use axum::{
    extract::{
        ws::{Message, WebSocket, WebSocketUpgrade},
        Path, State,
    },
    response::IntoResponse,
};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::{broadcast, RwLock};
use uuid::Uuid;

/// WebSocket message payload types.
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", content = "data")]
pub enum WsMessage {
    PointValueChange(crate::telemetry::WsPointMonitorInfo),
    PointSetValueBatchResult(crate::connection::BatchSetPointValueRes),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", content = "data", rename_all = "snake_case")]
pub enum WsClientMessage {
    AuthWrite(WsAuthWriteReq),
    PointSetValueBatch(crate::connection::BatchSetPointValueReq),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct WsAuthWriteReq {
    pub key: String,
}

/// Room manager: room_id -> broadcast sender.
#[derive(Clone)]
pub struct RoomManager {
    rooms: Arc<RwLock<HashMap<String, broadcast::Sender<WsMessage>>>>,
}

impl RoomManager {
    pub fn new() -> Self {
        Self {
            rooms: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// Get or create room sender.
    pub async fn get_or_create_room(&self, room_id: &str) -> broadcast::Sender<WsMessage> {
        let mut rooms = self.rooms.write().await;

        if let Some(sender) = rooms.get(room_id) {
            return sender.clone();
        }

        let (sender, _) = broadcast::channel(100);
        rooms.insert(room_id.to_string(), sender.clone());
        tracing::info!("Created new room: {}", room_id);
        sender
    }

    /// Get room sender if room exists.
    pub async fn get_room(&self, room_id: &str) -> Option<broadcast::Sender<WsMessage>> {
        let rooms = self.rooms.read().await;
        rooms.get(room_id).cloned()
    }

    /// Remove room if there are no receivers left.
    pub async fn remove_room_if_empty(&self, room_id: &str) {
        let mut rooms = self.rooms.write().await;
        let should_remove = rooms
            .get(room_id)
            .map(|sender| sender.receiver_count() == 0)
            .unwrap_or(false);

        if should_remove {
            rooms.remove(room_id);
            tracing::info!("Removed empty room: {}", room_id);
        }
    }

    /// Send message to room.
    ///
    /// Returns:
    /// - Ok(n): n subscribers received it
    /// - Ok(0): room missing or no active subscribers
    pub async fn send_to_room(&self, room_id: &str, message: WsMessage) -> Result<usize, String> {
        if let Some(sender) = self.get_room(room_id).await {
            match sender.send(message) {
                Ok(count) => Ok(count),
                // No receiver is not exceptional in push scenarios.
                Err(broadcast::error::SendError(_)) => Ok(0),
            }
        } else {
            Ok(0)
        }
    }

}

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

/// WebSocket manager.
#[derive(Clone)]
pub struct WebSocketManager {
    public_room: Arc<RoomManager>,
}

impl WebSocketManager {
    pub fn new() -> Self {
        Self {
            public_room: Arc::new(RoomManager::new()),
        }
    }

    /// Send message to public room.
    pub async fn send_to_public(&self, message: WsMessage) -> Result<usize, String> {
        self.public_room.get_or_create_room("public").await;
        self.public_room.send_to_room("public", message).await
    }

    /// Send message to a dedicated client room.
    pub async fn send_to_client(&self, client_id: Uuid, message: WsMessage) -> Result<usize, String> {
        self.public_room
            .send_to_room(&client_id.to_string(), message)
            .await
    }
}

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

/// Public websocket handler.
pub async fn public_websocket_handler(
    ws: WebSocketUpgrade,
    State(state): State<crate::AppState>,
) -> impl IntoResponse {
    let ws_manager = state.ws_manager.clone();
    let app_state = state.clone();
    ws.on_upgrade(move |socket| handle_socket(socket, ws_manager, "public".to_string(), app_state))
}

/// Client websocket handler.
pub async fn client_websocket_handler(
    ws: WebSocketUpgrade,
    Path(client_id): Path<Uuid>,
    State(state): State<crate::AppState>,
) -> impl IntoResponse {
    let ws_manager = state.ws_manager.clone();
    let room_id = client_id.to_string();
    let app_state = state.clone();
    ws.on_upgrade(move |socket| handle_socket(socket, ws_manager, room_id, app_state))
}

/// Handle websocket connection for one room.
async fn handle_socket(
    mut socket: WebSocket,
    ws_manager: Arc<WebSocketManager>,
    room_id: String,
    state: crate::AppState,
) {
    let room_sender = ws_manager.public_room.get_or_create_room(&room_id).await;
    let mut rx = room_sender.subscribe();
    let mut can_write = false;

    loop {
        tokio::select! {
            maybe_msg = socket.recv() => {
                match maybe_msg {
                    Some(Ok(msg)) => {
                        if matches!(msg, Message::Close(_)) {
                            break;
                        }
                        match msg {
                            Message::Text(text) => {
                                match serde_json::from_str::<WsClientMessage>(&text) {
                                    Ok(WsClientMessage::AuthWrite(payload)) => {
                                        can_write = state.config.verify_write_key(&payload.key);
                                        if !can_write {
                                            tracing::warn!("WebSocket write auth failed in room {}", room_id);
                                        }
                                    }
                                    Ok(WsClientMessage::PointSetValueBatch(payload)) => {
                                        let response = if !can_write {
                                            crate::connection::BatchSetPointValueRes {
                                                success: false,
                                                err_msg: Some("write permission denied".to_string()),
                                                success_count: 0,
                                                failed_count: 0,
                                                results: vec![],
                                            }
                                        } else {
                                            match state.connection_manager.write_point_values_batch(payload).await {
                                                Ok(v) => v,
                                                Err(e) => crate::connection::BatchSetPointValueRes {
                                                    success: false,
                                                    err_msg: Some(e),
                                                    success_count: 0,
                                                    failed_count: 1,
                                                    results: vec![crate::connection::SetPointValueResItem {
                                                        point_id: Uuid::nil(),
                                                        success: false,
                                                        err_msg: Some("Internal write error".to_string()),
                                                    }],
                                                },
                                            }
                                        };
                                        if let Err(e) = ws_manager
                                            .public_room
                                            .send_to_room(&room_id, WsMessage::PointSetValueBatchResult(response))
                                            .await
                                        {
                                            tracing::error!(
                                                "Failed to send PointSetValueBatchResult to room {}: {}",
                                                room_id,
                                                e
                                            );
                                        }
                                    }
                                    Err(e) => {
                                        tracing::warn!(
                                            "Invalid websocket message in room {}: {}",
                                            room_id,
                                            e
                                        );
                                    }
                                }
                            }
                            _ => {
                                tracing::debug!("Received WebSocket message from room {}: {:?}", room_id, msg);
                            }
                        }
                    }
                    Some(Err(e)) => {
                        tracing::error!("WebSocket error in room {}: {}", room_id, e);
                        break;
                    }
                    None => break,
                }
            }
            room_message = rx.recv() => {
                match room_message {
                    Ok(message) => match serde_json::to_string(&message) {
                        Ok(json_str) => {
                            if socket.send(Message::Text(json_str.into())).await.is_err() {
                                break;
                            }
                        }
                        Err(e) => {
                            tracing::error!("Failed to serialize websocket message: {}", e);
                        }
                    },
                    Err(broadcast::error::RecvError::Lagged(skipped)) => {
                        tracing::warn!("WebSocket room {} lagged, skipped {} messages", room_id, skipped);
                    }
                    Err(broadcast::error::RecvError::Closed) => break,
                }
            }
        }
    }

    ws_manager.public_room.remove_room_if_empty(&room_id).await;
}