derive(Serialize)]
    pub struct DummyCompletionRequest {
        pub name: String,
    }

    #[gpui::test]
    async fn test_strip_invalid_spans_from_codeblock() {
        assert_chunks("Lorem ipsum dolor", "Lorem ipsum dolor").await;
        assert_chunks("```\nLorem ipsum dolor", "Lorem ipsum dolor").await;
        assert_chunks("```\nLorem ipsum dolor\n```", "Lorem ipsum dolor").await;
        assert_chunks(
            "```html\n```js\nLorem ipsum dolor\n```\n```",
            "```js\nLorem ipsum dolor\n```",
        )
        .await;
        assert_chunks("``\nLorem ipsum dolor\n```", "``\nLorem ipsum dolor\n```").await;
        assert_chunks("Lorem<|CURSOR|> ipsum", "Lorem ipsum").await;
        assert_chunks("Lorem ipsum", "Lorem ipsum").await;
        assert_chunks("```\n<|CURSOR|>Lorem ipsum\n```", "Lorem ipsum").await;

        async fn assert_chunks(text: &str, expected_text: &str) {
            for chunk_size in 1..=text.len() {
                let actual_text = StripInvalidSpans::new(chunks(text, chunk_size))
                    .map(|chunk| chunk.unwrap())
                    .collect::<String>()
                    .await;
                assert_eq!(
                    actual_text, expected_text,
                    "failed to strip invalid spans, chunk size: {}",
                    chunk_size
                );
            }
        }

        fn chunks(text: &str, size: usize) -> impl Stream<Item = Result<String>> {
            stream::iter(
                text.chars()
                    .collect::<Vec<_>>()
                    .chunks(size)
                    .map(|chunk| Ok(chunk.iter().collect::<String>()))
                    .collect::<Vec<_>>(),
            )
        }
    }
}