package kernel.ui;

import kernel.log.Log;
import lib.Pos;
import lib.Vec.Vec2;
import lib.Color;

using tink.CoreApi;

/**
	Normal TermWriteable but without storing the the state in a buffer wehen disabled.
	When enabled or the screen size changes the render function is called.
	The render function is only called when needed.
	You can also request a re-render by calling `requestRender`.
**/
class StatelessVirtualTermWriter implements VirtualTermWriter {
	public var onResize(default, null):Signal<Vec2<Int>>;

	private var onResizeTrigger:SignalTrigger<Vec2<Int>> = Signal.trigger();
	private var target:TermWriteable;
	private var enabled:Bool = false;
	private var renderFunc:Null<Void->Void> = null;
	private var renderRequested:Bool = false;
	private var onResizeLink:CallbackLink;

	@:allow(kernel.ui)
	private function new(?target:TermWriteable) {
		onResize = onResizeTrigger.asSignal();
		setTarget(target);
	}

	public function setRenderFunc(func:(Void->Void)) {
		this.renderFunc = func;
	}

	public function requestRender() {
		if (renderFunc == null) {
			Log.warn("Render requested, but no render function set");
			return;
		}

		if (enabled) {
			target.reset();
			renderFunc();
			renderRequested = false;
		} else {
			renderRequested = true;
		}
	}

	//
	// VirtualTermWriter implementation
	//

	public function enable() {
		if (target == null) {
			return;
		}

		enabled = true;

		if (renderFunc != null) {
			renderFunc();
		}

		renderRequested = false;
	}

	public function disable() {
		enabled = false;
	}

	public function setTarget(newTarget:TermWriteable) {
		if (newTarget == null) {
			return;
		}

		if (target != null) {
			onResizeLink.cancel();
		}

		onResizeLink = newTarget.onResize.handle((size) -> {
			requestRender();
			onResizeTrigger.trigger(size);
		});

		target = newTarget;

		target.reset();
	}

	public function isEnabled():Bool {
		return enabled;
	}

	//
	// TermWriteable implementation
	//
	// Some functions return defualt values if the target is not set. This should not be an issue since
	// the render func is only called when the target is set.
	//

	public inline function write(text:String) {
		if (enabled)
			target.write(text);
	}

	public inline function scroll(y:Int) {
		if (enabled)
			target.scroll(y);
	}

	public inline function getCursorPos():Pos {
		return enabled ? target.getCursorPos() : new Pos({x: 0, y: 0});
	}

	public inline function setCursorPos(x:Int, y:Int) {
		if (enabled)
			target.setCursorPos(x, y);
	}

	public inline function getCursorBlink():Bool {
		return enabled ? target.getCursorBlink() : false;
	}

	public inline function setCursorBlink(blink:Bool) {
		if (enabled)
			target.setCursorBlink(blink);
	}

	public inline function getSize():Vec2<Int> {
		return enabled ? target.getSize() : {x: 0, y: 0};
	}

	public inline function clear() {
		if (enabled)
			target.clear();
	}

	public inline function clearLine() {
		if (enabled)
			target.clearLine();
	}

	public inline function getTextColor():Color {
		return enabled ? target.getTextColor() : Color.White;
	}

	public inline function setTextColor(color:Color) {
		if (enabled)
			target.setTextColor(color);
	}

	public inline function getBackgroundColor():Color {
		return enabled ? target.getBackgroundColor() : Color.Black;
	}

	public inline function setBackgroundColor(color:Color) {
		if (enabled)
			target.setBackgroundColor(color);
	}

	public inline function isColor():Bool {
		return enabled ? target.isColor() : false;
	}

	public inline function reset() {
		if (enabled)
			target.reset();
	}
}