//! WebSocket service implementation for real-time model serving

use crate::error::{ApiError, ApiResult};
use axum::extract::ws::{Message, WebSocket as AxumWebSocket};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::net::SocketAddr;
use std::sync::Arc;
use tokio::sync::{Mutex, RwLock};
use uuid::Uuid;

/// WebSocket server configuration
#[derive(Debug, Clone)]
pub struct WebSocketConfig {
    pub port: u16,
    pub max_connections: usize,
    pub heartbeat_interval: u64, // seconds
    pub message_buffer_size: usize,
}

impl Default for WebSocketConfig {
    fn default() -> Self {
        Self {
            port: 8080,
            max_connections: 1000,
            heartbeat_interval: 30,
            message_buffer_size: 1024,
        }
    }
}

impl WebSocketConfig {
    pub fn set_max_connections(&mut self, max: usize) {
        self.max_connections = max;
    }

    pub fn set_heartbeat_interval(&mut self, seconds: u64) {
        self.heartbeat_interval = seconds;
    }
}

/// WebSocket message types
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(tag = "type", content = "data")]
pub enum WebSocketMessage {
    Ping(Vec<u8>),
    Pong(Vec<u8>),
    Heartbeat(u64),
    Broadcast { content: String },
    Text(String),
    Binary(Vec<u8>),
    Close,
}

/// WebSocket request types
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum WebSocketRequest {
    Inference {
        model_name: String,
        input_data: Vec<f32>,
        stream: bool,
    },
    ModelInfo {
        model_name: String,
    },
    Subscribe {
        topic: String,
    },
    Unsubscribe {
        topic: String,
    },
}

/// WebSocket response types
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum WebSocketResponse {
    InferenceResult {
        model_name: String,
        outputs: Vec<f32>,
        latency_ms: f64,
    },
    StreamToken {
        model_name: String,
        token: String,
        is_final: bool,
    },
    ModelInfo {
        name: String,
        model_type: String,
        is_loaded: bool,
    },
    Error {
        message: String,
        code: u16,
    },
    Acknowledgment {
        request_id: String,
    },
}

/// WebSocket connection wrapper
#[derive(Debug)]
pub struct WebSocketConnection {
    id: Uuid,
    socket: Arc<Mutex<AxumWebSocket>>,
    is_active: Arc<RwLock<bool>>,
}

impl WebSocketConnection {
    fn new(socket: AxumWebSocket) -> Self {
        Self {
            id: Uuid::new_v4(),
            socket: Arc::new(Mutex::new(socket)),
            is_active: Arc::new(RwLock::new(true)),
        }
    }

    #[must_use]
    pub fn connection_id(&self) -> Uuid {
        self.id
    }

    #[must_use]
    pub fn is_active(&self) -> bool {
        futures::executor::block_on(async { *self.is_active.read().await })
    }

    pub async fn send(&self, msg: WebSocketMessage) -> ApiResult<()> {
        let message = match msg {
            WebSocketMessage::Ping(data) => Message::Ping(data),
            WebSocketMessage::Pong(data) => Message::Pong(data),
            WebSocketMessage::Text(text) => Message::Text(text),
            WebSocketMessage::Binary(data) => Message::Binary(data),
            WebSocketMessage::Close => Message::Close(None),
            _ => Message::Text(serde_json::to_string(&msg)?),
        };

        let mut socket = self.socket.lock().await;
        socket
            .send(message)
            .await
            .map_err(|e| ApiError::WebSocket(e.to_string()))?;
        Ok(())
    }

    pub async fn recv(&self) -> ApiResult<WebSocketMessage> {
        let mut socket = self.socket.lock().await;

        match socket.recv().await {
            Some(Ok(Message::Ping(data))) => Ok(WebSocketMessage::Pong(data)),
            Some(Ok(Message::Text(text))) => Ok(WebSocketMessage::Text(text)),
            Some(Ok(Message::Binary(data))) => Ok(WebSocketMessage::Binary(data)),
            Some(Ok(Message::Close(_))) => Ok(WebSocketMessage::Close),
            _ => Err(ApiError::WebSocket("Failed to receive message".to_string())),
        }
    }

    pub async fn send_json<T: Serialize>(&self, data: &T) -> ApiResult<()> {
        let json = serde_json::to_string(data)?;
        self.send(WebSocketMessage::Text(json)).await
    }

    pub async fn recv_json<T: for<'de> Deserialize<'de>>(&self) -> ApiResult<T> {
        let msg = self.recv().await?;

        match msg {
            WebSocketMessage::Text(text) => {
                serde_json::from_str(&text).map_err(|e| ApiError::WebSocket(e.to_string()))
            }
            _ => Err(ApiError::WebSocket("Expected text message".to_string())),
        }
    }

    pub async fn try_recv(&self) -> ApiResult<WebSocketMessage> {
        self.recv().await
    }

    pub async fn close(&self) -> ApiResult<()> {
        let mut is_active = self.is_active.write().await;
        *is_active = false;
        self.send(WebSocketMessage::Close).await
    }
}

/// Connection manager for WebSocket connections
#[derive(Debug)]
pub struct ConnectionManager {
    connections: Arc<RwLock<HashMap<Uuid, Arc<WebSocketConnection>>>>,
    max_connections: usize,
}

impl Default for ConnectionManager {
    fn default() -> Self {
        Self::new()
    }
}

impl ConnectionManager {
    #[must_use]
    pub fn new() -> Self {
        Self {
            connections: Arc::new(RwLock::new(HashMap::new())),
            max_connections: 1000,
        }
    }

    pub async fn add_connection(
        &self,
        ws: AxumWebSocket,
    ) -> Result<Arc<WebSocketConnection>, crate::ApiError> {
        let connections = self.connections.read().await;

        if connections.len() >= self.max_connections {
            return Err(crate::ApiError::WebSocket(
                "Connection limit reached".to_string(),
            ));
        }

        drop(connections);

        let conn = Arc::new(WebSocketConnection::new(ws));
        let mut connections = self.connections.write().await;
        connections.insert(conn.connection_id(), conn.clone());

        Ok(conn)
    }

    #[must_use]
    pub fn connection_count(&self) -> usize {
        futures::executor::block_on(async { self.connections.read().await.len() })
    }

    pub async fn get_connection(&self, conn_id: Uuid) -> Option<Arc<WebSocketConnection>> {
        let connections = self.connections.read().await;
        connections.get(&conn_id).cloned()
    }

    pub async fn broadcast(&self, msg: WebSocketMessage) -> ApiResult<()> {
        let connections = self.connections.read().await;

        for conn in connections.values() {
            if conn.is_active() {
                conn.send(msg.clone()).await?;
            }
        }

        Ok(())
    }

    pub async fn remove_connection(&self, conn_id: Uuid) {
        let mut connections = self.connections.write().await;
        connections.remove(&conn_id);
    }
}

/// WebSocket server for real-time model serving
#[derive(Debug)]
pub struct WebSocketServer {
    config: WebSocketConfig,
    models: Arc<RwLock<HashMap<String, String>>>,
    connection_manager: Arc<ConnectionManager>,
    is_ready: Arc<RwLock<bool>>,
}

impl WebSocketServer {
    #[must_use]
    pub fn new(config: WebSocketConfig) -> Self {
        Self {
            config,
            models: Arc::new(RwLock::new(HashMap::new())),
            connection_manager: Arc::new(ConnectionManager::new()),
            is_ready: Arc::new(RwLock::new(true)),
        }
    }

    #[must_use]
    pub fn port(&self) -> u16 {
        self.config.port
    }

    #[must_use]
    pub fn max_connections(&self) -> usize {
        self.config.max_connections
    }

    #[must_use]
    pub fn is_ready(&self) -> bool {
        futures::executor::block_on(async { *self.is_ready.read().await })
    }

    pub fn register_model(&mut self, name: &str, model_type: &str) {
        futures::executor::block_on(async {
            let mut models = self.models.write().await;
            models.insert(name.to_string(), model_type.to_string());
        });
    }

    pub async fn start(&self) -> ApiResult<SocketAddr> {
        let addr = SocketAddr::from(([127, 0, 0, 1], self.config.port));
        Ok(addr)
    }

    pub async fn handle_connection(&self, ws: AxumWebSocket) {
        let conn = Arc::new(WebSocketConnection::new(ws));
        let mut connections = self.connection_manager.connections.write().await;
        connections.insert(conn.connection_id(), conn.clone());

        // Handle messages
        loop {
            match conn.recv().await {
                Ok(WebSocketMessage::Close) => break,
                Ok(msg) => {
                    // Process message
                    self.process_message(&conn, msg).await;
                }
                Err(_) => break,
            }
        }

        // Remove connection
        self.connection_manager
            .remove_connection(conn.connection_id())
            .await;
    }

    async fn process_message(&self, conn: &WebSocketConnection, msg: WebSocketMessage) {
        match msg {
            WebSocketMessage::Ping(data) => {
                let _ = conn.send(WebSocketMessage::Pong(data)).await;
            }
            WebSocketMessage::Text(text) => {
                if let Ok(request) = serde_json::from_str::<WebSocketRequest>(&text) {
                    self.handle_request(conn, request).await;
                }
            }
            _ => {}
        }
    }

    async fn handle_request(&self, conn: &WebSocketConnection, request: WebSocketRequest) {
        match request {
            WebSocketRequest::Inference {
                model_name,
                input_data,
                stream,
            } => {
                if stream {
                    self.handle_streaming_inference(conn, &model_name, input_data)
                        .await;
                } else {
                    self.handle_inference(conn, &model_name, input_data).await;
                }
            }
            WebSocketRequest::ModelInfo { model_name } => {
                self.handle_model_info(conn, &model_name).await;
            }
            _ => {}
        }
    }

    async fn handle_inference(
        &self,
        conn: &WebSocketConnection,
        model_name: &str,
        _input_data: Vec<f32>,
    ) {
        let models = self.models.read().await;

        if !models.contains_key(model_name) {
            let error = WebSocketResponse::Error {
                message: format!("Model {model_name} not found"),
                code: 404,
            };
            let _ = conn.send_json(&error).await;
            return;
        }

        // Simulate inference
        let response = WebSocketResponse::InferenceResult {
            model_name: model_name.to_string(),
            outputs: vec![0.1, 0.2, 0.3],
            latency_ms: 10.0,
        };

        let _ = conn.send_json(&response).await;
    }

    async fn handle_streaming_inference(
        &self,
        conn: &WebSocketConnection,
        model_name: &str,
        _input_data: Vec<f32>,
    ) {
        let models = self.models.read().await;

        if !models.contains_key(model_name) {
            let error = WebSocketResponse::Error {
                message: format!("Model {model_name} not found"),
                code: 404,
            };
            let _ = conn.send_json(&error).await;
            return;
        }

        // Simulate streaming tokens
        for i in 0..5 {
            let response = WebSocketResponse::StreamToken {
                model_name: model_name.to_string(),
                token: format!("token_{i}"),
                is_final: i == 4,
            };

            if conn.send_json(&response).await.is_err() {
                break;
            }

            tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;
        }
    }

    async fn handle_model_info(&self, conn: &WebSocketConnection, model_name: &str) {
        let models = self.models.read().await;

        if let Some(model_type) = models.get(model_name) {
            let response = WebSocketResponse::ModelInfo {
                name: model_name.to_string(),
                model_type: model_type.clone(),
                is_loaded: true,
            };
            let _ = conn.send_json(&response).await;
        } else {
            let error = WebSocketResponse::Error {
                message: format!("Model {model_name} not found"),
                code: 404,
            };
            let _ = conn.send_json(&error).await;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn test_websocket_config() {
        let config = WebSocketConfig::default();
        assert_eq!(config.port, 8080);
        assert_eq!(config.max_connections, 1000);
    }

    #[test]
    fn test_websocket_message_serialization() {
        let msg = WebSocketMessage::Text("hello".to_string());
        let serialized = serde_json::to_string(&msg).unwrap();
        assert!(serialized.contains("hello"));
    }

    #[test]
    fn test_websocket_request_serialization() {
        let req = WebSocketRequest::Inference {
            model_name: "test".to_string(),
            input_data: vec![1.0, 2.0],
            stream: true,
        };
        let serialized = serde_json::to_string(&req).unwrap();
        assert!(serialized.contains("test"));
    }

    #[test]
    fn test_websocket_response_serialization() {
        let resp = WebSocketResponse::StreamToken {
            model_name: "test".to_string(),
            token: "hello".to_string(),
            is_final: false,
        };
        let serialized = serde_json::to_string(&resp).unwrap();
        assert!(serialized.contains("hello"));
    }
}