#region Copyright & License Information
/*
 * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation. For more information,
 * see COPYING.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using OpenRA.FileFormats;
using OpenRA.FileFormats.Graphics;

namespace OpenRA.Graphics
{
	public class VoxelRenderProxy
	{
		public readonly Sprite Sprite;
		public readonly Sprite ShadowSprite;
		public readonly float ShadowDirection;
		public readonly float2[] ProjectedShadowBounds;

		public VoxelRenderProxy(Sprite sprite, Sprite shadowSprite, float2[] projectedShadowBounds, float shadowDirection)
		{
			Sprite = sprite;
			ShadowSprite = shadowSprite;
			ProjectedShadowBounds = projectedShadowBounds;
			ShadowDirection = shadowDirection;
		}
	}

	public class VoxelRenderer
	{
		Renderer renderer;
		IShader shader;

		SheetBuilder sheetBuilder;
		Dictionary<Sheet, IFrameBuffer> mappedBuffers;
		Stack<KeyValuePair<Sheet, IFrameBuffer>> unmappedBuffers;
		List<Pair<Sheet, Action>> doRender;

		// Static constants
		static readonly float[] shadowDiffuse = new float[] {0,0,0};
		static readonly float[] shadowAmbient = new float[] {1,1,1};
		static readonly float2 spritePadding = new float2(2, 2);
		static readonly float[] zeroVector = new float[] {0,0,0,1};
		static readonly float[] zVector = new float[] {0,0,1,1};
		static readonly float[] flipMtx = Util.ScaleMatrix(1, -1, 1);
		static readonly float[] shadowScaleFlipMtx = Util.ScaleMatrix(2, -2, 2);

		public VoxelRenderer(Renderer renderer, IShader shader)
		{
			this.renderer = renderer;
			this.shader = shader;

			mappedBuffers = new Dictionary<Sheet, IFrameBuffer>();
			unmappedBuffers = new Stack<KeyValuePair<Sheet, IFrameBuffer>>();
			doRender = new List<Pair<Sheet, Action>>();
		}

		public void SetPalette(ITexture palette)
		{
			shader.SetTexture("Palette", palette);
		}

		public void SetViewportParams(Size screen, float zoom, float2 scroll)
		{
			var a = 2f / Renderer.SheetSize;
			var view = new float[]
			{
				a, 0, 0, 0,
				0, -a, 0, 0,
				0, 0, -2*a, 0,
				-1, 1, 0, 1
			};

			shader.SetMatrix("View", view);
		}

		public VoxelRenderProxy RenderAsync(WorldRenderer wr, IEnumerable<VoxelAnimation> voxels, WRot camera, float scale,
		                                    float[] groundNormal, WRot lightSource, float[] lightAmbientColor, float[] lightDiffuseColor,
		                                    PaletteReference color, PaletteReference normals, PaletteReference shadowPalette)
		{
			// Correct for inverted y-axis
			var scaleTransform = Util.ScaleMatrix(scale, scale, scale);

			// Correct for bogus light source definition
			var lightYaw = Util.MakeFloatMatrix(new WRot(WAngle.Zero, WAngle.Zero, -lightSource.Yaw).AsMatrix());
			var lightPitch = Util.MakeFloatMatrix(new WRot(WAngle.Zero, -lightSource.Pitch, WAngle.Zero).AsMatrix());
			var shadowTransform = Util.MatrixMultiply(lightPitch, lightYaw);

			var invShadowTransform = Util.MatrixInverse(shadowTransform);
			var cameraTransform = Util.MakeFloatMatrix(camera.AsMatrix());
			var invCameraTransform = Util.MatrixInverse(cameraTransform);

			// Sprite rectangle
			var tl = new float2(float.MaxValue, float.MaxValue);
			var br = new float2(float.MinValue, float.MinValue);

			// Shadow sprite rectangle
			var stl = new float2(float.MaxValue, float.MaxValue);
			var sbr = new float2(float.MinValue, float.MinValue);

			foreach (var v in voxels)
			{
				// Convert screen offset back to world coords
				var offsetVec = Util.MatrixVectorMultiply(invCameraTransform, wr.ScreenVector(v.OffsetFunc()));
				var offsetTransform = Util.TranslationMatrix(offsetVec[0], offsetVec[1], offsetVec[2]);

				var worldTransform = v.RotationFunc().Aggregate(Util.IdentityMatrix(),
					(x,y) => Util.MatrixMultiply(Util.MakeFloatMatrix(y.AsMatrix()), x));
				worldTransform = Util.MatrixMultiply(scaleTransform, worldTransform);
				worldTransform = Util.MatrixMultiply(offsetTransform, worldTransform);

				var bounds = v.Voxel.Bounds(v.FrameFunc());
				var worldBounds = Util.MatrixAABBMultiply(worldTransform, bounds);
				var screenBounds = Util.MatrixAABBMultiply(cameraTransform, worldBounds);
				var shadowBounds = Util.MatrixAABBMultiply(shadowTransform, worldBounds);

				// Aggregate bounds rects
				tl = float2.Min(tl, new float2(screenBounds[0], screenBounds[1]));
				br = float2.Max(br, new float2(screenBounds[3], screenBounds[4]));
				stl = float2.Min(stl, new float2(shadowBounds[0], shadowBounds[1]));
				sbr = float2.Max(sbr, new float2(shadowBounds[3], shadowBounds[4]));
			}

			// Inflate rects to ensure rendering is within bounds
			tl -= spritePadding;
			br += spritePadding;
			stl -= spritePadding;
			sbr += spritePadding;

			// Corners of the shadow quad, in shadow-space
			var corners = new float[][]
			{
				new float[] {stl.X, stl.Y, 0, 1},
				new float[] {sbr.X, sbr.Y, 0, 1},
				new float[] {sbr.X, stl.Y, 0, 1},
				new float[] {stl.X, sbr.Y, 0, 1}
			};

			var shadowScreenTransform = Util.MatrixMultiply(cameraTransform, invShadowTransform);
			var shadowGroundNormal = Util.MatrixVectorMultiply(shadowTransform, groundNormal);
			var screenCorners = new float2[4];
			for (var j = 0; j < 4; j++)
			{
				// Project to ground plane
				corners[j][2] = -(corners[j][1]*shadowGroundNormal[1]/shadowGroundNormal[2] +
								  corners[j][0]*shadowGroundNormal[0]/shadowGroundNormal[2]);

				// Rotate to camera-space
				corners[j] = Util.MatrixVectorMultiply(shadowScreenTransform, corners[j]);
				screenCorners[j] = new float2(corners[j][0], corners[j][1]);
			}

			// Shadows are rendered at twice the resolution to reduce artefacts
			Size spriteSize, shadowSpriteSize;
			int2 spriteOffset, shadowSpriteOffset;
			CalculateSpriteGeometry(tl, br, 1, out spriteSize, out spriteOffset);
			CalculateSpriteGeometry(stl, sbr, 2, out shadowSpriteSize, out shadowSpriteOffset);

			var sprite = sheetBuilder.Allocate(spriteSize, spriteOffset);
			var shadowSprite = sheetBuilder.Allocate(shadowSpriteSize, shadowSpriteOffset);
			var sb = sprite.bounds;
			var ssb = shadowSprite.bounds;
			var spriteCenter = new float2(sb.Left + sb.Width / 2, sb.Top + sb.Height / 2);
			var shadowCenter = new float2(ssb.Left + ssb.Width / 2, ssb.Top + ssb.Height / 2);

			var translateMtx = Util.TranslationMatrix(spriteCenter.X - spriteOffset.X, Renderer.SheetSize - (spriteCenter.Y - spriteOffset.Y), 0);
			var shadowTranslateMtx = Util.TranslationMatrix(shadowCenter.X - shadowSpriteOffset.X, Renderer.SheetSize - (shadowCenter.Y - shadowSpriteOffset.Y), 0);
			var correctionTransform = Util.MatrixMultiply(translateMtx, flipMtx);
			var shadowCorrectionTransform = Util.MatrixMultiply(shadowTranslateMtx, shadowScaleFlipMtx);

			doRender.Add(Pair.New<Sheet, Action>(sprite.sheet, () =>
			{
				foreach (var v in voxels)
				{
					// Convert screen offset to world offset
					var offsetVec = Util.MatrixVectorMultiply(invCameraTransform, wr.ScreenVector(v.OffsetFunc()));
					var offsetTransform = Util.TranslationMatrix(offsetVec[0], offsetVec[1], offsetVec[2]);

					var rotations = v.RotationFunc().Aggregate(Util.IdentityMatrix(),
						(x,y) => Util.MatrixMultiply(Util.MakeFloatMatrix(y.AsMatrix()), x));
					var worldTransform = Util.MatrixMultiply(scaleTransform, rotations);
					worldTransform = Util.MatrixMultiply(offsetTransform, worldTransform);

					var transform = Util.MatrixMultiply(cameraTransform, worldTransform);
					transform = Util.MatrixMultiply(correctionTransform, transform);

					var shadow = Util.MatrixMultiply(shadowTransform, worldTransform);
					shadow = Util.MatrixMultiply(shadowCorrectionTransform, shadow);

					var lightTransform = Util.MatrixMultiply(Util.MatrixInverse(rotations), invShadowTransform);

					var frame = v.FrameFunc();
					for (uint i = 0; i < v.Voxel.Limbs; i++)
					{
						var rd = v.Voxel.RenderData(i);
						var t = v.Voxel.TransformationMatrix(i, frame);

						// Transform light vector from shadow -> world -> limb coords
						var lightDirection = ExtractRotationVector(Util.MatrixMultiply(Util.MatrixInverse(t), lightTransform));

						Render(rd, Util.MatrixMultiply(transform, t), lightDirection,
						       lightAmbientColor, lightDiffuseColor, color.Index, normals.Index);

						// Disable shadow normals by forcing zero diffuse and identity ambient light
						Render(rd, Util.MatrixMultiply(shadow, t), lightDirection,
						       shadowAmbient, shadowDiffuse, shadowPalette.Index, normals.Index);
					}
				}
			}));

			var screenLightVector = Util.MatrixVectorMultiply(invShadowTransform, zVector);
			screenLightVector = Util.MatrixVectorMultiply(cameraTransform, screenLightVector);
			return new VoxelRenderProxy(sprite, shadowSprite, screenCorners, -screenLightVector[2]/screenLightVector[1]);
		}

		static void CalculateSpriteGeometry(float2 tl, float2 br, float scale, out Size size, out int2 offset)
		{
			var width = (int)(scale*(br.X - tl.X));
			var height = (int)(scale*(br.Y - tl.Y));
			offset = (0.5f*scale*(br + tl)).ToInt2();

			// Width and height must be even to avoid rendering glitches
			if ((width & 1) == 1)
				width += 1;
			if ((height & 1) == 1)
				height += 1;

			size = new Size(width, height);
		}

		static float[] ExtractRotationVector(float[] mtx)
		{
			var tVec = Util.MatrixVectorMultiply(mtx, zVector);
			var tOrigin = Util.MatrixVectorMultiply(mtx, zeroVector);
			tVec[0] -= tOrigin[0]*tVec[3]/tOrigin[3];
			tVec[1] -= tOrigin[1]*tVec[3]/tOrigin[3];
			tVec[2] -= tOrigin[2]*tVec[3]/tOrigin[3];

			// Renormalize
			var w = (float)Math.Sqrt(tVec[0]*tVec[0] + tVec[1]*tVec[1] + tVec[2]*tVec[2]);
			tVec[0] /= w;
			tVec[1] /= w;
			tVec[2] /= w;
			tVec[3] = 1f;

			return tVec;
		}

		void Render(VoxelRenderData renderData,
		            float[] t, float[] lightDirection,
		            float[] ambientLight, float[] diffuseLight,
		            int colorPalette, int normalsPalette)
		{
			shader.SetTexture("DiffuseTexture", renderData.Sheet.Texture);
			shader.SetVec("PaletteRows", (colorPalette + 0.5f) / HardwarePalette.MaxPalettes,
			              				 (normalsPalette + 0.5f) / HardwarePalette.MaxPalettes);
			shader.SetMatrix("TransformMatrix", t);
			shader.SetVec("LightDirection", lightDirection, 4);
			shader.SetVec("AmbientLight", ambientLight, 3);
			shader.SetVec("DiffuseLight", diffuseLight, 3);

			shader.Render(() => renderer.DrawBatch(Game.modData.VoxelLoader.VertexBuffer, renderData.Start, renderData.Count, PrimitiveType.QuadList));
		}

		public void BeginFrame()
		{
			foreach (var kv in mappedBuffers)
				unmappedBuffers.Push(kv);
			mappedBuffers.Clear();

			sheetBuilder = new SheetBuilder(SheetType.BGRA, AllocateSheet);
			doRender.Clear();
		}

		IFrameBuffer EnableFrameBuffer(Sheet s)
		{
			var fbo = mappedBuffers[s];
			Game.Renderer.Flush();
			fbo.Bind();

			Game.Renderer.Device.EnableDepthBuffer();
			return fbo;
		}

		void DisableFrameBuffer(IFrameBuffer fbo)
		{
			Game.Renderer.Flush();
			Game.Renderer.Device.DisableDepthBuffer();
			fbo.Unbind();
		}

		public void EndFrame()
		{
			if (doRender.Count == 0)
				return;

			Sheet currentSheet = null;
			IFrameBuffer fbo = null;
			foreach (var v in doRender)
			{
				// Change sheet
				if (v.First != currentSheet)
				{
					if (fbo != null)
						DisableFrameBuffer(fbo);

					currentSheet = v.First;
					fbo = EnableFrameBuffer(currentSheet);
				}

				v.Second();
			}

			DisableFrameBuffer(fbo);
		}

		public Sheet AllocateSheet()
		{
			// Reuse cached fbo
			if (unmappedBuffers.Count > 0)
			{
				var kv = unmappedBuffers.Pop();
				mappedBuffers.Add(kv.Key, kv.Value);
				return kv.Key;
			}

			var size = new Size(Renderer.SheetSize, Renderer.SheetSize);
			var framebuffer = renderer.Device.CreateFrameBuffer(size);
			var sheet = new Sheet(framebuffer.Texture);
			mappedBuffers.Add(sheet, framebuffer);

			return sheet;
		}
	}
}