package kernel.net;

import haxe.ds.ReadOnlyArray;
using tink.CoreApi;

import kernel.net.Package.NetworkID;
import kernel.peripherals.Peripherals.Peripheral;
import kernel.Log;
import kernel.Timer;
import cc.OS;

using Lambda;
using util.Extender.LambdaExtender;

/**
	Class responsible for everything network related.
	Used to send and recceive packages.
**/
class Net {
	/**
		Depends on: KernelEvents
	**/
	public static var instance:Net;
	public static inline final BRODCAST_PORT:Int = 65533;
	public static inline final MESSAGE_TIMEOUT:Int = 3;
	public static inline final DEFAULT_TTL:Int = 10;

	public final networkID:NetworkID = OS.getComputerID();
	private final responseBus:Map<Int, Callback<Package>> = new Map();
	private final protoHandlers:Map<String, Callback<Package>> = new Map();
	private var interfaces:Array<INetworkInterface>;

	@:allow(kernel.Init)
	private function new() {
		this.interfaces = [for (e in Peripheral.instance.getModems()) e ]; // TODO: is this the way to do it?
		this.interfaces.push(Loopback.instance);

		for (interf in interfaces){
			setupInterf(interf);
		}

		setupPingHandle();
	}

	private function setupPingHandle() {
		this.registerProto('ping', pack -> {
			this.respondTo(pack, pack.data);
		});
	}

	private function setupInterf(interf: INetworkInterface) {
		interf.onMessage.handle(pack -> handle(pack,interf));
		interf.listen(networkID);
		interf.listen(BRODCAST_PORT);
	}

	/**
		Called when a new package comes in.
	**/
	private function handle(pack:Package,interf: INetworkInterface) {
		if (pack.toID == this.networkID || pack.toID == Net.BRODCAST_PORT){
			switch pack.type {
				case Data(_) | DataNoResponse(_):
					// Let a local proccess handle it
					routeToProto(pack);
				case Response:
					// Got a response to a send message. Invoke the callback
					if (responseBus.exists(pack.msgID)) {
						responseBus[pack.msgID].invoke(pack);
					}
				case RouteDiscover(_) | RouteDiscoverResponse(_) | RouteDiscoverUpdate(_):
					// Delegate to Routing
					Routing.instance.handleRoutePackage(pack,interf);
			}
		}else{
			// New message received but its not ment for us. Forward if possible.
			forwardPackage(pack);
		}
	}

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

	/**
		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,
			ttl: Net.DEFAULT_TTL,
		}

		sendRaw(pack);
	}

	private function forwardPackage(pack: Package) {
		if (pack.ttl == 0){
			// Drop package
			return;
		}

		pack.ttl--;

		if (!sendRaw(pack)){
			// Cant forward
		}
	}

	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);
	}

	/**
		Send to package to the localy register handler based on the proto
	**/
	private function routeToProto(pack:Package) {
		var proto = switch pack.type {
			case Data(proto):
				proto;
			case DataNoResponse(proto):
				proto;
			default:
				return;
		}

		if (!protoHandlers.exists(proto)) {
			Log.warn('Trying to route package to proto: $proto but nothing was register');
			return;
		}

		protoHandlers[proto].invoke(pack);
	}

	/**
		Just send the package to the right modem.
		Returns true if message was send
	**/
	private function sendRaw(pack:Package): Bool {
		var route = Routing.instance.getRouteToID(pack.toID);
		if (route == null){
			return false;
		}

		route.interf.send(route.rep,this.networkID,pack);
		return true;
	}

	/**
		Send a message and wait for a response.
	**/
	public function sendAndAwait(dest:NetworkID, 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,
				ttl: Net.DEFAULT_TTL,
			}

			var timeout:Timer = null;

			responseBus[pack.msgID] = ((reponse:Package) -> {
				resolve(reponse);
				if (timeout != null) {
					timeout.cancle();
				}
			});

			timeout = new Timer(MESSAGE_TIMEOUT, () -> {
				responseBus.remove(pack.msgID);
				reject(new Error(InternalError,"Message timeout"));
			});

			if (!sendRaw(pack)){
				reject(new Error("ID unreachable"));
			}

			// No callback link for you
			return null;
		});
	}

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

		protoHandlers[proto] = callback;
	}

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

	/**
		Sends a ping package to the given id. Returns true if there was a response.
	**/
	public function ping(toID: NetworkID): Promise<Bool> {
		return new Promise<Bool>((resolve,reject)->{
			this.sendAndAwait(toID,"ping",null).handle(pack -> {
				switch pack {
					case Success(_):
						resolve(true);
					case Failure(err):
						resolve(false);
				}
			});
			return null;
		});
	}

	public function getActiveProtocols(): ReadOnlyArray<String> {
		var arr = new Array<String>();

		for (proto in protoHandlers.keys()) {
			arr.push(proto);
		}

		return arr;
	}
}