use std::sync::Arc;
use std::time::{Duration, Instant};

use actix_ws::{Message, Session};
use futures::StreamExt;
use log::{info, warn};

use crate::models::{ClientType, WsMessage};

/// ACTIX-WEB HTTP HANDLER
///
/// Upgrades the HTTP connection to a WebSocket and spawns an async task
/// that reads frames from the client and dispatches them.
///
/// The query parameter `client_type` must be `"viewer"` or `"agent"`.
pub async fn ws_index(
    req: actix_web::HttpRequest,
    body: actix_web::web::Payload,
    state: actix_web::web::Data<Arc<crate::state::AppState>>,
    path: actix_web::web::Path<String>,
) -> Result<actix_web::HttpResponse, actix_web::Error> {
    let session_id = path.into_inner();

    // Validate that the session exists.
    if !state.sessions.contains_key(&session_id) {
        return Ok(actix_web::HttpResponse::NotFound().json(
            crate::models::ApiResponse::<()>::err("session not found"),
        ));
    }

    // Determine client type from query string.
    let query_str = req.query_string();
    let client_type = if query_str.contains("client_type=agent") {
        ClientType::Agent
    } else {
        ClientType::Viewer
    };

    let ip = req
        .connection_info()
        .realip_remote_addr()
        .unwrap_or("unknown")
        .to_string();

    // Perform the WebSocket upgrade.
    let (response, mut session, mut msg_stream) = actix_ws::handle(&req, body)?;

    // Log the connection.
    info!(
        "[ws] {} connected to session {} (ip={})",
        match client_type {
            ClientType::Agent => "AGENT",
            ClientType::Viewer => "VIEWER",
        },
        session_id,
        ip
    );

    // Register agent in shared state.
    if client_type == ClientType::Agent {
        let agent_id = uuid::Uuid::new_v4().to_string();
        let agent = crate::models::AgentConnection {
            agent_id: agent_id.clone(),
            session_id: session_id.clone(),
            connected_at: chrono::Utc::now(),
            ip_address: ip.clone(),
            display_active: false,
            audio_active: false,
        };
        state.register_agent(agent);
    }

    // Clone references for the spawned task.
    let state_clone = state.clone();
    let session_id_clone = session_id.clone();
    let client_type_clone = client_type.clone();

    // Spawn the reader task – receives messages FROM the client.
    actix_web::rt::spawn(async move {
        let mut last_heartbeat = Instant::now();
        let timeout = Duration::from_secs(state_clone.idle_timeout_secs);

        while let Some(Ok(msg)) = msg_stream.next().await {
            match msg {
                Message::Text(text) => {
                    last_heartbeat = Instant::now();
                    handle_text_message(
                        &text,
                        &session_id_clone,
                        &client_type_clone,
                        &state_clone,
                        &mut session,
                    )
                    .await;
                }
                Message::Ping(bytes) => {
                    last_heartbeat = Instant::now();
                    let _ = session.pong(&bytes).await;
                }
                Message::Close(reason) => {
                    info!(
                        "[ws] {:?} disconnected from session {} (close: {:?})",
                        client_type_clone, session_id_clone, reason
                    );
                    cleanup(&state_clone, &session_id_clone, &client_type_clone);
                    return;
                }
                _ => {}
            }

            // Check for idle timeout.
            if last_heartbeat.elapsed() > timeout {
                warn!(
                    "[ws] {:?} timed out on session {}",
                    client_type_clone, session_id_clone
                );
                cleanup(&state_clone, &session_id_clone, &client_type_clone);
                let _ = session.close(None).await;
                return;
            }
        }

        info!(
            "[ws] {:?} stream ended for session {}",
            client_type_clone, session_id_clone
        );
        cleanup(&state_clone, &session_id_clone, &client_type_clone);
    });

    Ok(response)
}

// ── Internal helpers ─────────────────────────────────────────────────────────

/// Parse and dispatch an incoming text (JSON) WebSocket message.
async fn handle_text_message(
    raw: &str,
    session_id: &str,
    client_type: &ClientType,
    state: &Arc<crate::state::AppState>,
    ws_session: &mut Session,
) {
    let msg: WsMessage = match serde_json::from_str(raw) {
        Ok(m) => m,
        Err(e) => {
            warn!("[ws] invalid message: {} ({})", e, raw.chars().take(120).collect::<String>());
            let _ = ws_session
                .text(serde_json::to_string(&WsMessage::Error {
                    message: format!("invalid message: {}", e),
                }).unwrap_or_default())
                .await;
            return;
        }
    };

    match msg {
        // ── From Agent ────────────────────────────────────────────────────
        WsMessage::DisplayFrame { data, .. } if *client_type == ClientType::Agent => {
            state.push_frame(session_id, data.clone());
            broadcast_to_viewers(state, session_id, &WsMessage::FrameBroadcast {
                data,
                content_type: "image/jpeg".into(),
            }).await;
        }

        WsMessage::AudioFrame { data, .. } if *client_type == ClientType::Agent => {
            broadcast_to_viewers(state, session_id, &WsMessage::AudioBroadcast {
                data,
                content_type: "audio/opus".into(),
            }).await;
        }

        WsMessage::AgentInfo { agent_id, resolution, .. } if *client_type == ClientType::Agent => {
            state.activate_session(session_id, resolution.as_deref());
            if let Some(session) = state.get_session(session_id) {
                broadcast_to_viewers(state, session_id, &WsMessage::SessionUpdate {
                    session_id: session_id.to_string(),
                    status: session.status,
                    resolution: session.resolution,
                }).await;
            }
            info!("[ws] agent {} reported for session {}", agent_id, session_id);
            let _ = ws_session.text(serde_json::to_string(&WsMessage::Ack {
                message: "agent registered".into(),
            }).unwrap_or_default()).await;
        }

        WsMessage::Heartbeat if *client_type == ClientType::Agent => {
            // Keepalive — nothing to do.
        }

        // ── From Viewer ───────────────────────────────────────────────────
        WsMessage::HudCommand { command, params, .. } if *client_type == ClientType::Viewer => {
            forward_to_agent(state, session_id, &WsMessage::ForwardHudCommand { command, params }).await;
        }

        WsMessage::Resize { width, height, .. } if *client_type == ClientType::Viewer => {
            forward_to_agent(state, session_id, &WsMessage::ForwardResize { width, height }).await;
        }

        // ── Fallback ──────────────────────────────────────────────────────
        _ => {
            warn!("[ws] unexpected message type from {:?} for session {}", client_type, session_id);
        }
    }
}

/// Broadcast a message to all **viewer** WebSocket connections for a session.
///
/// TODO: maintain a registry of per-viewer Session senders in AppState.
///       For now we log and rely on the frame buffer for new viewers.
async fn broadcast_to_viewers(
    _state: &Arc<crate::state::AppState>,
    session_id: &str,
    msg: &WsMessage,
) {
    log::debug!("[ws] broadcast to viewers of session {}: {:?}", session_id, msg.msg_type_debug());
}

/// Forward a message to the agent connected to a session.
///
/// TODO: maintain per-agent mpsc channel in AppState.
async fn forward_to_agent(
    _state: &Arc<crate::state::AppState>,
    session_id: &str,
    msg: &WsMessage,
) {
    log::info!(
        "[ws] forward to agent in session {}: {:?}",
        session_id,
        msg.msg_type_debug()
    );
}

/// Clean up when a client disconnects.
fn cleanup(state: &Arc<crate::state::AppState>, session_id: &str, client_type: &ClientType) {
    if *client_type == ClientType::Agent {
        let agent_id = state
            .agents
            .iter()
            .find(|r| r.session_id == session_id)
            .map(|r| r.agent_id.clone());
        if let Some(aid) = agent_id {
            state.unregister_agent(&aid);
        }
    }
}

/// Helper trait to get a human-readable tag for logging.
trait MsgTypeDebug {
    fn msg_type_debug(&self) -> &'static str;
}

impl MsgTypeDebug for WsMessage {
    fn msg_type_debug(&self) -> &'static str {
        match self {
            WsMessage::DisplayFrame { .. } => "display_frame",
            WsMessage::AudioFrame { .. } => "audio_frame",
            WsMessage::AgentInfo { .. } => "agent_info",
            WsMessage::Heartbeat => "heartbeat",
            WsMessage::HudCommand { .. } => "hud_command",
            WsMessage::Resize { .. } => "resize",
            WsMessage::FrameBroadcast { .. } => "frame_broadcast",
            WsMessage::AudioBroadcast { .. } => "audio_broadcast",
            WsMessage::SessionUpdate { .. } => "session_update",
            WsMessage::ForwardHudCommand { .. } => "forward_hud_command",
            WsMessage::ForwardResize { .. } => "forward_resize",
            WsMessage::StreamControl { .. } => "stream_control",
            WsMessage::Error { .. } => "error",
            WsMessage::Ack { .. } => "ack",
        }
    }
}