#[cfg(feature = "pipes")]
use mtp_codec::{CommunicationType, DataType, DataValue};
use mtp_codec::{CommunicationValue, Version, registry::VersionedCodec};
use mtp_common::CommunicationError;
use std::net::SocketAddr;
#[cfg(feature = "pipes")]
use std::sync::Arc;
#[cfg(feature = "pipes")]
use tokio::sync::{Mutex, mpsc};

#[cfg(feature = "crypto")]
use crate::error::random_client_id;
#[cfg(feature = "pipes")]
use crate::pipe::{
    PendingCreationGuard, PipeDispatcher, PipeReceiver, PipeRequest, PipeSender,
    is_expired_creation, run_dispatcher,
};
#[cfg(feature = "pipes")]
use mtp_transport::Policy;

mod connection_capability {
    pub trait Sealed {}
}

pub trait MtpSenderLike: connection_capability::Sealed + Clone + Send + Sync {}
pub trait MtpReceiverLike: connection_capability::Sealed + Clone + Send + Sync {
    fn receive_message(
        &self,
    ) -> impl std::future::Future<Output = Result<CommunicationValue, CommunicationError>> + Send;
}

impl connection_capability::Sealed for mtp_transport::Sender {}
impl MtpSenderLike for mtp_transport::Sender {}
impl connection_capability::Sealed for mtp_transport::Receiver {}
impl MtpReceiverLike for mtp_transport::Receiver {
    async fn receive_message(&self) -> Result<CommunicationValue, CommunicationError> {
        self.receive().await
    }
}
impl<C: mtp_transport::TransportConnection> connection_capability::Sealed
    for mtp_transport::GenericSender<C>
{
}
impl<C: mtp_transport::TransportConnection> MtpSenderLike for mtp_transport::GenericSender<C> {}
impl<C: mtp_transport::TransportConnection> connection_capability::Sealed
    for mtp_transport::GenericReceiver<C>
{
}
impl<C: mtp_transport::TransportConnection> MtpReceiverLike for mtp_transport::GenericReceiver<C> {
    async fn receive_message(&self) -> Result<CommunicationValue, CommunicationError> {
        self.receive().await
    }
}

pub struct MTPConnection<
    S = mtp_transport::Sender,
    R = mtp_transport::Receiver,
    P = wtransport::RecvStream,
> {
    pub version: Version,
    pub codec: VersionedCodec,
    pub sender: S,
    pub receiver: R,
    /// The WebTransport request path used to establish this connection.
    ///
    /// Legacy `MTPHost` connections do not have an HTTP router in front of
    /// them, so they always use the root path.  Alternative hosts can retain
    /// the CONNECT request path when constructing an MTP connection.
    pub path: String,
    /// The address of the peer that established this connection, when exposed
    /// by the underlying transport.
    pub remote_addr: Option<SocketAddr>,
    #[cfg(feature = "pipes")]
    pub(crate) app_rx: Mutex<mpsc::Receiver<Result<CommunicationValue, CommunicationError>>>,
    #[cfg(feature = "pipes")]
    pub(crate) pipe_req_rx: Mutex<mpsc::Receiver<PipeRequest<S, R, P>>>,
    #[cfg(feature = "pipes")]
    pub(crate) pipe_dispatcher: Arc<PipeDispatcher<P>>,
    #[cfg(not(feature = "pipes"))]
    pub(crate) _pipe_stream: std::marker::PhantomData<P>,
    pub description: Option<String>,
    pub(crate) _dispatcher_task: tokio::task::JoinHandle<()>,
    /// Keeps an outer server admission permit alive for this MTP session.
    /// Native hosts leave it empty; WebTransport hosts use it to make the
    /// configured connection limit cover the session lifetime.
    pub(crate) _connection_guard: Option<tokio::sync::OwnedSemaphorePermit>,
    #[cfg(feature = "crypto")]
    pub auth_state: crate::error::AuthState,
    #[cfg(feature = "crypto")]
    pub client_id: u64,
    #[cfg(feature = "crypto")]
    pub client_public_key: Option<mtp_crypto::PublicKeyBundle>,
    #[cfg(feature = "crypto")]
    pub(crate) guest_id_lease: Option<crate::engine::GuestIdLease>,
}

impl<S, R, P> MTPConnection<S, R, P> {
    /// Keep an outer server admission permit until this connection is dropped.
    pub fn set_connection_guard(&mut self, guard: tokio::sync::OwnedSemaphorePermit) {
        self._connection_guard = Some(guard);
    }

    #[cfg(feature = "crypto")]
    pub fn set_guest_id_lease(&mut self, lease: Option<crate::engine::GuestIdLease>) {
        self.guest_id_lease = lease;
    }
}

#[cfg(feature = "pipes")]
impl<S, R, P> MTPConnection<S, R, P>
where
    S: PipeSender,
    R: PipeReceiver<P>,
    P: tokio::io::AsyncRead + Send + Unpin + 'static,
{
    /// Construct an MTP connection from an alternative transport backend.
    ///
    /// Native `MTPHost` users continue to receive the default
    /// `MTPConnection<Sender, Receiver>` type.  HTTP/3 WebTransport hosts use
    /// this constructor with their stream adapters while retaining the shared
    /// version, codec, path, and metadata representation.
    pub fn from_transport_parts(
        version: Version,
        codec: VersionedCodec,
        sender: S,
        receiver: R,
        path: String,
        description: Option<String>,
    ) -> Self {
        Self::from_transport_parts_with_remote_addr(
            version,
            codec,
            sender,
            receiver,
            path,
            description,
            None,
        )
    }

    pub fn from_transport_parts_with_remote_addr(
        version: Version,
        codec: VersionedCodec,
        sender: S,
        receiver: R,
        path: String,
        description: Option<String>,
        remote_addr: Option<SocketAddr>,
    ) -> Self {
        let policy = Arc::new(Policy::default());
        let receiver_queue_capacity = policy.receiver_queue_capacity.max(1);
        let (app_tx, app_rx) = mpsc::channel(receiver_queue_capacity);
        let (pipe_req_tx, pipe_req_rx) = mpsc::channel(receiver_queue_capacity);
        let dispatcher = Arc::new(PipeDispatcher {
            pending_creations: std::sync::Mutex::new(std::collections::HashMap::new()),
            expired_creations: std::sync::Mutex::new(std::collections::HashMap::new()),
            pending_pipes: Mutex::new(std::collections::HashMap::new()),
            policy,
            type_map: codec.type_map().clone(),
        });
        let task = tokio::spawn(run_dispatcher(
            receiver.clone(),
            sender.clone(),
            app_tx,
            pipe_req_tx,
            dispatcher.clone(),
        ));
        Self {
            version,
            codec,
            sender,
            receiver,
            path,
            remote_addr,
            app_rx: Mutex::new(app_rx),
            pipe_req_rx: Mutex::new(pipe_req_rx),
            pipe_dispatcher: dispatcher,
            description,
            _dispatcher_task: task,
            _connection_guard: None,
            #[cfg(feature = "crypto")]
            auth_state: crate::error::AuthState::Unauthenticated,
            #[cfg(feature = "crypto")]
            client_id: random_client_id(),
            #[cfg(feature = "crypto")]
            client_public_key: None,
            #[cfg(feature = "crypto")]
            guest_id_lease: None,
        }
    }

    /// Construct an MTP connection with an explicit policy for pipe dispatch.
    // The shared transport constructor keeps its argument order aligned with
    // `from_transport_parts_with_remote_addr`; policy is required only here.
    #[allow(clippy::too_many_arguments)]
    pub fn from_transport_parts_with_policy(
        version: Version,
        codec: VersionedCodec,
        sender: S,
        receiver: R,
        path: String,
        description: Option<String>,
        remote_addr: Option<SocketAddr>,
        policy: Arc<Policy>,
    ) -> Self {
        let receiver_queue_capacity = policy.receiver_queue_capacity.max(1);
        let (app_tx, app_rx) = mpsc::channel(receiver_queue_capacity);
        let (pipe_req_tx, pipe_req_rx) = mpsc::channel(receiver_queue_capacity);
        let dispatcher = Arc::new(PipeDispatcher {
            pending_creations: std::sync::Mutex::new(std::collections::HashMap::new()),
            expired_creations: std::sync::Mutex::new(std::collections::HashMap::new()),
            pending_pipes: Mutex::new(std::collections::HashMap::new()),
            policy,
            type_map: codec.type_map().clone(),
        });
        let task = tokio::spawn(run_dispatcher(
            receiver.clone(),
            sender.clone(),
            app_tx,
            pipe_req_tx,
            dispatcher.clone(),
        ));
        Self {
            version,
            codec,
            sender,
            receiver,
            path,
            remote_addr,
            app_rx: Mutex::new(app_rx),
            pipe_req_rx: Mutex::new(pipe_req_rx),
            pipe_dispatcher: dispatcher,
            description,
            _dispatcher_task: task,
            _connection_guard: None,
            #[cfg(feature = "crypto")]
            auth_state: crate::error::AuthState::Unauthenticated,
            #[cfg(feature = "crypto")]
            client_id: random_client_id(),
            #[cfg(feature = "crypto")]
            client_public_key: None,
            #[cfg(feature = "crypto")]
            guest_id_lease: None,
        }
    }
}

#[cfg(not(feature = "pipes"))]
impl<S, R, P> MTPConnection<S, R, P> {
    pub fn from_transport_parts(
        version: Version,
        codec: VersionedCodec,
        sender: S,
        receiver: R,
        path: String,
        description: Option<String>,
    ) -> Self {
        Self::from_transport_parts_with_remote_addr(
            version,
            codec,
            sender,
            receiver,
            path,
            description,
            None,
        )
    }

    pub fn from_transport_parts_with_remote_addr(
        version: Version,
        codec: VersionedCodec,
        sender: S,
        receiver: R,
        path: String,
        description: Option<String>,
        remote_addr: Option<SocketAddr>,
    ) -> Self {
        Self {
            version,
            codec,
            sender,
            receiver,
            path,
            remote_addr,
            description,
            _pipe_stream: std::marker::PhantomData,
            _dispatcher_task: tokio::spawn(async {}),
            _connection_guard: None,
            #[cfg(feature = "crypto")]
            auth_state: crate::error::AuthState::Unauthenticated,
            #[cfg(feature = "crypto")]
            client_id: random_client_id(),
            #[cfg(feature = "crypto")]
            client_public_key: None,
            #[cfg(feature = "crypto")]
            guest_id_lease: None,
        }
    }
}

#[cfg(not(feature = "pipes"))]
impl<S: MtpSenderLike, R: MtpReceiverLike> MTPConnection<S, R> {
    pub async fn receive(&self) -> Result<CommunicationValue, CommunicationError> {
        let mut message = self.receiver.receive_message().await?;
        message.set_type_map(self.codec.type_map());
        Ok(message)
    }
}

#[cfg(feature = "pipes")]
impl<S, R, P> MTPConnection<S, R, P>
where
    S: PipeSender,
    P: tokio::io::AsyncRead + Send + Unpin + 'static,
{
    pub async fn receive(&self) -> Result<CommunicationValue, CommunicationError> {
        let mut rx = self.app_rx.lock().await;
        match rx.recv().await {
            Some(Ok(mut message)) => {
                message.set_type_map(self.codec.type_map());
                Ok(message)
            }
            Some(Err(error)) => Err(error),
            None => Err(CommunicationError::StreamClosed),
        }
    }

    pub async fn create_pipe(
        &self,
        description: &str,
    ) -> Result<crate::pipe::PipeHandle<S, P>, mtp_common::PipeError> {
        let (response_tx, response_rx) = tokio::sync::oneshot::channel();
        let pipe_id = {
            let mut pending = self
                .pipe_dispatcher
                .pending_creations
                .lock()
                .map_err(|_| mtp_common::PipeError::ConnectionClosed)?;
            let pipe_id = loop {
                let candidate = rand::random::<u32>();
                if candidate != 0
                    && !pending.contains_key(&candidate)
                    && !is_expired_creation(&self.pipe_dispatcher, candidate)
                {
                    break candidate;
                }
            };
            let token = Arc::new(());
            pending.insert(
                pipe_id,
                crate::pipe::PendingCreation {
                    token: token.clone(),
                    sender: response_tx,
                },
            );
            drop(pending);
            (pipe_id, token)
        };
        let (pipe_id, token) = pipe_id;
        let mut creation_guard =
            PendingCreationGuard::new(self.pipe_dispatcher.clone(), pipe_id, token.clone());

        let request = CommunicationValue::new_with_type_map(
            CommunicationType::PipeRequest,
            self.codec.type_map(),
        )
        .with_id(pipe_id)
        .add_typed_default(DataType::Description, DataValue::Str(description.into()));
        if let Err(error) = self.sender.send_pipe_message(&request).await {
            return Err(mtp_common::PipeError::from(error));
        }

        creation_guard.disarm();
        Ok(crate::pipe::PipeHandle {
            pipe_id,
            description: description.to_owned(),
            sender: self.sender.clone(),
            response_rx,
            dispatcher: self.pipe_dispatcher.clone(),
            token,
        })
    }

    pub async fn receive_pipe(&self) -> Result<PipeRequest<S, R, P>, CommunicationError> {
        self.pipe_req_rx
            .lock()
            .await
            .recv()
            .await
            .ok_or(CommunicationError::StreamClosed)
    }
}