use crate::packet::{Packet, PacketReceiver};
use std::{
    io::{self, Read, Write},
    net::{Shutdown, SocketAddr, TcpListener, TcpStream, ToSocketAddrs},
    sync::{
        atomic::{AtomicBool, Ordering},
        mpsc::{channel, Receiver, Sender},
        Arc, Mutex,
    },
    thread,
};

/// Used to send [Packet] to the sending thread.
type ConnectionSender = Arc<Mutex<Sender<(u32, Vec<u8>)>>>;

/// A TCP [Connection] that can send and receive [Packet].
pub struct Connection {
    /// Whether or not the [Connection] is currently connected.
    connected: Arc<AtomicBool>,

    /// Used to store the received [Packet]s.
    packets: Arc<PacketReceiver>,

    /// Used to send [Packet] to the sending thread.
    sender: ConnectionSender,

    /// The [TcpStream] of the [Connection].
    stream: TcpStream,

    /// The address of the [Connection].
    address: SocketAddr,
}

impl Connection {
    /// Creates a new [Connection] with the given [TcpStream].
    pub fn new(stream: TcpStream) -> io::Result<Self> {
        let connected = Arc::new(AtomicBool::new(true));
        let packets = Arc::new(PacketReceiver::new());

        // Receiving part
        let mut thread_stream = stream.try_clone()?;
        let thread_packets = Arc::clone(&packets);
        let thread_connected = Arc::clone(&connected);
        thread::spawn(move || {
            let mut int_buffer = [0; 4];

            loop {
                // Check if the connection is closed
                if !thread_connected.load(Ordering::Relaxed) {
                    return;
                }

                // Read the length of the packet
                if thread_stream.read_exact(&mut int_buffer).is_err() {
                    break;
                }
                let len = u32::from_be_bytes(int_buffer);

                // Read the packet identifier
                if thread_stream.read_exact(&mut int_buffer).is_err() {
                    break;
                }
                let id = u32::from_be_bytes(int_buffer);

                // Read the packet
                let mut buffer = vec![0; len as usize];
                if thread_stream.read_exact(&mut buffer).is_err() {
                    break;
                }

                // Insert the packet
                thread_packets.insert(id, buffer);
            }

            // Close the connection
            thread_connected.store(false, Ordering::Relaxed);
        });

        // Sending part
        let mut thread_stream = stream.try_clone()?;
        let (sender, receiver) = channel();
        let thread_connected = Arc::clone(&connected);
        thread::spawn(move || {
            loop {
                // Check if the connection is closed
                if !thread_connected.load(Ordering::Relaxed) {
                    return;
                }

                // Get the data to send
                let (id, buffer): (u32, Vec<u8>) = match receiver.recv() {
                    Ok(data) => data,
                    Err(_) => break,
                };

                // Send the length of the data
                let len = buffer.len() as u32;
                if thread_stream.write_all(&len.to_be_bytes()).is_err() {
                    break;
                }

                // Send the packet identifier
                if thread_stream.write_all(&id.to_be_bytes()).is_err() {
                    break;
                }

                // Send the data
                if thread_stream.write_all(&buffer).is_err() {
                    break;
                }

                // Flush the stream
                if thread_stream.flush().is_err() {
                    break;
                }
            }

            // Close the connection
            thread_connected.store(false, Ordering::Relaxed);
        });

        Ok(Self {
            connected,
            packets,
            sender: Arc::new(Mutex::new(sender)),
            address: stream.peer_addr()?,
            stream,
        })
    }

    /// Creates a [Connection] to the given address.
    pub fn connect<A: ToSocketAddrs>(address: A) -> io::Result<Self> {
        Self::new(TcpStream::connect(address)?)
    }

    /// Returns whether or not the [Connection] is currently connected.
    pub fn connected(&self) -> bool {
        self.connected.load(Ordering::Relaxed)
    }

    /// Clears the [Packet] cache.
    pub fn clear(&self) {
        self.packets.clear();
    }

    /// Gets all the received [Packet]s of a certain type.
    pub fn recv<P: Packet>(&self) -> Vec<P> {
        self.packets.extract()
    }

    /// Sends the given [Packet] to the [Connection].
    /// Does nothing if the [Connection] is closed.
    pub fn send<P: Packet>(&self, packet: P) {
        let data = bincode::serialize(&packet).expect("Failed to serialize packet");
        self.sender
            .lock()
            .map(|sender| sender.send((P::ID, data)))
            .ok();
    }

    /// Returns the address of the [Connection].
    pub fn address(&self) -> SocketAddr {
        self.address
    }
}

impl Drop for Connection {
    fn drop(&mut self) {
        self.connected.store(false, Ordering::Relaxed);
        self.stream.shutdown(Shutdown::Both).ok();
    }
}

/// A TCP [Listener] that can accept [Connection]s.
pub struct Listener {
    /// Whether the [Listener] is listening.
    listening: Arc<AtomicBool>,

    /// The receiving part of the [Listener].
    receiver: Arc<Mutex<Receiver<Connection>>>,

    /// The address the [Listener] is bound to.
    address: SocketAddr,
}

impl Listener {
    /// Creates a new [Listener] binded to the given address.
    pub fn bind<A: ToSocketAddrs>(address: A) -> io::Result<Self> {
        let listener = TcpListener::bind(address)?;
        let address = listener.local_addr()?;
        let listening = Arc::new(AtomicBool::new(true));
        let listening_thread = Arc::clone(&listening);
        let (sender, receiver) = channel();
        thread::spawn(move || {
            for stream in listener.incoming() {
                let connection = match stream {
                    Ok(stream) => match Connection::new(stream) {
                        Ok(connection) => connection,
                        Err(_) => break,
                    },
                    Err(_) => break,
                };
                if sender.send(connection).is_err() {
                    break;
                }
            }
            listening_thread.store(false, Ordering::Relaxed);
        });
        Ok(Self {
            listening,
            receiver: Arc::new(Mutex::new(receiver)),
            address,
        })
    }

    /// Returns whether or not the [Listener] is listening.
    pub fn listening(&self) -> bool {
        self.listening.load(Ordering::Relaxed)
    }

    /// Receives the next [Connection] from the [Listener].
    pub fn accept(&self) -> Option<Connection> {
        self.receiver
            .lock()
            .ok()
            .and_then(|receiver| receiver.try_recv().ok())
    }

    /// Returns the address the [Listener] is bound to.
    pub fn address(&self) -> SocketAddr {
        self.address
    }
}