package kernel.net;

import kernel.peripherals.Peripherals.Peripheral;
import kernel.Log;
import kernel.KernelEvents;
import haxe.Exception;
import util.Promise;
import kernel.Timer;
import util.EventBus;
import cc.OS;

using Lambda;
using util.Extender.LambdaExtender;

/**
	Class responsible for everything network related.
	Used to send and recceive packages.
**/
class Net{
	public static var instance:Net;

	@:allow(kernel.Init)
	private function new () {
		KernelEvents.instance.on("modem_message",(params)->{
			var pack = Package.fromEvent(params);
			handelIncomming(pack,params[1]);
		});
		allModems = Peripheral.instance.getModems();
		open();
		discoverNeighbors();
	}
	
	public static inline final BRODCAST_PORT:Int = 65533;
	public static inline final MESSAGE_TIMEOUT:Int = 3;

	private var networkID:Int = OS.getComputerID();
	private var responseBus: util.EventBus<Package> = new EventBus();
	private var protoHandlers: Map<String,Package -> Void> = new Map();
	private var allModems:Array<kernel.peripherals.Modem>;
	private var routingTable: Map<Int,kernel.peripherals.Modem> = new Map();

	private function handelIncomming(pack: Package, ?addr:String) {
		switch pack.type {
			case Data(_):
				routeTo(pack);
			case DataNoResponse(_):
				routeTo(pack);
			case Response | RouteDiscoverResponse:
				responseBus.emit(Std.string(pack.msgID),pack);
			case RouteDiscover:
				handleRoute(pack,addr);
				
		}
	}

	private function newRoutPackage(): Package {
		var pack: Package = {
			type: RouteDiscover,
			toID: BRODCAST_PORT,
			msgID: generateMessageID(),
			fromID: networkID,
			data: null,
		}

		return pack;
	}

	private function discoverNeighbors() {
		for (modem in allModems) {
			var pack = newRoutPackage();

			var timeout: Timer = null;
			var responeListner = responseBus.on(Std.string(pack.msgID),pack -> {
				addRoute(pack.fromID,modem.addr);
			});

			timeout = new Timer(MESSAGE_TIMEOUT,() -> {
				responseBus.removeListner(responeListner);
			});

			modem.transmit(BRODCAST_PORT,OS.getComputerID(),pack);
		}
	}

	private function handleRoute(pack: Package, addr: String) {
		addRoute(pack.fromID,addr);
		
		// Respond to peer
		var response: Package = {
			toID: pack.fromID,
			fromID: OS.getComputerID(),
			msgID: pack.msgID,
			type: RouteDiscoverResponse,
			data: null
		}

		for (reponseModem in allModems.filter(m -> m.addr == addr)) {
			reponseModem.transmit(pack.fromID,networkID,response);
		}
	}

	private function addRoute(toID: Int,addr: String) {
		Log.debug("Added new route to "+toID+" via "+addr);
		routingTable.set(toID,allModems.find(item -> item.addr == addr));
	}

	public function getAllNeighbors(): Array<Int> {
		return routingTable.mapi((index, item) -> index);
	}

	private function generateMessageID(): Int {
		return Std.random(2147483647); // TODO: better uniqe number
	}

	/**
		Open all wireless and wired modem.
	**/
	private function open() {
		for (m in allModems) {
			m.open(networkID);
			m.open(BRODCAST_PORT);
		}
	}

	/**
		Send a message. Dont care if its reaches its destination nor it has a response.
	**/
	public function sendAndForget(dest:Int,proto:String,data: Dynamic){

		var pack: Package = {
			toID: dest,
			fromID: networkID,
			msgID: generateMessageID(),
			type: DataNoResponse(proto),
			data: data
		}

		sendRaw(pack);
	}

	public function respondTo(pack: Package,data: Dynamic) {
		if (pack.type.match(DataNoResponse(_))){
			Log.warn("Responed to a no response package. Ignoring");
			return;
		}

		var response = pack.createResponse(data);

		sendRaw(response);
	}

	private function routeTo(pack: Package) {
		var proto: String = switch pack.type {
			case Data(proto):
				proto;
			case DataNoResponse(proto):
				proto;
			case _:
				return;
		}

		if (!protoHandlers.exists(proto) && protoHandlers[proto] != null){
			return;
		}

		protoHandlers[proto](pack);
	}

	private function sendRaw(pack: Package){

		if (pack.toID == networkID){
			// Loopback
			handelIncomming(pack);
		}else{
			if (routingTable.exists(pack.toID)){
				routingTable[pack.toID].transmit(pack.toID,pack.fromID,pack);
			}else{
				// Route not found
				// TODO: forward package or report not reachable
			}
		}
	}

	public function sendAndAwait(dest: Int,proto:String,data: Dynamic): Promise<Package> {
		return new Promise<Package>((resolve, reject) -> {
			var pack: Package = {
				toID: dest,
				fromID: networkID,
				msgID: generateMessageID(),
				type: Data(proto),
				data: data
			}
	
			var timeout: Timer = null;
			var responeListner = responseBus.once(Std.string(pack.msgID),p -> {
				resolve(p);
				if (timeout != null){
					timeout.cancle();
				}
			});
			
			timeout = new Timer(MESSAGE_TIMEOUT,() -> {
				responseBus.removeListner(responeListner);
				reject(new Exception("Timeout"));
			});
	
			sendRaw(pack);
		});
	}

	public function registerProto(proto: String,cb: Package -> Void) {
		if (protoHandlers.exists(proto)){
			// Failed. Handler already exist.
			// TODO: return error
			return;
		}

		protoHandlers[proto] = cb;
	}

	public function removeProto(proto: String) {
		protoHandlers.remove(proto);
	}
}