package kernel.net;

using tink.CoreApi;

import kernel.net.Package.NetworkID;
import kernel.peripherals.Peripherals.Peripheral;
import kernel.Log;
import kernel.KernelEvents;
import haxe.Exception;
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 {
	public static var instance:Net;
	public static inline final BRODCAST_PORT:Int = 65533;
	public static inline final MESSAGE_TIMEOUT:Int = 3;

	public final onNewNeigbor:Signal<Int>;

	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 allModems:Array<kernel.peripherals.Modem>;
	private final routingTable:Map<NetworkID, kernel.peripherals.Modem> = new Map();
	private final onNewNeigborTrigger:SignalTrigger<NetworkID> = Signal.trigger();

	@:allow(kernel.Init)
	private function new() {
		onNewNeigbor = onNewNeigborTrigger.asSignal();
		KernelEvents.instance.onModemMessage.handle(params -> {
			var pack:Package = {
				fromID: params.replyChannel,
				toID: params.channel,
				msgID: params.message.msgID,
				type: params.message.type,
				data: params.message.data,
			};

			handelIncomming(pack, params.addr);
		});

		allModems = Peripheral.instance.getModems();

		open();
		discoverNeighbors();
	}

	/**
		Called when a new package comes in.
	**/
	private function handelIncomming(pack:Package, ?addr:String) {
		switch pack.type {
			case Data(_):
				routeToProto(pack);
			case DataNoResponse(_):
				routeToProto(pack);
			case Response:
				if (responseBus.exists(pack.msgID)) {
					responseBus[pack.msgID].invoke(pack);
				}
			case RouteDiscover(_) | RouteDiscoverResponse(_):
				handleRouteDiscover(pack, addr);
		}
	}

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

		return pack;
	}

	/**
		Send out discover packages on all modems.
	**/
	private function discoverNeighbors() {
		for (modem in allModems) {
			var pack = newRoutDiscoverPackage();

			modem.transmit(BRODCAST_PORT, networkID, pack);
		}
	}

	/**
		Handle incomming packages that involve route discovery.
	**/
	private function handleRouteDiscover(pack:Package, addr:String) {
		addRoute(pack.fromID, addr);

		var forward = getAllNeighbors().filter(i -> i == pack.fromID);

		switch pack.type{
			case RouteDiscoverResponse(reachableIDs):
				for (id in reachableIDs) {
					addRoute(id, addr);
				}
				return; // Dont respond to a response
			case RouteDiscover(reachableIDs):
				for (id in reachableIDs) {
					addRoute(id, addr);
				}
			default:
				throw new Error("Expcted RouteDiscover or RouteDiscoverResponse type");
		}

		// Respond to peer
		var response:Package = {
			toID: pack.fromID,
			fromID: networkID,
			msgID: pack.msgID,
			type: RouteDiscoverResponse(forward),
			data: null
		}

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

	/**
		Called when a route to a client has been disoverd.
		Its posible to be called multiple times with the same id but different addr.
	**/
	private function addRoute(toID:Int, addr:String) {
		Log.info("Added new route to " + toID + " via " + addr);
		routingTable.set(toID, allModems.find(item -> item.addr == addr));
		this.onNewNeigborTrigger.trigger(toID);
	}

	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);
	}

	/**
		Send to package to the localy register handler based on the proto
	**/
	private function routeToProto(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].invoke(pack);
	}

	/**
		Just send the package to the right modem.
	**/
	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
			}
		}
	}

	/**
		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
			}

			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"));
			});

			sendRaw(pack);

			// 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);
	}
}