/*  RetroArch - A frontend for libretro.
 *  Copyright (C) 2010-2017 - Hans-Kristian Arntzen
 *
 *  RetroArch 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.
 *
 *  RetroArch 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 RetroArch.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <string.h>
#include <string>
#include <algorithm>

#include <retro_miscellaneous.h>
#include <file/file_path.h>
#include <file/config_file.h>
#include <streams/file_stream.h>
#include <string/stdstring.h>

#ifdef HAVE_CONFIG_H
#include "../../config.h"
#endif

#include "glslang_util.h"
#include "glslang_util_cxx.h"
#if defined(HAVE_GLSLANG)
#include "glslang.hpp"
#endif
#include "../../verbosity.h"

static std::string build_stage_source(
      const struct string_list *lines, const char *stage)
{
   size_t i;
   std::string str;
   bool active = true;

   if (!lines)
      return "";

   if (lines->size < 1)
      return "";
   str.reserve(lines->size);

   /* Version header. */
   str.append(lines->elems[0].data);
   str.append("\n");

   for (i = 1; i < lines->size; i++)
   {
      const char *line = lines->elems[i].data;

      if (string_starts_with_size(line, "#pragma", STRLEN_CONST("#pragma")))
      {
         /* Identify 'stage' (fragment/vertex) */
         if (!strncmp("#pragma stage ", line, STRLEN_CONST("#pragma stage ")))
         {
            if (!string_is_empty(stage))
            {
               char expected[128];
               strlcpy(expected, "#pragma stage ", sizeof(expected));
               strlcat(expected, stage,            sizeof(expected));
               active = string_is_equal(expected, line);
            }
         }
         else if (
               !strncmp("#pragma name ", line,
                  STRLEN_CONST("#pragma name ")) ||
               !strncmp("#pragma format ", line,
                  STRLEN_CONST("#pragma format ")))
         {
            /* Ignore */
         }
         else if (active)
            str.append(line);
      }
      else if (active)
         str.append(line);

      str.append("\n");
   }

   return str;
}

bool glslang_parse_meta(const struct string_list *lines, glslang_meta *meta)
{
   char id[64];
   char desc[64];
   size_t i;

   id[0]   = '\0';
   desc[0] = '\0';

   for (i = 0; i < lines->size; i++)
   {
      const char *line = lines->elems[i].data;

      if (string_starts_with_size(line, "#pragma", STRLEN_CONST("#pragma")))
      {
         /* Check for shader identifier */
         if (!strncmp("#pragma name ", line,
                  STRLEN_CONST("#pragma name ")))
         {
            const char *str = NULL;

            if (!meta->name.empty())
            {
               RARCH_ERR("[slang]: Trying to declare multiple names for file.\n");
               return false;
            }

            str = line + STRLEN_CONST("#pragma name ");
            while (*str == ' ')
               str++;

            meta->name = str;
         }
         /* Check for shader parameters */
         else if (!strncmp("#pragma parameter ", line,
                  STRLEN_CONST("#pragma parameter ")))
         {
            float initial, minimum, maximum, step;
            int ret = sscanf(
                  line, "#pragma parameter %63s \"%63[^\"]\" %f %f %f %f",
                  id, desc, &initial, &minimum, &maximum, &step);

            if (ret == 5)
            {
               step = 0.1f * (maximum - minimum);
               ret  = 6;
            }

            if (ret == 6)
            {
               bool parameter_found   = false;
               size_t parameter_index = 0;
               size_t j;

               for (j = 0; j < meta->parameters.size(); j++)
               {
                  /* Note: LHS is a std:string, RHS is a C string.
                   * (the glslang_meta stuff has to be C++) */
                  if (meta->parameters[j].id == id)
                  {
                     parameter_found = true;
                     parameter_index = j;
                     break;
                  }
               }

               /* Allow duplicate #pragma parameter, but only
                * if they are exactly the same. */
               if (parameter_found)
               {
                  const glslang_parameter *parameter = 
                     &meta->parameters[parameter_index];

                  if (   parameter->desc    != desc    ||
                        parameter->initial != initial ||
                        parameter->minimum != minimum ||
                        parameter->maximum != maximum ||
                        parameter->step    != step
                     )
                  {
                     RARCH_ERR("[slang]: Duplicate parameters found for \"%s\", but arguments do not match.\n", id);
                     return false;
                  }
               }
               else
                  meta->parameters.push_back({ id, desc, initial, minimum, maximum, step });
            }
            else
            {
               RARCH_ERR("[slang]: Invalid #pragma parameter line: \"%s\".\n",
                     line);
               return false;
            }
         }
         /* Check for framebuffer format */
         else if (!strncmp("#pragma format ", line,
                  STRLEN_CONST("#pragma format ")))
         {
            const char *str = NULL;

            if (meta->rt_format != SLANG_FORMAT_UNKNOWN)
            {
               RARCH_ERR("[slang]: Trying to declare format multiple times for file.\n");
               return false;
            }

            str = line + STRLEN_CONST("#pragma format ");
            while (*str == ' ')
               str++;

            meta->rt_format = glslang_find_format(str);

            if (meta->rt_format == SLANG_FORMAT_UNKNOWN)
            {
               RARCH_ERR("[slang]: Failed to find format \"%s\".\n", str);
               return false;
            }
         }
      }
   }

   return true;
}

bool glslang_compile_shader(const char *shader_path, glslang_output *output)
{
#if defined(HAVE_GLSLANG)
   struct string_list lines;
   
   if (!string_list_initialize(&lines))
      return false;

   RARCH_LOG("[slang]: Compiling shader: \"%s\".\n", shader_path);

   if (!glslang_read_shader_file(shader_path, &lines, true))
      goto error;
   output->meta = glslang_meta{};
   if (!glslang_parse_meta(&lines, &output->meta))
      goto error;

   if (!glslang::compile_spirv(build_stage_source(&lines, "vertex"),
            glslang::StageVertex, &output->vertex))
   {
      RARCH_ERR("[slang]: Failed to compile vertex shader stage.\n");
      goto error;
   }

   if (!glslang::compile_spirv(build_stage_source(&lines, "fragment"),
            glslang::StageFragment, &output->fragment))
   {
      RARCH_ERR("[slang]: Failed to compile fragment shader stage.\n");
      goto error;
   }

   string_list_deinitialize(&lines);

   return true;

error:
   string_list_deinitialize(&lines);
#endif

   return false;
}
