//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <fstream>
#include <iostream>
#include <map>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

static std::pair<std::string, std::string> split(std::string s, char delimiter = ' ') {
  auto delimiter_pos = s.find(delimiter);
  if (delimiter_pos == std::string::npos) {
    return {std::move(s), ""};
  } else {
    auto head = s.substr(0, delimiter_pos);
    auto tail = s.substr(delimiter_pos + 1);
    return {head, tail};
  }
}

static bool generate(const char *file_name, const char *from_name, const char *to_name,
                     const std::map<std::string, std::string> &map) {
  // binary mode is needed for MSYS2 gperf
  std::ofstream out(file_name, std::ios_base::trunc | std::ios_base::binary);
  if (!out) {
    std::cerr << "Can't open output file \"" << file_name << std::endl;
    return false;
  }

  out << "%struct-type\n";
  out << "%ignore-case\n";
  out << "%language=ANSI-C\n";
  out << "%readonly-tables\n";
  out << "%includes\n";
  out << "%enum\n";
  out << "%define slot-name " << from_name << "\n";
  out << "%define initializer-suffix ,nullptr\n";
  out << "%define slot-name " << from_name << "\n";
  out << "%define hash-function-name " << from_name << "_hash\n";
  out << "%define lookup-function-name search_" << from_name << "\n";
  //  out << "%define class-name " << from_name << "_to_" << to_name << "\n";
  out << "struct " << from_name << "_and_" << to_name << " {\n";
  out << "  const char *" << from_name << ";\n";
  out << "  const char *" << to_name << ";\n";
  out << "}\n";
  out << "%%\n";

  for (auto &value : map) {
    out << '"' << value.first << "\", \"" << value.second << '"' << "\n";
  }

  out << "%%\n";
  out << "const char *" << from_name << "_to_" << to_name << "(const char *" << from_name << ", size_t " << from_name
      << "_len) {\n";
  out << "  const auto &result = search_" << from_name << "(" << from_name << ", " << from_name << "_len);\n";
  out << "  if (result == nullptr) {\n";
  out << "    return nullptr;\n";
  out << "  }\n";
  out << "\n";
  out << "  return result->" << to_name << ";\n";
  out << "}\n";

  return true;
}

static bool is_private_mime_type(const std::string &mime_type) {
  return mime_type.find("/x-") != std::string::npos;
}

int main(int argc, char *argv[]) {
  if (argc != 4) {
    std::cerr << "Wrong number of arguments supplied. Expected 'generate_mime_types_gperf <mime_types.txt> "
                 "<mime_type_to_extension.cpp> <extension_to_mime_type.cpp>'"
              << std::endl;
    return EXIT_FAILURE;
  }

  std::ifstream mime_types_file(argv[1]);
  if (!mime_types_file) {
    std::cerr << "Can't open input file \"" << argv[1] << std::endl;
    return EXIT_FAILURE;
  }

  std::map<std::string, std::string> mime_type_to_extension;
  std::map<std::string, std::string> extension_to_mime_type;

  std::string line;
  while (std::getline(mime_types_file, line)) {
    while (!line.empty() && (line.back() == '\r' || line.back() == '\n')) {
      line.pop_back();
    }

    std::string mime_type;
    std::string extensions_string;
    std::tie(mime_type, extensions_string) = split(line, '\t');

    if (mime_type.empty()) {
      std::cerr << "Wrong MIME type description \"" << line << "\"" << std::endl;
      continue;
    }

    auto extensions_start_position = extensions_string.find_first_not_of(" \t");
    if (extensions_start_position == std::string::npos) {
      std::cerr << "Wrong MIME type description \"" << line << "\"" << std::endl;
      continue;
    }
    extensions_string = extensions_string.substr(extensions_start_position);

    std::vector<std::string> extensions;
    while (!extensions_string.empty()) {
      extensions.emplace_back();
      std::tie(extensions.back(), extensions_string) = split(extensions_string);
    }
    assert(!extensions.empty());

    std::map<std::string, std::string> preffered_extensions{{"image/jpeg", "jpg"},  {"audio/mpeg", "mp3"},
                                                            {"audio/midi", "midi"}, {"text/x-pascal", "pas"},
                                                            {"text/x-asm", "asm"},  {"video/quicktime", "mov"}};
    std::size_t index = 0;
    if (preffered_extensions.count(mime_type) != 0) {
      index = std::find(extensions.begin(), extensions.end(), preffered_extensions[mime_type]) - extensions.begin();
      assert(index < extensions.size());
    }
    if (mime_type_to_extension.emplace_hint(mime_type_to_extension.end(), mime_type, extensions[index])->second !=
        extensions[index]) {
      std::cerr << "MIME type \"" << mime_type << "\" has more than one list of extensions" << std::endl;
    }

    for (auto &extension : extensions) {
      if (!extension_to_mime_type.emplace(extension, mime_type).second) {
        if (is_private_mime_type(extension_to_mime_type[extension]) == is_private_mime_type(mime_type)) {
          std::cerr << "Extension \"" << extension << "\" matches more than one type" << std::endl;
        } else {
          if (!is_private_mime_type(mime_type)) {
            extension_to_mime_type[extension] = mime_type;
          }
        }
      }
    }
  }

  if (!generate(argv[2], "mime_type", "extension", mime_type_to_extension)) {
    return EXIT_FAILURE;
  }
  if (!generate(argv[3], "extension", "mime_type", extension_to_mime_type)) {
    return EXIT_FAILURE;
  }
}
