#include "Dengine/Renderer.h"
#include "Dengine/AssetManager.h"
#include "Dengine/Assets.h"
#include "Dengine/Debug.h"
#include "Dengine/Entity.h"
#include "Dengine/MemoryArena.h"
#include "Dengine/OpenGL.h"
#include "Dengine/Shader.h"
#include "Dengine/Texture.h"

typedef struct RenderQuad
{
	RenderVertex vertexList[4];
} RenderQuad;

// NOTE(doyle): A vertex batch is the batch of vertexes comprised to make one
// shape
INTERNAL void beginVertexBatch(Renderer *renderer)
{
	ASSERT(renderer->vertexBatchState == vertexbatchstate_off);
	ASSERT(renderer->groupIndexForVertexBatch == -1);
	renderer->vertexBatchState = vertexbatchstate_initial_add;
}

/*
   NOTE(doyle): Entity rendering is always done in two pairs of
   triangles, i.e. quad. To batch render quads as a triangle strip, we
   need to create zero-area triangles which OGL will omit from
   rendering.

   The implementation is recognising if the rendered
   entity is the first in its render group, then we don't need to init
   a degenerate vertex, and only at the end of its vertex list. But on
   subsequent renders, we need a degenerate vertex at the front to
   create the zero-area triangle strip.
   */
INTERNAL void endVertexBatch(Renderer *renderer)
{
	ASSERT(renderer->vertexBatchState != vertexbatchstate_off);
	ASSERT(renderer->groupIndexForVertexBatch != -1);

	i32 numDegenerateVertexes = 1;
	RenderGroup *group = &renderer->groups[renderer->groupIndexForVertexBatch];

	i32 freeVertexSlots = renderer->groupCapacity - group->vertexIndex;
	if (numDegenerateVertexes < freeVertexSlots)
	{
		RenderVertex degenerateVertex =
		    group->vertexList[group->vertexIndex - 1];
		group->vertexList[group->vertexIndex++] = degenerateVertex;
	}

	renderer->vertexBatchState         = vertexbatchstate_off;
	renderer->groupIndexForVertexBatch = -1;
}

INTERNAL void applyRotationToVertexes(v2 pos, v2 pivotPoint, Radians rotate,
                                      RenderVertex *vertexList,
                                      i32 vertexListSize)
{
	if (rotate == 0) return;
	// NOTE(doyle): Move the world origin to the base position of the object.
	// Then move the origin to the pivot point (e.g. center of object) and
	// rotate from that point.
	v2 pointOfRotation = v2_add(pivotPoint, pos);

	mat4 rotateMat = mat4_translate(pointOfRotation.x, pointOfRotation.y, 0.0f);
	rotateMat      = mat4_mul(rotateMat, mat4_rotate(rotate, 0.0f, 0.0f, 1.0f));
	rotateMat      = mat4_mul(rotateMat, mat4_translate(-pointOfRotation.x,
	                                               -pointOfRotation.y, 0.0f));
	for (i32 i = 0; i < vertexListSize; i++)
	{
		// NOTE(doyle): Manual matrix multiplication since vertex pos is 2D and
		// matrix is 4D
		v2 oldP = vertexList[i].pos;
		v2 newP = {0};

		newP.x = (oldP.x * rotateMat.e[0][0]) + (oldP.y * rotateMat.e[1][0]) +
		         (rotateMat.e[3][0]);
		newP.y = (oldP.x * rotateMat.e[0][1]) + (oldP.y * rotateMat.e[1][1]) +
		         (rotateMat.e[3][1]);

		vertexList[i].pos = newP;
	}
}

INTERNAL void addVertexToRenderGroup_(Renderer *renderer, Texture *tex,
                                      v4 color, RenderVertex *vertexList,
                                      i32 numVertexes,
                                      enum RenderMode targetRenderMode,
                                      RenderFlags flags)
{
	ASSERT(renderer->vertexBatchState != vertexbatchstate_off);
	ASSERT(numVertexes > 0);

#ifdef DENGINE_DEBUG
	for (i32 i = 0; i < numVertexes; i++)
		debug_countIncrement(debugcount_numVertex);
#endif

	/* Find vacant/matching render group */
	RenderGroup *targetGroup = NULL;
	for (i32 i = 0; i < ARRAY_COUNT(renderer->groups); i++)
	{
		RenderGroup *group = &renderer->groups[i];
		b32 groupIsValid = FALSE;
		if (group->init)
		{
			/* If the textures match and have the same color modulation, we can
			 * add these vertices to the current group */

			b32 renderModeMatches = FALSE;
			if (group->mode == targetRenderMode) renderModeMatches = TRUE;

			b32 colorMatches = FALSE;
			if (v4_equals(group->color, color)) colorMatches = TRUE;

			b32 flagsMatches = FALSE;
			if (group->flags == flags) flagsMatches = TRUE;

			b32 texMatches = TRUE;
			if (!tex && !group->tex)
			{
				texMatches = TRUE;
			}
			else if (tex && group->tex)
			{
				if (group->tex->id == tex->id)
				{
					texMatches = TRUE;
				}
			}

			if (texMatches && colorMatches && renderModeMatches && flagsMatches)
				groupIsValid = TRUE;
		}
		else
		{
			/* New group, unused so initialise it */
			groupIsValid = TRUE;

			group->init  = TRUE;
			group->tex   = tex;
			group->color = color;
			group->mode  = targetRenderMode;
			group->flags = flags;

#ifdef DENGINE_DEBUG
			debug_countIncrement(debugcount_renderGroups);
#endif
		}

		if (groupIsValid)
		{
			i32 freeVertexSlots = renderer->groupCapacity - group->vertexIndex;

			// NOTE(doyle): Two at start, two at end
			i32 numDegenerateVertexes = 0;

			if (renderer->vertexBatchState == vertexbatchstate_initial_add)
				numDegenerateVertexes = 1;

			if ((numDegenerateVertexes + numVertexes) < freeVertexSlots)
			{
				if (i != 0)
				{
					RenderGroup tmp     = renderer->groups[0];
					renderer->groups[0] = renderer->groups[i];
					renderer->groups[i] = tmp;
				}
				targetGroup = &renderer->groups[0];
				break;
			}
		}
	}

	/* Valid group, add to the render group for rendering */
	if (targetGroup)
	{
		// NOTE(doyle): If we are adding 3 vertexes, then we are adding a
		// triangle to the triangle strip. If so, then depending on which "n-th"
		// triangle it is we're adding, the winding order in a t-strip
		// alternates with each triangle (including degenerates). Hence we track
		// so we know the last winding order in the group.

		// For this to work, we must ensure all incoming vertexes are winding in
		// ccw order initially. There is also the presumption that, other
		// rendering methods, such as the quad, consists of an even number of
		// triangles such that the winding order gets alternated back to the
		// same order it started with.
		if (numVertexes == 3)
		{
			if (targetGroup->clockwiseWinding)
			{
				RenderVertex tmp = vertexList[0];
				vertexList[0]    = vertexList[2];
				vertexList[2]    = tmp;
			}

			targetGroup->clockwiseWinding =
			    (targetGroup->clockwiseWinding) ? FALSE : TRUE;
		}

		if (renderer->vertexBatchState == vertexbatchstate_initial_add)
		{
			if (targetGroup->vertexIndex != 0)
			{
				targetGroup->vertexList[targetGroup->vertexIndex++] =
				    vertexList[0];
			}
			renderer->vertexBatchState = vertexbatchstate_active;

			// NOTE(doyle): We swap groups to the front if it is valid, so
			// target group should always be 0
			ASSERT(renderer->groupIndexForVertexBatch == -1);
			renderer->groupIndexForVertexBatch = 0;
		}


		for (i32 i = 0; i < numVertexes; i++)
		{
			targetGroup->vertexList[targetGroup->vertexIndex++] = vertexList[i];
		}
	}
	else
	{
		// TODO(doyle): Log no remaining render groups
		DEBUG_LOG(
		    "WARNING: All render groups used up, some items will not be "
		    "rendered!");

		printf(
		    "WARNING: All render groups used up, some items will not be "
		    "rendered!\n");
	}
}

INTERNAL inline void flipTexCoord(v4 *texCoords, b32 flipX, b32 flipY)
{
	if (flipX)
	{
		v4 tmp       = *texCoords;
		texCoords->x = tmp.z;
		texCoords->z = tmp.x;
	}

	if (flipY)
	{
		v4 tmp       = *texCoords;
		texCoords->y = tmp.w;
		texCoords->w = tmp.y;
	}
}

INTERNAL void bufferRenderGroupToGL(Renderer *renderer, RenderGroup *group)
{
	RenderVertex *vertexList = group->vertexList;
	i32 numVertex = group->vertexIndex;

	// TODO(doyle): We assume that vbo and vao are assigned
	renderer->numVertexesInVbo = numVertex;
	glBindBuffer(GL_ARRAY_BUFFER, renderer->vbo[group->mode]);
	glBufferData(GL_ARRAY_BUFFER, numVertex * sizeof(RenderVertex), vertexList,
	             GL_STREAM_DRAW);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
}

INTERNAL v4 getTexRectNormaliseDeviceCoords(RenderTex renderTex)
{
	/* Convert texture coordinates to normalised texture coordinates */
	v4 result = renderTex.texRect;
	if (renderTex.tex)
	{
		v2 texNdcFactor =
		    V2(1.0f / renderTex.tex->width, 1.0f / renderTex.tex->height);
		result.e[0] *= texNdcFactor.w;
		result.e[1] *= texNdcFactor.h;
		result.e[2] *= texNdcFactor.w;
		result.e[3] *= texNdcFactor.h;
	}

	return result;

}

INTERNAL RenderQuad createRenderQuad(Renderer *renderer, v2 pos, v2 size,
                                     v2 pivotPoint, Radians rotate,
                                     RenderTex renderTex)
{
	/*
	 * Rendering order
	 *
	 * 0   2
	 * +---+
	 * +  /+
	 * + / +
	 * +/  +
	 * +---+
	 * 1   3
	 *
	 */

	v4 vertexPair       = {0};
	vertexPair.vec2[0]  = pos;
	vertexPair.vec2[1]  = v2_add(pos, size);
	v4 texRectNdc = getTexRectNormaliseDeviceCoords(renderTex);

	// NOTE(doyle): Create a quad composed of 4 vertexes to be rendered as
	// a triangle strip using vertices v0, v1, v2, then v2, v1, v3 (note the
	// order)
	v2 vertexList[4] = {0};
	v2 texCoordList[4] = {0};

	// Top left
	vertexList[0]   = V2(vertexPair.x, vertexPair.w);
	texCoordList[0] = V2(texRectNdc.x, texRectNdc.w);

	// Bottom left
	vertexList[1]   = V2(vertexPair.x, vertexPair.y);
	texCoordList[1] = V2(texRectNdc.x, texRectNdc.y);

	// Top right
	vertexList[2]   = V2(vertexPair.z, vertexPair.w);
	texCoordList[2] = V2(texRectNdc.z, texRectNdc.w);

	// Bottom right
	vertexList[3]   = V2(vertexPair.z, vertexPair.y);
	texCoordList[3] = V2(texRectNdc.z, texRectNdc.y);

	// NOTE(doyle): Precalculate rotation on vertex positions
	// NOTE(doyle): No translation/scale matrix as we pre-calculate it from
	// entity data and work in world space until GLSL uses the projection matrix

	math_applyRotationToVertexes(pos, pivotPoint, rotate, vertexList,
	                             ARRAY_COUNT(vertexList));

	RenderQuad result = {0};

	ASSERT(ARRAY_COUNT(vertexList) == ARRAY_COUNT(result.vertexList));
	for (i32 i = 0; i < ARRAY_COUNT(vertexList); i++)
	{
		result.vertexList[i].pos = vertexList[i];
		result.vertexList[i].texCoord = texCoordList[i];
	}

	return result;
}

INTERNAL inline RenderQuad
createDefaultTexQuad(Renderer *renderer, RenderTex *renderTex)
{
	RenderQuad result = {0};
	result = createRenderQuad(renderer, V2(0, 0), V2(0, 0), V2(0, 0), 0.0f,
	                          *renderTex);
	return result;
}

INTERNAL void renderGLBufferedData(Renderer *renderer, RenderGroup *group)
{
	ASSERT(group->mode < rendermode_invalid);

	if (group->flags & renderflag_wireframe)
	{
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
	}
	else
	{
		glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
	}
	GL_CHECK_ERROR();

	if (group->flags & renderflag_no_texture)
	{
		renderer->activeShaderId =
		    renderer->shaderList[shaderlist_default_no_tex];
		shader_use(renderer->activeShaderId);
	}
	else
	{
		renderer->activeShaderId = renderer->shaderList[shaderlist_default];
		shader_use(renderer->activeShaderId);
		Texture *tex = group->tex;
		if (tex)
		{
			glActiveTexture(GL_TEXTURE0);
			glBindTexture(GL_TEXTURE_2D, tex->id);
			shader_uniformSet1i(renderer->activeShaderId, "tex", 0);
			GL_CHECK_ERROR();
		}
	}

#if 0
	glDisable(GL_CULL_FACE);
#endif

	/* Set color modulation value */
	shader_uniformSetVec4f(renderer->activeShaderId, "spriteColor",
	                       group->color);

	glBindVertexArray(renderer->vao[group->mode]);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, renderer->numVertexesInVbo);
	GL_CHECK_ERROR();
	debug_countIncrement(debugcount_drawArrays);

	/* Unbind */
	glBindVertexArray(0);
	glBindTexture(GL_TEXTURE_2D, 0);
	GL_CHECK_ERROR();

}

RenderTex renderer_createNullRenderTex(AssetManager *const assetManager)
{
	Texture *emptyTex = asset_getTex(assetManager, "nullTex");
	RenderTex result  = {emptyTex, V4(0, 1, 1, 0)};
	return result;
}

void renderer_rect(Renderer *const renderer, Rect camera, v2 pos, v2 size,
                   v2 pivotPoint, Radians rotate, RenderTex *renderTex, v4 color,
                   RenderFlags flags)
{
	// NOTE(doyle): Bottom left and top right position of quad in world space
	v2 posInCameraSpace = v2_sub(pos, camera.min);

	RenderTex emptyRenderTex = {0};
	if (!renderTex) renderTex = &emptyRenderTex;

	RenderQuad quad = createRenderQuad(renderer, posInCameraSpace, size,
	                                   pivotPoint, rotate, *renderTex);

	beginVertexBatch(renderer);
	addVertexToRenderGroup_(renderer, renderTex->tex, color, quad.vertexList,
	                        ARRAY_COUNT(quad.vertexList), rendermode_quad,
	                        flags);
	endVertexBatch(renderer);
}

void renderer_polygon(Renderer *const renderer, Rect camera,
                      v2 *polygonPoints, i32 numPoints, v2 pivotPoint,
                      Radians rotate, RenderTex *renderTex, v4 color,
                      RenderFlags flags)
{
	ASSERT(numPoints >= 3);

	for (i32 i           = 0; i < numPoints; i++)
		polygonPoints[i] = v2_sub(polygonPoints[i], camera.min);

	// TODO(doyle): Do something with render texture
	RenderTex emptyRenderTex  = {0};
	if (!renderTex) renderTex = &emptyRenderTex;

	v2 triangulationBaseP                = polygonPoints[0];
	RenderVertex triangulationBaseVertex = {0};
	triangulationBaseVertex.pos          = triangulationBaseP;

	i32 numTrisInTriangulation = numPoints - 2;
	i32 triangulationIndex     = 0;
	for (i32 i = 1; triangulationIndex < numTrisInTriangulation; i++)
	{
		ASSERT((i + 1) < numPoints);

		v2 vertexList[3] = {triangulationBaseP, polygonPoints[i],
		                    polygonPoints[i + 1]};

		beginVertexBatch(renderer);

		RenderVertex triangle[3] = {0};
		triangle[0].pos          = vertexList[0];
		triangle[1].pos          = vertexList[1];
		triangle[2].pos          = vertexList[2];

		addVertexToRenderGroup_(renderer, renderTex->tex, color, triangle,
		                        ARRAY_COUNT(triangle), rendermode_polygon,
		                        flags);
		endVertexBatch(renderer);
		triangulationIndex++;
	}
}

void renderer_string(Renderer *const renderer, MemoryArena_ *arena, Rect camera,
                     Font *const font, const char *const string, v2 pos,
                     v2 pivotPoint, Radians rotate, v4 color, RenderFlags flags)
{
	i32 strLen = common_strlen(string);
	if (strLen <= 0) return;

	// TODO(doyle): Slightly incorrect string length in pixels calculation,
	// because we use the advance metric of each character for length not
	// maximum character size in rendering
	v2 rightAlignedP =
	    v2_add(pos, V2((CAST(f32) font->maxSize.w * CAST(f32) strLen),
	                   CAST(f32) font->maxSize.h));
	v2 leftAlignedP = pos;
	if (math_pointInRect(camera, leftAlignedP) ||
	    math_pointInRect(camera, rightAlignedP))
	{
		i32 vertexIndex        = 0;
		i32 numVertexPerQuad   = 4;
		i32 numVertexesToAlloc = (strLen * (numVertexPerQuad + 2));
		RenderVertex *vertexList =
		    memory_pushBytes(arena, numVertexesToAlloc * sizeof(RenderVertex));

		v2 posInCameraSpace = v2_sub(pos, camera.min);
		pos = posInCameraSpace;

		// TODO(doyle): Find why font is 1px off, might be arial font semantics
		Texture *tex = font->atlas->tex;
		f32 baseline = pos.y - font->verticalSpacing + 1;
		for (i32 i = 0; i < strLen; i++)
		{
			i32 codepoint     = string[i];
			i32 relativeIndex = CAST(i32)(codepoint - font->codepointRange.x);
			CharMetrics metric = font->charMetrics[relativeIndex];
			pos.y              = baseline - (metric.offset.y);

			/* Get texture out */
			SubTexture subTexture =
			    asset_getAtlasSubTex(font->atlas, &CAST(char)codepoint);

			v4 charTexRect      = {0};
			charTexRect.vec2[0] = subTexture.rect.min;
			charTexRect.vec2[1] =
			    v2_add(subTexture.rect.min, subTexture.rect.max);
			flipTexCoord(&charTexRect, FALSE, TRUE);

			RenderTex renderTex = {tex, charTexRect};
			RenderQuad quad     = createRenderQuad(renderer, pos, font->maxSize,
			                                   pivotPoint, rotate, renderTex);

			beginVertexBatch(renderer);
			addVertexToRenderGroup_(renderer, tex, color, quad.vertexList,
			                        ARRAY_COUNT(quad.vertexList),
			                        rendermode_quad, flags);
			endVertexBatch(renderer);
			pos.x += metric.advance;
		}
	}
}

void renderer_entity(Renderer *renderer, MemoryArena_ *transientArena,
                     Rect camera, Entity *entity, v2 pivotPoint, Degrees rotate,
                     v4 color, RenderFlags flags)
{
	// TODO(doyle): Add early exit on entities out of camera bounds
	Radians totalRotation = DEGREES_TO_RADIANS((entity->rotation + rotate));
	RenderTex renderTex   = {0};
	if (entity->tex)
	{
		EntityAnim *entityAnim = &entity->animList[entity->animListIndex];
		v4 texRect             = {0};
		if (entityAnim->anim)
		{
			Animation *anim   = entityAnim->anim;
			char *frameName   = anim->frameList[entityAnim->currFrame];
			SubTexture subTex = asset_getAtlasSubTex(anim->atlas, frameName);

			texRect.vec2[0] = subTex.rect.min;
			texRect.vec2[1] = v2_add(subTex.rect.min, subTex.rect.max);
			flipTexCoord(&texRect, entity->flipX, entity->flipY);
		}
		else
		{
			texRect = V4(0.0f, 0.0f, (f32)entity->tex->width,
			             (f32)entity->tex->height);
		}

		if (entity->direction == direction_east)
		{
			flipTexCoord(&texRect, TRUE, FALSE);
		}

		renderTex.tex     = entity->tex;
		renderTex.texRect = texRect;
	}

	// TODO(doyle): Proper blending
	v4 renderColor = color;
	if (v4_equals(color, V4(0, 0, 0, 0))) renderColor = entity->color;

	if (entity->renderMode == rendermode_quad)
	{
		renderer_rect(renderer, camera, entity->pos, entity->size,
		              v2_add(entity->offset, pivotPoint), totalRotation,
		              &renderTex, entity->color, flags);
	}
	else if (entity->renderMode == rendermode_polygon)
	{
		ASSERT(entity->numVertexPoints >= 3);
		ASSERT(entity->vertexPoints);

		v2 *offsetVertexPoints =
		    entity_generateUpdatedVertexList(transientArena, entity);

		renderer_polygon(renderer, camera, offsetVertexPoints,
		                 entity->numVertexPoints,
		                 v2_add(entity->offset, pivotPoint), totalRotation,
		                 &renderTex, renderColor, flags);
	}
	else
	{
		ASSERT(INVALID_CODE_PATH);
	}
}

void renderer_renderGroups(Renderer *renderer)
{
	for (i32 i = 0; i < ARRAY_COUNT(renderer->groups); i++)
	{
		RenderGroup *currGroup = &renderer->groups[i];
		if (currGroup->init)
		{
			bufferRenderGroupToGL(renderer, currGroup);
			renderGLBufferedData(renderer, currGroup);

			RenderGroup cleanGroup = {0};
			cleanGroup.vertexList = currGroup->vertexList;
			*currGroup = cleanGroup;
		}
		else
		{
			break;
		}
	}
}