/*  SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
 *  Copyright (C) 2010-2011 - Hans-Kristian Arntzen
 *
 *  Some code herein may be based on code found in BSNES.
 * 
 *  SSNES is free software: you can redistribute it and/or modify it under the terms
 *  of the GNU General Public License as published by the Free Software Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  SSNES is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 *  PURPOSE.  See the GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along with SSNES.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

//
// GLSL code here is mostly copypasted from bSNES.
//

#include <stdbool.h>
#include <string.h>
#include "general.h"

#ifdef __APPLE__
#include <OpenGL/gl.h>
#else
#define GL_GLEXT_PROTOTYPES
#include <GL/gl.h>
#include <GL/glext.h>
#endif


#define NO_SDL_GLEXT
#include "SDL.h"
#include "SDL_opengl.h"
#include <stdlib.h>
#include <libxml/parser.h>
#include <libxml/tree.h>

#include "gl_common.h"

#ifdef __APPLE__
#define pglCreateProgram glCreateProgram
#define pglUseProgram glUseProgram
#define pglCreateShader glCreateShader
#define pglDeleteShader glDeleteShader
#define pglShaderSource glShaderSource
#define pglCompileShader glCompileShader
#define pglAttachShader glAttachShader
#define pglDetachShader glDetachShader
#define pglLinkProgram glLinkProgram
#define pglGetUniformLocation glGetUniformLocation
#define pglUniform1i glUniform1i
#define pglUniform2fv glUniform2fv
#define pglUniform4fv glUniform4fv
#define pglGetShaderiv glGetShaderiv
#define pglGetShaderInfoLog glGetShaderInfoLog
#define pglGetProgramiv glGetProgramiv
#define pglGetProgramInfoLog glGetProgramInfoLog
#else
static PFNGLCREATEPROGRAMPROC pglCreateProgram = NULL;
static PFNGLUSEPROGRAMPROC pglUseProgram = NULL;
static PFNGLCREATESHADERPROC pglCreateShader = NULL;
static PFNGLDELETESHADERPROC pglDeleteShader = NULL;
static PFNGLSHADERSOURCEPROC pglShaderSource = NULL;
static PFNGLCOMPILESHADERPROC pglCompileShader = NULL;
static PFNGLATTACHSHADERPROC pglAttachShader = NULL;
static PFNGLDETACHSHADERPROC pglDetachShader = NULL;
static PFNGLLINKPROGRAMPROC pglLinkProgram = NULL;
static PFNGLGETUNIFORMLOCATIONPROC pglGetUniformLocation = NULL;
static PFNGLUNIFORM1IPROC pglUniform1i = NULL;
static PFNGLUNIFORM2FVPROC pglUniform2fv = NULL;
static PFNGLUNIFORM4FVPROC pglUniform4fv = NULL;
static PFNGLGETSHADERIVPROC pglGetShaderiv = NULL;
static PFNGLGETSHADERINFOLOGPROC pglGetShaderInfoLog = NULL;
static PFNGLGETPROGRAMIVPROC pglGetProgramiv = NULL;
static PFNGLGETPROGRAMINFOLOGPROC pglGetProgramInfoLog = NULL;
#endif

static bool glsl_enable = false;
static GLuint gl_program[3] = {0};
static GLuint fragment_shader;
static GLuint vertex_shader;
static unsigned active_index = 0;

static bool get_xml_shaders(const char *path, char **vertex_shader, char **fragment_shader)
{
   LIBXML_TEST_VERSION;

   xmlParserCtxtPtr ctx = xmlNewParserCtxt();
   if (!ctx)
   {
      SSNES_ERR("Failed to load libxml2 context.\n");
      return false;
   }

   SSNES_LOG("Loading XML shader: %s\n", path);
   xmlDocPtr doc = xmlCtxtReadFile(ctx, path, NULL, 0);
   if (!doc)
   {
      SSNES_ERR("Failed to parse XML file: %s\n", path);
      goto error;
   }

   if (ctx->valid == 0)
   {
      SSNES_ERR("Cannot validate XML shader: %s\n", path);
      goto error;
   }

   xmlNodePtr head = xmlDocGetRootElement(doc);
   xmlNodePtr cur = NULL;
   for (cur = head; cur; cur = cur->next)
   {
      if (cur->type == XML_ELEMENT_NODE && strcmp((const char*)cur->name, "shader") == 0)
      {
         xmlChar *attr;
         if ((attr = xmlGetProp(cur, (const xmlChar*)"language")) && strcmp((const char*)attr, "GLSL") == 0)
            break;
      }
   }

   if (!cur) // We couldn't find any GLSL shader :(
      goto error;

   bool vertex_found = false;
   bool fragment_found = false;
   // Iterate to check if we find fragment and/or vertex shaders.
   for (cur = cur->children; cur; cur = cur->next)
   {
      if (cur->type != XML_ELEMENT_NODE)
         continue;

      xmlChar *content = xmlNodeGetContent(cur);
      if (!content)
         continue;

      if (strcmp((const char*)cur->name, "vertex") == 0 && !vertex_found)
      {
         *vertex_shader = malloc(xmlStrlen(content) + 1);
         strcpy(*vertex_shader, (const char*)content);
         vertex_found = true;
      }
      else if (strcmp((const char*)cur->name, "fragment") == 0 && !fragment_found)
      {
         *fragment_shader = malloc(xmlStrlen(content) + 1);
         strcpy(*fragment_shader, (const char*)content);
         fragment_found = true;
      }
   }

   if (!vertex_found && !fragment_found)
   {
      SSNES_ERR("Couldn't find vertex shader nor fragment shader in XML file.\n");
      goto error;
   }


   xmlFreeDoc(doc);
   xmlFreeParserCtxt(ctx);
   return true;

error:
   SSNES_ERR("Failed to load XML shader ...\n");
   if (doc)
      xmlFreeDoc(doc);
   xmlFreeParserCtxt(ctx);
   return false;
}

static void print_shader_log(GLuint obj)
{
   int info_len = 0;
   int max_len;

   pglGetShaderiv(obj, GL_INFO_LOG_LENGTH, &max_len);

   char info_log[max_len];
   pglGetShaderInfoLog(obj, max_len, &info_len, info_log);

   if (info_len > 0)
      SSNES_LOG("Shader log: %s\n", info_log);
}

static void print_linker_log(GLuint obj)
{
   int info_len = 0;
   int max_len;

   pglGetProgramiv(obj, GL_INFO_LOG_LENGTH, &max_len);

   char info_log[max_len];
   pglGetProgramInfoLog(obj, max_len, &info_len, info_log);

   if (info_len > 0)
      SSNES_LOG("Linker log: %s\n", info_log);
}

bool gl_glsl_init(const char *path)
{

#ifndef __APPLE__
   // Load shader functions.
   pglCreateProgram = SDL_GL_GetProcAddress("glCreateProgram");
   pglUseProgram = SDL_GL_GetProcAddress("glUseProgram");
   pglCreateShader = SDL_GL_GetProcAddress("glCreateShader");
   pglDeleteShader = SDL_GL_GetProcAddress("glDeleteShader");
   pglShaderSource = SDL_GL_GetProcAddress("glShaderSource");
   pglCompileShader = SDL_GL_GetProcAddress("glCompileShader");
   pglAttachShader = SDL_GL_GetProcAddress("glAttachShader");
   pglDetachShader = SDL_GL_GetProcAddress("glDetachShader");
   pglLinkProgram = SDL_GL_GetProcAddress("glLinkProgram");
   pglGetUniformLocation = SDL_GL_GetProcAddress("glGetUniformLocation");
   pglUniform1i = SDL_GL_GetProcAddress("glUniform1i");
   pglUniform2fv = SDL_GL_GetProcAddress("glUniform2fv");
   pglUniform4fv = SDL_GL_GetProcAddress("glUniform4fv");
   pglGetShaderiv = SDL_GL_GetProcAddress("glGetShaderiv");
   pglGetShaderInfoLog = SDL_GL_GetProcAddress("glGetShaderInfoLog");
   pglGetProgramiv = SDL_GL_GetProcAddress("glGetProgramiv");
   pglGetProgramInfoLog = SDL_GL_GetProcAddress("glGetProgramInfoLog");
#endif

   SSNES_LOG("Checking GLSL shader support ...\n");
#ifdef __APPLE__
   const bool shader_support = true;
#else
   bool shader_support = pglCreateProgram && pglUseProgram && pglCreateShader
      && pglDeleteShader && pglShaderSource && pglCompileShader && pglAttachShader
      && pglDetachShader && pglLinkProgram && pglGetUniformLocation
      && pglUniform1i && pglUniform2fv && pglUniform4fv
      && pglGetShaderiv && pglGetShaderInfoLog && pglGetProgramiv && pglGetProgramInfoLog;
#endif

   if (!shader_support)
   {
      SSNES_ERR("GLSL shaders aren't supported by your GL driver.\n");
      return false;
   }

   const char *paths[] = {NULL, path, 
      (strlen(g_settings.video.second_pass_shader) > 0) ? g_settings.video.second_pass_shader : NULL};

   for (int i = 1; i < 3; i++)
   {
      if (paths[i] == NULL)
         continue;

      gl_program[i] = pglCreateProgram();

      char *vertex_prog = NULL;
      char *fragment_prog = NULL;
      if (!get_xml_shaders(paths[i], &vertex_prog, &fragment_prog))
         return false;

      if (vertex_prog)
      {
         vertex_shader = pglCreateShader(GL_VERTEX_SHADER);
         pglShaderSource(vertex_shader, 1, (const char**)&vertex_prog, 0);
         pglCompileShader(vertex_shader);
         print_shader_log(vertex_shader);

         pglAttachShader(gl_program[i], vertex_shader);
         free(vertex_prog);
      }
      if (fragment_prog)
      {
         fragment_shader = pglCreateShader(GL_FRAGMENT_SHADER);
         pglShaderSource(fragment_shader, 1, (const char**)&fragment_prog, 0);
         pglCompileShader(fragment_shader);
         print_shader_log(fragment_shader);

         pglAttachShader(gl_program[i], fragment_shader);
         free(fragment_prog);
      }

      if (vertex_prog || fragment_prog)
      {
         pglLinkProgram(gl_program[i]);
         pglUseProgram(gl_program[i]);
         print_linker_log(gl_program[i]);

         GLint location = pglGetUniformLocation(gl_program[i], "rubyTexture");
         pglUniform1i(location, 0);
      }
   }

   if (!gl_check_error())
      return false;
   
   glsl_enable = true;
   return true;
}

void gl_glsl_deinit(void)
{}

void gl_glsl_set_params(unsigned width, unsigned height, 
      unsigned tex_width, unsigned tex_height, 
      unsigned out_width, unsigned out_height)
{
   if (glsl_enable && gl_program[active_index] > 0)
   {
      GLint location;

      float inputSize[2] = {width, height};
      location = pglGetUniformLocation(gl_program[active_index], "rubyInputSize");
      pglUniform2fv(location, 1, inputSize);

      float outputSize[2] = {out_width, out_height};
      location = pglGetUniformLocation(gl_program[active_index], "rubyOutputSize");
      pglUniform2fv(location, 1, outputSize);

      float textureSize[2] = {tex_width, tex_height};
      location = pglGetUniformLocation(gl_program[active_index], "rubyTextureSize");
      pglUniform2fv(location, 1, textureSize);

   }
}

void gl_glsl_set_proj_matrix(void)
{}

void gl_glsl_use(unsigned index)
{
   if (glsl_enable)
   {
      active_index = index;
      pglUseProgram(gl_program[index]);
   }
}