use std::sync::Arc;

use dashmap::DashMap;
use tokio::sync::mpsc;

use crate::engine::packet::Packet as EnginePacket;
use crate::engine::packet::PacketData as EnginePacketData;
use crate::engine::server::{EngineConfig, EngineServer};
use crate::engine::session::SessionStore;
use crate::socket::adapter::{Adapter, LocalAdapter};
use crate::socket::namespace::NamespaceManager;
use crate::socket::packet::{Packet, PacketType};
use crate::socket::parser;
use crate::socket::socket::Socket;

pub struct SocketServer {
    pub engine: Arc<EngineServer>,
    pub namespaces: Arc<NamespaceManager>,
    pub adapter: Arc<dyn Adapter>,
    socket_txs: Arc<DashMap<String, mpsc::Sender<Packet>>>,
}

impl SocketServer {
    pub fn new(config: EngineConfig) -> Self {
        SocketServerBuilder::new(config).build()
    }

    pub fn builder(config: EngineConfig) -> SocketServerBuilder {
        SocketServerBuilder::new(config)
    }

    pub fn of(&self, path: impl Into<String>) -> Arc<crate::socket::namespace::Namespace> {
        self.namespaces.get_or_create_namespace(&path.into())
    }

    pub async fn run_http(self: Arc<Self>, addr: &str) -> std::io::Result<()> {
        self.engine.clone().run_http(addr).await
    }

    pub fn register_socket(&self, sid: String, tx: mpsc::Sender<Packet>) {
        self.socket_txs.insert(sid, tx);
    }

    pub fn unregister_socket(&self, sid: &str) {
        self.socket_txs.remove(sid);
    }
}

pub struct SocketServerBuilder {
    config: EngineConfig,
    adapter: Option<Arc<dyn Adapter>>,
}

impl SocketServerBuilder {
    pub fn new(config: EngineConfig) -> Self {
        Self {
            config,
            adapter: None,
        }
    }

    pub fn adapter(mut self, adapter: Arc<dyn Adapter>) -> Self {
        self.adapter = Some(adapter);
        self
    }

    pub fn build(self) -> SocketServer {
        let namespaces = Arc::new(NamespaceManager::new());
        let socket_txs: Arc<DashMap<String, mpsc::Sender<Packet>>> = Arc::new(DashMap::new());
        let engine_store = SessionStore::new();

        let namespaces_clone = namespaces.clone();
        let socket_txs_clone = socket_txs.clone();
        let engine_store_clone = engine_store.clone();

        let adapter: Arc<dyn Adapter> = self.adapter.unwrap_or_else(|| {
            let ns_clone = namespaces.clone();
            let send_fn = move |engine_sid: &str, packet: &Packet| {
                if let Some(ns) = ns_clone.get_namespace(&packet.namespace) {
                    if let Some(socket) = ns.get_socket_by_engine_sid(engine_sid) {
                        socket.send_packet(packet).map_err(|e| e.to_string())
                    } else {
                        Err(format!(
                            "Socket with engine_sid {} not found in namespace {}",
                            engine_sid, packet.namespace
                        ))
                    }
                } else {
                    Err(format!("Namespace {} not found", packet.namespace))
                }
            };
            Arc::new(LocalAdapter::new(send_fn))
        });

        let adapter_clone = adapter.clone();
        let engine = Arc::new(EngineServer::with_store(
            self.config,
            engine_store,
            move |sid, engine_packet| {
                let namespaces = namespaces_clone.clone();
                let socket_txs = socket_txs_clone.clone();
                let engine_store = engine_store_clone.clone();
                let adapter = adapter_clone.clone();
                tokio::spawn(async move {
                    handle_engine_message(
                        sid,
                        engine_packet,
                        &namespaces,
                        &socket_txs,
                        &engine_store,
                        &adapter,
                    )
                    .await;
                });
            },
        ));

        let server = SocketServer {
            engine,
            namespaces,
            adapter,
            socket_txs,
        };

        for ns in server.namespaces.all_namespaces() {
            let adapter_ref = server.adapter.clone();
            tokio::spawn(async move {
                ns.set_adapter(adapter_ref).await;
            });
        }

        server
    }
}

async fn handle_engine_message(
    engine_sid: String,
    engine_packet: EnginePacket,
    namespaces: &Arc<NamespaceManager>,
    socket_txs: &Arc<DashMap<String, mpsc::Sender<Packet>>>,
    engine_store: &SessionStore,
    adapter: &Arc<dyn Adapter>,
) {
    if let EnginePacketData::Text(ref text) = engine_packet.data {
        match parser::decode(text) {
            Ok(socket_packet) => match socket_packet.packet_type {
                PacketType::Connect => {
                    handle_connect(
                        &engine_sid,
                        &socket_packet,
                        namespaces,
                        socket_txs,
                        engine_store,
                        adapter,
                    )
                    .await;
                }
                PacketType::Disconnect => {
                    handle_disconnect(&engine_sid, &socket_packet, namespaces, socket_txs);
                }
                PacketType::Event => {
                    handle_event(&engine_sid, &socket_packet, namespaces);
                }
                PacketType::Ack => {
                    handle_ack(&engine_sid, &socket_packet);
                }
                _ => {}
            },
            Err(e) => {
                tracing::warn!(engine_sid = %engine_sid, error = %e, "Invalid Socket.IO packet");
            }
        }
    }
}

async fn handle_connect(
    engine_sid: &str,
    packet: &Packet,
    namespaces: &Arc<NamespaceManager>,
    socket_txs: &Arc<DashMap<String, mpsc::Sender<Packet>>>,
    engine_store: &SessionStore,
    adapter: &Arc<dyn Adapter>,
) {
    // Validate namespace path to prevent DoS via arbitrary namespace creation
    if !crate::socket::namespace::is_valid_namespace(&packet.namespace) {
        tracing::warn!(
            "Rejected connect with invalid namespace: {}",
            packet.namespace
        );
        return;
    }

    let namespace = namespaces.get_or_create_namespace(&packet.namespace);

    // Ensure newly created namespaces get the shared adapter before registration.
    {
        let ns_adapter = namespace.adapter.read().await;
        if ns_adapter.is_none() {
            drop(ns_adapter);
            namespace.set_adapter(adapter.clone()).await;
        }
    }

    let socket_sid = crate::engine::session::generate_sid();
    let (tx, mut rx) = mpsc::channel::<Packet>(256);
    socket_txs.insert(socket_sid.clone(), tx.clone());

    let socket = Arc::new(Socket::new(
        socket_sid.clone(),
        packet.namespace.clone(),
        engine_sid.to_string(),
        tx,
    ));

    // Run connect handler and add to namespace.
    // If the handler rejects, clean up and do NOT send a Connect response.
    if let Err(msg) = namespace
        .add_socket(socket.clone(), packet.data.as_ref())
        .await
    {
        tracing::warn!("Socket {} connection rejected: {}", socket_sid, msg);
        socket_txs.remove(&socket_sid);
        return;
    }

    // Connect handler passed — spawn forwarding task
    let engine_store_clone = engine_store.clone();
    let engine_sid_clone = engine_sid.to_string();
    let socket_sid_clone = socket_sid.clone();
    let socket_txs_clone = socket_txs.clone();
    let namespace_clone = namespace.clone();
    tokio::spawn(async move {
        while let Some(socket_packet) = rx.recv().await {
            let encoded = parser::encode(&socket_packet);
            let engine_packet = EnginePacket::message_text(encoded);

            if let Some(session) = engine_store_clone.get(&engine_sid_clone) {
                let mut s = session.write().await;
                if s.state == crate::engine::session::SessionState::Closed {
                    break;
                }
                s.push_packet(engine_packet);
            } else {
                break;
            }
        }
        // Forwarding task ended — ensure socket is cleaned up from namespace
        socket_txs_clone.remove(&socket_sid_clone);
        namespace_clone
            .remove_socket_by_sid(&socket_sid_clone)
            .await;
    });

    // Send Connect response (only after handler passed)
    let response = Packet::connect(
        &socket.namespace,
        Some(serde_json::json!({ "sid": &socket.sid })),
    );

    if socket.send_packet(&response).is_err() {
        tracing::warn!("Failed to send connect response to socket {}", socket.sid);
    }
}

fn handle_disconnect(
    engine_sid: &str,
    packet: &Packet,
    namespaces: &Arc<NamespaceManager>,
    socket_txs: &Arc<DashMap<String, mpsc::Sender<Packet>>>,
) {
    if let Some(namespace) = namespaces.get_namespace(&packet.namespace) {
        // Look up socket by engine_sid, then remove by socket_sid
        if let Some(socket) = namespace.get_socket_by_engine_sid(engine_sid) {
            socket_txs.remove(&socket.sid);
            let socket_sid = socket.sid.clone();
            let ns_clone = namespace.clone();
            tokio::spawn(async move {
                ns_clone.remove_socket_by_sid(&socket_sid).await;
            });
        }
    }
}

fn handle_event(engine_sid: &str, packet: &Packet, namespaces: &Arc<NamespaceManager>) {
    if let Some(namespace) = namespaces.get_namespace(&packet.namespace)
        && let Some(socket) = namespace.get_socket_by_engine_sid(engine_sid)
        && let Some(ref data) = packet.data
        && let Some(arr) = data.as_array()
        && let Some(event) = arr.first().and_then(|v| v.as_str())
    {
        let event_data = if arr.len() > 1 {
            serde_json::Value::Array(arr[1..].to_vec())
        } else {
            serde_json::Value::Null
        };

        let namespace_clone = namespace.clone();
        let event = event.to_string();
        let socket_clone = socket.clone();
        tokio::spawn(async move {
            namespace_clone
                .handle_event(socket_clone, &event, &event_data)
                .await;
        });
    }
}

fn handle_ack(engine_sid: &str, packet: &Packet) {
    tracing::debug!(
        "Received ACK from {} for namespace {} with id {:?}",
        engine_sid,
        packet.namespace,
        packet.id
    );
}