package org.nativescript.widgets;

import android.view.View;

import java.util.WeakHashMap;

/**
 * A class encapsulating the logic of setting an origin point.
 * The origin acts as a pivot point but is relative to the View size,
 * Where 0 is the left or top of the view, 0.5 is at the middle and 1 is right or bottom.
 * Under the hood the pivot point is set but is updated when the View's layout is changed.
 */
public class OriginPoint {
	private static WeakHashMap<View, PivotSetter> layoutListeners;

	public static void setX(View view, float x) {
		getSetter(view).setOriginX(view, x);
	}

	public static void setY(View view, float y) {
		getSetter(view).setOriginY(view, y);
	}

	private static PivotSetter getSetter(View view) {
		PivotSetter setter = null;

		if (layoutListeners == null) {
			layoutListeners = new WeakHashMap<>();
		} else {
			setter = layoutListeners.get(view);
		}

		if (setter == null) {
			setter = new PivotSetter();
			view.addOnLayoutChangeListener(setter);
			layoutListeners.put(view, setter);
		}

		return setter;
	}

	private static class PivotSetter implements View.OnLayoutChangeListener {
		private float originX;
		private float originY;

		public PivotSetter() {
			originX = 0.5f;
			originY = 0.5f;
		}

		public void setOriginX(View view, float x) {
			originX = x;
			updateX(view, view.getWidth());
		}

		public void setOriginY(View view, float y) {
			originY = y;
			updateY(view, view.getHeight());
		}

		public void onLayoutChange(View view, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
			updateX(view, right - left);
			updateY(view, bottom - top);
		}

		private void updateX(View view, int width) {
			view.setPivotX(originX * width);
		}

		private void updateY(View view, int height) {
			view.setPivotY(originY * height);
		}
	}
}