use std::{
    net::SocketAddr,
    sync::{
        atomic::{AtomicBool, Ordering},
        Arc,
    },
    time::Instant,
};

use uuid::Uuid;

use hbb_common::{
    allow_err,
    anyhow::{self, bail},
    config::{self, keys::*, option2bool, Config, CONNECT_TIMEOUT, REG_INTERVAL, RENDEZVOUS_PORT},
    futures::future::join_all,
    log,
    protobuf::Message as _,
    proxy::Proxy,
    rendezvous_proto::*,
    sleep,
    socket_client::{self, connect_tcp, is_ipv4},
    tcp::FramedStream,
    tokio::{self, select, sync::Mutex, time::interval},
    udp::FramedSocket,
    AddrMangle, IntoTargetAddr, ResultType, TargetAddr,
};

use crate::{
    check_port,
    server::{check_zombie, new as new_server, ServerPtr},
    ui_interface::get_builtin_option,
};

type Message = RendezvousMessage;

lazy_static::lazy_static! {
    static ref SOLVING_PK_MISMATCH: Arc<Mutex<String>> = Default::default();
}
static SHOULD_EXIT: AtomicBool = AtomicBool::new(false);
static MANUAL_RESTARTED: AtomicBool = AtomicBool::new(false);

#[derive(Clone)]
pub struct RendezvousMediator {
    addr: TargetAddr<'static>,
    host: String,
    host_prefix: String,
    keep_alive: i32,
}

impl RendezvousMediator {
    pub fn restart() {
        SHOULD_EXIT.store(true, Ordering::SeqCst);
        MANUAL_RESTARTED.store(true, Ordering::SeqCst);
        log::info!("server restart");
    }

    pub async fn start_all() {
        if config::is_outgoing_only() {
            loop {
                sleep(1.).await;
            }
        }
        crate::hbbs_http::sync::start();
        let mut nat_tested = false;
        check_zombie();
        let server = new_server();
        if Config::get_nat_type() == NatType::UNKNOWN_NAT as i32 {
            crate::test_nat_type();
            nat_tested = true;
        }
        if config::option2bool("stop-service", &Config::get_option("stop-service")) {
            crate::test_rendezvous_server();
        }
        let server_cloned = server.clone();
        tokio::spawn(async move {
            direct_server(server_cloned).await;
        });
        #[cfg(target_os = "android")]
        let start_lan_listening = true;
        #[cfg(not(any(target_os = "android", target_os = "ios")))]
        let start_lan_listening = crate::platform::is_installed();
        if start_lan_listening {
            std::thread::spawn(move || {
                allow_err!(super::lan::start_listening());
            });
        }
        // It is ok to run xdesktop manager when the headless function is not allowed.
        #[cfg(target_os = "linux")]
        if crate::is_server() {
            crate::platform::linux_desktop_manager::start_xdesktop();
        }
        loop {
            let conn_start_time = Instant::now();
            *SOLVING_PK_MISMATCH.lock().await = "".to_owned();
            if !config::option2bool("stop-service", &Config::get_option("stop-service"))
                && !crate::platform::installing_service()
            {
                if !nat_tested {
                    crate::test_nat_type();
                    nat_tested = true;
                }
                let mut futs = Vec::new();
                let servers = Config::get_rendezvous_servers();
                SHOULD_EXIT.store(false, Ordering::SeqCst);
                MANUAL_RESTARTED.store(false, Ordering::SeqCst);
                for host in servers.clone() {
                    let server = server.clone();
                    futs.push(tokio::spawn(async move {
                        if let Err(err) = Self::start(server, host).await {
                            log::error!("rendezvous mediator error: {err}");
                        }
                        // SHOULD_EXIT here is to ensure once one exits, the others also exit.
                        SHOULD_EXIT.store(true, Ordering::SeqCst);
                    }));
                }
                join_all(futs).await;
            } else {
                server.write().unwrap().close_connections();
            }
            Config::reset_online();
            if !MANUAL_RESTARTED.load(Ordering::SeqCst) {
                let elapsed = conn_start_time.elapsed().as_millis() as u64;
                if elapsed < CONNECT_TIMEOUT {
                    sleep(((CONNECT_TIMEOUT - elapsed) / 1000) as _).await;
                }
            }
        }
    }

    fn get_host_prefix(host: &str) -> String {
        host.split(".")
            .next()
            .map(|x| {
                if x.parse::<i32>().is_ok() {
                    host.to_owned()
                } else {
                    x.to_owned()
                }
            })
            .unwrap_or(host.to_owned())
    }

    pub async fn start_udp(server: ServerPtr, host: String) -> ResultType<()> {
        let host = check_port(&host, RENDEZVOUS_PORT);
        let (mut socket, mut addr) = socket_client::new_udp_for(&host, CONNECT_TIMEOUT).await?;
        let mut rz = Self {
            addr: addr.clone(),
            host: host.clone(),
            host_prefix: Self::get_host_prefix(&host),
            keep_alive: crate::DEFAULT_KEEP_ALIVE,
        };

        let mut timer = crate::rustdesk_interval(interval(crate::TIMER_OUT));
        const MIN_REG_TIMEOUT: i64 = 3_000;
        const MAX_REG_TIMEOUT: i64 = 30_000;
        let mut reg_timeout = MIN_REG_TIMEOUT;
        const MAX_FAILS1: i64 = 2;
        const MAX_FAILS2: i64 = 4;
        const DNS_INTERVAL: i64 = 60_000;
        let mut fails = 0;
        let mut last_register_resp: Option<Instant> = None;
        let mut last_register_sent: Option<Instant> = None;
        let mut last_dns_check = Instant::now();
        let mut old_latency = 0;
        let mut ema_latency = 0;
        loop {
            let mut update_latency = || {
                last_register_resp = Some(Instant::now());
                fails = 0;
                reg_timeout = MIN_REG_TIMEOUT;
                let mut latency = last_register_sent
                    .map(|x| x.elapsed().as_micros() as i64)
                    .unwrap_or(0);
                last_register_sent = None;
                if latency < 0 || latency > 1_000_000 {
                    return;
                }
                if ema_latency == 0 {
                    ema_latency = latency;
                } else {
                    ema_latency = latency / 30 + (ema_latency * 29 / 30);
                    latency = ema_latency;
                }
                let mut n = latency / 5;
                if n < 3000 {
                    n = 3000;
                }
                if (latency - old_latency).abs() > n || old_latency <= 0 {
                    Config::update_latency(&host, latency);
                    log::debug!("Latency of {}: {}ms", host, latency as f64 / 1000.);
                    old_latency = latency;
                }
            };
            select! {
                n = socket.next() => {
                    match n {
                        Some(Ok((bytes, _))) => {
                            if let Ok(msg) = Message::parse_from_bytes(&bytes) {
                                rz.handle_resp(msg.union, Sink::Framed(&mut socket, &addr), &server, &mut update_latency).await?;
                            } else {
                                log::debug!("Non-protobuf message bytes received: {:?}", bytes);
                            }
                        },
                        Some(Err(e)) => bail!("Failed to receive next {}", e),  // maybe socks5 tcp disconnected
                        None => {
                            bail!("Socket receive none. Maybe socks5 server is down.");
                        },
                    }
                },
                _ = timer.tick() => {
                    if SHOULD_EXIT.load(Ordering::SeqCst) {
                        break;
                    }
                    let now = Some(Instant::now());
                    let expired = last_register_resp.map(|x| x.elapsed().as_millis() as i64 >= REG_INTERVAL).unwrap_or(true);
                    let timeout = last_register_sent.map(|x| x.elapsed().as_millis() as i64 >= reg_timeout).unwrap_or(false);
                    // temporarily disable exponential backoff for android before we add wakeup trigger to force connect in android
                    #[cfg(not(any(target_os = "android", target_os = "ios")))]
                    if crate::using_public_server() { // only turn on this for public server, may help DDNS self-hosting user.
                        if timeout && reg_timeout < MAX_REG_TIMEOUT {
                            reg_timeout += MIN_REG_TIMEOUT;
                        }
                    }
                    if timeout || (last_register_sent.is_none() && expired) {
                        if timeout {
                            fails += 1;
                            if fails >= MAX_FAILS2 {
                                Config::update_latency(&host, -1);
                                old_latency = 0;
                                if last_dns_check.elapsed().as_millis() as i64 > DNS_INTERVAL {
                                    // in some case of network reconnect (dial IP network),
                                    // old UDP socket not work any more after network recover
                                    if let Some((s, new_addr)) = socket_client::rebind_udp_for(&rz.host).await? {
                                        socket = s;
                                        rz.addr = new_addr.clone();
                                        addr = new_addr;
                                    }
                                    last_dns_check = Instant::now();
                                }
                            } else if fails >= MAX_FAILS1 {
                                Config::update_latency(&host, 0);
                                old_latency = 0;
                            }
                        }
                        rz.register_peer(Sink::Framed(&mut socket, &addr)).await?;
                        last_register_sent = now;
                    }
                }
            }
        }
        Ok(())
    }

    #[inline]
    async fn handle_resp(
        &mut self,
        msg: Option<rendezvous_message::Union>,
        sink: Sink<'_>,
        server: &ServerPtr,
        update_latency: &mut impl FnMut(),
    ) -> ResultType<()> {
        match msg {
            Some(rendezvous_message::Union::RegisterPeerResponse(rpr)) => {
                update_latency();
                if rpr.request_pk {
                    log::info!("request_pk received from {}", self.host);
                    self.register_pk(sink).await?;
                }
            }
            Some(rendezvous_message::Union::RegisterPkResponse(rpr)) => {
                update_latency();
                match rpr.result.enum_value() {
                    Ok(register_pk_response::Result::OK) => {
                        Config::set_key_confirmed(true);
                        Config::set_host_key_confirmed(&self.host_prefix, true);
                        *SOLVING_PK_MISMATCH.lock().await = "".to_owned();
                    }
                    Ok(register_pk_response::Result::UUID_MISMATCH) => {
                        self.handle_uuid_mismatch(sink).await?;
                    }
                    _ => {
                        log::error!("unknown RegisterPkResponse");
                    }
                }
                if rpr.keep_alive > 0 {
                    self.keep_alive = rpr.keep_alive * 1000;
                    log::info!("keep_alive: {}ms", self.keep_alive);
                }
            }
            Some(rendezvous_message::Union::PunchHole(ph)) => {
                let rz = self.clone();
                let server = server.clone();
                tokio::spawn(async move {
                    allow_err!(rz.handle_punch_hole(ph, server).await);
                });
            }
            Some(rendezvous_message::Union::RequestRelay(rr)) => {
                let rz = self.clone();
                let server = server.clone();
                tokio::spawn(async move {
                    allow_err!(rz.handle_request_relay(rr, server).await);
                });
            }
            Some(rendezvous_message::Union::FetchLocalAddr(fla)) => {
                let rz = self.clone();
                let server = server.clone();
                tokio::spawn(async move {
                    allow_err!(rz.handle_intranet(fla, server).await);
                });
            }
            Some(rendezvous_message::Union::ConfigureUpdate(cu)) => {
                let v0 = Config::get_rendezvous_servers();
                Config::set_option(
                    "rendezvous-servers".to_owned(),
                    cu.rendezvous_servers.join(","),
                );
                Config::set_serial(cu.serial);
                if v0 != Config::get_rendezvous_servers() {
                    Self::restart();
                }
            }
            _ => {}
        }
        Ok(())
    }

    pub async fn start_tcp(server: ServerPtr, host: String) -> ResultType<()> {
        let host = check_port(&host, RENDEZVOUS_PORT);
        let mut conn = connect_tcp(host.clone(), CONNECT_TIMEOUT).await?;
        let key = crate::get_key(true).await;
        crate::secure_tcp(&mut conn, &key).await?;
        let mut rz = Self {
            addr: conn.local_addr().into_target_addr()?,
            host: host.clone(),
            host_prefix: Self::get_host_prefix(&host),
            keep_alive: crate::DEFAULT_KEEP_ALIVE,
        };
        let mut timer = crate::rustdesk_interval(interval(crate::TIMER_OUT));
        let mut last_register_sent: Option<Instant> = None;
        let mut last_recv_msg = Instant::now();
        // we won't support connecting to multiple rendzvous servers any more, so we can use a global variable here.
        Config::set_host_key_confirmed(&host, false);
        loop {
            let mut update_latency = || {
                let latency = last_register_sent
                    .map(|x| x.elapsed().as_micros() as i64)
                    .unwrap_or(0);
                Config::update_latency(&host, latency);
                log::debug!("Latency of {}: {}ms", host, latency as f64 / 1000.);
            };
            select! {
                res = conn.next() => {
                    last_recv_msg = Instant::now();
                    let bytes = res.ok_or_else(|| anyhow::anyhow!("Rendezvous connection is reset by the peer"))??;
                    if bytes.is_empty() {
                        conn.send_bytes(bytes::Bytes::new()).await?;
                        continue; // heartbeat
                    }
                    let msg = Message::parse_from_bytes(&bytes)?;
                    rz.handle_resp(msg.union, Sink::Stream(&mut conn), &server, &mut update_latency).await?
                }
                _ = timer.tick() => {
                    if SHOULD_EXIT.load(Ordering::SeqCst) {
                        break;
                    }
                    // https://www.emqx.com/en/blog/mqtt-keep-alive
                    if last_recv_msg.elapsed().as_millis() as u64 > rz.keep_alive as u64 * 3 / 2 {
                        bail!("Rendezvous connection is timeout");
                    }
                    if (!Config::get_key_confirmed() ||
                        !Config::get_host_key_confirmed(&host)) &&
                        last_register_sent.map(|x| x.elapsed().as_millis() as i64).unwrap_or(REG_INTERVAL) >= REG_INTERVAL {
                        rz.register_pk(Sink::Stream(&mut conn)).await?;
                        last_register_sent = Some(Instant::now());
                    }
                }
            }
        }
        Ok(())
    }

    pub async fn start(server: ServerPtr, host: String) -> ResultType<()> {
        log::info!("start rendezvous mediator of {}", host);
        //If the investment agent type is http or https, then tcp forwarding is enabled.
        let is_http_proxy = if let Some(conf) = Config::get_socks() {
            let proxy = Proxy::from_conf(&conf, None)?;
            proxy.is_http_or_https()
        } else {
            false
        };
        if (cfg!(debug_assertions) && option_env!("TEST_TCP").is_some())
            || is_http_proxy
            || get_builtin_option(config::keys::OPTION_DISABLE_UDP) == "Y"
        {
            Self::start_tcp(server, host).await
        } else {
            Self::start_udp(server, host).await
        }
    }

    async fn handle_request_relay(&self, rr: RequestRelay, server: ServerPtr) -> ResultType<()> {
        self.create_relay(
            rr.socket_addr.into(),
            rr.relay_server,
            rr.uuid,
            server,
            rr.secure,
            false,
        )
        .await
    }

    async fn create_relay(
        &self,
        socket_addr: Vec<u8>,
        relay_server: String,
        uuid: String,
        server: ServerPtr,
        secure: bool,
        initiate: bool,
    ) -> ResultType<()> {
        let peer_addr = AddrMangle::decode(&socket_addr);
        log::info!(
            "create_relay requested from {:?}, relay_server: {}, uuid: {}, secure: {}",
            peer_addr,
            relay_server,
            uuid,
            secure,
        );

        let mut socket = connect_tcp(&*self.host, CONNECT_TIMEOUT).await?;

        let mut msg_out = Message::new();
        let mut rr = RelayResponse {
            socket_addr: socket_addr.into(),
            version: crate::VERSION.to_owned(),
            ..Default::default()
        };
        if initiate {
            rr.uuid = uuid.clone();
            rr.relay_server = relay_server.clone();
            rr.set_id(Config::get_id());
        }
        msg_out.set_relay_response(rr);
        socket.send(&msg_out).await?;
        crate::create_relay_connection(
            server,
            relay_server,
            uuid,
            peer_addr,
            secure,
            is_ipv4(&self.addr),
        )
        .await;
        Ok(())
    }

    async fn handle_intranet(&self, fla: FetchLocalAddr, server: ServerPtr) -> ResultType<()> {
        let relay_server = self.get_relay_server(fla.relay_server.clone());
        // nat64, go relay directly, because current hbbs will crash if demangle ipv6 address
        if is_ipv4(&self.addr) && !config::is_disable_tcp_listen() && !Config::is_proxy() {
            if let Err(err) = self
                .handle_intranet_(fla.clone(), server.clone(), relay_server.clone())
                .await
            {
                log::debug!("Failed to handle intranet: {:?}, will try relay", err);
            } else {
                return Ok(());
            }
        }
        let uuid = Uuid::new_v4().to_string();
        self.create_relay(
            fla.socket_addr.into(),
            relay_server,
            uuid,
            server,
            true,
            true,
        )
        .await
    }

    async fn handle_intranet_(
        &self,
        fla: FetchLocalAddr,
        server: ServerPtr,
        relay_server: String,
    ) -> ResultType<()> {
        let peer_addr = AddrMangle::decode(&fla.socket_addr);
        log::debug!("Handle intranet from {:?}", peer_addr);
        let mut socket = connect_tcp(&*self.host, CONNECT_TIMEOUT).await?;
        let local_addr = socket.local_addr();
        // we saw invalid local_addr while using proxy, local_addr.ip() == "::1"
        let local_addr: SocketAddr =
            format!("{}:{}", local_addr.ip(), local_addr.port()).parse()?;
        let mut msg_out = Message::new();
        msg_out.set_local_addr(LocalAddr {
            id: Config::get_id(),
            socket_addr: AddrMangle::encode(peer_addr).into(),
            local_addr: AddrMangle::encode(local_addr).into(),
            relay_server,
            version: crate::VERSION.to_owned(),
            ..Default::default()
        });
        let bytes = msg_out.write_to_bytes()?;
        socket.send_raw(bytes).await?;
        crate::accept_connection(server.clone(), socket, peer_addr, true).await;
        Ok(())
    }

    async fn handle_punch_hole(&self, ph: PunchHole, server: ServerPtr) -> ResultType<()> {
        let relay_server = self.get_relay_server(ph.relay_server);
        if ph.nat_type.enum_value() == Ok(NatType::SYMMETRIC)
            || Config::get_nat_type() == NatType::SYMMETRIC as i32
            || config::is_disable_tcp_listen()
        {
            let uuid = Uuid::new_v4().to_string();
            return self
                .create_relay(
                    ph.socket_addr.into(),
                    relay_server,
                    uuid,
                    server,
                    true,
                    true,
                )
                .await;
        }
        let peer_addr = AddrMangle::decode(&ph.socket_addr);
        log::debug!("Punch hole to {:?}", peer_addr);
        let mut socket = {
            let socket = connect_tcp(&*self.host, CONNECT_TIMEOUT).await?;
            let local_addr = socket.local_addr();
            // key important here for punch hole to tell my gateway incoming peer is safe.
            // it can not be async here, because local_addr can not be reused, we must close the connection before use it again.
            allow_err!(socket_client::connect_tcp_local(peer_addr, Some(local_addr), 30).await);
            socket
        };
        let mut msg_out = Message::new();
        use hbb_common::protobuf::Enum;
        let nat_type = NatType::from_i32(Config::get_nat_type()).unwrap_or(NatType::UNKNOWN_NAT);
        msg_out.set_punch_hole_sent(PunchHoleSent {
            socket_addr: ph.socket_addr,
            id: Config::get_id(),
            relay_server,
            nat_type: nat_type.into(),
            version: crate::VERSION.to_owned(),
            ..Default::default()
        });
        let bytes = msg_out.write_to_bytes()?;
        socket.send_raw(bytes).await?;
        crate::accept_connection(server.clone(), socket, peer_addr, true).await;
        Ok(())
    }

    async fn register_pk(&mut self, socket: Sink<'_>) -> ResultType<()> {
        let mut msg_out = Message::new();
        let pk = Config::get_key_pair().1;
        let uuid = hbb_common::get_uuid();
        let id = Config::get_id();
        msg_out.set_register_pk(RegisterPk {
            id,
            uuid: uuid.into(),
            pk: pk.into(),
            ..Default::default()
        });
        socket.send(&msg_out).await?;
        Ok(())
    }

    async fn handle_uuid_mismatch(&mut self, socket: Sink<'_>) -> ResultType<()> {
        {
            let mut solving = SOLVING_PK_MISMATCH.lock().await;
            if solving.is_empty() || *solving == self.host {
                log::info!("UUID_MISMATCH received from {}", self.host);
                Config::set_key_confirmed(false);
                Config::update_id();
                *solving = self.host.clone();
            } else {
                return Ok(());
            }
        }
        self.register_pk(socket).await
    }

    async fn register_peer(&mut self, socket: Sink<'_>) -> ResultType<()> {
        let solving = SOLVING_PK_MISMATCH.lock().await;
        if !(solving.is_empty() || *solving == self.host) {
            return Ok(());
        }
        drop(solving);
        if !Config::get_key_confirmed() || !Config::get_host_key_confirmed(&self.host_prefix) {
            log::info!(
                "register_pk of {} due to key not confirmed",
                self.host_prefix
            );
            return self.register_pk(socket).await;
        }
        let id = Config::get_id();
        log::trace!(
            "Register my id {:?} to rendezvous server {:?}",
            id,
            self.addr,
        );
        let mut msg_out = Message::new();
        let serial = Config::get_serial();
        msg_out.set_register_peer(RegisterPeer {
            id,
            serial,
            ..Default::default()
        });
        socket.send(&msg_out).await?;
        Ok(())
    }

    fn get_relay_server(&self, provided_by_rendezvous_server: String) -> String {
        let mut relay_server = Config::get_option("relay-server");
        if relay_server.is_empty() {
            relay_server = provided_by_rendezvous_server;
        }
        if relay_server.is_empty() {
            relay_server = crate::increase_port(&self.host, 1);
        }
        relay_server
    }
}

fn get_direct_port() -> i32 {
    let mut port = Config::get_option("direct-access-port")
        .parse::<i32>()
        .unwrap_or(0);
    if port <= 0 {
        port = RENDEZVOUS_PORT + 2;
    }
    port
}

async fn direct_server(server: ServerPtr) {
    let mut listener = None;
    let mut port = 0;
    loop {
        let disabled = !option2bool(
            OPTION_DIRECT_SERVER,
            &Config::get_option(OPTION_DIRECT_SERVER),
        ) || option2bool("stop-service", &Config::get_option("stop-service"));
        if !disabled && listener.is_none() {
            port = get_direct_port();
            match hbb_common::tcp::listen_any(port as _).await {
                Ok(l) => {
                    listener = Some(l);
                    log::info!(
                        "Direct server listening on: {:?}",
                        listener.as_ref().map(|l| l.local_addr())
                    );
                }
                Err(err) => {
                    // to-do: pass to ui
                    log::error!(
                        "Failed to start direct server on port: {}, error: {}",
                        port,
                        err
                    );
                    loop {
                        if port != get_direct_port() {
                            break;
                        }
                        sleep(1.).await;
                    }
                }
            }
        }
        if let Some(l) = listener.as_mut() {
            if disabled || port != get_direct_port() {
                log::info!("Exit direct access listen");
                listener = None;
                continue;
            }
            if let Ok(Ok((stream, addr))) = hbb_common::timeout(1000, l.accept()).await {
                stream.set_nodelay(true).ok();
                log::info!("direct access from {}", addr);
                let local_addr = stream
                    .local_addr()
                    .unwrap_or(Config::get_any_listen_addr(true));
                let server = server.clone();
                tokio::spawn(async move {
                    allow_err!(
                        crate::server::create_tcp_connection(
                            server,
                            hbb_common::Stream::from(stream, local_addr),
                            addr,
                            false,
                        )
                        .await
                    );
                });
            } else {
                sleep(0.1).await;
            }
        } else {
            sleep(1.).await;
        }
    }
}

enum Sink<'a> {
    Framed(&'a mut FramedSocket, &'a TargetAddr<'a>),
    Stream(&'a mut FramedStream),
}

impl Sink<'_> {
    async fn send(self, msg: &Message) -> ResultType<()> {
        match self {
            Sink::Framed(socket, addr) => socket.send(msg, addr.to_owned()).await,
            Sink::Stream(stream) => stream.send(msg).await,
        }
    }
}
