-- Fix Multi-Render Target
-- This script patches LOVE rendering pipeline to workaround MRT bandwidth problem in some GPU drivers.
-- See: https://github.com/love2d/love/commit/1896f82f5d40d33a551f7c5fd9662db3b4ccdf31

if love.getVersion() ~= 11 or love._version >= "11.3" then
	-- LOVE pre-11.0 does not have this problem.
	-- LOVE 11.3 already have this problem worked around.
	return true
end

local love_graphics = package.preload["love.graphics"]

package.preload["love.graphics"] = function()
	local graphics = love_graphics()
	local table_concat = table.concat
	local ipairs = ipairs

	-- SHADERS

	local GLSL = {}

	GLSL.VERSION = { -- index using [target][gles]
		glsl1 = {[false]="#version 120",      [true]="#version 100"},
		glsl3 = {[false]="#version 330 core", [true]="#version 300 es"},
	}

	GLSL.SYNTAX = [[
	#if !defined(GL_ES) && __VERSION__ < 140
		#define lowp
		#define mediump
		#define highp
	#endif
	#if defined(VERTEX) || __VERSION__ > 100 || defined(GL_FRAGMENT_PRECISION_HIGH)
		#define LOVE_HIGHP_OR_MEDIUMP highp
	#else
		#define LOVE_HIGHP_OR_MEDIUMP mediump
	#endif
	#define number float
	#define Image sampler2D
	#define ArrayImage sampler2DArray
	#define CubeImage samplerCube
	#define VolumeImage sampler3D
	#if __VERSION__ >= 300 && !defined(LOVE_GLSL1_ON_GLSL3)
		#define DepthImage sampler2DShadow
		#define DepthArrayImage sampler2DArrayShadow
		#define DepthCubeImage samplerCubeShadow
	#endif
	#define extern uniform
	#ifdef GL_EXT_texture_array
	#extension GL_EXT_texture_array : enable
	#endif
	#ifdef GL_OES_texture_3D
	#extension GL_OES_texture_3D : enable
	#endif
	#ifdef GL_OES_standard_derivatives
	#extension GL_OES_standard_derivatives : enable
	#endif
	]]

	-- Uniforms shared by the vertex and pixel shader stages.
	GLSL.UNIFORMS = [[
	// According to the GLSL ES 1.0 spec, uniform precision must match between stages,
	// but we can't guarantee that highp is always supported in fragment shaders...
	// We *really* don't want to use mediump for these in vertex shaders though.
	uniform LOVE_HIGHP_OR_MEDIUMP mat4 ViewSpaceFromLocal;
	uniform LOVE_HIGHP_OR_MEDIUMP mat4 ClipSpaceFromView;
	uniform LOVE_HIGHP_OR_MEDIUMP mat4 ClipSpaceFromLocal;
	uniform LOVE_HIGHP_OR_MEDIUMP mat3 ViewNormalFromLocal;
	uniform LOVE_HIGHP_OR_MEDIUMP vec4 love_ScreenSize;
	// Compatibility
	#define TransformMatrix ViewSpaceFromLocal
	#define ProjectionMatrix ClipSpaceFromView
	#define TransformProjectionMatrix ClipSpaceFromLocal
	#define NormalMatrix ViewNormalFromLocal
	]]

	GLSL.FUNCTIONS = [[
	#ifdef GL_ES
		#if __VERSION__ >= 300 || defined(GL_EXT_texture_array)
			precision lowp sampler2DArray;
		#endif
		#if __VERSION__ >= 300 || defined(GL_OES_texture_3D)
			precision lowp sampler3D;
		#endif
		#if __VERSION__ >= 300
			precision lowp sampler2DShadow;
			precision lowp samplerCubeShadow;
			precision lowp sampler2DArrayShadow;
		#endif
	#endif
	#if __VERSION__ >= 130 && !defined(LOVE_GLSL1_ON_GLSL3)
		#define Texel texture
	#else
		#if __VERSION__ >= 130
			#define texture2D Texel
			#define texture3D Texel
			#define textureCube Texel
			#define texture2DArray Texel
			#define love_texture2D texture
			#define love_texture3D texture
			#define love_textureCube texture
			#define love_texture2DArray texture
		#else
			#define love_texture2D texture2D
			#define love_texture3D texture3D
			#define love_textureCube textureCube
			#define love_texture2DArray texture2DArray
		#endif
		vec4 Texel(sampler2D s, vec2 c) { return love_texture2D(s, c); }
		vec4 Texel(samplerCube s, vec3 c) { return love_textureCube(s, c); }
		#if __VERSION__ > 100 || defined(GL_OES_texture_3D)
			vec4 Texel(sampler3D s, vec3 c) { return love_texture3D(s, c); }
		#endif
		#if __VERSION__ >= 130 || defined(GL_EXT_texture_array)
			vec4 Texel(sampler2DArray s, vec3 c) { return love_texture2DArray(s, c); }
		#endif
		#ifdef PIXEL
			vec4 Texel(sampler2D s, vec2 c, float b) { return love_texture2D(s, c, b); }
			vec4 Texel(samplerCube s, vec3 c, float b) { return love_textureCube(s, c, b); }
			#if __VERSION__ > 100 || defined(GL_OES_texture_3D)
				vec4 Texel(sampler3D s, vec3 c, float b) { return love_texture3D(s, c, b); }
			#endif
			#if __VERSION__ >= 130 || defined(GL_EXT_texture_array)
				vec4 Texel(sampler2DArray s, vec3 c, float b) { return love_texture2DArray(s, c, b); }
			#endif
		#endif
		#define texture love_texture
	#endif
	float gammaToLinearPrecise(float c) {
		return c <= 0.04045 ? c * 0.077399380804954 : pow((c + 0.055) * 0.9478672985782, 2.4);
	}
	vec3 gammaToLinearPrecise(vec3 c) {
		bvec3 leq = lessThanEqual(c, vec3(0.04045));
		c.r = leq.r ? c.r * 0.077399380804954 : pow((c.r + 0.055) * 0.9478672985782, 2.4);
		c.g = leq.g ? c.g * 0.077399380804954 : pow((c.g + 0.055) * 0.9478672985782, 2.4);
		c.b = leq.b ? c.b * 0.077399380804954 : pow((c.b + 0.055) * 0.9478672985782, 2.4);
		return c;
	}
	vec4 gammaToLinearPrecise(vec4 c) { return vec4(gammaToLinearPrecise(c.rgb), c.a); }
	float linearToGammaPrecise(float c) {
		return c < 0.0031308 ? c * 12.92 : 1.055 * pow(c, 1.0 / 2.4) - 0.055;
	}
	vec3 linearToGammaPrecise(vec3 c) {
		bvec3 lt = lessThanEqual(c, vec3(0.0031308));
		c.r = lt.r ? c.r * 12.92 : 1.055 * pow(c.r, 1.0 / 2.4) - 0.055;
		c.g = lt.g ? c.g * 12.92 : 1.055 * pow(c.g, 1.0 / 2.4) - 0.055;
		c.b = lt.b ? c.b * 12.92 : 1.055 * pow(c.b, 1.0 / 2.4) - 0.055;
		return c;
	}
	vec4 linearToGammaPrecise(vec4 c) { return vec4(linearToGammaPrecise(c.rgb), c.a); }
	// http://chilliant.blogspot.com.au/2012/08/srgb-approximations-for-hlsl.html?m=1
	mediump float gammaToLinearFast(mediump float c) { return c * (c * (c * 0.305306011 + 0.682171111) + 0.012522878); }
	mediump vec3 gammaToLinearFast(mediump vec3 c) { return c * (c * (c * 0.305306011 + 0.682171111) + 0.012522878); }
	mediump vec4 gammaToLinearFast(mediump vec4 c) { return vec4(gammaToLinearFast(c.rgb), c.a); }
	mediump float linearToGammaFast(mediump float c) { return max(1.055 * pow(max(c, 0.0), 0.41666666) - 0.055, 0.0); }
	mediump vec3 linearToGammaFast(mediump vec3 c) { return max(1.055 * pow(max(c, vec3(0.0)), vec3(0.41666666)) - 0.055, vec3(0.0)); }
	mediump vec4 linearToGammaFast(mediump vec4 c) { return vec4(linearToGammaFast(c.rgb), c.a); }
	#define gammaToLinear gammaToLinearFast
	#define linearToGamma linearToGammaFast
	#ifdef LOVE_GAMMA_CORRECT
		#define gammaCorrectColor gammaToLinear
		#define unGammaCorrectColor linearToGamma
		#define gammaCorrectColorPrecise gammaToLinearPrecise
		#define unGammaCorrectColorPrecise linearToGammaPrecise
		#define gammaCorrectColorFast gammaToLinearFast
		#define unGammaCorrectColorFast linearToGammaFast
	#else
		#define gammaCorrectColor
		#define unGammaCorrectColor
		#define gammaCorrectColorPrecise
		#define unGammaCorrectColorPrecise
		#define gammaCorrectColorFast
		#define unGammaCorrectColorFast
	#endif]]

	GLSL.VERTEX = {
		HEADER = [[
	#define love_Position gl_Position
	#if __VERSION__ >= 130
		#define attribute in
		#define varying out
		#ifndef LOVE_GLSL1_ON_GLSL3
			#define love_VertexID gl_VertexID
			#define love_InstanceID gl_InstanceID
		#endif
	#endif
	#ifdef GL_ES
		uniform mediump float love_PointSize;
	#endif]],

		FUNCTIONS = [[
	void setPointSize() {
	#ifdef GL_ES
		gl_PointSize = love_PointSize;
	#endif
	}]],

		MAIN = [[
	attribute vec4 VertexPosition;
	attribute vec4 VertexTexCoord;
	attribute vec4 VertexColor;
	attribute vec4 ConstantColor;
	varying vec4 VaryingTexCoord;
	varying vec4 VaryingColor;
	vec4 position(mat4 clipSpaceFromLocal, vec4 localPosition);
	void main() {
		VaryingTexCoord = VertexTexCoord;
		VaryingColor = gammaCorrectColor(VertexColor) * ConstantColor;
		setPointSize();
		love_Position = position(ClipSpaceFromLocal, VertexPosition);
	}]],
	}

	GLSL.PIXEL = {
		HEADER = [[
	#ifdef GL_ES
		precision mediump float;
	#endif
	#define love_MaxCanvases gl_MaxDrawBuffers
	#if __VERSION__ >= 130
		#define varying in
		// Some drivers seem to make the pixel shader do more work when multiple
		// pixel shader outputs are defined, even when only one is actually used.
		// TODO: We should use reflection or something instead of this, to determine
		// how many outputs are actually used in the shader code.
		#ifdef LOVE_MULTI_CANVAS
			layout(location = 0) out vec4 love_Canvases[love_MaxCanvases];
			#define love_PixelColor love_Canvases[0]
		#else
			layout(location = 0) out vec4 love_PixelColor;
		#endif
	#else
		#ifdef LOVE_MULTI_CANVAS
			#define love_Canvases gl_FragData
		#endif
		#define love_PixelColor gl_FragColor
	#endif
	// See Shader::updateScreenParams in Shader.cpp.
	#define love_PixelCoord (vec2(gl_FragCoord.x, (gl_FragCoord.y * love_ScreenSize.z) + love_ScreenSize.w))]],

		FUNCTIONS = [[
	uniform sampler2D love_VideoYChannel;
	uniform sampler2D love_VideoCbChannel;
	uniform sampler2D love_VideoCrChannel;
	vec4 VideoTexel(vec2 texcoords) {
		vec3 yuv;
		yuv[0] = Texel(love_VideoYChannel, texcoords).r;
		yuv[1] = Texel(love_VideoCbChannel, texcoords).r;
		yuv[2] = Texel(love_VideoCrChannel, texcoords).r;
		yuv += vec3(-0.0627451017, -0.501960814, -0.501960814);
		vec4 color;
		color.r = dot(yuv, vec3(1.164,  0.000,  1.596));
		color.g = dot(yuv, vec3(1.164, -0.391, -0.813));
		color.b = dot(yuv, vec3(1.164,  2.018,  0.000));
		color.a = 1.0;
		return gammaCorrectColor(color);
	}]],

		MAIN = [[
	uniform sampler2D MainTex;
	varying LOVE_HIGHP_OR_MEDIUMP vec4 VaryingTexCoord;
	varying mediump vec4 VaryingColor;
	vec4 effect(vec4 vcolor, Image tex, vec2 texcoord, vec2 pixcoord);
	void main() {
		love_PixelColor = effect(VaryingColor, MainTex, VaryingTexCoord.st, love_PixelCoord);
	}]],

		MAIN_CUSTOM = [[
	varying LOVE_HIGHP_OR_MEDIUMP vec4 VaryingTexCoord;
	varying mediump vec4 VaryingColor;
	void effect();
	void main() {
		effect();
	}]],
	}

	local function getLanguageTarget(code)
		if not code then return nil end
		return (code:match("^%s*#pragma language (%w+)")) or "glsl1"
	end

	local function createShaderStageCode(stage, code, lang, gles, glsl1on3, gammacorrect, custom, multicanvas)
		stage = stage:upper()
		return table_concat({
			GLSL.VERSION[lang][gles],
			"#define " ..stage .. " " .. stage,
			glsl1on3 and "#define LOVE_GLSL1_ON_GLSL3 1" or "",
			gammacorrect and "#define LOVE_GAMMA_CORRECT 1" or "",
			multicanvas and "#define LOVE_MULTI_CANVAS 1" or "",
			GLSL.SYNTAX,
			GLSL[stage].HEADER,
			GLSL.UNIFORMS,
			GLSL.FUNCTIONS,
			GLSL[stage].FUNCTIONS,
			custom and GLSL[stage].MAIN_CUSTOM or GLSL[stage].MAIN,
			((lang == "glsl1" or glsl1on3) and not gles) and "#line 0" or "#line 1",
			code,
		}, "\n")
	end

	local function isVertexCode(code)
		return code:match("vec4%s+position%s*%(") ~= nil
	end

	local function isPixelCode(code)
		if code:match("vec4%s+effect%s*%(") then
			return true
		elseif code:match("void%s+effect%s*%(") then -- custom effect function
			local multicanvas = code:match("love_Canvases") ~= nil
			return true, true, multicanvas
		else
			return false
		end
	end

	function graphics._shaderCodeToGLSL(gles, arg1, arg2)
		local vertexcode, pixelcode
		local is_custompixel = false -- whether pixel code has "effects" function instead of "effect"
		local is_multicanvas = false

		if arg1 then
			if isVertexCode(arg1) then
				vertexcode = arg1 -- first arg contains vertex shader code
			end

			local ispixel, isCustomPixel, isMultiCanvas = isPixelCode(arg1)
			if ispixel then
				pixelcode = arg1 -- first arg contains pixel shader code
				is_custompixel = isCustomPixel
				is_multicanvas = isMultiCanvas
			end
		end
		
		if arg2 then
			if isVertexCode(arg2) then
				vertexcode = arg2 -- second arg contains vertex shader code
			end

			local ispixel, isCustomPixel, isMultiCanvas = isPixelCode(arg2)
			if ispixel then
				pixelcode = arg2 -- second arg contains pixel shader code
				is_custompixel = isCustomPixel
				is_multicanvas = isMultiCanvas
			end
		end

		local supportsGLSL3 = graphics.getSupported().glsl3
		local gammacorrect = graphics.isGammaCorrect()

		local targetlang = getLanguageTarget(pixelcode or vertexcode)
		if getLanguageTarget(vertexcode or pixelcode) ~= targetlang then
			error("vertex and pixel shader languages must match", 2)
		end

		if targetlang == "glsl3" and not supportsGLSL3 then
			error("GLSL 3 shaders are not supported on this system!", 2)
		end

		if targetlang ~= nil and not GLSL.VERSION[targetlang] then
			error("Invalid shader language: " .. targetlang, 2)
		end

		local lang = targetlang or "glsl1"
		local glsl1on3 = false
		if lang == "glsl1" and supportsGLSL3 then
			lang = "glsl3"
			glsl1on3 = true
		end

		if vertexcode then
			vertexcode = createShaderStageCode("VERTEX", vertexcode, lang, gles, glsl1on3, gammacorrect)
		end
		if pixelcode then
			pixelcode = createShaderStageCode("PIXEL", pixelcode, lang, gles, glsl1on3, gammacorrect, is_custompixel, is_multicanvas)
		end

		return vertexcode, pixelcode
	end

	if love.graphics then
		love.graphics._shaderCodeToGLSL = graphics._shaderCodeToGLSL
	end

	local defaultcode = {
		vertex = [[
	vec4 position(mat4 clipSpaceFromLocal, vec4 localPosition) {
		return clipSpaceFromLocal * localPosition;
	}]],
		pixel = [[
	vec4 effect(vec4 vcolor, Image tex, vec2 texcoord, vec2 pixcoord) {
		return Texel(tex, texcoord) * vcolor;
	}]],
		videopixel = [[
	void effect() {
		love_PixelColor = VideoTexel(VaryingTexCoord.xy) * VaryingColor;
	}]],
		arraypixel = [[
	uniform ArrayImage MainTex;
	void effect() {
		love_PixelColor = Texel(MainTex, VaryingTexCoord.xyz) * VaryingColor;
	}]],
	}

	local defaults = {}
	local defaults_gammacorrect = {}

	local langs = {
		glsl1 = {target="glsl1", gles=false},
		essl1 = {target="glsl1", gles=true},
		glsl3 = {target="glsl3", gles=false},
		essl3 = {target="glsl3", gles=true},
	}

	for lang, info in pairs(langs) do
		for _, gammacorrect in ipairs{false, true} do
			local t = gammacorrect and defaults_gammacorrect or defaults
			t[lang] = {
				vertex = createShaderStageCode("VERTEX", defaultcode.vertex, info.target, info.gles, false, gammacorrect),
				pixel = createShaderStageCode("PIXEL", defaultcode.pixel, info.target, info.gles, false, gammacorrect, false),
				videopixel = createShaderStageCode("PIXEL", defaultcode.videopixel, info.target, info.gles, false, gammacorrect, true),
				arraypixel = createShaderStageCode("PIXEL", defaultcode.arraypixel, info.target, info.gles, false, gammacorrect, true),
			}
		end
	end

	graphics._setDefaultShaderCode(defaults, defaults_gammacorrect)
	graphics._nfmrt = true
	return graphics
end

return true
