use hyper::{
	Body,
	Request,
	Response,
	Server,
	service::{
		make_service_fn,
		service_fn,
	},
	StatusCode,
};
use structopt::StructOpt;
use tokio::{
	net::UdpSocket,
};

use crate::prelude::*;
use protocol::PeerId;

#[derive (Debug, StructOpt)]
pub struct Opt {
	#[structopt (long)]
	pub (crate) listen_addr: Option <String>,
	#[structopt (long)]
	pub (crate) tcp_listen_port: Option <u16>,
}

pub struct App {
	endpoint: quinn::Endpoint,
	listen_addr: SocketAddr,
	pub (crate) metrics: Arc <RwLock <Metrics>>,
	server_cert: Vec <u8>,
	tcp_listener: Option <udp_over_tcp::server::Listener>,
}

#[derive (Default)]
pub (crate) struct Metrics {
	pub (crate) connected_end_servers: usize,
}

impl App {
	pub async fn new (opt: Opt) -> anyhow::Result <Self> {
		let config = load_config ().await.ok ();
		
		let listen_addr = opt.listen_addr.unwrap_or_else (|| String::from ("0.0.0.0:30380")).parse ()?;
		let (endpoint, server_cert) = make_server_endpoint (listen_addr)?;
		
		let listen_addr = endpoint.local_addr ()?;
		let tcp_port = opt.tcp_listen_port.or (config.map (|cfg| cfg.tcp_listen_port).flatten ());
		
		let tcp_listener = if let Some (tcp_port) = tcp_port {
			let cfg = udp_over_tcp::server::Config {
				tcp_port,
				udp_port: listen_addr.port (),
			};
			
			Some (udp_over_tcp::server::Listener::new (cfg).await?)
		}
		else {
			None
		};
		
		Ok (Self {
			endpoint,
			listen_addr,
			metrics: Default::default (),
			server_cert,
			tcp_listener,
		})
	}
	
	pub fn listen_addr (&self) -> SocketAddr {
		self.listen_addr
	}
	
	pub fn server_cert (&self) -> &[u8] {
		&self.server_cert
	}
	
	pub fn tcp_listen_port (&self) -> anyhow::Result <Option <u16>> {
		match self.tcp_listener.as_ref () {
			None => Ok (None),
			Some (tcp_listener) => Ok (tcp_listener.tcp_port ()?.into ()),
		}
	}
	
	pub async fn run (self) -> anyhow::Result <()> {
		let Self {
			endpoint,
			listen_addr,
			metrics,
			server_cert,
			tcp_listener,
		} = self;
		
		let mut relay_state = RelayState::default ();
		relay_state.metrics = metrics;
		if let Err (e) = relay_state.reload_config ().await {
			error! ("{:?}", e);
		}
		let relay_state = Arc::new (relay_state);
		
		let make_svc = {
			let relay_state = Arc::clone (&relay_state);
			make_service_fn (move |_conn| {
				let relay_state = Arc::clone (&relay_state);
				
				async move {
					Ok::<_, String> (service_fn (move |req| {
						let relay_state = Arc::clone (&relay_state);
						
						handle_http (req, relay_state)
					}))
				}
			})
		};
		
		let http_addr = SocketAddr::from (([0, 0, 0, 0], 4004));
		let http_server = Server::bind (&http_addr);
		
		let _task_reload_config = {
			let relay_state = Arc::clone (&relay_state);
			tokio::spawn (async move {
				let mut interval = tokio::time::interval (std::time::Duration::from_secs (60));
				interval.set_missed_tick_behavior (tokio::time::MissedTickBehavior::Skip);
				
				loop {
					interval.tick ().await;
					
					relay_state.reload_config ().await.ok ();
				}
			})
		};
		
		let task_quic_server = {
			let relay_state = Arc::clone (&relay_state);
			tokio::spawn (async move {
				while let Some (conn) = endpoint.accept ().await {
					let relay_state = Arc::clone (&relay_state);
					
					// Each new peer QUIC connection gets its own task
					tokio::spawn (async move {
						let active = relay_state.stats.quic.connect ();
						
						debug! ("QUIC connections: {}", active);
						
						match handle_quic_connection (Arc::clone (&relay_state), conn).await {
							Ok (_) => (),
							Err (e) => warn! ("handle_quic_connection `{:?}`", e),
						}
						
						let active = relay_state.stats.quic.disconnect ();
						debug! ("QUIC connections: {}", active);
					});
				}
				
				Ok::<_, anyhow::Error> (())
			})
		};
		
		let task_direc_server = {
			let relay_state = Arc::clone (&relay_state);
			
			tokio::spawn (async move {
				let sock = UdpSocket::bind("0.0.0.0:30379").await?;
				let mut buf = [0; 2048];
				loop {
					let (len, addr) = sock.recv_from (&mut buf).await?;
					debug! ("{:?} bytes received from {:?}", len, addr);
					
					let packet = Vec::from_iter ((&buf [0..len]).into_iter ().map (|x| *x));
					
					{
						let mut direc_cookies = relay_state.direc_cookies.lock ().await;
						
						if let Some (direc_state) = direc_cookies.remove (&packet) {
							debug! ("Got PTTH_DIREC cookie for {}", direc_state.p2_id);
							direc_state.p2_addr.send (addr).ok ();
						}
						else {
							debug! ("UDP packet didn't match any PTTH_DIREC cookie");
						}
					}
				}
				
				Ok::<_, anyhow::Error> (())
			})
		};
		
		let task_http_server = tokio::spawn (async move {
			http_server.serve (make_svc).await?;
			Ok::<_, anyhow::Error> (())
		});
		
		debug! ("Serving HTTP on {:?}", http_addr);
		
		if let Some (tcp_listener) = tcp_listener {
			tokio::spawn (async move {
				if let Err (e) = tcp_listener.run ().await {
					eprintln! ("udp_over_tcp::server::main exited with err {:?}", e);
				}
				
				Ok::<_, anyhow::Error> (())
			});
		}
		
		{
			let config = relay_state.config.load ();
			dbg! (&config.webhook_url);
			if let Some (webhook_url) = config.webhook_url.clone () {
				let j = json! ({
					"text": "Booting up",
				}).to_string ();
				let http_client = relay_state.http_client.clone ();
				tokio::spawn (async move {
					http_client.post (webhook_url).body (j).send ().await
				});
			}
		}
		
		tokio::select! {
			_val = task_quic_server => {
				eprintln! ("QUIC relay server exited, exiting");
			},
			_val = task_http_server => {
				eprintln! ("HTTP server exited, exiting");
			},
			_val = task_direc_server => {
				eprintln! ("PTTH_DIREC server exited, exiting");
			},
		}
		
		Ok (())
	}
}

async fn handle_http (_req: Request <Body>, relay_state: Arc <RelayState>)
-> anyhow::Result <Response <Body>>
{
	let debug_string;
	{
		let p4_server_proxies = relay_state.p4_server_proxies.lock ().await;
		
		debug_string = format! ("{:#?}\n", p4_server_proxies.keys ().collect::<Vec<_>> ());
	}
	
	let resp = Response::builder ()
	.status (StatusCode::OK)
	.header ("content-type", "text/plain")
	.body (Body::from (debug_string))?;
	
	Ok (resp)
}

#[derive (Default)]
struct RelayState {
	config: arc_swap::ArcSwap <Config>,
	p4_server_proxies: Mutex <HashMap <PeerId, P4State>>,
	direc_cookies: Mutex <HashMap <Vec <u8>, DirecState>>,
	metrics: Arc <RwLock <Metrics>>,
	stats: Stats,
	http_client: reqwest::Client,
}

#[derive (Default)]
struct Config {
	ip_nicknames: BTreeMap <[u8; 4], String>,
	tcp_listen_port: Option <u16>,
	webhook_url: Option <String>,
}

impl From <ConfigFile> for Config {
	fn from (x: ConfigFile) -> Self {
		Self {
			ip_nicknames: x.ip_nicknames.into_iter ().collect (),
			tcp_listen_port: x.tcp_listen_port,
			webhook_url: x.webhook_url,
		}
	}
}

#[derive (Deserialize)]
struct ConfigFile {
	ip_nicknames: Vec <([u8; 4], String)>,
	tcp_listen_port: Option <u16>,
	webhook_url: Option <String>,
}

struct DirecState {
	start_time: Instant,
	p2_id: PeerId,
	p2_addr: tokio::sync::oneshot::Sender <SocketAddr>,
}

#[derive (Default)]
struct Stats {
	quic: ConnectEvents,
}

#[derive (Default)]
struct ConnectEvents {
	connects: AtomicU64,
	disconnects: AtomicU64,
}

impl ConnectEvents {
	fn connect (&self) -> u64 {
		let connects = self.connects.fetch_add (1, Ordering::Relaxed) + 1;
		let disconnects = self.disconnects.load (Ordering::Relaxed);
		connects - disconnects
	}
	
	fn disconnect (&self) -> u64 {
		let disconnects = self.disconnects.fetch_add (1, Ordering::Relaxed) + 1;
		let connects = self.connects.load (Ordering::Relaxed);
		connects - disconnects
	}
	
	fn _active (&self) -> u64 {
		let connects = self.connects.load (Ordering::Relaxed);
		let disconnects = self.disconnects.load (Ordering::Relaxed);
		connects - disconnects
	}
}

struct P4State {
	req_channel: mpsc::Sender <RequestP2ToP4>,
}

async fn load_config () -> anyhow::Result <ConfigFile>
{
	let s = tokio::fs::read_to_string ("config/ptth_quic_relay_server.json").await?;
	let cfg: ConfigFile = serde_json::from_str (&s)?;
	Ok (cfg)
}

impl RelayState {
	async fn reload_config (&self) -> anyhow::Result <()> {
		let config = load_config ().await?;
		let config = Arc::new (Config::from (config));
		
		self.config.store (config);
		
		Ok (())
	}
}

struct RequestP2ToP4 {
	client_send: quinn::SendStream,
	client_recv: quinn::RecvStream,
	client_id: String,
}

struct PtthNewConnection {
	client_send: quinn::SendStream,
	client_recv: quinn::RecvStream,
	server_send: quinn::SendStream,
	server_recv: quinn::RecvStream,
}

struct PtthConnection {
	uplink_task: JoinHandle <anyhow::Result <()>>,
	downlink_task: JoinHandle <anyhow::Result <()>>,
}

impl PtthNewConnection {
	fn build (self) -> PtthConnection {
		let Self {
			mut client_send,
			mut client_recv,
			mut server_send,
			mut server_recv,
		} = self;
		
		let uplink_task = tokio::spawn (async move {
			// Uplink - Client to end server
			
			let mut buf = vec! [0u8; 65_536];
			while let Some (bytes_read) = client_recv.read (&mut buf).await? {
				if bytes_read == 0 {
					break;
				}
				let buf_slice = &buf [0..bytes_read];
				trace! ("Uplink relaying {} bytes", bytes_read);
				server_send.write_all (buf_slice).await?;
			}
			
			trace! ("Uplink closed");
			
			Ok::<_, anyhow::Error> (())
		});
		
		let downlink_task = tokio::spawn (async move {
			// Downlink - End server to client
			
			let mut buf = vec! [0u8; 65_536];
			while let Some (bytes_read) = server_recv.read (&mut buf).await? {
				let buf_slice = &buf [0..bytes_read];
				trace! ("Downlink relaying {} bytes", bytes_read);
				client_send.write_all (buf_slice).await?;
			}
			
			trace! ("Downlink closed");
			
			Ok::<_, anyhow::Error> (())
		});
		
		PtthConnection {
			uplink_task,
			downlink_task,
		}
	}
}

async fn handle_quic_connection (
	relay_state: Arc <RelayState>,
	conn: quinn::Connecting,
) -> anyhow::Result <()> 
{
	let id = Ulid::generate ();
	
	let config = relay_state.config.load ();
	
	let remote_addr = conn.remote_address ();
	let ip_nickname = match remote_addr {
		SocketAddr::V4 (x) => {
			let ip = x.ip ().octets ();
			
			match config.ip_nicknames.get (&ip) {
				Some (nick) => nick.as_str (),
				_ => "Unknown",
			}
		},
		_ => "Unknown, not IPv4",
	};
	
	debug! ("EHG7NVUD Incoming QUIC connection {} from {:?} ({})", id, remote_addr, ip_nickname);
	
	if let Some (webhook_url) = config.webhook_url.clone () {
		let j = json! ({
			"text": format! ("Incoming QUIC connection from {:?} ({})", remote_addr, ip_nickname),
		}).to_string ();
		let http_client = relay_state.http_client.clone ();
		tokio::spawn (async move {
			http_client.post (webhook_url).body (j).send ().await
		});
	}
	
	let conn = conn.await?;
	
	// Everyone who connects must identify themselves with the first
	// bi stream
	// TODO: Timeout
	
	let (mut send, mut recv) = conn.accept_bi ().await?;
	
	let peer = protocol::p3_accept_peer (&mut recv).await?;
	
	match peer {
		protocol::P3Peer::P2ClientProxy (peer) => {
			trace! ("H36JTVE5 Handling connection {} as P2 client", id);
			// TODO: Check authorization for P2 peers
			
			protocol::p3_authorize_p2_peer (&mut send).await?;
			handle_p2_connection (relay_state, conn, peer).await?;
		},
		protocol::P3Peer::P4ServerProxy (peer) => {
			trace! ("LRHUKB7K Handling connection {} as P4 end server", id);
			// TODO: Check authorization for P4 peers
			
			protocol::p3_authorize_p4_peer (&mut send).await?;
			let metrics = Arc::clone (&relay_state.metrics);
			
			{
				let mut m = metrics.write ().await;
				m.connected_end_servers += 1;
			}
			handle_p4_connection (relay_state, conn, peer).await?;
			{
				let mut m = metrics.write ().await;
				m.connected_end_servers -= 1;
			}
		},
	}
	
	Ok::<_, anyhow::Error> (())
}

async fn handle_p2_connection (
	relay_state: Arc <RelayState>,
	conn: quinn::Connection,
	peer: protocol::P2ClientProxy,
) -> anyhow::Result <()>
{
	let client_id = peer.id;
	
	while let Ok ((send, mut recv)) = conn.accept_bi ().await {
		let relay_state = Arc::clone (&relay_state);
		let client_id = client_id.clone ();
		
		tokio::spawn (async move {
			debug! ("Request started for P2");
			
			match protocol::p3_accept_p2_stream (&mut recv).await? {
				protocol::P2ToP3Stream::ConnectP2ToP4 {
					server_id,
				} => {
					handle_request_p2_to_p4 (
						relay_state, 
						client_id, 
						server_id, 
						send, 
						recv
					).await?
				},
				protocol::P2ToP3Stream::DirecP2ToP4 {
					server_id,
					cookie,
				} => {
					handle_direc_p2_to_p4 (
						relay_state, 
						client_id, 
						server_id,
						cookie,
						send, 
						recv
					).await?
				},
			}
			
			debug! ("Request ended for P2");
			
			Ok::<_, anyhow::Error> (())
		});
	}
	
	debug! ("P2 {} disconnected", client_id);
	Ok (())
}

async fn handle_request_p2_to_p4 (
	relay_state: Arc <RelayState>,
	client_id: String,
	server_id: PeerId,
	mut client_send: quinn::SendStream,
	client_recv: quinn::RecvStream,
) -> anyhow::Result <()>
{
	trace! ("P2 {} wants to connect to P4 {}", client_id, server_id);
	
	// TODO: Check authorization for P2 to connect to P4
	
	protocol::p3_authorize_p2_to_p4_connection (&mut client_send).await?;
	
	{
		let p4_server_proxies = relay_state.p4_server_proxies.lock ().await;
		match p4_server_proxies.get (&server_id) {
			Some (p4_state) => {
				p4_state.req_channel.send (RequestP2ToP4 {
					client_send,
					client_recv,
					client_id,
				}).await.map_err (|_| anyhow::anyhow! ("Can't send request to P4 server"))?;
			},
			None => warn! ("That server isn't connected"),
		}
	}
				
	Ok (())
}

async fn handle_direc_p2_to_p4 (
	relay_state: Arc <RelayState>,
	client_id: String,
	server_id: PeerId,
	cookie: Vec <u8>,
	mut client_send: quinn::SendStream,
	client_recv: quinn::RecvStream,
) -> anyhow::Result <()>
{
	debug! ("P2 {} wants a P2P connection to P4 {}", client_id, server_id);
	
	// TODO: Check authorization
	
	protocol::p3_authorize_p2_to_p4_direc (&mut client_send).await?;
	
	let (tx, rx) = tokio::sync::oneshot::channel ();
	
	{
		let mut direc_cookies = relay_state.direc_cookies.lock ().await;
		direc_cookies.insert (cookie, DirecState {
			start_time: Instant::now (),
			p2_id: client_id.clone (),
			p2_addr: tx,
		});
	}
	
	debug! ("Waiting to learn P2's WAN address...");
	
	let wan_addr = rx.await?;
	
	debug! ("And that WAN address is {}", wan_addr);
	
	Ok (())
}

async fn handle_p4_connection (
	relay_state: Arc <RelayState>,
	connection: quinn::Connection,
	peer: protocol::P4ServerProxy,
) -> anyhow::Result <()>
{
	let server_id = peer.id;
	let (tx, mut rx) = mpsc::channel (2);
	
	let p4_state = P4State {
		req_channel: tx,
	};
	
	{
		let mut p4_server_proxies = relay_state.p4_server_proxies.lock ().await;
		p4_server_proxies.insert (server_id.clone (), p4_state);
	}
	
	while let Some (req) = rx.recv ().await {
		let connection = connection.clone ();
		let server_id = server_id.clone ();
		
		tokio::spawn (async move {
			let RequestP2ToP4 {
				client_send,
				client_recv,
				client_id,
			} = req;
			
			debug! ("P4 {} got a request from P2 {}", server_id, client_id);
			
			let (server_send, server_recv) = protocol::p3_connect_p2_to_p4 (&connection, &client_id).await?;
			
			trace! ("Relaying bytes...");
			
			let ptth_conn = PtthNewConnection {
				client_send,
				client_recv,
				server_send,
				server_recv,
			}.build ();
			
			ptth_conn.uplink_task.await??;
			ptth_conn.downlink_task.await??;
			
			debug! ("Request ended for P4");
			Ok::<_, anyhow::Error> (())
		});
	}
	
	debug! ("P4 {} disconnected", server_id);
	Ok (())
}