use axum::{
    extract::{
        connect_info::ConnectInfo,
        ws::{Message, WebSocket, WebSocketUpgrade},
        State,
    },
    response::{Html, IntoResponse},
    routing::get,
    Router,
};
use clap::Parser;
use dashmap::DashMap;
use futures::{SinkExt, StreamExt};
use serde::{Deserialize, Serialize};
use std::{net::SocketAddr, path::PathBuf, sync::Arc, time::Duration};
use tokio::sync::broadcast;
use tower_http::cors::CorsLayer;
use tracing::{info, warn};
use uuid::Uuid;
use axum_server::tls_rustls::RustlsConfig;

/// LAN Share - Peer-to-peer screen sharing for local networks
///
/// A lightweight WebRTC-based screen sharing application that runs entirely
/// on your local network. No accounts, no cloud services — just open a
/// browser and share.
///
/// The server only handles signaling (peer discovery, connection setup).
/// Video/audio streams flow directly between browsers via WebRTC P2P.
#[derive(Parser, Debug)]
#[command(name = "lanshare")]
#[command(version, about, long_about = None)]
struct Args {
    /// IP address to bind to
    ///
    /// Use 0.0.0.0 to listen on all network interfaces (default),
    /// 127.0.0.1 for localhost only, or a specific IP address.
    #[arg(short = 'H', long, default_value = "0.0.0.0", value_name = "IP")]
    host: String,

    /// Port to listen on
    #[arg(short, long, default_value_t = 8080, value_name = "PORT")]
    port: u16,

    /// Enable verbose/debug logging
    #[arg(short, long)]
    verbose: bool,

    /// Quiet mode - only show errors
    #[arg(short, long, conflicts_with = "verbose")]
    quiet: bool,

    /// TLS certificate file (PEM format)
    ///
    /// When provided along with --key, the server will use HTTPS/WSS.
    /// A plain HTTP listener is also started on --http-port for clients
    /// that cannot validate the certificate (e.g. iOS with self-signed certs).
    /// If omitted, the server runs over plain HTTP only.
    #[arg(short, long)]
    certificate: Option<PathBuf>,

    /// TLS private key file (PEM format)
    #[arg(short, long)]
    key: Option<PathBuf>,

    /// Port for the plain HTTP listener (used alongside HTTPS)
    ///
    /// When TLS is enabled, a second HTTP-only listener is started on this
    /// port so that iOS devices (which reject self-signed WSS certs) can
    /// connect via ws:// instead.
    #[arg(long, default_value_t = 8081, value_name = "PORT")]
    http_port: u16,

    /// Trust proxy headers (X-Forwarded-For, X-Real-IP) for client IPs
    ///
    /// Enable this when running behind a reverse proxy (e.g. nginx, caddy,
    /// traefik). The server will use the IP from proxy headers instead of
    /// the direct connection address. Do NOT enable this without a trusted
    /// proxy, as clients can spoof these headers.
    #[arg(long)]
    trust_proxy: bool,
}

/// Messages sent between peers via the signaling server
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum SignalMessage {
    /// Server assigns an ID to a new peer
    Welcome {
        peer_id: String,
        ip: String,
        peers: Vec<PeerInfo>,
    },
    /// Peer announces themselves (with optional name)
    Announce {
        name: String,
    },
    /// Broadcast: a peer joined
    PeerJoined {
        peer_id: String,
        name: String,
        ip: String,
    },
    /// Broadcast: a peer left
    PeerLeft {
        peer_id: String,
    },
    /// Peer started sharing their screen
    StartedSharing {
        peer_id: String,
        has_audio: bool,
    },
    /// Peer stopped sharing
    StoppedSharing {
        peer_id: String,
    },
    /// WebRTC offer (peer-to-peer, relayed by server)
    Offer {
        from: String,
        to: String,
        sdp: String,
    },
    /// WebRTC answer
    Answer {
        from: String,
        to: String,
        sdp: String,
    },
    /// ICE candidate
    IceCandidate {
        from: String,
        to: String,
        candidate: String,
    },
    /// Request to connect to a sharing peer
    RequestStream {
        from: String,
        to: String,
    },
    /// Error message
    Error {
        message: String,
    },
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct PeerInfo {
    peer_id: String,
    name: String,
    ip: String,
    is_sharing: bool,
    has_audio: bool,
}

/// State for a connected peer
struct PeerState {
    name: String,
    ip: String,
    is_sharing: bool,
    has_audio: bool,
    tx: broadcast::Sender<SignalMessage>,
}

/// Application state shared across all connections
struct AppState {
    peers: DashMap<String, PeerState>,
    trust_proxy: bool,
}

impl AppState {
    fn new(trust_proxy: bool) -> Self {
        Self {
            peers: DashMap::new(),
            trust_proxy,
        }
    }

    fn get_peer_list(&self) -> Vec<PeerInfo> {
        self.peers
            .iter()
            .map(|entry| PeerInfo {
                peer_id: entry.key().clone(),
                name: entry.value().name.clone(),
                ip: entry.value().ip.clone(),
                is_sharing: entry.value().is_sharing,
                has_audio: entry.value().has_audio,
            })
            .collect()
    }

    fn broadcast(&self, msg: SignalMessage, exclude: Option<&str>) {
        for entry in self.peers.iter() {
            if exclude.map_or(true, |ex| entry.key() != ex) {
                let _ = entry.value().tx.send(msg.clone());
            }
        }
    }

    fn send_to(&self, peer_id: &str, msg: SignalMessage) {
        if let Some(peer) = self.peers.get(peer_id) {
            let _ = peer.tx.send(msg);
        }
    }
}

#[tokio::main]
async fn main() {
    let args = Args::parse();

    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::from_default_env()
        )
        .init();

    let state = Arc::new(AppState::new(args.trust_proxy));

    let app = Router::new()
        .route("/", get(serve_index))
        .route("/ws", get(ws_handler))
        .layer(CorsLayer::permissive())
        .with_state(state);

    let addr: SocketAddr = format!("{}:{}", args.host, args.port)
        .parse()
        .expect("Invalid host:port combination");

    let use_tls = args.certificate.is_some() && args.key.is_some();

    println!();
    println!("  ╭─────────────────────────────────────────╮");
    println!("  │             \x1b[1;33mLAN Share\x1b[0m                   │");
    println!("  │   P2P Screen Sharing for Local Networks │");
    println!("  ╰─────────────────────────────────────────╯");
    println!();
    println!("  \x1b[1mServer running at:\x1b[0m");

    if use_tls {
        println!("    → https://{}", addr);
        let http_addr: SocketAddr = format!("{}:{}", args.host, args.http_port)
            .parse()
            .expect("Invalid host:http_port combination");
        println!("    → http://{}  \x1b[90m(plain HTTP for iOS)\x1b[0m", http_addr);
        if args.host == "0.0.0.0" {
            if let Ok(local_ip) = local_ip_address::local_ip() {
                println!("    → https://{}:{}", local_ip, args.port);
                println!("    → http://{}:{}  \x1b[90m(plain HTTP for iOS)\x1b[0m", local_ip, args.http_port);
            }
        }
    } else {
        println!("    → http://{}", addr);
        if args.host == "0.0.0.0" {
            if let Ok(local_ip) = local_ip_address::local_ip() {
                println!("    → http://{}:{}", local_ip, args.port);
            }
        }
    }
    if args.trust_proxy {
        println!("  \x1b[1;36mProxy mode:\x1b[0m trusting X-Forwarded-For / X-Real-IP headers");
    }
    println!();
    println!("  \x1b[90mOpen this URL in browsers on your local network.\x1b[0m");
    println!("  \x1b[90mPress Ctrl+C to stop the server.\x1b[0m");
    println!();

    info!("Server starting on {}", addr);

    if use_tls {
        let cert = args.certificate.unwrap();
        let key = args.key.unwrap();
        let config = RustlsConfig::from_pem_file(cert, key).await.unwrap();

        // Start a plain HTTP listener alongside HTTPS so that iOS devices
        // (which silently reject self-signed WSS certificates) can connect
        // via ws:// instead.
        let http_addr: SocketAddr = format!("{}:{}", args.host, args.http_port)
            .parse()
            .expect("Invalid host:http_port combination");
        let http_app = app.clone();
        info!("Plain HTTP listener on {}", http_addr);
        tokio::spawn(async move {
            let listener = tokio::net::TcpListener::bind(http_addr).await.unwrap();
            axum::serve(listener, http_app.into_make_service_with_connect_info::<SocketAddr>())
                .await
                .unwrap();
        });

        axum_server::bind_rustls(addr, config)
            .serve(app.into_make_service_with_connect_info::<SocketAddr>())
            .await
            .unwrap();
    } else {
        let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
        axum::serve(listener, app.into_make_service_with_connect_info::<SocketAddr>())
            .await
            .unwrap();
    }
}

async fn serve_index() -> impl IntoResponse {
    Html(include_str!("../static/index.html"))
}

async fn ws_handler(
    ws: WebSocketUpgrade,
    ConnectInfo(addr): ConnectInfo<SocketAddr>,
    headers: axum::http::HeaderMap,
    State(state): State<Arc<AppState>>,
) -> impl IntoResponse {
    let peer_ip = if state.trust_proxy {
        extract_proxy_ip(&headers).unwrap_or_else(|| addr.ip().to_string())
    } else {
        addr.ip().to_string()
    };
    ws.on_upgrade(move |socket| handle_socket(socket, state, peer_ip))
}

/// Extract the client IP from proxy headers.
/// Checks X-Forwarded-For first (uses the leftmost/first IP), then X-Real-IP.
fn extract_proxy_ip(headers: &axum::http::HeaderMap) -> Option<String> {
    // X-Forwarded-For: client, proxy1, proxy2
    if let Some(forwarded_for) = headers.get("x-forwarded-for") {
        if let Ok(value) = forwarded_for.to_str() {
            if let Some(first_ip) = value.split(',').next() {
                let trimmed = first_ip.trim();
                if !trimmed.is_empty() {
                    return Some(trimmed.to_string());
                }
            }
        }
    }

    // X-Real-IP: client
    if let Some(real_ip) = headers.get("x-real-ip") {
        if let Ok(value) = real_ip.to_str() {
            let trimmed = value.trim();
            if !trimmed.is_empty() {
                return Some(trimmed.to_string());
            }
        }
    }

    None
}

async fn handle_socket(socket: WebSocket, state: Arc<AppState>, peer_ip: String) {
    let peer_id = Uuid::new_v4().to_string();
    let (tx, _) = broadcast::channel::<SignalMessage>(64);

    // Add peer to state with default name
    state.peers.insert(
        peer_id.clone(),
        PeerState {
            name: format!("Peer {}", &peer_id[..8]),
            ip: peer_ip.clone(),
            is_sharing: false,
            has_audio: false,
            tx: tx.clone(),
        },
    );

    let peers = state.get_peer_list();
    info!("Peer {} connected ({} total peers)", &peer_id[..8], peers.len());

    let (mut sender, mut receiver) = socket.split();

    // Send welcome message with current peer list
    let welcome = SignalMessage::Welcome {
        peer_id: peer_id.clone(),
        ip: peer_ip,
        peers: peers.into_iter().filter(|p| p.peer_id != peer_id).collect(),
    };

    if sender
        .send(Message::Text(serde_json::to_string(&welcome).unwrap().into()))
        .await
        .is_err()
    {
        state.peers.remove(&peer_id);
        return;
    }

    // Subscribe to broadcast messages for this peer
    let mut rx = tx.subscribe();
    let peer_id_clone = peer_id.clone();

    // Task to forward broadcast messages to this peer's websocket
    let mut send_task = tokio::spawn(async move {
        loop {
            let timer = tokio::time::sleep(Duration::from_secs(1));
            tokio::select! {
                msg = rx.recv() => {
                    if let Ok(msg) = msg {
                        let text = serde_json::to_string(&msg).unwrap();
                        if sender.send(Message::Text(text.into())).await.is_err() {
                            break;
                        }
                    } else {
                        break
                    }
                }
                _ = timer => {
                    if sender.send(Message::Ping(Default::default())).await.is_err() {
                        break;
                    }
                }
            }
        }

    });

    // Task to handle incoming messages from this peer
    let state_clone = state.clone();
    let peer_id_for_recv = peer_id.clone();
    let mut recv_task = tokio::spawn(async move {
        while let Some(Ok(msg)) = receiver.next().await {
            if let Message::Text(text) = msg {
                match serde_json::from_str::<SignalMessage>(&text) {
                    Ok(signal) => {
                        handle_signal(&state_clone, &peer_id_for_recv, signal).await;
                    }
                    Err(e) => {
                        warn!("Failed to parse message from {}: {}", &peer_id_for_recv[..8], e);
                    }
                }
            }
        }
    });

    // Wait for either task to complete (connection closed)
    tokio::select! {
        _ = &mut send_task => recv_task.abort(),
        _ = &mut recv_task => send_task.abort(),
    }

    // Clean up: remove peer and notify others
    if let Some((_, peer_state)) = state.peers.remove(&peer_id_clone) {
        info!(
            "Peer {} ({}) disconnected",
            &peer_id_clone[..8],
            peer_state.name
        );
        state.broadcast(
            SignalMessage::PeerLeft {
                peer_id: peer_id_clone,
            },
            None,
        );
    }
}

async fn handle_signal(state: &AppState, from_peer: &str, signal: SignalMessage) {
    match signal {
        SignalMessage::Announce { name } => {
            let ip = state
                .peers
                .get(from_peer)
                .map(|p| p.ip.clone())
                .unwrap_or_default();
            if let Some(mut peer) = state.peers.get_mut(from_peer) {
                peer.name = name.clone();
            }
            state.broadcast(
                SignalMessage::PeerJoined {
                    peer_id: from_peer.to_string(),
                    name,
                    ip,
                },
                Some(from_peer),
            );
        }

        SignalMessage::StartedSharing { has_audio, .. } => {
            if let Some(mut peer) = state.peers.get_mut(from_peer) {
                peer.is_sharing = true;
                peer.has_audio = has_audio;
            }
            state.broadcast(
                SignalMessage::StartedSharing {
                    peer_id: from_peer.to_string(),
                    has_audio,
                },
                Some(from_peer),
            );
        }

        SignalMessage::StoppedSharing { .. } => {
            if let Some(mut peer) = state.peers.get_mut(from_peer) {
                peer.is_sharing = false;
                peer.has_audio = false;
            }
            state.broadcast(
                SignalMessage::StoppedSharing {
                    peer_id: from_peer.to_string(),
                },
                Some(from_peer),
            );
        }

        SignalMessage::Offer { to, sdp, .. } => {
            state.send_to(
                &to,
                SignalMessage::Offer {
                    from: from_peer.to_string(),
                    to: to.clone(),
                    sdp,
                },
            );
        }

        SignalMessage::Answer { to, sdp, .. } => {
            state.send_to(
                &to,
                SignalMessage::Answer {
                    from: from_peer.to_string(),
                    to: to.clone(),
                    sdp,
                },
            );
        }

        SignalMessage::IceCandidate { to, candidate, .. } => {
            state.send_to(
                &to,
                SignalMessage::IceCandidate {
                    from: from_peer.to_string(),
                    to: to.clone(),
                    candidate,
                },
            );
        }

        SignalMessage::RequestStream { to, .. } => {
            state.send_to(
                &to,
                SignalMessage::RequestStream {
                    from: from_peer.to_string(),
                    to: to.clone(),
                },
            );
        }

        _ => {}
    }
}