//! A source of tasks, based on a static configuration, deserialized from the tasks config file, and related infrastructure for tracking changes to the file.

use std::sync::Arc;

use futures::StreamExt;
use gpui::AppContext;
use parking_lot::RwLock;
use serde::Deserialize;
use util::ResultExt;

use crate::TaskTemplates;
use futures::channel::mpsc::UnboundedReceiver;

/// The source of tasks defined in a tasks config file.
pub struct StaticSource {
    tasks: TrackedFile<TaskTemplates>,
}

/// A Wrapper around deserializable T that keeps track of its contents
/// via a provided channel. Once T value changes, the observers of [`TrackedFile`] are
/// notified.
pub struct TrackedFile<T> {
    parsed_contents: Arc<RwLock<T>>,
}

impl<T: PartialEq + 'static + Sync> TrackedFile<T> {
    /// Initializes new [`TrackedFile`] with a type that's deserializable.
    pub fn new(mut tracker: UnboundedReceiver<String>, cx: &mut AppContext) -> Self
    where
        T: for<'a> Deserialize<'a> + Default + Send,
    {
        let parsed_contents: Arc<RwLock<T>> = Arc::default();
        cx.background_executor()
            .spawn({
                let parsed_contents = parsed_contents.clone();
                async move {
                    while let Some(new_contents) = tracker.next().await {
                        if Arc::strong_count(&parsed_contents) == 1 {
                            // We're no longer being observed. Stop polling.
                            break;
                        }
                        if !new_contents.trim().is_empty() {
                            let Some(new_contents) =
                                serde_json_lenient::from_str::<T>(&new_contents).log_err()
                            else {
                                continue;
                            };
                            let mut contents = parsed_contents.write();
                            *contents = new_contents;
                        }
                    }
                    anyhow::Ok(())
                }
            })
            .detach_and_log_err(cx);
        Self { parsed_contents }
    }

    /// Initializes new [`TrackedFile`] with a type that's convertible from another deserializable type.
    pub fn new_convertible<U: for<'a> Deserialize<'a> + TryInto<T, Error = anyhow::Error>>(
        mut tracker: UnboundedReceiver<String>,
        cx: &mut AppContext,
    ) -> Self
    where
        T: Default + Send,
    {
        let parsed_contents: Arc<RwLock<T>> = Arc::default();
        cx.background_executor()
            .spawn({
                let parsed_contents = parsed_contents.clone();
                async move {
                    while let Some(new_contents) = tracker.next().await {
                        if Arc::strong_count(&parsed_contents) == 1 {
                            // We're no longer being observed. Stop polling.
                            break;
                        }

                        if !new_contents.trim().is_empty() {
                            let Some(new_contents) =
                                serde_json_lenient::from_str::<U>(&new_contents).log_err()
                            else {
                                continue;
                            };
                            let Some(new_contents) = new_contents.try_into().log_err() else {
                                continue;
                            };
                            let mut contents = parsed_contents.write();
                            *contents = new_contents;
                        }
                    }
                    anyhow::Ok(())
                }
            })
            .detach_and_log_err(cx);
        Self {
            parsed_contents: Default::default(),
        }
    }
}

impl StaticSource {
    /// Initializes the static source, reacting on tasks config changes.
    pub fn new(tasks: TrackedFile<TaskTemplates>) -> Self {
        Self { tasks }
    }
    /// Returns current list of tasks
    pub fn tasks_to_schedule(&self) -> TaskTemplates {
        self.tasks.parsed_contents.read().clone()
    }
}