package lib.turtle;

// Check usage of NativeStringTools
// here https://api.haxe.org/lua/NativeStringTools.html
// and here http://lua-users.org/wiki/StringLibraryTutorial
import kernel.turtle.Types.TurtleSlot;
import kernel.turtle.Turtle;
import lua.NativeStringTools;

using tink.CoreApi;

/**
	Save a set of turtle instructions to a string and execute them.
**/
class TurtleInstructionParser {
	public function new() {}

	public function encode(instructions:Array<TurtleInstruction>):String {
		var s = "";

		var times = 0;
		var lastInstruction:TurtleInstruction = null;

		for (inst in instructions) {
			if (inst == lastInstruction) {
				times++;
				continue;
			}

			if (lastInstruction != null) {
				var encoded = encodeInstruction(lastInstruction);
				s = s + '${times + 1}$encoded';
			}

			times = 0;
			lastInstruction = inst;
		}

		var encoded = encodeInstruction(lastInstruction);
		s = s + '${times + 1}$encoded';

		return s;
	}

	private function encodeInstruction(inst:TurtleInstruction):String {
		for (k => v in cmdMap) {
			if (v == inst) {
				return k;
			}
		}

		switch inst {
			case Select(slot):
				return "m" + encodeSlot(slot);
			default:
				return "";
		}

		return "";
	}

	private function encodeSlot(slot:TurtleSlot):String {
		return String.fromCharCode(slot + 97);
	}

	public function parse(instructionsString:String):Array<TurtleInstruction> {
		var rtn:Array<TurtleInstruction> = [];
		var mfunc = NativeStringTools.gmatch(instructionsString, "%d+%D+");

		while (true) {
			var found = mfunc();

			if (found == null) {
				break;
			}

			var times = Std.parseInt(NativeStringTools.match(found, "%d+"));
			var command = NativeStringTools.match(found, "%D+");

			var cmd = cmdMap.get(command);
			if (cmd != null) {
				rtn = rtn.concat([for (i in 0...times) cmd]);
			}

			switch command.charAt(0) {
				case "m": // select
					var slot = parseSlot(command.charAt(1));
					rtn = rtn.concat([for (i in 0...times) Select(slot)]);
			}
		}

		return rtn;
	}

	private static function parseSlot(slot:String):TurtleSlot {
		var slot = slot.charCodeAt(0) - 97;

		if (slot < 0 || slot > Turtle.MAX_SLOTS) {
			// TODO: better error handling
			throw new Error("Invalid slot: " + slot);
		}

		return slot;
	}

	private var cmdMap:Map<String, TurtleInstruction> = [
		"a" => Forward, "b" => Back, "c" => TurnLeft, "d" => TurnRight, "e" => Up, "f" => Down, "g" => Dig(Front), "h" => Dig(Up), "i" => Dig(Down),
		"j" => Place(Front), "k" => Place(Up), "l" => Place(Down),
	];
}