/************************************************************//**
*
*	@file: mtl_canvas.m
*	@author: Martin Fouilleul
*	@date: 12/07/2020
*	@revision: 24/01/2023
*
*****************************************************************/
#import<Metal/Metal.h>
#import<QuartzCore/CAMetalLayer.h>
#include<simd/simd.h>

#include"graphics_internal.h"
#include"macro_helpers.h"
#include"osx_app.h"

#include"mtl_renderer.h"

#define LOG_SUBSYSTEM "Graphics"

const int MG_MTL_INPUT_BUFFERS_COUNT = 3,
          MG_MTL_TILE_SIZE = 16,
          MG_MTL_MSAA_COUNT = 8;

typedef struct mg_mtl_canvas_backend
{
	mg_canvas_backend interface;
	mg_surface surface;

	id<MTLComputePipelineState> pathPipeline;
	id<MTLComputePipelineState> segmentPipeline;
	id<MTLComputePipelineState> backpropPipeline;
	id<MTLComputePipelineState> mergePipeline;
	id<MTLComputePipelineState> rasterPipeline;
	id<MTLRenderPipelineState> blitPipeline;

	id<MTLTexture> outTexture;

	int bufferIndex;
	dispatch_semaphore_t bufferSemaphore;

	id<MTLBuffer> pathBuffer[MG_MTL_INPUT_BUFFERS_COUNT];
	id<MTLBuffer> elementBuffer[MG_MTL_INPUT_BUFFERS_COUNT];
	id<MTLBuffer> logBuffer[MG_MTL_INPUT_BUFFERS_COUNT];
	id<MTLBuffer> logOffsetBuffer[MG_MTL_INPUT_BUFFERS_COUNT];

	id<MTLBuffer> segmentCountBuffer;
	id<MTLBuffer> segmentBuffer;
	id<MTLBuffer> pathQueueBuffer;
	id<MTLBuffer> tileQueueBuffer;
	id<MTLBuffer> tileQueueCountBuffer;
	id<MTLBuffer> tileOpBuffer;
	id<MTLBuffer> tileOpCountBuffer;
	id<MTLBuffer> screenTilesBuffer;

	int msaaCount;

} mg_mtl_canvas_backend;


static void mg_update_path_extents(vec4* extents, vec2 p)
{
	extents->x = minimum(extents->x, p.x);
	extents->y = minimum(extents->y, p.y);
	extents->z = maximum(extents->z, p.x);
	extents->w = maximum(extents->w, p.y);
}

void mg_mtl_print_log(int bufferIndex, id<MTLBuffer> logBuffer, id<MTLBuffer> logOffsetBuffer)
{
	char* log = [logBuffer contents];
	int size = *(int*)[logOffsetBuffer contents];

	if(size)
	{
		LOG_MESSAGE("Log from buffer %i:\n", bufferIndex);

		int index = 0;
		while(index < size)
		{
			int len = strlen(log+index);
			printf("%s", log+index);
			index += (len+1);
		}
	}
}


typedef struct mg_mtl_encoding_context
{
	int mtlEltCount;
	mg_mtl_path_elt* elementBufferData;
	int pathIndex;
	int localEltIndex;
	mg_primitive* primitive;
	vec4 pathScreenExtents;

} mg_mtl_encoding_context;

void mg_mtl_canvas_encode_element(mg_mtl_encoding_context* context, mg_path_elt_type kind, vec2* p)
{
	mg_mtl_path_elt* mtlElt = &context->elementBufferData[context->mtlEltCount];
	context->mtlEltCount++;

	mtlElt->pathIndex = context->pathIndex;
	int count = 0;
	switch(kind)
	{
		case MG_PATH_LINE:
			mtlElt->kind = MG_MTL_LINE;
			count = 2;
			break;

		case MG_PATH_QUADRATIC:
			mtlElt->kind = MG_MTL_QUADRATIC;
			count = 3;
			break;

		case MG_PATH_CUBIC:
			mtlElt->kind = MG_MTL_CUBIC;
			count = 4;
			break;

		default:
			break;
	}

	mtlElt->localEltIndex = context->localEltIndex;

	for(int i=0; i<count; i++)
	{
		vec2 screenP = mg_mat2x3_mul(context->primitive->attributes.transform, p[i]);
		mg_update_path_extents(&context->pathScreenExtents, screenP);
		mtlElt->p[i] = (vector_float2){screenP.x, screenP.y};
	}
}

void mg_mtl_render_stroke_line(mg_mtl_encoding_context* context, vec2* p)
{
	f32 width = context->primitive->attributes.width;

	vec2 v = {p[1].x-p[0].x, p[1].y-p[0].y};
	vec2 n = {v.y, -v.x};
	f32 norm = sqrt(n.x*n.x + n.y*n.y);
	vec2 offset = vec2_mul(0.5*width/norm, n);

	vec2 left[2] = {vec2_add(p[0], offset), vec2_add(p[1], offset)};
	vec2 right[2] = {vec2_add(p[1], vec2_mul(-1, offset)), vec2_add(p[0], vec2_mul(-1, offset))};
	vec2 joint0[2] = {vec2_add(p[0], vec2_mul(-1, offset)), vec2_add(p[0], offset)};
	vec2 joint1[2] = {vec2_add(p[1], offset), vec2_add(p[1], vec2_mul(-1, offset))};

	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, right);

	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, left);
	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint0);
	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint1);
}

void mg_mtl_render_stroke_quadratic(mg_mtl_encoding_context* context, vec2* p)
{
	f32 width = context->primitive->attributes.width;
	f32 tolerance = minimum(context->primitive->attributes.tolerance, 0.5 * width);

	//NOTE: check for degenerate line case
	const f32 equalEps = 1e-3;
	if(vec2_close(p[0], p[1], equalEps))
	{
		mg_mtl_render_stroke_line(context, p+1);
		return;
	}
	else if(vec2_close(p[1], p[2], equalEps))
	{
		mg_mtl_render_stroke_line(context, p);
		return;
	}

	vec2 leftHull[3];
	vec2 rightHull[3];

	if(  !mg_offset_hull(3, p, leftHull, width/2)
	  || !mg_offset_hull(3, p, rightHull, -width/2))
	{
		//TODO split and recurse
		//NOTE: offsetting the hull failed, split the curve
		vec2 splitLeft[3];
		vec2 splitRight[3];
		mg_quadratic_split(p, 0.5, splitLeft, splitRight);
		mg_mtl_render_stroke_quadratic(context, splitLeft);
		mg_mtl_render_stroke_quadratic(context, splitRight);
	}
	else
	{
		const int CHECK_SAMPLE_COUNT = 5;
		f32 checkSamples[CHECK_SAMPLE_COUNT] = {1./6, 2./6, 3./6, 4./6, 5./6};

		f32 d2LowBound = Square(0.5 * width - tolerance);
		f32 d2HighBound = Square(0.5 * width + tolerance);

		f32 maxOvershoot = 0;
		f32 maxOvershootParameter = 0;

		for(int i=0; i<CHECK_SAMPLE_COUNT; i++)
		{
			f32 t = checkSamples[i];

			vec2 c = mg_quadratic_get_point(p, t);
			vec2 cp =  mg_quadratic_get_point(leftHull, t);
			vec2 cn =  mg_quadratic_get_point(rightHull, t);

			f32 positiveDistSquare = Square(c.x - cp.x) + Square(c.y - cp.y);
			f32 negativeDistSquare = Square(c.x - cn.x) + Square(c.y - cn.y);

			f32 positiveOvershoot = maximum(positiveDistSquare - d2HighBound, d2LowBound - positiveDistSquare);
			f32 negativeOvershoot = maximum(negativeDistSquare - d2HighBound, d2LowBound - negativeDistSquare);

			f32 overshoot = maximum(positiveOvershoot, negativeOvershoot);

			if(overshoot > maxOvershoot)
			{
				maxOvershoot = overshoot;
				maxOvershootParameter = t;
			}
		}

		if(maxOvershoot > 0)
		{
			vec2 splitLeft[3];
			vec2 splitRight[3];
			mg_quadratic_split(p, maxOvershootParameter, splitLeft, splitRight);
			mg_mtl_render_stroke_quadratic(context, splitLeft);
			mg_mtl_render_stroke_quadratic(context, splitRight);
		}
		else
		{
			vec2 tmp = leftHull[0];
			leftHull[0] = leftHull[2];
			leftHull[2] = tmp;

			mg_mtl_canvas_encode_element(context, MG_PATH_QUADRATIC, rightHull);
			mg_mtl_canvas_encode_element(context, MG_PATH_QUADRATIC, leftHull);

			vec2 joint0[2] = {rightHull[2], leftHull[0]};
			vec2 joint1[2] = {leftHull[2], rightHull[0]};
			mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint0);
			mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint1);
		}
	}
}

void mg_mtl_render_stroke_cubic(mg_mtl_encoding_context* context, vec2* p)
{
	f32 width = context->primitive->attributes.width;
	f32 tolerance = minimum(context->primitive->attributes.tolerance, 0.5 * width);

	//NOTE: check degenerate line cases
	f32 equalEps = 1e-3;

	if( (vec2_close(p[0], p[1], equalEps) && vec2_close(p[2], p[3], equalEps))
	  ||(vec2_close(p[0], p[1], equalEps) && vec2_close(p[1], p[2], equalEps))
	  ||(vec2_close(p[1], p[2], equalEps) && vec2_close(p[2], p[3], equalEps)))
	{
		vec2 line[2] = {p[0], p[3]};
		mg_mtl_render_stroke_line(context, line);
		return;
	}
	else if(vec2_close(p[0], p[1], equalEps) && vec2_close(p[1], p[3], equalEps))
	{
		vec2 line[2] = {p[0], vec2_add(vec2_mul(5./9, p[0]), vec2_mul(4./9, p[2]))};
		mg_mtl_render_stroke_line(context, line);
		return;
	}
	else if(vec2_close(p[0], p[2], equalEps) && vec2_close(p[2], p[3], equalEps))
	{
		vec2 line[2] = {p[0], vec2_add(vec2_mul(5./9, p[0]), vec2_mul(4./9, p[1]))};
		mg_mtl_render_stroke_line(context, line);
		return;
	}

	vec2 leftHull[4];
	vec2 rightHull[4];

	if(  !mg_offset_hull(4, p, leftHull, width/2)
	  || !mg_offset_hull(4, p, rightHull, -width/2))
	{
		//TODO split and recurse
		//NOTE: offsetting the hull failed, split the curve
		vec2 splitLeft[4];
		vec2 splitRight[4];
		mg_cubic_split(p, 0.5, splitLeft, splitRight);
		mg_mtl_render_stroke_cubic(context, splitLeft);
		mg_mtl_render_stroke_cubic(context, splitRight);
	}
	else
	{
		const int CHECK_SAMPLE_COUNT = 5;
		f32 checkSamples[CHECK_SAMPLE_COUNT] = {1./6, 2./6, 3./6, 4./6, 5./6};

		f32 d2LowBound = Square(0.5 * width - tolerance);
		f32 d2HighBound = Square(0.5 * width + tolerance);

		f32 maxOvershoot = 0;
		f32 maxOvershootParameter = 0;

		for(int i=0; i<CHECK_SAMPLE_COUNT; i++)
		{
			f32 t = checkSamples[i];

			vec2 c = mg_cubic_get_point(p, t);
			vec2 cp =  mg_cubic_get_point(leftHull, t);
			vec2 cn =  mg_cubic_get_point(rightHull, t);

			f32 positiveDistSquare = Square(c.x - cp.x) + Square(c.y - cp.y);
			f32 negativeDistSquare = Square(c.x - cn.x) + Square(c.y - cn.y);

			f32 positiveOvershoot = maximum(positiveDistSquare - d2HighBound, d2LowBound - positiveDistSquare);
			f32 negativeOvershoot = maximum(negativeDistSquare - d2HighBound, d2LowBound - negativeDistSquare);

			f32 overshoot = maximum(positiveOvershoot, negativeOvershoot);

			if(overshoot > maxOvershoot)
			{
				maxOvershoot = overshoot;
				maxOvershootParameter = t;
			}
		}

		if(maxOvershoot > 0)
		{
			vec2 splitLeft[4];
			vec2 splitRight[4];
			mg_cubic_split(p, maxOvershootParameter, splitLeft, splitRight);
			mg_mtl_render_stroke_cubic(context, splitLeft);
			mg_mtl_render_stroke_cubic(context, splitRight);
		}
		else
		{
			vec2 tmp = leftHull[0];
			leftHull[0] = leftHull[3];
			leftHull[3] = tmp;
			tmp = leftHull[1];
			leftHull[1] = leftHull[2];
			leftHull[2] = tmp;

			mg_mtl_canvas_encode_element(context, MG_PATH_CUBIC, rightHull);
			mg_mtl_canvas_encode_element(context, MG_PATH_CUBIC, leftHull);

			vec2 joint0[2] = {rightHull[3], leftHull[0]};
			vec2 joint1[2] = {leftHull[3], rightHull[0]};
			mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint0);
			mg_mtl_canvas_encode_element(context, MG_PATH_LINE, joint1);
		}
	}
}

void mg_mtl_render_stroke_element(mg_mtl_encoding_context* context,
                                  mg_path_elt* element,
                                  vec2 currentPoint,
                                  vec2* startTangent,
                                  vec2* endTangent,
                                  vec2* endPoint)
{
	vec2 controlPoints[4] = {currentPoint, element->p[0], element->p[1], element->p[2]};
	int endPointIndex = 0;

	switch(element->type)
	{
		case MG_PATH_LINE:
			mg_mtl_render_stroke_line(context, controlPoints);
			endPointIndex = 1;
			break;

		case MG_PATH_QUADRATIC:
			mg_mtl_render_stroke_quadratic(context, controlPoints);
			endPointIndex = 2;
			break;

		case MG_PATH_CUBIC:
			mg_mtl_render_stroke_cubic(context, controlPoints);
			endPointIndex = 3;
			break;

		case MG_PATH_MOVE:
			ASSERT(0, "should be unreachable");
			break;
	}

	//NOTE: ensure tangents are properly computed even in presence of coincident points
	//TODO: see if we can do this in a less hacky way

	for(int i=1; i<4; i++)
	{
		if(  controlPoints[i].x != controlPoints[0].x
		  || controlPoints[i].y != controlPoints[0].y)
		{
			*startTangent = (vec2){.x = controlPoints[i].x - controlPoints[0].x,
			                       .y = controlPoints[i].y - controlPoints[0].y};
			break;
		}
	}
	*endPoint = controlPoints[endPointIndex];

	for(int i=endPointIndex-1; i>=0; i++)
	{
		if(  controlPoints[i].x != endPoint->x
		  || controlPoints[i].y != endPoint->y)
		{
			*endTangent = (vec2){.x = endPoint->x - controlPoints[i].x,
			                     .y = endPoint->y - controlPoints[i].y};
			break;
		}
	}
	DEBUG_ASSERT(startTangent->x != 0 || startTangent->y != 0);
}

void mg_mtl_stroke_cap(mg_mtl_encoding_context* context,
                   vec2 p0,
                   vec2 direction)
{
	mg_attributes* attributes = &context->primitive->attributes;

	//NOTE(martin): compute the tangent and normal vectors (multiplied by half width) at the cap point
	f32 dn = sqrt(Square(direction.x) + Square(direction.y));
	f32 alpha = 0.5 * attributes->width/dn;

	vec2 n0 = {-alpha*direction.y,
		    alpha*direction.x};

	vec2 m0 = {alpha*direction.x,
	           alpha*direction.y};

	vec2 points[] = {{p0.x + n0.x, p0.y + n0.y},
	                 {p0.x + n0.x + m0.x, p0.y + n0.y + m0.y},
	                 {p0.x - n0.x + m0.x, p0.y - n0.y + m0.y},
	                 {p0.x - n0.x, p0.y - n0.y},
	                 {p0.x + n0.x, p0.y + n0.y}};

	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points);
	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+1);
	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+2);
	mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+3);
}

void mg_mtl_stroke_joint(mg_mtl_encoding_context* context,
                         vec2 p0,
                         vec2 t0,
                         vec2 t1)
{
	mg_attributes* attributes = &context->primitive->attributes;

	//NOTE(martin): compute the normals at the joint point
	f32 norm_t0 = sqrt(Square(t0.x) + Square(t0.y));
	f32 norm_t1 = sqrt(Square(t1.x) + Square(t1.y));

	vec2 n0 = {-t0.y, t0.x};
	n0.x /= norm_t0;
	n0.y /= norm_t0;

	vec2 n1 = {-t1.y, t1.x};
	n1.x /= norm_t1;
	n1.y /= norm_t1;

	//NOTE(martin): the sign of the cross product determines if the normals are facing outwards or inwards the angle.
	//              we flip them to face outwards if needed
	f32 crossZ = n0.x*n1.y - n0.y*n1.x;
	if(crossZ > 0)
	{
		n0.x *= -1;
		n0.y *= -1;
		n1.x *= -1;
		n1.y *= -1;
	}

	//NOTE(martin): use the same code as hull offset to find mitter point...
	/*NOTE(martin): let vector u = (n0+n1) and vector v = pIntersect - p1
		then v = u * (2*offset / norm(u)^2)
		(this can be derived from writing the pythagoras theorems in the triangles of the joint)
	*/
	f32 halfW = 0.5 * attributes->width;
	vec2 u = {n0.x + n1.x, n0.y + n1.y};
	f32 uNormSquare = u.x*u.x + u.y*u.y;
	f32 alpha = attributes->width / uNormSquare;
	vec2 v = {u.x * alpha, u.y * alpha};

	f32 excursionSquare = uNormSquare * Square(alpha - attributes->width/4);

	if(  attributes->joint == MG_JOINT_MITER
	  && excursionSquare <= Square(attributes->maxJointExcursion))
	{
		//NOTE(martin): add a mitter joint
		vec2 points[] = {p0,
		                 {p0.x + n0.x*halfW, p0.y + n0.y*halfW},
		                 {p0.x + v.x, p0.y + v.y},
		                 {p0.x + n1.x*halfW, p0.y + n1.y*halfW},
		                 p0};

		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points);
		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+1);
		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+2);
		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+3);
	}
	else
	{
		//NOTE(martin): add a bevel joint
		vec2 points[] = {p0,
		                 {p0.x + n0.x*halfW, p0.y + n0.y*halfW},
		                 {p0.x + n1.x*halfW, p0.y + n1.y*halfW},
		                 p0};

		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points);
		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+1);
		mg_mtl_canvas_encode_element(context, MG_PATH_LINE, points+2);
	}
}

u32 mg_mtl_render_stroke_subpath(mg_mtl_encoding_context* context,
                                 mg_path_elt* elements,
                                 mg_path_descriptor* path,
                                 u32 startIndex,
                                 vec2 startPoint)
{
	u32 eltCount = path->count;
	DEBUG_ASSERT(startIndex < eltCount);

	vec2 currentPoint = startPoint;
	vec2 endPoint = {0, 0};
	vec2 previousEndTangent = {0, 0};
	vec2 firstTangent = {0, 0};
	vec2 startTangent = {0, 0};
	vec2 endTangent = {0, 0};

	//NOTE(martin): render first element and compute first tangent
	mg_mtl_render_stroke_element(context, elements + startIndex, currentPoint, &startTangent, &endTangent, &endPoint);

	firstTangent = startTangent;
	previousEndTangent = endTangent;
	currentPoint = endPoint;

	//NOTE(martin): render subsequent elements along with their joints

	mg_attributes* attributes = &context->primitive->attributes;

	u32 eltIndex = startIndex + 1;
	for(;
	    eltIndex<eltCount && elements[eltIndex].type != MG_PATH_MOVE;
	    eltIndex++)
	{
		mg_mtl_render_stroke_element(context, elements + eltIndex, currentPoint, &startTangent, &endTangent, &endPoint);

		if(attributes->joint != MG_JOINT_NONE)
		{
			mg_mtl_stroke_joint(context, currentPoint, previousEndTangent, startTangent);
		}
		previousEndTangent = endTangent;
		currentPoint = endPoint;
	}
	u32 subPathEltCount = eltIndex - startIndex;

	//NOTE(martin): draw end cap / joint. We ensure there's at least two segments to draw a closing joint
	if(  subPathEltCount > 1
	  && startPoint.x == endPoint.x
	  && startPoint.y == endPoint.y)
	{
		if(attributes->joint != MG_JOINT_NONE)
		{
			//NOTE(martin): add a closing joint if the path is closed
			mg_mtl_stroke_joint(context, endPoint, endTangent, firstTangent);
		}
	}
	else if(attributes->cap == MG_CAP_SQUARE)
	{
		//NOTE(martin): add start and end cap
		mg_mtl_stroke_cap(context, startPoint, (vec2){-startTangent.x, -startTangent.y});
		mg_mtl_stroke_cap(context, endPoint, endTangent);
	}
	return(eltIndex);
}

void mg_mtl_render_stroke(mg_mtl_encoding_context* context,
                          mg_path_elt* elements,
                          mg_path_descriptor* path)
{
	u32 eltCount = path->count;
	DEBUG_ASSERT(eltCount);

	vec2 startPoint = path->startPoint;
	u32 startIndex = 0;

	while(startIndex < eltCount)
	{
		//NOTE(martin): eliminate leading moves
		while(startIndex < eltCount && elements[startIndex].type == MG_PATH_MOVE)
		{
			startPoint = elements[startIndex].p[0];
			startIndex++;
		}
		if(startIndex < eltCount)
		{
			startIndex = mg_mtl_render_stroke_subpath(context, elements, path, startIndex, startPoint);
		}
	}
}

void mg_mtl_canvas_render(mg_canvas_backend* interface,
                          mg_color clearColor,
                          u32 primitiveCount,
                          mg_primitive* primitives,
                          u32 eltCount,
                          mg_path_elt* pathElements)
{
	mg_mtl_canvas_backend* backend = (mg_mtl_canvas_backend*)interface;

	//NOTE: update rolling buffers
	dispatch_semaphore_wait(backend->bufferSemaphore, DISPATCH_TIME_FOREVER);
	backend->bufferIndex = (backend->bufferIndex + 1) % MG_MTL_INPUT_BUFFERS_COUNT;

	mg_mtl_path_elt* elementBufferData = (mg_mtl_path_elt*)[backend->elementBuffer[backend->bufferIndex] contents];
	mg_mtl_path* pathBufferData = (mg_mtl_path*)[backend->pathBuffer[backend->bufferIndex] contents];

	//NOTE: fill renderer input buffers
	int pathCount = 0;
	vec2 currentPos = {0};

	mg_mtl_encoding_context context = {.mtlEltCount = 0,
	                                   .elementBufferData = elementBufferData};

	for(int primitiveIndex = 0; primitiveIndex < primitiveCount; primitiveIndex++)
	{
		mg_primitive* primitive = &primitives[primitiveIndex];

		if(primitive->path.count)
		{
			context.primitive = primitive;
			context.pathIndex = pathCount;
			context.pathScreenExtents = (vec4){FLT_MAX, FLT_MAX, -FLT_MAX, -FLT_MAX};

			if(primitive->cmd == MG_CMD_STROKE)
			{
				mg_mtl_render_stroke(&context, pathElements + primitive->path.startIndex, &primitive->path);
			}
			else
			{
				int segCount = 0;
				for(int eltIndex = 0;
			    	(eltIndex < primitive->path.count) && (primitive->path.startIndex + eltIndex < eltCount);
			    	eltIndex++)
				{
					context.localEltIndex = segCount;

					mg_path_elt* elt = &pathElements[primitive->path.startIndex + eltIndex];

					if(elt->type != MG_PATH_MOVE)
					{
						vec2 p[4] = {currentPos, elt->p[0], elt->p[1], elt->p[2]};
						mg_mtl_canvas_encode_element(&context, elt->type, p);
						segCount++;
					}
					switch(elt->type)
					{
						case MG_PATH_MOVE:
							currentPos = elt->p[0];
							break;

						case MG_PATH_LINE:
							currentPos = elt->p[0];
							break;

						case MG_PATH_QUADRATIC:
							currentPos = elt->p[1];
							break;

						case MG_PATH_CUBIC:
							currentPos = elt->p[2];
							break;
					}
				}
			}
			//NOTE: push path
			mg_mtl_path* path = &pathBufferData[pathCount];
			pathCount++;

			path->cmd =	(mg_mtl_cmd)primitive->cmd;
			path->box = (vector_float4){maximum(primitive->attributes.clip.x, context.pathScreenExtents.x),
		                                maximum(primitive->attributes.clip.y, context.pathScreenExtents.y),
		                                minimum(primitive->attributes.clip.x + primitive->attributes.clip.w, context.pathScreenExtents.z),
		                                minimum(primitive->attributes.clip.y + primitive->attributes.clip.h, context.pathScreenExtents.w)};

			path->color = (vector_float4){primitive->attributes.color.r,
			                              primitive->attributes.color.g,
			                              primitive->attributes.color.b,
			                              primitive->attributes.color.a};
			//TODO: compute uv transform
		}
	}

	mg_mtl_surface* surface = (mg_mtl_surface*)mg_surface_data_from_handle(backend->surface);
	ASSERT(surface && surface->interface.backend == MG_BACKEND_METAL);

	mp_rect frame = mg_surface_get_frame(backend->surface);
	f32 scale = surface->mtlLayer.contentsScale;
	vec2 viewportSize = {frame.w * scale, frame.h * scale};
	int tileSize = MG_MTL_TILE_SIZE;
	int nTilesX = (int)(frame.w * scale + tileSize - 1)/tileSize;
	int nTilesY = (int)(frame.h * scale + tileSize - 1)/tileSize;

	/////////////////////////////////////////////////////////////////////////////////////
	//TODO: ensure screen tiles buffer is correct size
	/////////////////////////////////////////////////////////////////////////////////////

	//NOTE: encode GPU commands
	@autoreleasepool
	{
		mg_mtl_surface_acquire_command_buffer(surface);

		//NOTE: clear counters
		id<MTLBlitCommandEncoder> blitEncoder = [surface->commandBuffer blitCommandEncoder];
		blitEncoder.label = @"clear counters";
		[blitEncoder fillBuffer: backend->segmentCountBuffer range: NSMakeRange(0, sizeof(int)) value: 0];
		[blitEncoder fillBuffer: backend->tileQueueCountBuffer range: NSMakeRange(0, sizeof(int)) value: 0];
		[blitEncoder fillBuffer: backend->tileOpCountBuffer range: NSMakeRange(0, sizeof(int)) value: 0];
		[blitEncoder fillBuffer: backend->logOffsetBuffer[backend->bufferIndex] range: NSMakeRange(0, sizeof(int)) value: 0];
		[blitEncoder endEncoding];

		//NOTE: path setup pass
		id<MTLComputeCommandEncoder> pathEncoder = [surface->commandBuffer computeCommandEncoder];
		pathEncoder.label = @"path pass";
		[pathEncoder setComputePipelineState: backend->pathPipeline];

		[pathEncoder setBytes:&pathCount length:sizeof(int) atIndex:0];
		[pathEncoder setBuffer:backend->pathBuffer[backend->bufferIndex] offset:0 atIndex:1];
		[pathEncoder setBuffer:backend->pathQueueBuffer offset:0 atIndex:2];
		[pathEncoder setBuffer:backend->tileQueueBuffer offset:0 atIndex:3];
		[pathEncoder setBuffer:backend->tileQueueCountBuffer offset:0 atIndex:4];
		[pathEncoder setBytes:&tileSize length:sizeof(int) atIndex:5];
		[pathEncoder setBytes:&scale length:sizeof(int) atIndex:6];

		MTLSize pathGridSize = MTLSizeMake(pathCount, 1, 1);
		MTLSize pathGroupSize = MTLSizeMake([backend->pathPipeline maxTotalThreadsPerThreadgroup], 1, 1);

		[pathEncoder dispatchThreads: pathGridSize threadsPerThreadgroup: pathGroupSize];
		[pathEncoder endEncoding];

		//NOTE: segment setup pass
		id<MTLComputeCommandEncoder> segmentEncoder = [surface->commandBuffer computeCommandEncoder];
		segmentEncoder.label = @"segment pass";
		[segmentEncoder setComputePipelineState: backend->segmentPipeline];

		[segmentEncoder setBytes:&eltCount length:sizeof(int) atIndex:0];
		[segmentEncoder setBuffer:backend->elementBuffer[backend->bufferIndex] offset:0 atIndex:1];
		[segmentEncoder setBuffer:backend->segmentCountBuffer offset:0 atIndex:2];
		[segmentEncoder setBuffer:backend->segmentBuffer offset:0 atIndex:3];
		[segmentEncoder setBuffer:backend->pathQueueBuffer offset:0 atIndex:4];
		[segmentEncoder setBuffer:backend->tileQueueBuffer offset:0 atIndex:5];
		[segmentEncoder setBuffer:backend->tileOpBuffer offset:0 atIndex:6];
		[segmentEncoder setBuffer:backend->tileOpCountBuffer offset:0 atIndex:7];
		[segmentEncoder setBytes:&tileSize length:sizeof(int) atIndex:8];
		[segmentEncoder setBytes:&scale length:sizeof(int) atIndex:9];
		[segmentEncoder setBuffer:backend->logBuffer[backend->bufferIndex] offset:0 atIndex:10];
		[segmentEncoder setBuffer:backend->logOffsetBuffer[backend->bufferIndex] offset:0 atIndex:11];

		MTLSize segmentGridSize = MTLSizeMake(context.mtlEltCount, 1, 1);
		MTLSize segmentGroupSize = MTLSizeMake([backend->segmentPipeline maxTotalThreadsPerThreadgroup], 1, 1);

		[segmentEncoder dispatchThreads: segmentGridSize threadsPerThreadgroup: segmentGroupSize];
		[segmentEncoder endEncoding];

		//NOTE: backprop pass
		id<MTLComputeCommandEncoder> backpropEncoder = [surface->commandBuffer computeCommandEncoder];
		backpropEncoder.label = @"backprop pass";
		[backpropEncoder setComputePipelineState: backend->backpropPipeline];

		[backpropEncoder setBuffer:backend->pathQueueBuffer offset:0 atIndex:0];
		[backpropEncoder setBuffer:backend->tileQueueBuffer offset:0 atIndex:1];
		[backpropEncoder setBuffer:backend->logBuffer[backend->bufferIndex] offset:0 atIndex:2];
		[backpropEncoder setBuffer:backend->logOffsetBuffer[backend->bufferIndex] offset:0 atIndex:3];

		MTLSize backpropGroupSize = MTLSizeMake([backend->backpropPipeline maxTotalThreadsPerThreadgroup], 1, 1);
		MTLSize backpropGridSize = MTLSizeMake(pathCount*backpropGroupSize.width, 1, 1);

		[backpropEncoder dispatchThreads: backpropGridSize threadsPerThreadgroup: backpropGroupSize];
		[backpropEncoder endEncoding];

		//NOTE: merge pass
		id<MTLComputeCommandEncoder> mergeEncoder = [surface->commandBuffer computeCommandEncoder];
		mergeEncoder.label = @"merge pass";
		[mergeEncoder setComputePipelineState: backend->mergePipeline];

		[mergeEncoder setBytes:&pathCount length:sizeof(int) atIndex:0];
		[mergeEncoder setBuffer:backend->pathBuffer[backend->bufferIndex] offset:0 atIndex:1];
		[mergeEncoder setBuffer:backend->pathQueueBuffer offset:0 atIndex:2];
		[mergeEncoder setBuffer:backend->tileQueueBuffer offset:0 atIndex:3];
		[mergeEncoder setBuffer:backend->tileOpBuffer offset:0 atIndex:4];
		[mergeEncoder setBuffer:backend->tileOpCountBuffer offset:0 atIndex:5];
		[mergeEncoder setBuffer:backend->screenTilesBuffer offset:0 atIndex:6];
		[mergeEncoder setBuffer:backend->logBuffer[backend->bufferIndex] offset:0 atIndex:7];
		[mergeEncoder setBuffer:backend->logOffsetBuffer[backend->bufferIndex] offset:0 atIndex:8];

		MTLSize mergeGridSize = MTLSizeMake(nTilesX, nTilesY, 1);
		MTLSize mergeGroupSize = MTLSizeMake(16, 16, 1);

		[mergeEncoder dispatchThreads: mergeGridSize threadsPerThreadgroup: mergeGroupSize];
		[mergeEncoder endEncoding];

		//NOTE: raster pass
		id<MTLComputeCommandEncoder> rasterEncoder = [surface->commandBuffer computeCommandEncoder];
		rasterEncoder.label = @"raster pass";
		[rasterEncoder setComputePipelineState: backend->rasterPipeline];

		[rasterEncoder setBuffer:backend->screenTilesBuffer offset:0 atIndex:0];
		[rasterEncoder setBuffer:backend->tileOpBuffer offset:0 atIndex:1];
		[rasterEncoder setBuffer:backend->pathBuffer[backend->bufferIndex] offset:0 atIndex:2];
		[rasterEncoder setBuffer:backend->segmentBuffer offset:0 atIndex:3];
		[rasterEncoder setBytes:&tileSize length:sizeof(int) atIndex:4];
		[rasterEncoder setBytes:&backend->msaaCount length:sizeof(int) atIndex:5];
		[rasterEncoder setBuffer:backend->logBuffer[backend->bufferIndex] offset:0 atIndex:6];
		[rasterEncoder setBuffer:backend->logOffsetBuffer[backend->bufferIndex] offset:0 atIndex:7];

		[rasterEncoder setTexture:backend->outTexture atIndex:0];

		MTLSize rasterGridSize = MTLSizeMake(viewportSize.x, viewportSize.y, 1);
		MTLSize rasterGroupSize = MTLSizeMake(16, 16, 1);
		[rasterEncoder dispatchThreads: rasterGridSize threadsPerThreadgroup: rasterGroupSize];

		[rasterEncoder endEncoding];

		//NOTE: blit pass
		mg_mtl_surface_acquire_drawable(surface);
		if(surface->drawable != nil)
		{
			MTLViewport viewport = {0, 0, viewportSize.x, viewportSize.y, 0, 1};

			//TODO: clear here?
			MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
			renderPassDescriptor.colorAttachments[0].texture = surface->drawable.texture;
			renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
			renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(clearColor.r, clearColor.g, clearColor.b, clearColor.a);
			renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;

			id<MTLRenderCommandEncoder> renderEncoder = [surface->commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
			renderEncoder.label = @"blit pass";
			[renderEncoder setViewport: viewport];
			[renderEncoder setRenderPipelineState: backend->blitPipeline];
			[renderEncoder setFragmentTexture: backend->outTexture atIndex: 0];
			[renderEncoder drawPrimitives: MTLPrimitiveTypeTriangle
			 	vertexStart: 0
			 	vertexCount: 3 ];
			[renderEncoder endEncoding];
		}

		//NOTE: finalize
		[surface->commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> commandBuffer)
			{
				mg_mtl_print_log(backend->bufferIndex, backend->logBuffer[backend->bufferIndex], backend->logOffsetBuffer[backend->bufferIndex]);
				dispatch_semaphore_signal(backend->bufferSemaphore);
			}];
	}
}

void mg_mtl_canvas_destroy(mg_canvas_backend* interface)
{
	mg_mtl_canvas_backend* backend = (mg_mtl_canvas_backend*)interface;

	@autoreleasepool
	{
		[backend->pathPipeline release];
		[backend->segmentPipeline release];
		[backend->backpropPipeline release];
		[backend->mergePipeline release];
		[backend->rasterPipeline release];
		[backend->blitPipeline release];

		for(int i=0; i<MG_MTL_INPUT_BUFFERS_COUNT; i++)
		{
			[backend->pathBuffer[i] release];
			[backend->elementBuffer[i] release];
			[backend->logBuffer[i] release];
			[backend->logOffsetBuffer[i] release];
		}
		[backend->segmentCountBuffer release];
		[backend->segmentBuffer release];
		[backend->tileQueueBuffer release];
		[backend->tileQueueCountBuffer release];
		[backend->tileOpBuffer release];
		[backend->tileOpCountBuffer release];
		[backend->screenTilesBuffer release];
	}

	free(backend);
}

const u32 MG_MTL_PATH_BUFFER_SIZE       = (4<<20)*sizeof(mg_mtl_path),
          MG_MTL_ELEMENT_BUFFER_SIZE    = (4<<20)*sizeof(mg_mtl_path_elt),
          MG_MTL_SEGMENT_BUFFER_SIZE    = (4<<20)*sizeof(mg_mtl_segment),
          MG_MTL_PATH_QUEUE_BUFFER_SIZE = (4<<20)*sizeof(mg_mtl_path_queue),
          MG_MTL_TILE_QUEUE_BUFFER_SIZE = (4<<20)*sizeof(mg_mtl_tile_queue),
          MG_MTL_TILE_OP_BUFFER_SIZE    = (4<<20)*sizeof(mg_mtl_tile_op);

mg_canvas_backend* mg_mtl_canvas_create(mg_surface surface)
{
	mg_mtl_canvas_backend* backend = 0;

	mg_surface_data* surfaceData = mg_surface_data_from_handle(surface);
	if(surfaceData && surfaceData->backend == MG_BACKEND_METAL)
	{
		mg_mtl_surface* metalSurface = (mg_mtl_surface*)surfaceData;

		backend = malloc_type(mg_mtl_canvas_backend);
		memset(backend, 0, sizeof(mg_mtl_canvas_backend));

		backend->msaaCount = MG_MTL_MSAA_COUNT;
		backend->surface = surface;

		//NOTE(martin): setup interface functions
		backend->interface.destroy = mg_mtl_canvas_destroy;
		backend->interface.render = mg_mtl_canvas_render;

		@autoreleasepool{
			//NOTE: load metal library
			str8 shaderPath = mp_app_get_resource_path(mem_scratch(), "../resources/mtl_renderer.metallib");
			NSString* metalFileName = [[NSString alloc] initWithBytes: shaderPath.ptr length:shaderPath.len encoding: NSUTF8StringEncoding];
			NSError* err = 0;
			id<MTLLibrary> library = [metalSurface->device newLibraryWithFile: metalFileName error:&err];
			if(err != nil)
			{
				const char* errStr = [[err localizedDescription] UTF8String];
				LOG_ERROR("error : %s\n", errStr);
				return(0);
			}
			id<MTLFunction> pathFunction = [library newFunctionWithName:@"mtl_path_setup"];
			id<MTLFunction> segmentFunction = [library newFunctionWithName:@"mtl_segment_setup"];
			id<MTLFunction> backpropFunction = [library newFunctionWithName:@"mtl_backprop"];
			id<MTLFunction> mergeFunction = [library newFunctionWithName:@"mtl_merge"];
			id<MTLFunction> rasterFunction = [library newFunctionWithName:@"mtl_raster"];
			id<MTLFunction> vertexFunction = [library newFunctionWithName:@"mtl_vertex_shader"];
			id<MTLFunction> fragmentFunction = [library newFunctionWithName:@"mtl_fragment_shader"];

			//NOTE: create pipelines
			NSError* error = NULL;

			backend->pathPipeline = [metalSurface->device newComputePipelineStateWithFunction: pathFunction
		                                                                           	error:&error];

			backend->segmentPipeline = [metalSurface->device newComputePipelineStateWithFunction: segmentFunction
		                                                                           	error:&error];

			backend->backpropPipeline = [metalSurface->device newComputePipelineStateWithFunction: backpropFunction
		                                                                           	error:&error];

			backend->mergePipeline = [metalSurface->device newComputePipelineStateWithFunction: mergeFunction
		                                                                           	error:&error];

			backend->rasterPipeline = [metalSurface->device newComputePipelineStateWithFunction: rasterFunction
		                                                                           	error:&error];


			MTLRenderPipelineDescriptor *pipelineStateDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
			pipelineStateDescriptor.label = @"blit pipeline";
			pipelineStateDescriptor.vertexFunction = vertexFunction;
			pipelineStateDescriptor.fragmentFunction = fragmentFunction;
			pipelineStateDescriptor.colorAttachments[0].pixelFormat = metalSurface->mtlLayer.pixelFormat;
			pipelineStateDescriptor.colorAttachments[0].blendingEnabled = YES;
			pipelineStateDescriptor.colorAttachments[0].rgbBlendOperation = MTLBlendOperationAdd;
			pipelineStateDescriptor.colorAttachments[0].sourceRGBBlendFactor = MTLBlendFactorOne;
			pipelineStateDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
			pipelineStateDescriptor.colorAttachments[0].alphaBlendOperation = MTLBlendOperationAdd;
			pipelineStateDescriptor.colorAttachments[0].sourceAlphaBlendFactor = MTLBlendFactorOne;
			pipelineStateDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactorOneMinusSourceAlpha;

			backend->blitPipeline = [metalSurface->device newRenderPipelineStateWithDescriptor: pipelineStateDescriptor error:&err];

			//NOTE: create textures
			mp_rect frame = mg_surface_get_frame(surface);
			f32 scale = metalSurface->mtlLayer.contentsScale;

			MTLTextureDescriptor* texDesc = [[MTLTextureDescriptor alloc] init];
			texDesc.textureType = MTLTextureType2D;
			texDesc.storageMode = MTLStorageModePrivate;
			texDesc.usage = MTLTextureUsageShaderRead | MTLTextureUsageShaderWrite;
			texDesc.pixelFormat = MTLPixelFormatRGBA8Unorm;
			texDesc.width = frame.w * scale;
			texDesc.height = frame.h * scale;

			backend->outTexture = [metalSurface->device newTextureWithDescriptor:texDesc];

			//NOTE: create buffers

			backend->bufferSemaphore = dispatch_semaphore_create(MG_MTL_INPUT_BUFFERS_COUNT);
			backend->bufferIndex = 0;

			MTLResourceOptions bufferOptions = MTLResourceCPUCacheModeWriteCombined
			                                 | MTLResourceStorageModeShared;

			for(int i=0; i<MG_MTL_INPUT_BUFFERS_COUNT; i++)
			{
				backend->pathBuffer[i] = [metalSurface->device newBufferWithLength: MG_MTL_PATH_BUFFER_SIZE
			                                                 	options: bufferOptions];

				backend->elementBuffer[i] = [metalSurface->device newBufferWithLength: MG_MTL_ELEMENT_BUFFER_SIZE
			                                                   	options: bufferOptions];
			}

			bufferOptions = MTLResourceStorageModePrivate;
			backend->segmentBuffer = [metalSurface->device newBufferWithLength: MG_MTL_SEGMENT_BUFFER_SIZE
			                                                   options: bufferOptions];

			backend->segmentCountBuffer = [metalSurface->device newBufferWithLength: sizeof(int)
			                                                   options: bufferOptions];


			backend->pathQueueBuffer = [metalSurface->device newBufferWithLength: MG_MTL_PATH_QUEUE_BUFFER_SIZE
			                                                   options: bufferOptions];

			backend->tileQueueBuffer = [metalSurface->device newBufferWithLength: MG_MTL_TILE_QUEUE_BUFFER_SIZE
			                                                   options: bufferOptions];

			backend->tileQueueCountBuffer = [metalSurface->device newBufferWithLength: sizeof(int)
			                                                   options: bufferOptions];

			backend->tileOpBuffer = [metalSurface->device newBufferWithLength: MG_MTL_TILE_OP_BUFFER_SIZE
			                                                   options: bufferOptions];

			backend->tileOpCountBuffer = [metalSurface->device newBufferWithLength: sizeof(int)
			                                                   options: bufferOptions];

			int tileSize = MG_MTL_TILE_SIZE;
			int nTilesX = (int)(frame.w * scale + tileSize - 1)/tileSize;
			int nTilesY = (int)(frame.h * scale + tileSize - 1)/tileSize;
			backend->screenTilesBuffer = [metalSurface->device newBufferWithLength: nTilesX*nTilesY*sizeof(int)
			                                                   options: bufferOptions];


			bufferOptions = MTLResourceStorageModeShared;
			for(int i=0; i<MG_MTL_INPUT_BUFFERS_COUNT; i++)
			{
				backend->logBuffer[i] = [metalSurface->device newBufferWithLength: 1<<20
			                                                   options: bufferOptions];

				backend->logOffsetBuffer[i] = [metalSurface->device newBufferWithLength: sizeof(int)
			                                                   options: bufferOptions];
			}
		}
	}
	return((mg_canvas_backend*)backend);
}

#undef LOG_SUBSYSTEM