// Copyright 2013 Dolphin Emulator Project
// Licensed under GPLv2
// Refer to the license.txt file included.

#include <cmath>
#include <locale.h>
#ifdef __APPLE__
	#include <xlocale.h>
#endif

#include "VideoCommon/GeometryShaderGen.h"
#include "VideoCommon/LightingShaderGen.h"
#include "VideoCommon/VertexShaderGen.h"
#include "VideoCommon/VideoConfig.h"

static char text[16384];

template<class T>
static inline void GenerateGeometryShader(T& out, u32 components, API_TYPE ApiType)
{
	// Non-uid template parameters will write to the dummy data (=> gets optimized out)
	geometry_shader_uid_data dummy_data;
	geometry_shader_uid_data* uid_data = out.template GetUidData<geometry_shader_uid_data>();
	if (uid_data == nullptr)
		uid_data = &dummy_data;

	out.SetBuffer(text);
	const bool is_writing_shadercode = (out.GetBuffer() != nullptr);
#ifndef ANDROID
	locale_t locale;
	locale_t old_locale;
	if (is_writing_shadercode)
	{
		locale = newlocale(LC_NUMERIC_MASK, "C", nullptr); // New locale for compilation
		old_locale = uselocale(locale); // Apply the locale for this thread
	}
#endif

	if (is_writing_shadercode)
		text[sizeof(text) - 1] = 0x7C;  // canary

	out.Write("//Geometry Shader for 3D stereoscopy\n");

	uid_data->stereo = g_ActiveConfig.iStereoMode > 0;
	if (ApiType == API_OPENGL)
	{
		// Insert layout parameters
		if (g_ActiveConfig.backend_info.bSupportsGSInstancing)
			out.Write("layout(triangles, invocations = %d) in;\n", g_ActiveConfig.iStereoMode > 0 ? 2 : 1);
		else
			out.Write("layout(triangles) in;\n");
		out.Write("layout(triangle_strip, max_vertices = %d) out;\n", g_ActiveConfig.backend_info.bSupportsGSInstancing ? 3 : 6);
	}

	out.Write("%s", s_lighting_struct);

	// uniforms
	if (ApiType == API_OPENGL)
		out.Write("layout(std140%s) uniform VSBlock {\n", g_ActiveConfig.backend_info.bSupportsBindingLayout ? ", binding = 2" : "");
	else
		out.Write("cbuffer VSBlock {\n");
	out.Write(s_shader_uniforms);
	out.Write("};\n");

	uid_data->numTexGens = xfmem.numTexGen.numTexGens;
	uid_data->pixel_lighting = g_ActiveConfig.bEnablePixelLighting;

	GenerateVSOutputStruct(out, ApiType);

	out.Write("centroid in VS_OUTPUT o[3];\n");
	out.Write("centroid out VS_OUTPUT f;\n");

	out.Write("flat out int layer;\n");

	out.Write("void main()\n{\n");

	// If the GPU supports invocation we don't need a for loop and can simply use the
	// invocation identifier to determine which layer we're rendering.
	if (g_ActiveConfig.backend_info.bSupportsGSInstancing)
		out.Write("\tint l = gl_InvocationID;\n");
	else
		out.Write("\tfor (int l = 0; l < %d; ++l) {\n", g_ActiveConfig.iStereoMode > 0 ? 2 : 1);

	out.Write("\tfor (int i = 0; i < 3; ++i) {\n");
	out.Write("\t\tlayer = l;\n");
	out.Write("\t\tgl_Layer = l;\n");
	out.Write("\t\tf = o[i];\n");
	out.Write("\t\tfloat4 pos = o[i].pos;\n");

	if (g_ActiveConfig.iStereoMode > 0)
	{
		// For stereoscopy add a small horizontal offset in Normalized Device Coordinates proportional
		// to the depth of the vertex. We retrieve the depth value from the w-component of the projected
		// vertex which contains the negated z-component of the original vertex.
		// For negative parallax (out-of-screen effects) we subtract a convergence value from
		// the depth value. This results in objects at a distance smaller than the convergence
		// distance to seemingly appear in front of the screen.
		// This formula is based on page 13 of the "Nvidia 3D Vision Automatic, Best Practices Guide"
		out.Write("\t\tf.clipPos.x = o[i].clipPos.x + " I_STEREOPARAMS"[l] * (o[i].clipPos.w - " I_STEREOPARAMS"[2]);\n");
		out.Write("\t\tpos.x = o[i].pos.x + " I_STEREOPARAMS"[l] * (o[i].pos.w - " I_STEREOPARAMS"[2]);\n");
	}

	out.Write("\t\tf.pos.x = pos.x;\n");
	out.Write("\t\tgl_Position = pos;\n");
	out.Write("\t\tEmitVertex();\n");
	out.Write("\t}\n");
	out.Write("\tEndPrimitive();\n");

	if (!g_ActiveConfig.backend_info.bSupportsGSInstancing)
		out.Write("\t}\n");

	out.Write("}\n");

	if (is_writing_shadercode)
	{
		if (text[sizeof(text) - 1] != 0x7C)
			PanicAlert("GeometryShader generator - buffer too small, canary has been eaten!");

#ifndef ANDROID
		uselocale(old_locale); // restore locale
		freelocale(locale);
#endif
	}
}

void GetGeometryShaderUid(GeometryShaderUid& object, u32 components, API_TYPE ApiType)
{
	GenerateGeometryShader<GeometryShaderUid>(object, components, ApiType);
}

void GenerateGeometryShaderCode(ShaderCode& object, u32 components, API_TYPE ApiType)
{
	GenerateGeometryShader<ShaderCode>(object, components, ApiType);
}