use crate::db::ConnectionPool;
use crate::message_broker::MessageBroker;
use crate::worker::Worker;
use futures_util::{FutureExt, SinkExt, StreamExt};
use serde::Deserialize;
use serde_json::Value as Json;
use std::collections::HashMap;
use std::fs::File;
use std::io::BufReader;
use std::net::SocketAddr;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use tokio::io::{AsyncRead, AsyncWrite};
use tokio::net::TcpListener;
use tokio::runtime::{Builder, Runtime};
use tokio::sync::{broadcast, mpsc, Mutex};
use tokio_rustls::rustls::{self, ServerConfig};
use tokio_rustls::TlsAcceptor;
use tokio_tungstenite::tungstenite::Message;
use tokio_tungstenite::accept_async;
use rustls_pemfile::{certs, pkcs8_private_keys, rsa_private_keys};
use rustls::pki_types::{CertificateDer, PrivateKeyDer, PrivatePkcs1KeyDer, PrivatePkcs8KeyDer};

/// Einfacher WebSocket-Server auf Basis von Tokio + tokio-tungstenite.
///
/// Unterstützt:
/// - `setUserId`-Event vom Client (`{"event":"setUserId","data":{"userId":"..."}}`)
/// - Versenden von Broker-Nachrichten mit `user_id`-Feld an passende Verbindungen
/// - Broadcasting von Nachrichten ohne `user_id` an alle
pub struct WebSocketServer {
    port: u16,
    pool: ConnectionPool,
    broker: MessageBroker,
    use_ssl: bool,
    cert_path: Option<String>,
    key_path: Option<String>,
    workers: Vec<*const dyn Worker>,
    running: Arc<AtomicBool>,
    runtime: Option<Runtime>,
}

/// Einfache Registry, um Verbindungsstatistiken für `getConnections` zu liefern.
#[derive(Default)]
struct ConnectionRegistry {
    total: usize,
    unauthenticated: usize,
    by_user: HashMap<String, usize>,
}

fn create_tls_acceptor(
    cert_path: Option<&str>,
    key_path: Option<&str>,
) -> Result<TlsAcceptor, Box<dyn std::error::Error>> {
    let cert_path = cert_path.ok_or("SSL aktiviert, aber kein Zertifikatspfad gesetzt")?;
    let key_path = key_path.ok_or("SSL aktiviert, aber kein Key-Pfad gesetzt")?;

    let cert_file = File::open(cert_path)?;
    let mut cert_reader = BufReader::new(cert_file);

    let mut cert_chain: Vec<CertificateDer<'static>> = Vec::new();
    for cert_result in certs(&mut cert_reader) {
        let cert: CertificateDer<'static> = cert_result?;
        cert_chain.push(cert);
    }

    if cert_chain.is_empty() {
        return Err("Zertifikatsdatei enthält keine Zertifikate".into());
    }

    let key_file = File::open(key_path)?;
    let mut key_reader = BufReader::new(key_file);

    // Versuche zuerst PKCS8, dann ggf. RSA-Key
    let mut keys: Vec<PrivateKeyDer<'static>> = pkcs8_private_keys(&mut key_reader)
        .map(|res: Result<PrivatePkcs8KeyDer<'static>, _>| res.map(PrivateKeyDer::Pkcs8))
        .collect::<Result<_, _>>()?;

    if keys.is_empty() {
        // Leser zurücksetzen und RSA-Keys versuchen
        let key_file = File::open(key_path)?;
        let mut key_reader = BufReader::new(key_file);
        keys = rsa_private_keys(&mut key_reader)
            .map(|res: Result<PrivatePkcs1KeyDer<'static>, _>| res.map(PrivateKeyDer::Pkcs1))
            .collect::<Result<_, _>>()?;
    }

    if keys.is_empty() {
        return Err("Key-Datei enthält keinen privaten Schlüssel (PKCS8 oder RSA)".into());
    }

    let private_key = keys.remove(0);

    let config = ServerConfig::builder()
        .with_no_client_auth()
        .with_single_cert(cert_chain, private_key)?;

    Ok(TlsAcceptor::from(Arc::new(config)))
}

impl WebSocketServer {
    pub fn new(
        port: u16,
        pool: ConnectionPool,
        broker: MessageBroker,
        use_ssl: bool,
        cert_path: Option<String>,
        key_path: Option<String>,
    ) -> Self {
        Self {
            port,
            pool,
            broker,
            use_ssl,
            cert_path,
            key_path,
            workers: Vec::new(),
            running: Arc::new(AtomicBool::new(false)),
            runtime: None,
        }
    }

    pub fn set_workers(&mut self, workers: &[Box<dyn Worker>]) {
        self.workers.clear();
        for w in workers {
            self.workers.push(&**w as *const dyn Worker);
        }
    }

    pub fn run(&mut self) {
        if self.running.swap(true, Ordering::SeqCst) {
            eprintln!("[WebSocketServer] Läuft bereits.");
            return;
        }

        if self.use_ssl {
            println!(
                "Starte WebSocket-Server auf Port {} mit SSL (cert: {:?}, key: {:?})",
                self.port, self.cert_path, self.key_path
            );
            // Hinweis: SSL-Unterstützung ist noch nicht implementiert.
        } else {
            println!("Starte WebSocket-Server auf Port {} (ohne SSL)", self.port);
        }

        let addr = format!("0.0.0.0:{}", self.port);
        let running_flag = self.running.clone();
        let broker = self.broker.clone();

        // Gemeinsame Registry für alle Verbindungen
        let registry = Arc::new(Mutex::new(ConnectionRegistry::default()));

        // Broadcast-Kanal für Broker-Nachrichten
        let (tx, _) = broadcast::channel::<String>(1024);
        let tx_clone = tx.clone();

        // Broker-Subscription: jede gepublishte Nachricht geht in den Broadcast-Kanal
        broker.subscribe(move |msg: String| {
            let _ = tx_clone.send(msg);
        });

        // Optionalen TLS-Akzeptor laden, falls SSL aktiviert ist
        let tls_acceptor = if self.use_ssl {
            match create_tls_acceptor(
                self.cert_path.as_deref(),
                self.key_path.as_deref(),
            ) {
                Ok(acc) => Some(acc),
                Err(err) => {
                    eprintln!(
                        "[WebSocketServer] TLS-Initialisierung fehlgeschlagen, starte ohne SSL: {err}"
                    );
                    None
                }
            }
        } else {
            None
        };

        let rt = Builder::new_multi_thread()
            .enable_all()
            .build()
            .expect("Tokio Runtime konnte nicht erstellt werden");

        rt.spawn(run_accept_loop(
            addr,
            running_flag,
            tx,
            self.pool.clone(),
            registry,
            tls_acceptor,
        ));

        self.runtime = Some(rt);
    }

    pub fn stop(&mut self) {
        if !self.running.swap(false, Ordering::SeqCst) {
            return;
        }
        println!("WebSocket-Server wird gestoppt.");
        if let Some(rt) = self.runtime.take() {
            rt.shutdown_background();
        }
    }
}

#[derive(Debug, Deserialize)]
struct IncomingMessage {
    #[serde(default)]
    event: String,
    #[serde(default)]
    data: Json,
}

async fn run_accept_loop(
    addr: String,
    running: Arc<AtomicBool>,
    tx: broadcast::Sender<String>,
    _pool: ConnectionPool,
    registry: Arc<Mutex<ConnectionRegistry>>,
    tls_acceptor: Option<TlsAcceptor>,
) {
    let listener = match TcpListener::bind(&addr).await {
        Ok(l) => l,
        Err(e) => {
            eprintln!("[WebSocketServer] Fehler beim Binden an {}: {}", addr, e);
            running.store(false, Ordering::SeqCst);
            return;
        }
    };

    println!("[WebSocketServer] Lauscht auf {}", addr);

    while running.load(Ordering::SeqCst) {
        let (stream, peer) = match listener.accept().await {
            Ok(v) => v,
            Err(e) => {
                eprintln!("[WebSocketServer] accept() fehlgeschlagen: {}", e);
                continue;
            }
        };

        let peer_addr = peer;
        let rx = tx.subscribe();
        let registry_clone = registry.clone();
        let tls_acceptor_clone = tls_acceptor.clone();

        tokio::spawn(async move {
            if let Some(acc) = tls_acceptor_clone {
                match acc.accept(stream).await {
                    Ok(tls_stream) => {
                        handle_connection(tls_stream, peer_addr, rx, registry_clone).await
                    }
                    Err(err) => {
                        eprintln!(
                            "[WebSocketServer] TLS-Handshake fehlgeschlagen ({peer_addr}): {err}"
                        );
                    }
                }
            } else {
                handle_connection(stream, peer_addr, rx, registry_clone).await;
            }
        });
    }
}

async fn handle_connection<S>(
    stream: S,
    peer_addr: SocketAddr,
    mut broker_rx: broadcast::Receiver<String>,
    registry: Arc<Mutex<ConnectionRegistry>>,
) where
    S: AsyncRead + AsyncWrite + Unpin + Send + 'static,
{
    let ws_stream = match accept_async(stream).await {
        Ok(ws) => ws,
        Err(e) => {
            eprintln!("[WebSocketServer] WebSocket-Handshake fehlgeschlagen ({peer_addr}): {e}");
            return;
        }
    };

    println!("[WebSocketServer] Neue Verbindung von {}", peer_addr);

    let (mut ws_sender, mut ws_receiver) = ws_stream.split();

    // Kanal für Antworten direkt an diesen Client (z.B. getConnections)
    let (client_tx, mut client_rx) = mpsc::channel::<String>(32);

    // Neue Verbindung in der Registry zählen (zunächst als unauthentifiziert)
    {
        let mut reg = registry.lock().await;
        reg.total += 1;
        reg.unauthenticated += 1;
    }

    // user_id der Verbindung (nach setUserId)
    let user_id = Arc::new(tokio::sync::Mutex::new(Option::<String>::None));
    let user_id_for_incoming = user_id.clone();
    let user_id_for_broker = user_id.clone();
    let registry_for_incoming = registry.clone();
    let client_tx_incoming = client_tx.clone();

    // Eingehende Nachrichten vom Client
    let incoming = async move {
        while let Some(msg) = ws_receiver.next().await {
            match msg {
                Ok(Message::Text(txt)) => {
                    if let Ok(parsed) = serde_json::from_str::<IncomingMessage>(&txt) {
                        match parsed.event.as_str() {
                            "setUserId" => {
                                if let Some(uid) =
                                    parsed.data.get("userId").and_then(|v| v.as_str())
                                {
                                    {
                                        // Registry aktualisieren: von unauthentifiziert -> Nutzer
                                        let mut reg = registry_for_incoming.lock().await;
                                        if reg.unauthenticated > 0 {
                                            reg.unauthenticated -= 1;
                                        }
                                        *reg.by_user.entry(uid.to_string()).or_insert(0) += 1;
                                    }

                                    let mut guard = user_id_for_incoming.lock().await;
                                    *guard = Some(uid.to_string());
                                    println!(
                                        "[WebSocketServer] User-ID gesetzt für {}: {}",
                                        peer_addr, uid
                                    );
                                }
                            }
                            "getConnections" => {
                                // Einfache Übersicht über aktuelle Verbindungen zurückgeben.
                                let snapshot = {
                                    let reg = registry_for_incoming.lock().await;
                                    serde_json::json!({
                                        "event": "getConnectionsResponse",
                                        "total": reg.total,
                                        "unauthenticated": reg.unauthenticated,
                                        "users": reg.by_user,
                                    })
                                    .to_string()
                                };
                                let _ = client_tx_incoming.send(snapshot).await;
                            }
                            _ => {
                                // Unbekannte Events ignorieren
                            }
                        }
                    }
                }
                Ok(Message::Ping(_)) => {
                    // Ping wird aktuell nur geloggt/ignoriert; optional könnte man hier ein eigenes
                    // Ping/Pong-Handling ergänzen.
                }
                Ok(Message::Close(_)) => break,
                Err(e) => {
                    eprintln!("[WebSocketServer] Fehler bei Nachricht von {peer_addr}: {e}");
                    break;
                }
                _ => {}
            }
        }
    };

    // Broker-Nachrichten an den Client
    let outgoing = async move {
        loop {
            tokio::select! {
                // Nachrichten aus dem MessageBroker
                broker_msg = broker_rx.recv() => {
                    let msg = match broker_msg {
                        Ok(m) => m,
                        Err(_) => break,
                    };

                    // Filter nach user_id, falls gesetzt
                    let target_user = {
                        let guard = user_id_for_broker.lock().await;
                        guard.clone()
                    };

                    if let Some(uid) = target_user.clone() {
                        if let Ok(json) = serde_json::from_str::<Json>(&msg) {
                            let matches_user = json
                                .get("user_id")
                                .and_then(|v| {
                                    if let Some(s) = v.as_str() {
                                        Some(s.to_string())
                                    } else if let Some(n) = v.as_i64() {
                                        Some(n.to_string())
                                    } else {
                                        None
                                    }
                                })
                                .map(|v| v == uid)
                                .unwrap_or(false);

                            if !matches_user {
                                continue;
                            }
                        }
                    }

                    if let Err(e) = ws_sender.send(Message::Text(msg)).await {
                        eprintln!(
                            "[WebSocketServer] Fehler beim Senden an {}: {}",
                            peer_addr, e
                        );
                        break;
                    }
                }
                // Antworten aus der Verbindung selbst (z.B. getConnections)
                client_msg = client_rx.recv() => {
                    match client_msg {
                        Some(msg) => {
                            if let Err(e) = ws_sender.send(Message::Text(msg)).await {
                                eprintln!(
                                    "[WebSocketServer] Fehler beim Senden an {}: {}",
                                    peer_addr, e
                                );
                                break;
                            }
                        }
                        None => {
                            // Kanal wurde geschlossen
                            break;
                        }
                    }
                }
            }
        }
    };

    futures_util::future::select(incoming.boxed(), outgoing.boxed()).await;

    // Verbindung aus der Registry entfernen
    let final_uid = {
        let guard = user_id.lock().await;
        guard.clone()
    };
    {
        let mut reg = registry.lock().await;
        if reg.total > 0 {
            reg.total -= 1;
        }
        if let Some(uid) = final_uid {
            if let Some(count) = reg.by_user.get_mut(&uid) {
                if *count > 0 {
                    *count -= 1;
                }
                if *count == 0 {
                    reg.by_user.remove(&uid);
                }
            }
        } else if reg.unauthenticated > 0 {
            reg.unauthenticated -= 1;
        }
    }

    println!("[WebSocketServer] Verbindung geschlossen: {}", peer_addr);
}