/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_config.h"

#if SDL_VIDEO_RENDER_OGL && !SDL_RENDER_DISABLED

#include "SDL_stdinc.h"
#include "SDL_log.h"
#include "SDL_opengl.h"
#include "SDL_video.h"
#include "SDL_shaders_gl.h"

/* OpenGL shader implementation */

/*#define DEBUG_SHADERS*/

typedef struct
{
    GLenum program;
    GLenum vert_shader;
    GLenum frag_shader;
} GL_ShaderData;

struct GL_ShaderContext
{
    GLenum (*glGetError)(void);

    PFNGLATTACHOBJECTARBPROC glAttachObjectARB;
    PFNGLCOMPILESHADERARBPROC glCompileShaderARB;
    PFNGLCREATEPROGRAMOBJECTARBPROC glCreateProgramObjectARB;
    PFNGLCREATESHADEROBJECTARBPROC glCreateShaderObjectARB;
    PFNGLDELETEOBJECTARBPROC glDeleteObjectARB;
    PFNGLGETINFOLOGARBPROC glGetInfoLogARB;
    PFNGLGETOBJECTPARAMETERIVARBPROC glGetObjectParameterivARB;
    PFNGLGETUNIFORMLOCATIONARBPROC glGetUniformLocationARB;
    PFNGLLINKPROGRAMARBPROC glLinkProgramARB;
    PFNGLSHADERSOURCEARBPROC glShaderSourceARB;
    PFNGLUNIFORM1IARBPROC glUniform1iARB;
    PFNGLUNIFORM1FARBPROC glUniform1fARB;
    PFNGLUSEPROGRAMOBJECTARBPROC glUseProgramObjectARB;

    SDL_bool GL_ARB_texture_rectangle_supported;

    GL_ShaderData shaders[NUM_SHADERS];
};

/*
 * NOTE: Always use sampler2D, etc here. We'll #define them to the
 *  texture_rectangle versions if we choose to use that extension.
 */
static const char *shader_source[NUM_SHADERS][2] =
{
    /* SHADER_NONE */
    { NULL, NULL },

    /* SHADER_SOLID */
    {
        /* vertex shader */
"varying vec4 v_color;\n"
"\n"
"void main()\n"
"{\n"
"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
"    v_color = gl_Color;\n"
"}",
        /* fragment shader */
"varying vec4 v_color;\n"
"\n"
"void main()\n"
"{\n"
"    gl_FragColor = v_color;\n"
"}"
    },

    /* SHADER_RGB */
    {
        /* vertex shader */
"varying vec4 v_color;\n"
"varying vec2 v_texCoord;\n"
"\n"
"void main()\n"
"{\n"
"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
"    v_color = gl_Color;\n"
"    v_texCoord = vec2(gl_MultiTexCoord0);\n"
"}",
        /* fragment shader */
"varying vec4 v_color;\n"
"varying vec2 v_texCoord;\n"
"uniform sampler2D tex0;\n"
"\n"
"void main()\n"
"{\n"
"    gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
"}"
    },

    /* SHADER_YV12 */
    {
        /* vertex shader */
"varying vec4 v_color;\n"
"varying vec2 v_texCoord;\n"
"\n"
"void main()\n"
"{\n"
"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
"    v_color = gl_Color;\n"
"    v_texCoord = vec2(gl_MultiTexCoord0);\n"
"}",
        /* fragment shader */
"varying vec4 v_color;\n"
"varying vec2 v_texCoord;\n"
"uniform sampler2D tex0; // Y \n"
"uniform sampler2D tex1; // U \n"
"uniform sampler2D tex2; // V \n"
"\n"
"// YUV offset \n"
"const vec3 offset = vec3(-0.0625, -0.5, -0.5);\n"
"\n"
"// RGB coefficients \n"
"const vec3 Rcoeff = vec3(1.164,  0.000,  1.596);\n"
"const vec3 Gcoeff = vec3(1.164, -0.391, -0.813);\n"
"const vec3 Bcoeff = vec3(1.164,  2.018,  0.000);\n"
"\n"
"void main()\n"
"{\n"
"    vec2 tcoord;\n"
"    vec3 yuv, rgb;\n"
"\n"
"    // Get the Y value \n"
"    tcoord = v_texCoord;\n"
"    yuv.x = texture2D(tex0, tcoord).r;\n"
"\n"
"    // Get the U and V values \n"
"    tcoord *= 0.5;\n"
"    yuv.y = texture2D(tex1, tcoord).r;\n"
"    yuv.z = texture2D(tex2, tcoord).r;\n"
"\n"
"    // Do the color transform \n"
"    yuv += offset;\n"
"    rgb.r = dot(yuv, Rcoeff);\n"
"    rgb.g = dot(yuv, Gcoeff);\n"
"    rgb.b = dot(yuv, Bcoeff);\n"
"\n"
"    // That was easy. :) \n"
"    gl_FragColor = vec4(rgb, 1.0) * v_color;\n"
"}"
    },
};

static SDL_bool
CompileShader(GL_ShaderContext *ctx, GLenum shader, const char *defines, const char *source)
{
    GLint status;
    const char *sources[2];

    sources[0] = defines;
    sources[1] = source;

    ctx->glShaderSourceARB(shader, SDL_arraysize(sources), sources, NULL);
    ctx->glCompileShaderARB(shader);
    ctx->glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
    if (status == 0) {
        GLint length;
        char *info;

        ctx->glGetObjectParameterivARB(shader, GL_OBJECT_INFO_LOG_LENGTH_ARB, &length);
        info = SDL_stack_alloc(char, length+1);
        ctx->glGetInfoLogARB(shader, length, NULL, info);
        SDL_LogError(SDL_LOG_CATEGORY_RENDER,
            "Failed to compile shader:\n%s%s\n%s", defines, source, info);
#ifdef DEBUG_SHADERS
        fprintf(stderr,
            "Failed to compile shader:\n%s%s\n%s", defines, source, info);
#endif
        SDL_stack_free(info);

        return SDL_FALSE;
    } else {
        return SDL_TRUE;
    }
}

static SDL_bool
CompileShaderProgram(GL_ShaderContext *ctx, int index, GL_ShaderData *data)
{
    const int num_tmus_bound = 4;
    const char *vert_defines = "";
    const char *frag_defines = "";
    int i;
    GLint location;

    if (index == SHADER_NONE) {
        return SDL_TRUE;
    }

    ctx->glGetError();

    /* Make sure we use the correct sampler type for our texture type */
    if (ctx->GL_ARB_texture_rectangle_supported) {
        frag_defines = 
"#define sampler2D sampler2DRect\n"
"#define texture2D texture2DRect\n";
    }

    /* Create one program object to rule them all */
    data->program = ctx->glCreateProgramObjectARB();

    /* Create the vertex shader */
    data->vert_shader = ctx->glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
    if (!CompileShader(ctx, data->vert_shader, vert_defines, shader_source[index][0])) {
        return SDL_FALSE;
    }

    /* Create the fragment shader */
    data->frag_shader = ctx->glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
    if (!CompileShader(ctx, data->frag_shader, frag_defines, shader_source[index][1])) {
        return SDL_FALSE;
    }

    /* ... and in the darkness bind them */
    ctx->glAttachObjectARB(data->program, data->vert_shader);
    ctx->glAttachObjectARB(data->program, data->frag_shader);
    ctx->glLinkProgramARB(data->program);

    /* Set up some uniform variables */
    ctx->glUseProgramObjectARB(data->program);
    for (i = 0; i < num_tmus_bound; ++i) {
        char tex_name[5];
        SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
        location = ctx->glGetUniformLocationARB(data->program, tex_name);
        if (location >= 0) {
            ctx->glUniform1iARB(location, i);
        }
    }
    ctx->glUseProgramObjectARB(0);
    
    return (ctx->glGetError() == GL_NO_ERROR);
}

static void
DestroyShaderProgram(GL_ShaderContext *ctx, GL_ShaderData *data)
{
    ctx->glDeleteObjectARB(data->vert_shader);
    ctx->glDeleteObjectARB(data->frag_shader);
    ctx->glDeleteObjectARB(data->program);
}

GL_ShaderContext *
GL_CreateShaderContext()
{
    GL_ShaderContext *ctx;
    SDL_bool shaders_supported;
    int i;

    ctx = (GL_ShaderContext *)SDL_calloc(1, sizeof(*ctx));
    if (!ctx) {
        return NULL;
    }

    if (SDL_GL_ExtensionSupported("GL_ARB_texture_rectangle")
        || SDL_GL_ExtensionSupported("GL_EXT_texture_rectangle")) {
        ctx->GL_ARB_texture_rectangle_supported = SDL_TRUE;
    }

    /* Check for shader support */
    shaders_supported = SDL_FALSE;
    if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
        SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
        SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
        SDL_GL_ExtensionSupported("GL_ARB_fragment_shader")) {
        ctx->glGetError = (GLenum (*)(void)) SDL_GL_GetProcAddress("glGetError");
        ctx->glAttachObjectARB = (PFNGLATTACHOBJECTARBPROC) SDL_GL_GetProcAddress("glAttachObjectARB");
        ctx->glCompileShaderARB = (PFNGLCOMPILESHADERARBPROC) SDL_GL_GetProcAddress("glCompileShaderARB");
        ctx->glCreateProgramObjectARB = (PFNGLCREATEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glCreateProgramObjectARB");
        ctx->glCreateShaderObjectARB = (PFNGLCREATESHADEROBJECTARBPROC) SDL_GL_GetProcAddress("glCreateShaderObjectARB");
        ctx->glDeleteObjectARB = (PFNGLDELETEOBJECTARBPROC) SDL_GL_GetProcAddress("glDeleteObjectARB");
        ctx->glGetInfoLogARB = (PFNGLGETINFOLOGARBPROC) SDL_GL_GetProcAddress("glGetInfoLogARB");
        ctx->glGetObjectParameterivARB = (PFNGLGETOBJECTPARAMETERIVARBPROC) SDL_GL_GetProcAddress("glGetObjectParameterivARB");
        ctx->glGetUniformLocationARB = (PFNGLGETUNIFORMLOCATIONARBPROC) SDL_GL_GetProcAddress("glGetUniformLocationARB");
        ctx->glLinkProgramARB = (PFNGLLINKPROGRAMARBPROC) SDL_GL_GetProcAddress("glLinkProgramARB");
        ctx->glShaderSourceARB = (PFNGLSHADERSOURCEARBPROC) SDL_GL_GetProcAddress("glShaderSourceARB");
        ctx->glUniform1iARB = (PFNGLUNIFORM1IARBPROC) SDL_GL_GetProcAddress("glUniform1iARB");
        ctx->glUniform1fARB = (PFNGLUNIFORM1FARBPROC) SDL_GL_GetProcAddress("glUniform1fARB");
        ctx->glUseProgramObjectARB = (PFNGLUSEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glUseProgramObjectARB");
        if (ctx->glGetError &&
            ctx->glAttachObjectARB &&
            ctx->glCompileShaderARB &&
            ctx->glCreateProgramObjectARB &&
            ctx->glCreateShaderObjectARB &&
            ctx->glDeleteObjectARB &&
            ctx->glGetInfoLogARB &&
            ctx->glGetObjectParameterivARB &&
            ctx->glGetUniformLocationARB &&
            ctx->glLinkProgramARB &&
            ctx->glShaderSourceARB &&
            ctx->glUniform1iARB &&
            ctx->glUniform1fARB &&
            ctx->glUseProgramObjectARB) {
            shaders_supported = SDL_TRUE;
        }
    }

    if (!shaders_supported) {
        SDL_free(ctx);
        return NULL;
    }

    /* Compile all the shaders */
    for (i = 0; i < NUM_SHADERS; ++i) {
        if (!CompileShaderProgram(ctx, i, &ctx->shaders[i])) {
            GL_DestroyShaderContext(ctx);
            return NULL;
        }
    }

    /* We're done! */
    return ctx;
}

void
GL_SelectShader(GL_ShaderContext *ctx, GL_Shader shader)
{
    ctx->glUseProgramObjectARB(ctx->shaders[shader].program);
}

void
GL_DestroyShaderContext(GL_ShaderContext *ctx)
{
    int i;

    for (i = 0; i < NUM_SHADERS; ++i) {
        DestroyShaderProgram(ctx, &ctx->shaders[i]);
    }
    SDL_free(ctx);
}

#endif /* SDL_VIDEO_RENDER_OGL && !SDL_RENDER_DISABLED */

/* vi: set ts=4 sw=4 expandtab: */