// Copyright 2005-2020 Google LLC
//
// 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.
//
// Google-style flag handling definitions.

#include <fst/flags.h>

#include <cstdint>
#include <cstring>
#include <iostream>
#include <ostream>
#include <set>
#include <string>
#include <string_view>
#include <utility>

#include <fst/log.h>

static const char *private_tmpdir = getenv("TMPDIR");

DEFINE_int32(v, 0, "verbosity level");
DEFINE_bool(help, false, "show usage information");
DEFINE_bool(helpshort, false, "show brief usage information");
DEFINE_string(tmpdir, private_tmpdir ? private_tmpdir : "/tmp",
              "temporary directory");

static std::string flag_usage;
static std::string prog_src;

// Sets prog_src to src.
static void SetProgSrc(const char *src) {
  prog_src = src;
  // Remove "-main" in src filename. Flags are defined in fstx.cc but SetFlags()
  // is called in fstx-main.cc, which results in a filename mismatch in
  // ShowUsageRestrict() below.
  static constexpr std::string_view kMainSuffix = "-main.cc";
  const int prefix_length = prog_src.size() - kMainSuffix.size();
  if (prefix_length > 0 &&
      std::string_view(prog_src).substr(prefix_length) == kMainSuffix) {
    static constexpr size_t kDashMainSize = std::string_view("-main").size();
    prog_src.erase(prefix_length, kDashMainSize);
  }
}

void SetFlags(const char *usage, int *argc, char ***argv,
              bool remove_flags, const char *src) {
  flag_usage = usage;
  SetProgSrc(src);

  int index = 1;
  for (; index < *argc; ++index) {
    std::string_view argval = (*argv)[index];
    if (argval[0] != '-' || argval == "-") break;
    while (argval[0] == '-') argval.remove_prefix(1);  // Removes initial '-'.
    std::string arg(argval);
    std::string val("");
    // Splits argval (arg=val) into arg and val.
    auto pos = argval.find('=');
    if (pos != std::string::npos) {
      arg = argval.substr(0, pos);
      val = argval.substr(pos + 1);
    }
    auto bool_register = FlagRegister<bool>::GetRegister();
    if (bool_register->SetFlag(arg, val))
      continue;
    auto string_register = FlagRegister<std::string>::GetRegister();
    if (string_register->SetFlag(arg, val)) continue;
    auto int32_register = FlagRegister<int32_t>::GetRegister();
    if (int32_register->SetFlag(arg, val)) continue;
    auto int64_register = FlagRegister<int64_t>::GetRegister();
    if (int64_register->SetFlag(arg, val)) continue;
    auto uint64_register = FlagRegister<uint64_t>::GetRegister();
    if (uint64_register->SetFlag(arg, val)) continue;
    auto double_register = FlagRegister<double>::GetRegister();
    if (double_register->SetFlag(arg, val)) continue;
    LOG(FATAL) << "SetFlags: Bad option: " << (*argv)[index];
  }
  if (remove_flags) {
    for (auto i = 0; i < *argc - index; ++i) {
      (*argv)[i + 1] = (*argv)[i + index];
    }
    *argc -= index - 1;
  }
  if (FST_FLAGS_help) {
    ShowUsage(true);
    exit(1);
  }
  if (FST_FLAGS_helpshort) {
    ShowUsage(false);
    exit(1);
  }
}

// If flag is defined in file 'src' and 'in_src' true or is not
// defined in file 'src' and 'in_src' is false, then print usage.
static void ShowUsageRestrict(
    const std::set<std::pair<std::string, std::string>> &usage_set,
    const std::string &src, bool in_src, bool show_file) {
  std::string old_file;
  bool file_out = false;
  bool usage_out = false;
  for (const auto &pair : usage_set) {
    const auto &file = pair.first;
    const auto &usage = pair.second;
    bool match = file == src;
    if ((match && !in_src) || (!match && in_src)) continue;
    if (file != old_file) {
      if (show_file) {
        if (file_out) std::cout << std::endl;
        std::cout << "Flags from: " << file << std::endl;
        file_out = true;
      }
      old_file = file;
    }
    std::cout << usage << std::endl;
    usage_out = true;
  }
  if (usage_out) std::cout << std::endl;
}

void ShowUsage(bool long_usage) {
  std::set<std::pair<std::string, std::string>> usage_set;
  std::cout << flag_usage << std::endl;
  auto bool_register = FlagRegister<bool>::GetRegister();
  bool_register->GetUsage(&usage_set);
  auto string_register = FlagRegister<std::string>::GetRegister();
  string_register->GetUsage(&usage_set);
  auto int32_register = FlagRegister<int32_t>::GetRegister();
  int32_register->GetUsage(&usage_set);
  auto int64_register = FlagRegister<int64_t>::GetRegister();
  int64_register->GetUsage(&usage_set);
  auto uint64_register = FlagRegister<uint64_t>::GetRegister();
  uint64_register->GetUsage(&usage_set);
  auto double_register = FlagRegister<double>::GetRegister();
  double_register->GetUsage(&usage_set);
  if (!prog_src.empty()) {
    std::cout << "PROGRAM FLAGS:" << std::endl << std::endl;
    ShowUsageRestrict(usage_set, prog_src, true, false);
  }
  if (!long_usage) return;
  if (!prog_src.empty()) {
    std::cout << "LIBRARY FLAGS:" << std::endl << std::endl;
  }
  ShowUsageRestrict(usage_set, prog_src, false, true);
}
