use std::{
    collections::{
        hash_map::{Iter, IterMut},
        HashMap,
    },
    error::Error,
    net::SocketAddr,
    sync::{Arc, Mutex},
};

use bevy::prelude::*;
use bytes::Bytes;
use futures::sink::SinkExt;
use futures_util::StreamExt;
use quinn::{ClientConfig, Connection as QuinnConnection, Endpoint};
use quinn_proto::ConnectionStats;
use serde::Deserialize;
use tokio::{
    runtime::{self},
    sync::{
        broadcast,
        mpsc::{
            self,
            error::{TryRecvError, TrySendError},
        },
        oneshot,
    },
    task::JoinSet,
};
use tokio_util::codec::{FramedRead, FramedWrite, LengthDelimitedCodec};

use crate::shared::{
    AsyncRuntime, QuinnetError, DEFAULT_KILL_MESSAGE_QUEUE_SIZE, DEFAULT_MESSAGE_QUEUE_SIZE,
};

use self::certificate::{
    load_known_hosts_store_from_config, CertConnectionAbortEvent, CertInteractionEvent,
    CertTrustUpdateEvent, CertVerificationInfo, CertVerificationStatus, CertVerifierAction,
    CertificateVerificationMode, SkipServerVerification, TofuServerVerification,
};

pub mod certificate;

pub const DEFAULT_INTERNAL_MESSAGE_CHANNEL_SIZE: usize = 100;
pub const DEFAULT_KNOWN_HOSTS_FILE: &str = "quinnet/known_hosts";

pub type ConnectionId = u64;

/// Connection event raised when the client just connected to the server. Raised in the CoreStage::PreUpdate stage.
pub struct ConnectionEvent {
    pub id: ConnectionId,
}
/// ConnectionLost event raised when the client is considered disconnected from the server. Raised in the CoreStage::PreUpdate stage.
pub struct ConnectionLostEvent {
    pub id: ConnectionId,
}

/// Configuration of the client, used when connecting to a server
#[derive(Debug, Deserialize, Clone)]
pub struct ConnectionConfiguration {
    server_host: String,
    server_port: u16,
    local_bind_host: String,
    local_bind_port: u16,
}

impl ConnectionConfiguration {
    /// Creates a new ClientConfigurationData
    ///
    /// # Arguments
    ///
    /// * `server_host` - Address of the server
    /// * `server_port` - Port that the server is listening on
    /// * `local_bind_host` - Local address to bind to, which should usually be a wildcard address like `0.0.0.0` or `[::]`, which allow communication with any reachable IPv4 or IPv6 address. See [`quinn::endpoint::Endpoint`] for more precision
    /// * `local_bind_port` - Local port to bind to. Use 0 to get an OS-assigned port.. See [`quinn::endpoint::Endpoint`] for more precision
    ///
    /// # Examples
    ///
    /// ```
    /// use bevy_quinnet::client::ConnectionConfiguration;
    /// let config = ConnectionConfiguration::new(
    ///         "127.0.0.1".to_string(),
    ///         6000,
    ///         "0.0.0.0".to_string(),
    ///         0,
    ///     );
    /// ```
    pub fn new(
        server_host: String,
        server_port: u16,
        local_bind_host: String,
        local_bind_port: u16,
    ) -> Self {
        Self {
            server_host,
            server_port,
            local_bind_host,
            local_bind_port,
        }
    }
}

type InternalConnectionRef = QuinnConnection;

/// Current state of a client connection
#[derive(Debug)]
enum ConnectionState {
    Disconnected,
    Connected(InternalConnectionRef),
}

#[derive(Debug)]
pub(crate) enum InternalAsyncMessage {
    Connected(InternalConnectionRef),
    LostConnection,
    CertificateInteractionRequest {
        status: CertVerificationStatus,
        info: CertVerificationInfo,
        action_sender: oneshot::Sender<CertVerifierAction>,
    },
    CertificateTrustUpdate(CertVerificationInfo),
    CertificateConnectionAbort {
        status: CertVerificationStatus,
        cert_info: CertVerificationInfo,
    },
}

#[derive(Debug)]
pub(crate) struct ConnectionSpawnConfig {
    connection_config: ConnectionConfiguration,
    cert_mode: CertificateVerificationMode,
    to_sync_client: mpsc::Sender<InternalAsyncMessage>,
    close_sender: tokio::sync::broadcast::Sender<()>,
    close_receiver: tokio::sync::broadcast::Receiver<()>,
    to_server_receiver: mpsc::Receiver<Bytes>,
    from_server_sender: mpsc::Sender<Bytes>,
}

#[derive(Debug)]
pub struct Connection {
    state: ConnectionState,
    // TODO Perf: multiple channels
    sender: mpsc::Sender<Bytes>,
    receiver: mpsc::Receiver<Bytes>,
    close_sender: broadcast::Sender<()>,
    pub(crate) internal_receiver: mpsc::Receiver<InternalAsyncMessage>,
}

impl Connection {
    pub fn receive_message<T: serde::de::DeserializeOwned>(
        &mut self,
    ) -> Result<Option<T>, QuinnetError> {
        match self.receive_payload()? {
            Some(payload) => match bincode::deserialize(&payload) {
                Ok(msg) => Ok(Some(msg)),
                Err(_) => Err(QuinnetError::Deserialization),
            },
            None => Ok(None),
        }
    }

    /// Same as [Connection::receive_message] but will log the error instead of returning it
    pub fn try_receive_message<T: serde::de::DeserializeOwned>(&mut self) -> Option<T> {
        match self.receive_message() {
            Ok(message) => message,
            Err(err) => {
                error!("try_receive_message: {}", err);
                None
            }
        }
    }

    pub fn send_message<T: serde::Serialize>(&self, message: T) -> Result<(), QuinnetError> {
        match bincode::serialize(&message) {
            Ok(payload) => self.send_payload(payload),
            Err(_) => Err(QuinnetError::Serialization),
        }
    }

    /// Same as [Connection::send_message] but will log the error instead of returning it
    pub fn try_send_message<T: serde::Serialize>(&self, message: T) {
        match self.send_message(message) {
            Ok(_) => {}
            Err(err) => error!("try_send_message: {}", err),
        }
    }

    pub fn send_payload<T: Into<Bytes>>(&self, payload: T) -> Result<(), QuinnetError> {
        match self.sender.try_send(payload.into()) {
            Ok(_) => Ok(()),
            Err(err) => match err {
                TrySendError::Full(_) => Err(QuinnetError::FullQueue),
                TrySendError::Closed(_) => Err(QuinnetError::ChannelClosed),
            },
        }
    }

    /// Same as [Connection::send_payload] but will log the error instead of returning it
    pub fn try_send_payload<T: Into<Bytes>>(&self, payload: T) {
        match self.send_payload(payload) {
            Ok(_) => {}
            Err(err) => error!("try_send_payload: {}", err),
        }
    }

    pub fn receive_payload(&mut self) -> Result<Option<Bytes>, QuinnetError> {
        match self.receiver.try_recv() {
            Ok(msg_payload) => Ok(Some(msg_payload)),
            Err(err) => match err {
                TryRecvError::Empty => Ok(None),
                TryRecvError::Disconnected => Err(QuinnetError::ChannelClosed),
            },
        }
    }

    /// Same as [Connection::receive_payload] but will log the error instead of returning it
    pub fn try_receive_payload(&mut self) -> Option<Bytes> {
        match self.receive_payload() {
            Ok(payload) => payload,
            Err(err) => {
                error!("try_receive_payload: {}", err);
                None
            }
        }
    }

    /// Disconnect from the server on this connection. This does not send any message to the server, and simply closes all the connection's tasks locally.
    fn disconnect(&mut self) -> Result<(), QuinnetError> {
        if self.is_connected() {
            if let Err(_) = self.close_sender.send(()) {
                return Err(QuinnetError::ChannelClosed);
            }
        }
        self.state = ConnectionState::Disconnected;
        Ok(())
    }

    pub fn is_connected(&self) -> bool {
        match self.state {
            ConnectionState::Disconnected => false,
            ConnectionState::Connected(_) => true,
        }
    }

    /// Returns statistics about the current connection if connected.
    pub fn stats(&self) -> Option<ConnectionStats> {
        match &self.state {
            ConnectionState::Disconnected => None,
            ConnectionState::Connected(connection) => Some(connection.stats()),
        }
    }
}

#[derive(Resource)]
pub struct Client {
    runtime: runtime::Handle,
    connections: HashMap<ConnectionId, Connection>,
    last_gen_id: ConnectionId,
    default_connection_id: Option<ConnectionId>,
}

impl Client {
    /// Returns the default connection or None.
    pub fn get_connection(&self) -> Option<&Connection> {
        match self.default_connection_id {
            Some(id) => self.connections.get(&id),
            None => None,
        }
    }

    /// Returns the default connection as mut or None.
    pub fn get_connection_mut(&mut self) -> Option<&mut Connection> {
        match self.default_connection_id {
            Some(id) => self.connections.get_mut(&id),
            None => None,
        }
    }

    /// Returns the default connection. **Warning**, this function panics if there is no default connection.
    pub fn connection(&self) -> &Connection {
        self.connections
            .get(&self.default_connection_id.unwrap())
            .unwrap()
    }

    /// Returns the default connection as mut. **Warning**, this function panics if there is no default connection.
    pub fn connection_mut(&mut self) -> &mut Connection {
        self.connections
            .get_mut(&self.default_connection_id.unwrap())
            .unwrap()
    }

    /// Returns the requested connection.
    pub fn get_connection_by_id(&self, id: ConnectionId) -> Option<&Connection> {
        self.connections.get(&id)
    }

    /// Returns the requested connection as mut.
    pub fn get_connection_mut_by_id(&mut self, id: ConnectionId) -> Option<&mut Connection> {
        self.connections.get_mut(&id)
    }

    /// Returns an iterator over all connections
    pub fn connections(&self) -> Iter<ConnectionId, Connection> {
        self.connections.iter()
    }

    /// Returns an iterator over all connections as muts
    pub fn connections_mut(&mut self) -> IterMut<ConnectionId, Connection> {
        self.connections.iter_mut()
    }

    /// Open a connection to a server with the given [ConnectionConfiguration] and [CertificateVerificationMode]. The connection will raise an event when fully connected, see [ConnectionEvent]
    pub fn open_connection(
        &mut self,
        config: ConnectionConfiguration,
        cert_mode: CertificateVerificationMode,
    ) -> ConnectionId {
        let (from_server_sender, from_server_receiver) =
            mpsc::channel::<Bytes>(DEFAULT_MESSAGE_QUEUE_SIZE);
        let (to_server_sender, to_server_receiver) =
            mpsc::channel::<Bytes>(DEFAULT_MESSAGE_QUEUE_SIZE);

        let (to_sync_client, from_async_client) =
            mpsc::channel::<InternalAsyncMessage>(DEFAULT_INTERNAL_MESSAGE_CHANNEL_SIZE);

        // Create a close channel for this connection
        let (close_sender, close_receiver): (
            tokio::sync::broadcast::Sender<()>,
            tokio::sync::broadcast::Receiver<()>,
        ) = broadcast::channel(DEFAULT_KILL_MESSAGE_QUEUE_SIZE);

        let connection = Connection {
            state: ConnectionState::Disconnected,
            sender: to_server_sender,
            receiver: from_server_receiver,
            close_sender: close_sender.clone(),
            internal_receiver: from_async_client,
        };

        // Async connection
        self.runtime.spawn(async move {
            connection_task(ConnectionSpawnConfig {
                connection_config: config,
                cert_mode,
                to_sync_client,
                close_sender,
                close_receiver,
                to_server_receiver,
                from_server_sender,
            })
            .await
        });

        self.last_gen_id += 1;
        let connection_id = self.last_gen_id;
        self.connections.insert(connection_id, connection);
        if self.default_connection_id.is_none() {
            self.default_connection_id = Some(connection_id);
        }

        connection_id
    }

    /// Set the default connection
    pub fn set_default_connection(&mut self, connection_id: ConnectionId) {
        self.default_connection_id = Some(connection_id);
    }

    /// Get the default Connection Id
    pub fn get_default_connection(&self) -> Option<ConnectionId> {
        self.default_connection_id
    }

    /// Close a specific connection. This will call disconnect on the connection and remove it from the client. This may fail if the [Connection] fails to disconnect or if no [Connection] if found for connection_id
    pub fn close_connection(&mut self, connection_id: ConnectionId) -> Result<(), QuinnetError> {
        match self.connections.remove(&connection_id) {
            Some(mut connection) => {
                connection.disconnect()?;
                if let Some(default_id) = self.default_connection_id {
                    if connection_id == default_id {
                        self.default_connection_id = None;
                    }
                }
                Ok(())
            }
            None => Err(QuinnetError::UnknownConnection(connection_id)),
        }
    }

    /// Calls close_connection on all the open connections.
    pub fn close_all_connections(&mut self) -> Result<(), QuinnetError> {
        for connection_id in self
            .connections
            .keys()
            .cloned()
            .collect::<Vec<ConnectionId>>()
        {
            self.close_connection(connection_id)?;
        }
        Ok(())
    }
}

fn configure_client(
    cert_mode: CertificateVerificationMode,
    to_sync_client: mpsc::Sender<InternalAsyncMessage>,
) -> Result<ClientConfig, Box<dyn Error>> {
    match cert_mode {
        CertificateVerificationMode::SkipVerification => {
            let crypto = rustls::ClientConfig::builder()
                .with_safe_defaults()
                .with_custom_certificate_verifier(SkipServerVerification::new())
                .with_no_client_auth();

            Ok(ClientConfig::new(Arc::new(crypto)))
        }
        CertificateVerificationMode::SignedByCertificateAuthority => {
            Ok(ClientConfig::with_native_roots())
        }
        CertificateVerificationMode::TrustOnFirstUse(config) => {
            let (store, store_file) = load_known_hosts_store_from_config(config.known_hosts)?;
            let crypto = rustls::ClientConfig::builder()
                .with_safe_defaults()
                .with_custom_certificate_verifier(TofuServerVerification::new(
                    store,
                    config.verifier_behaviour,
                    to_sync_client,
                    store_file,
                ))
                .with_no_client_auth();
            Ok(ClientConfig::new(Arc::new(crypto)))
        }
    }
}

async fn connection_task(mut spawn_config: ConnectionSpawnConfig) {
    let config = spawn_config.connection_config;
    let server_adr_str = format!("{}:{}", config.server_host, config.server_port);
    let srv_host = config.server_host.clone();
    let local_bind_adr = format!("{}:{}", config.local_bind_host, config.local_bind_port);

    info!("Trying to connect to server on: {} ...", server_adr_str);

    let server_addr: SocketAddr = server_adr_str
        .parse()
        .expect("Failed to parse server address");

    let client_cfg = configure_client(spawn_config.cert_mode, spawn_config.to_sync_client.clone())
        .expect("Failed to configure client");

    let mut endpoint = Endpoint::client(local_bind_adr.parse().unwrap())
        .expect("Failed to create client endpoint");
    endpoint.set_default_client_config(client_cfg);

    let connection = endpoint
        .connect(server_addr, &srv_host) // TODO Clean: error handling
        .expect("Failed to connect: configuration error")
        .await;
    match connection {
        Err(e) => error!("Error while connecting: {}", e),
        Ok(connection) => {
            info!("Connected to {}", connection.remote_address());

            spawn_config
                .to_sync_client
                .send(InternalAsyncMessage::Connected(connection.clone()))
                .await
                .expect("Failed to signal connection to sync client");

            let send = connection
                .open_uni()
                .await
                .expect("Failed to open send stream");
            let mut frame_send = FramedWrite::new(send, LengthDelimitedCodec::new());

            let close_sender_clone = spawn_config.close_sender.clone();
            let _network_sends = tokio::spawn(async move {
                tokio::select! {
                    _ = spawn_config.close_receiver.recv() => {
                        trace!("Unidirectional send Stream forced to disconnected")
                    }
                    _ = async {
                        while let Some(msg_bytes) = spawn_config.to_server_receiver.recv().await {
                            if let Err(err) = frame_send.send(msg_bytes).await {
                                error!("Error while sending, {}", err); // TODO Clean: error handling
                                error!("Client seems disconnected, closing resources");
                                if let Err(_) = close_sender_clone.send(()) {
                                    error!("Failed to close all client streams & resources")
                                }
                                spawn_config.to_sync_client.send(
                                    InternalAsyncMessage::LostConnection)
                                    .await
                                    .expect("Failed to signal connection lost to sync client");
                            }
                        }
                    } => {
                        trace!("Unidirectional send Stream ended")
                    }
                }
            });

            let mut uni_receivers: JoinSet<()> = JoinSet::new();
            let mut close_receiver = spawn_config.close_sender.subscribe();
            let _network_reads = tokio::spawn(async move {
                tokio::select! {
                    _ = close_receiver.recv() => {
                        trace!("New Stream listener forced to disconnected")
                    }
                    _ = async {
                        while let Ok(recv)= connection.accept_uni().await {
                            let mut frame_recv = FramedRead::new(recv, LengthDelimitedCodec::new());
                            let from_server_sender = spawn_config.from_server_sender.clone();

                            uni_receivers.spawn(async move {
                                while let Some(Ok(msg_bytes)) = frame_recv.next().await {
                                    from_server_sender.send(msg_bytes.into()).await.unwrap(); // TODO Clean: error handling
                                }
                            });
                        }
                    } => {
                        trace!("New Stream listener ended ")
                    }
                }
                uni_receivers.shutdown().await;
                trace!("All unidirectional stream receivers cleaned");
            });
        }
    }
}

// Receive messages from the async client tasks and update the sync client.
fn update_sync_client(
    mut connection_events: EventWriter<ConnectionEvent>,
    mut connection_lost_events: EventWriter<ConnectionLostEvent>,
    mut certificate_interaction_events: EventWriter<CertInteractionEvent>,
    mut cert_trust_update_events: EventWriter<CertTrustUpdateEvent>,
    mut cert_connection_abort_events: EventWriter<CertConnectionAbortEvent>,
    mut client: ResMut<Client>,
) {
    for (connection_id, mut connection) in &mut client.connections {
        while let Ok(message) = connection.internal_receiver.try_recv() {
            match message {
                InternalAsyncMessage::Connected(internal_connection) => {
                    connection.state = ConnectionState::Connected(internal_connection);
                    connection_events.send(ConnectionEvent { id: *connection_id });
                }
                InternalAsyncMessage::LostConnection => {
                    connection.state = ConnectionState::Disconnected;
                    connection_lost_events.send(ConnectionLostEvent { id: *connection_id });
                }
                InternalAsyncMessage::CertificateInteractionRequest {
                    status,
                    info,
                    action_sender,
                } => {
                    certificate_interaction_events.send(CertInteractionEvent {
                        connection_id: *connection_id,
                        status,
                        info,
                        action_sender: Mutex::new(Some(action_sender)),
                    });
                }
                InternalAsyncMessage::CertificateTrustUpdate(info) => {
                    cert_trust_update_events.send(CertTrustUpdateEvent {
                        connection_id: *connection_id,
                        cert_info: info,
                    });
                }
                InternalAsyncMessage::CertificateConnectionAbort { status, cert_info } => {
                    cert_connection_abort_events.send(CertConnectionAbortEvent {
                        connection_id: *connection_id,
                        status,
                        cert_info,
                    });
                }
            }
        }
    }
}

fn create_client(mut commands: Commands, runtime: Res<AsyncRuntime>) {
    commands.insert_resource(Client {
        connections: HashMap::new(),
        runtime: runtime.handle().clone(),
        last_gen_id: 0,
        default_connection_id: None,
    });
}

pub struct QuinnetClientPlugin {}

impl Default for QuinnetClientPlugin {
    fn default() -> Self {
        Self {}
    }
}

impl Plugin for QuinnetClientPlugin {
    fn build(&self, app: &mut App) {
        app.add_event::<ConnectionEvent>()
            .add_event::<ConnectionLostEvent>()
            .add_event::<CertInteractionEvent>()
            .add_event::<CertTrustUpdateEvent>()
            .add_event::<CertConnectionAbortEvent>()
            // StartupStage::PreStartup so that resources created in commands are available to default startup_systems
            .add_startup_system_to_stage(StartupStage::PreStartup, create_client)
            .add_system_to_stage(CoreStage::PreUpdate, update_sync_client);

        if app.world.get_resource_mut::<AsyncRuntime>().is_none() {
            app.insert_resource(AsyncRuntime(
                tokio::runtime::Builder::new_multi_thread()
                    .enable_all()
                    .build()
                    .unwrap(),
            ));
        }
    }
}