use anyhow::{Context as _, Result};
use futures::{AsyncBufReadExt, AsyncReadExt, StreamExt, io::BufReader, stream::BoxStream};
use http_client::{AsyncBody, HttpClient, Method, Request as HttpRequest, http};
use serde::{Deserialize, Serialize};
use serde_json::Value;
use std::{convert::TryFrom, sync::Arc, time::Duration};

pub const LMSTUDIO_API_URL: &str = "http://localhost:1234/api/v0";

#[derive(Clone, Copy, Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum Role {
    User,
    Assistant,
    System,
    Tool,
}

impl TryFrom<String> for Role {
    type Error = anyhow::Error;

    fn try_from(value: String) -> Result<Self> {
        match value.as_str() {
            "user" => Ok(Self::User),
            "assistant" => Ok(Self::Assistant),
            "system" => Ok(Self::System),
            "tool" => Ok(Self::Tool),
            _ => anyhow::bail!("invalid role '{value}'"),
        }
    }
}

impl From<Role> for String {
    fn from(val: Role) -> Self {
        match val {
            Role::User => "user".to_owned(),
            Role::Assistant => "assistant".to_owned(),
            Role::System => "system".to_owned(),
            Role::Tool => "tool".to_owned(),
        }
    }
}

#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq)]
pub struct Model {
    pub name: String,
    pub display_name: Option<String>,
    pub max_tokens: usize,
    pub supports_tool_calls: bool,
}

impl Model {
    pub fn new(
        name: &str,
        display_name: Option<&str>,
        max_tokens: Option<usize>,
        supports_tool_calls: bool,
    ) -> Self {
        Self {
            name: name.to_owned(),
            display_name: display_name.map(|s| s.to_owned()),
            max_tokens: max_tokens.unwrap_or(2048),
            supports_tool_calls,
        }
    }

    pub fn id(&self) -> &str {
        &self.name
    }

    pub fn display_name(&self) -> &str {
        self.display_name.as_ref().unwrap_or(&self.name)
    }

    pub fn max_token_count(&self) -> usize {
        self.max_tokens
    }

    pub fn supports_tool_calls(&self) -> bool {
        self.supports_tool_calls
    }
}

#[derive(Debug, Serialize, Deserialize)]
#[serde(untagged)]
pub enum ToolChoice {
    Auto,
    Required,
    None,
    Other(ToolDefinition),
}

#[derive(Clone, Deserialize, Serialize, Debug)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ToolDefinition {
    #[allow(dead_code)]
    Function { function: FunctionDefinition },
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct FunctionDefinition {
    pub name: String,
    pub description: Option<String>,
    pub parameters: Option<Value>,
}

#[derive(Serialize, Deserialize, Debug)]
#[serde(tag = "role", rename_all = "lowercase")]
pub enum ChatMessage {
    Assistant {
        #[serde(default)]
        content: Option<String>,
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        tool_calls: Vec<ToolCall>,
    },
    User {
        content: String,
    },
    System {
        content: String,
    },
    Tool {
        content: String,
        tool_call_id: String,
    },
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ToolCall {
    pub id: String,
    #[serde(flatten)]
    pub content: ToolCallContent,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
#[serde(tag = "type", rename_all = "lowercase")]
pub enum ToolCallContent {
    Function { function: FunctionContent },
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct FunctionContent {
    pub name: String,
    pub arguments: String,
}

#[derive(Serialize, Debug)]
pub struct ChatCompletionRequest {
    pub model: String,
    pub messages: Vec<ChatMessage>,
    pub stream: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub max_tokens: Option<i32>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub stop: Option<Vec<String>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub temperature: Option<f32>,
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub tools: Vec<ToolDefinition>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub tool_choice: Option<ToolChoice>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ChatResponse {
    pub id: String,
    pub object: String,
    pub created: u64,
    pub model: String,
    pub choices: Vec<ChoiceDelta>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ChoiceDelta {
    pub index: u32,
    pub delta: ResponseMessageDelta,
    pub finish_reason: Option<String>,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ToolCallChunk {
    pub index: usize,
    pub id: Option<String>,

    // There is also an optional `type` field that would determine if a
    // function is there. Sometimes this streams in with the `function` before
    // it streams in the `type`
    pub function: Option<FunctionChunk>,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct FunctionChunk {
    pub name: Option<String>,
    pub arguments: Option<String>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct Usage {
    pub prompt_tokens: u32,
    pub completion_tokens: u32,
    pub total_tokens: u32,
}

#[derive(Debug, Default, Clone, Deserialize, PartialEq)]
#[serde(transparent)]
pub struct Capabilities(Vec<String>);

impl Capabilities {
    pub fn supports_tool_calls(&self) -> bool {
        self.0.iter().any(|cap| cap == "tool_use")
    }
}

#[derive(Serialize, Deserialize, Debug)]
#[serde(untagged)]
pub enum ResponseStreamResult {
    Ok(ResponseStreamEvent),
    Err { error: String },
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ResponseStreamEvent {
    pub created: u32,
    pub model: String,
    pub object: String,
    pub choices: Vec<ChoiceDelta>,
    pub usage: Option<Usage>,
}

#[derive(Deserialize)]
pub struct ListModelsResponse {
    pub data: Vec<ModelEntry>,
}

#[derive(Clone, Debug, Deserialize, PartialEq)]
pub struct ModelEntry {
    pub id: String,
    pub object: String,
    pub r#type: ModelType,
    pub publisher: String,
    pub arch: Option<String>,
    pub compatibility_type: CompatibilityType,
    pub quantization: Option<String>,
    pub state: ModelState,
    pub max_context_length: Option<u32>,
    pub loaded_context_length: Option<u32>,
    #[serde(default)]
    pub capabilities: Capabilities,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum ModelType {
    Llm,
    Embeddings,
    Vlm,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "kebab-case")]
pub enum ModelState {
    Loaded,
    Loading,
    NotLoaded,
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum CompatibilityType {
    Gguf,
    Mlx,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct ResponseMessageDelta {
    pub role: Option<Role>,
    pub content: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub tool_calls: Option<Vec<ToolCallChunk>>,
}

pub async fn complete(
    client: &dyn HttpClient,
    api_url: &str,
    request: ChatCompletionRequest,
) -> Result<ChatResponse> {
    let uri = format!("{api_url}/chat/completions");
    let request_builder = HttpRequest::builder()
        .method(Method::POST)
        .uri(uri)
        .header("Content-Type", "application/json");

    let serialized_request = serde_json::to_string(&request)?;
    let request = request_builder.body(AsyncBody::from(serialized_request))?;

    let mut response = client.send(request).await?;
    if response.status().is_success() {
        let mut body = Vec::new();
        response.body_mut().read_to_end(&mut body).await?;
        let response_message: ChatResponse = serde_json::from_slice(&body)?;
        Ok(response_message)
    } else {
        let mut body = Vec::new();
        response.body_mut().read_to_end(&mut body).await?;
        let body_str = std::str::from_utf8(&body)?;
        anyhow::bail!(
            "Failed to connect to API: {} {}",
            response.status(),
            body_str
        );
    }
}

pub async fn stream_chat_completion(
    client: &dyn HttpClient,
    api_url: &str,
    request: ChatCompletionRequest,
) -> Result<BoxStream<'static, Result<ResponseStreamEvent>>> {
    let uri = format!("{api_url}/chat/completions");
    let request_builder = http::Request::builder()
        .method(Method::POST)
        .uri(uri)
        .header("Content-Type", "application/json");

    let request = request_builder.body(AsyncBody::from(serde_json::to_string(&request)?))?;
    let mut response = client.send(request).await?;
    if response.status().is_success() {
        let reader = BufReader::new(response.into_body());

        Ok(reader
            .lines()
            .filter_map(|line| async move {
                match line {
                    Ok(line) => {
                        let line = line.strip_prefix("data: ")?;
                        if line == "[DONE]" {
                            None
                        } else {
                            let result = serde_json::from_str(&line)
                                .context("Unable to parse chat completions response");
                            if let Err(ref e) = result {
                                eprintln!("Error parsing line: {e}\nLine content: '{line}'");
                            }
                            Some(result)
                        }
                    }
                    Err(e) => {
                        eprintln!("Error reading line: {e}");
                        Some(Err(e.into()))
                    }
                }
            })
            .boxed())
    } else {
        let mut body = String::new();
        response.body_mut().read_to_string(&mut body).await?;
        anyhow::bail!(
            "Failed to connect to LM Studio API: {} {}",
            response.status(),
            body,
        );
    }
}

pub async fn get_models(
    client: &dyn HttpClient,
    api_url: &str,
    _: Option<Duration>,
) -> Result<Vec<ModelEntry>> {
    let uri = format!("{api_url}/models");
    let request_builder = HttpRequest::builder()
        .method(Method::GET)
        .uri(uri)
        .header("Accept", "application/json");

    let request = request_builder.body(AsyncBody::default())?;

    let mut response = client.send(request).await?;

    let mut body = String::new();
    response.body_mut().read_to_string(&mut body).await?;

    anyhow::ensure!(
        response.status().is_success(),
        "Failed to connect to LM Studio API: {} {}",
        response.status(),
        body,
    );
    let response: ListModelsResponse =
        serde_json::from_str(&body).context("Unable to parse LM Studio models response")?;
    Ok(response.data)
}

/// Sends an empty request to LM Studio to trigger loading the model
pub async fn preload_model(client: Arc<dyn HttpClient>, api_url: &str, model: &str) -> Result<()> {
    let uri = format!("{api_url}/completions");
    let request = HttpRequest::builder()
        .method(Method::POST)
        .uri(uri)
        .header("Content-Type", "application/json")
        .body(AsyncBody::from(serde_json::to_string(
            &serde_json::json!({
                "model": model,
                "messages": [],
                "stream": false,
                "max_tokens": 0,
            }),
        )?))?;

    let mut response = client.send(request).await?;

    if response.status().is_success() {
        Ok(())
    } else {
        let mut body = String::new();
        response.body_mut().read_to_string(&mut body).await?;
        anyhow::bail!(
            "Failed to connect to LM Studio API: {} {}",
            response.status(),
            body,
        );
    }
}