/*
 * Copyright (C)2005-2019 Haxe Foundation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

package cpp.net;

import cpp.vm.Thread;
import cpp.net.Poll;
import cpp.vm.Lock;

private typedef ThreadInfos = {
	var id:Int;
	var t:Thread;
	var p:Poll;
	var socks:Array<sys.net.Socket>;
}

private typedef ClientInfos<Client> = {
	var client:Client;
	var sock:sys.net.Socket;
	var thread:ThreadInfos;
	var buf:haxe.io.Bytes;
	var bufpos:Int;
}

/**
	The ThreadServer can be used to easily create a multithreaded server where each thread polls multiple connections.
	To use it, at a minimum you must override or rebind clientConnected, readClientMessage, and clientMessage and you must define your Client and Message.
**/
class ThreadServer<Client, Message> {
	var threads:Array<ThreadInfos>;
	var sock:sys.net.Socket;
	var worker:Thread;
	var timer:Thread;

	/**
		Number of total connections the server will accept.
	**/
	public var listen:Int;

	/**
		Number of server threads.
	**/
	public var nthreads:Int;

	/**
		Polling timeout.
	**/
	public var connectLag:Float;

	/**
		Stream to send error messages.
	**/
	public var errorOutput:haxe.io.Output;

	/**
		Space allocated to buffers when they are created.
	**/
	public var initialBufferSize:Int;

	/**
		Maximum size of buffered data read from a socket. An exception is thrown if the buffer exceeds this value.
	**/
	public var maxBufferSize:Int;

	/**
		Minimum message size.
	**/
	public var messageHeaderSize:Int;

	/**
		Time between calls to update.
	**/
	public var updateTime:Float;

	/**
		The most sockets a thread will handle.
	**/
	public var maxSockPerThread:Int;

	/**
		Creates a ThreadServer.
	**/
	public function new() {
		threads = new Array();
		nthreads = if (Sys.systemName() == "Windows") 150 else 10;
		messageHeaderSize = 1;
		listen = 10;
		connectLag = 0.5;
		errorOutput = Sys.stderr();
		initialBufferSize = (1 << 10);
		maxBufferSize = (1 << 16);
		maxSockPerThread = 64;
		updateTime = 1;
	}

	function runThread(t) {
		while (true) {
			try {
				loopThread(t);
			} catch (e:Dynamic) {
				logError(e);
			}
		}
	}

	function readClientData(c:ClientInfos<Client>) {
		var available = c.buf.length - c.bufpos;
		if (available == 0) {
			var newsize = c.buf.length * 2;
			if (newsize > maxBufferSize) {
				newsize = maxBufferSize;
				if (c.buf.length == maxBufferSize)
					throw "Max buffer size reached";
			}
			var newbuf = haxe.io.Bytes.alloc(newsize);
			newbuf.blit(0, c.buf, 0, c.bufpos);
			c.buf = newbuf;
			available = newsize - c.bufpos;
		}
		var bytes = c.sock.input.readBytes(c.buf, c.bufpos, available);
		var pos = 0;
		var len = c.bufpos + bytes;
		while (len >= messageHeaderSize) {
			var m = readClientMessage(c.client, c.buf, pos, len);
			if (m == null)
				break;
			pos += m.bytes;
			len -= m.bytes;
			work(clientMessage.bind(c.client, m.msg));
		}
		if (pos > 0)
			c.buf.blit(0, c.buf, pos, len);
		c.bufpos = len;
	}

	function loopThread(t:ThreadInfos) {
		if (t.socks.length > 0)
			for (s in t.p.poll(t.socks, connectLag)) {
				var infos:ClientInfos<Client> = s.custom;
				try {
					readClientData(infos);
				} catch (e:Dynamic) {
					t.socks.remove(s);
					if (!Std.isOfType(e, haxe.io.Eof) && !Std.isOfType(e, haxe.io.Error))
						logError(e);
					work(doClientDisconnected.bind(s, infos.client));
				}
			}
		while (true) {
			var m:{s:sys.net.Socket, cnx:Bool} = Thread.readMessage(t.socks.length == 0);
			if (m == null)
				break;
			if (m.cnx)
				t.socks.push(m.s);
			else if (t.socks.remove(m.s)) {
				var infos:ClientInfos<Client> = m.s.custom;
				work(doClientDisconnected.bind(m.s, infos.client));
			}
		}
	}

	function doClientDisconnected(s:sys.net.Socket, c) {
		try
			s.close()
		catch (e:Dynamic) {};
		clientDisconnected(c);
	}

	function runWorker() {
		while (true) {
			var f = Thread.readMessage(true);
			try {
				f();
			} catch (e:Dynamic) {
				logError(e);
			}
			try {
				afterEvent();
			} catch (e:Dynamic) {
				logError(e);
			}
		}
	}

	/**
		Internally used to delegate something to the worker thread.
	**/
	public function work(f:Void->Void) {
		worker.sendMessage(f);
	}

	function logError(e:Dynamic) {
		var stack = haxe.CallStack.exceptionStack();
		if (Thread.current() == worker)
			onError(e, stack);
		else
			work(onError.bind(e, stack));
	}

	function addClient(sock:sys.net.Socket) {
		var start = Std.random(nthreads);
		for (i in 0...nthreads) {
			var t = threads[(start + i) % nthreads];
			if (t.socks.length < maxSockPerThread) {
				var infos:ClientInfos<Client> = {
					thread: t,
					client: clientConnected(sock),
					sock: sock,
					buf: haxe.io.Bytes.alloc(initialBufferSize),
					bufpos: 0,
				};
				sock.custom = infos;
				infos.thread.t.sendMessage({s: sock, cnx: true});
				return;
			}
		}
		refuseClient(sock);
	}

	function refuseClient(sock:sys.net.Socket) {
		// we have reached maximum number of active clients
		sock.close();
	}

	function runTimer() {
		var l = new Lock();
		while (true) {
			l.wait(updateTime);
			work(update);
		}
	}

	function init() {
		worker = Thread.create(runWorker);
		timer = Thread.create(runTimer);
		for (i in 0...nthreads) {
			var t = {
				id: i,
				t: null,
				socks: new Array(),
				p: new Poll(maxSockPerThread),
			};
			threads.push(t);
			t.t = Thread.create(runThread.bind(t));
		}
	}

	/**
		Called when the server gets a new connection.
	**/
	public function addSocket(s:sys.net.Socket) {
		s.setBlocking(false);
		work(addClient.bind(s));
	}

	/**
		Start the server at the specified host and port.
	**/
	public function run(host, port) {
		sock = new sys.net.Socket();
		sock.bind(new sys.net.Host(host), port);
		sock.listen(listen);
		init();
		while (true) {
			try {
				addSocket(sock.accept());
			} catch (e:Dynamic) {
				logError(e);
			}
		}
	}

	/**
		Send data to a client.
	**/
	public function sendData(s:sys.net.Socket, data:String) {
		try {
			s.write(data);
		} catch (e:Dynamic) {
			stopClient(s);
		}
	}

	/**
		Shutdown a client's connection and remove them from the server.
	**/
	public function stopClient(s:sys.net.Socket) {
		var infos:ClientInfos<Client> = s.custom;
		try
			s.shutdown(true, true)
		catch (e:Dynamic) {};
		infos.thread.t.sendMessage({s: s, cnx: false});
	}

	// --- CUSTOMIZABLE API ---

	/**
		Called when an error has ocurred.
	**/
	public dynamic function onError(e:Dynamic, stack) {
		var estr = try Std.string(e) catch (e2:Dynamic) "???" + try "[" + Std.string(e2) + "]" catch (e:Dynamic) "";
		errorOutput.writeString(estr + "\n" + haxe.CallStack.toString(stack));
		errorOutput.flush();
	}

	/**
		Called when a client connects. Returns a client object.
	**/
	public dynamic function clientConnected(s:sys.net.Socket):Client {
		return null;
	}

	/**
		Called when a client disconnects or an error forces the connection to close.
	**/
	public dynamic function clientDisconnected(c:Client) {}

	/**
		Called when data has been read from a socket. This method should try to extract a message from the buffer.
		The available data resides in buf, starts at pos, and is len bytes wide. Return the new message and the number of bytes read from the buffer.
		If no message could be read, return null.
	**/
	public dynamic function readClientMessage(c:Client, buf:haxe.io.Bytes, pos:Int, len:Int):{msg:Message, bytes:Int} {
		return {
			msg: null,
			bytes: len,
		};
	}

	/**
		Called when a message has been recieved. Message handling code should go here.
	**/
	public dynamic function clientMessage(c:Client, msg:Message) {}

	/**
		This method is called periodically. It can be used to do server maintenance.
	**/
	public dynamic function update() {}

	/**
		Called after a client connects, disconnects, a message is received, or an update is performed.
	**/
	public dynamic function afterEvent() {}
}