/*
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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.
 */

#include <sys/wait.h>

#include <cstdlib>
#include <optional>
#include <string>
#include <string_view>
#include <vector>

#include <android-base/strings.h>

#include "common/libs/utils/contains.h"
#include "common/libs/utils/result.h"
#include "common/libs/utils/subprocess.h"
#include "host/commands/process_restarter/parser.h"
#include "host/libs/config/cuttlefish_config.h"
#include "host/libs/config/logging.h"

namespace cuttlefish {
namespace {

static bool ShouldRestartProcess(siginfo_t const& info, const Parser& parsed) {
  if (info.si_code == CLD_DUMPED && parsed.when_dumped) {
    return true;
  }
  if (info.si_code == CLD_KILLED && parsed.when_killed) {
    return true;
  }
  if (info.si_code == CLD_EXITED && parsed.when_exited_with_failure &&
      info.si_status != 0) {
    return true;
  }
  if (info.si_code == CLD_EXITED &&
      info.si_status == parsed.when_exited_with_code) {
    return true;
  }
  return false;
}

std::string_view ExecutableShortName(std::string_view short_name) {
  auto last_slash = short_name.find_last_of('/');
  if (last_slash != std::string::npos) {
    short_name = short_name.substr(last_slash + 1);
  }
  return short_name;
}

Result<SubprocessOptions> OptionsForExecutable(std::string_view name) {
  const auto& config = CF_EXPECT(CuttlefishConfig::Get());
  auto options = SubprocessOptions().ExitWithParent(true);
  std::string short_name{ExecutableShortName(name)};
  if (Contains(config->straced_host_executables(), short_name)) {
    const auto& instance = config->ForDefaultInstance();
    options.Strace(instance.PerInstanceLogPath("/strace-" + short_name));
  }
  return options;
}

Result<int> RunProcessRestarter(std::vector<std::string> args) {
  LOG(VERBOSE) << "process_restarter starting";
  auto parsed = CF_EXPECT(Parser::ConsumeAndParse(args));

  // move-assign the remaining args to exec_args
  std::vector<std::string> exec_args = std::move(args);

  bool needs_pop = false;
  if (!parsed.first_time_argument.empty()) {
    exec_args.push_back(parsed.first_time_argument);
    needs_pop = true;
  }

  for (;;) {
    CF_EXPECT(!exec_args.empty());
    LOG(VERBOSE) << "Starting monitored process " << exec_args.front();
    // The Execute() API and all APIs effectively called by it show the proper
    // error message using LOG(ERROR).
    auto options = CF_EXPECT(OptionsForExecutable(exec_args.front()));
    siginfo_t info =
        CF_EXPECTF(Execute(exec_args, std::move(options), WEXITED),
                   "Executing '{}' failed.", fmt::join(exec_args, "' '"));

    if (needs_pop) {
      needs_pop = false;
      exec_args.pop_back();
    }

    if (ShouldRestartProcess(info, parsed)) {
      continue;
    }
    if (info.si_code == CLD_EXITED) {
      return info.si_status;
    }
    LOG(ERROR) << "Process exited with unexpected si_code: " << info.si_code;
    return 1;
  }
}

}  // namespace
}  // namespace cuttlefish

int main(int argc, char** argv) {
  cuttlefish::DefaultSubprocessLogging(argv);
  auto result = cuttlefish::RunProcessRestarter(
      cuttlefish::ArgsToVec(argc - 1, argv + 1));
  if (!result.ok()) {
    LOG(DEBUG) << result.error().FormatForEnv();
    return EXIT_FAILURE;
  }
  return result.value();
}