/*
 *
 *	Adventure Creator
 *	by Chris Burton, 2013-2014
 *	
 *	"EditorZoomArea.cs"
 * 
 *	This script was written by Martin Ecker, and
 *  is freely available at: http://martinecker.com/martincodes/unity-editor-window-zooming/
 * 
 */

using UnityEngine;

namespace AC
{

	public static class RectExtensions
	{

		public static Vector2 TopLeft (this Rect rect)
		{
			return new Vector2(rect.xMin, rect.yMin);
		}


		public static Vector2 BottomLeft (this Rect rect)
		{
			return new Vector2(rect.xMin, rect.yMax);
		}


		public static Vector2 TopRight (this Rect rect)
		{
			return new Vector2(rect.xMax, rect.yMin);
		}


		public static Vector2 BottomRight (this Rect rect)
		{
			return new Vector2(rect.xMax, rect.yMax);
		}


		public static Rect ScaleSizeBy(this Rect rect, float scale)
		{
			return rect.ScaleSizeBy(scale, rect.center);
		}


		public static Rect ScaleSizeBy(this Rect rect, float scale, Vector2 pivotPoint)
		{
			Rect result = rect;
			result.x -= pivotPoint.x;
			result.y -= pivotPoint.y;
			result.xMin *= scale;
			result.xMax *= scale;
			result.yMin *= scale;
			result.yMax *= scale;
			result.x += pivotPoint.x;
			result.y += pivotPoint.y;
			return result;
		}


		public static Rect ScaleSizeBy(this Rect rect, Vector2 scale)
		{
			return rect.ScaleSizeBy(scale, rect.center);
		}


		public static Rect ScaleSizeBy(this Rect rect, Vector2 scale, Vector2 pivotPoint)
		{
			Rect result = rect;
			result.x -= pivotPoint.x;
			result.y -= pivotPoint.y;
			result.xMin *= scale.x;
			result.xMax *= scale.x;
			result.yMin *= scale.y;
			result.yMax *= scale.y;
			result.x += pivotPoint.x;
			result.y += pivotPoint.y;
			return result;
		}

	}


	public class EditorZoomArea
	{

		private const float kEditorWindowTabHeight = 21.0f;
		private static Matrix4x4 _prevGuiMatrix;


		public static Rect Begin(float zoomScale, Rect screenCoordsArea)
		{
			GUI.EndGroup();
			
			Rect clippedArea = screenCoordsArea.ScaleSizeBy(1.0f / zoomScale, screenCoordsArea.TopLeft());
			clippedArea.y += kEditorWindowTabHeight;
			GUI.BeginGroup(clippedArea);
			
			_prevGuiMatrix = GUI.matrix;
			Matrix4x4 translation = Matrix4x4.TRS(clippedArea.TopLeft(), Quaternion.identity, Vector3.one);
			Matrix4x4 scale = Matrix4x4.Scale(new Vector3(zoomScale, zoomScale, 1.0f));
			GUI.matrix = translation * scale * translation.inverse * GUI.matrix;
			
			return clippedArea;
		}

		
		public static void End()
		{
			GUI.matrix = _prevGuiMatrix;
			GUI.EndGroup();
			GUI.BeginGroup(new Rect(0.0f, kEditorWindowTabHeight, Screen.width, Screen.height));
		}

	}

}