/*
 * Copyright (c) 2014-2021, NVIDIA CORPORATION.  All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-FileCopyrightText: Copyright (c) 2014-2021 NVIDIA CORPORATION
 * SPDX-License-Identifier: Apache-2.0
 */


/*
 * This file contains code derived from glf by Christophe Riccio, www.g-truc.net
 * Copyright (c) 2005 - 2015 G-Truc Creation (www.g-truc.net)
 * https://github.com/g-truc/ogl-samples/blob/master/framework/compiler.cpp
 */

#include "shaderfilemanager.hpp"
#include <algorithm>
#include <assert.h>
#include <fstream>
#include <iostream>
#include <sstream>
#include <stdarg.h>
#include <stdio.h>

#include "fileoperations.hpp"


namespace nvh {

std::string ShaderFileManager::format(const char* msg, ...)
{
  char    text[8192];
  va_list list;

  if(msg == 0)
    return std::string();

  va_start(list, msg);
  vsnprintf(text, sizeof(text), msg, list);
  va_end(list);

  return std::string(text);
}

inline std::string ShaderFileManager::markerString(int line, std::string const& filename, int fileid)
{
  if(m_supportsExtendedInclude || m_forceLineFilenames)
  {
#if defined(_WIN32) && 1
    std::string fixedname;
    for(size_t i = 0; i < filename.size(); i++)
    {
      char c = filename[i];
      if(c == '/' || c == '\\')
      {
        fixedname.append("\\\\");
      }
      else
      {
        fixedname.append(1, c);
      }
    }
#else
    std::string fixedname = filename;
#endif
    return ShaderFileManager::format("#line %d \"", line) + fixedname + std::string("\"\n");
  }
  else
  {
    return ShaderFileManager::format("#line %d %d\n", line, fileid);
  }
}

std::string ShaderFileManager::getIncludeContent(IncludeID idx, std::string& filename)
{
  IncludeEntry& entry = m_includes[idx];

  filename = entry.filename;

  if(m_forceIncludeContent)
  {
    return entry.content;
  }

  if(!entry.content.empty() && !findFile(entry.filename, m_directories).empty())
  {
    return entry.content;
  }

  std::string content = loadFile(entry.filename, false, m_directories, filename, true);
  return content.empty() ? entry.content : content;
}

std::string ShaderFileManager::getContent(std::string const& filename, std::string& filenameFound)
{
  if(filename.empty())
  {
    return std::string();
  }

  IncludeID idx = findInclude(filename);

  if(idx.isValid())
  {
    return getIncludeContent(idx, filenameFound);
  }

  // fall back
  filenameFound = filename;
  return loadFile(filename, false, m_directories, filenameFound, true);
}

std::string ShaderFileManager::getContentWithRequestingSourceDirectory(std::string const& filename,
                                                                       std::string&       filenameFound,
                                                                       std::string const& requestingSource)
{
  if(filename.empty())
  {
    return std::string();
  }

  IncludeID idx = findInclude(filename);

  if(idx.isValid())
  {
    return getIncludeContent(idx, filenameFound);
  }

  // fall back; check requestingSource's directory first.
  filenameFound = filename;
  m_extendedDirectories.resize(m_directories.size() + 1);
  m_extendedDirectories[0] = getDirectoryComponent(requestingSource);
  for(size_t i = 0; i < m_directories.size(); ++i)
  {
    m_extendedDirectories[i + 1] = m_directories[i];
  }
  return loadFile(filename, false, m_extendedDirectories, filenameFound, true);
}

std::string ShaderFileManager::getDirectoryComponent(std::string filename)
{
  while(!filename.empty())
  {
    auto popped = filename.back();
    filename.pop_back();
    switch(popped)
    {
      case '/':
        goto exitLoop;
#if defined(_WIN32)
      case '\\':
        goto exitLoop;
#endif
    }
  }
exitLoop:
  if(filename.empty())
    filename.push_back('.');
  return filename;
}

std::string ShaderFileManager::manualInclude(std::string const& filename, std::string& filenameFound, std::string const& prepend, bool foundVersion)
{
  std::string source = getContent(filename, filenameFound);
  return manualIncludeText(source, filenameFound, prepend, foundVersion);
}

std::string ShaderFileManager::manualIncludeText(std::string const& sourceText, std::string const& textFilename, std::string const& prepend, bool foundVersion)
{
  if(sourceText.empty())
  {
    return std::string();
  }

  std::stringstream stream;
  stream << sourceText;
  std::string line, text;

  // Handle command line defines
  text += prepend;
  if(m_lineMarkers)
  {
    text += markerString(1, textFilename, 0);
  }

  int lineCount = 0;
  while(std::getline(stream, line))
  {
    std::size_t offset = 0;
    lineCount++;

    // Version
    offset = line.find("#version");
    if(offset != std::string::npos)
    {
      std::size_t commentOffset = line.find("//");
      if(commentOffset != std::string::npos && commentOffset < offset)
        continue;

      if(foundVersion)
      {
        // someone else already set the version, so just comment out
        text += std::string("//") + line + std::string("\n");
      }
      else
      {
        // Reorder so that the #version line is always the first of a shader text
        text         = line + std::string("\n") + text + std::string("//") + line + std::string("\n");
        foundVersion = true;
      }
      continue;
    }

    // Handle replacing #include with text if configured to do so.
    // Otherwise just insert the #include command verbatim, for shaderc to handle.
    if(m_handleIncludePasting)
    {
      offset = line.find("#include");
      if(offset != std::string::npos)
      {
        std::size_t commentOffset = line.find("//");
        if(commentOffset != std::string::npos && commentOffset < offset)
          continue;

        size_t firstQuote  = line.find("\"", offset);
        size_t secondQuote = line.find("\"", firstQuote + 1);

        std::string include = line.substr(firstQuote + 1, secondQuote - firstQuote - 1);

        std::string includeFound;
        std::string includeContent = manualInclude(include, includeFound, std::string(), foundVersion);

        if(!includeContent.empty())
        {
          text += includeContent;
          if(m_lineMarkers)
          {
            text += std::string("\n") + markerString(lineCount + 1, textFilename, 0);
          }
        }
        continue; // Skip adding the original #include line.
      }
    }

    text += line + "\n";
  }

  return text;
}


ShaderFileManager::IncludeID ShaderFileManager::registerInclude(std::string const& name, std::string const& filename, std::string const& content)
{
  // find if already registered
  for(size_t i = 0; i < m_includes.size(); i++)
  {
    if(m_includes[i].name == name)
    {
      m_includes[i].content = content;
      return i;
    }
  }

  IncludeEntry entry;
  entry.name     = name;
  entry.filename = filename.empty() ? name : filename;
  entry.content  = content;

  m_includes.push_back(entry);

  return m_includes.size() - 1;
}


ShaderFileManager::IncludeID ShaderFileManager::findInclude(std::string const& name) const
{
  // check registered includes first
  for(std::size_t i = 0; i < m_includes.size(); ++i)
  {
    if(m_includes[i].name == name)
    {
      return IncludeID(i);
    }
  }

  return IncludeID();
}

bool ShaderFileManager::loadIncludeContent(IncludeID idx)
{
  std::string filenameFound;
  m_includes[idx].content = getIncludeContent(idx, filenameFound);
  return !m_includes[idx].content.empty();
}

const ShaderFileManager::IncludeEntry& ShaderFileManager::getIncludeEntry(IncludeID idx) const
{
  return m_includes[idx];
}

std::string ShaderFileManager::getProcessedContent(std::string const& filename, std::string& filenameFound)
{
  return manualInclude(filename, filenameFound, "", false);
}

}  // namespace nvh