// Copyright (c) 2019 PaddlePaddle Authors. 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.

#include "paddle/fluid/framework/io/shell.h"

namespace paddle {
namespace framework {

std::shared_ptr<FILE> shell_fopen(const std::string& path,
                                  const std::string& mode) {
#if defined _WIN32 || defined __APPLE__
  return nullptr;
#else
  if (shell_verbose()) {
    LOG(INFO) << "Opening file[" << path << "] with mode[" << mode << "]";
  }
  FILE* fp;
  if (!(fp = fopen(path.c_str(), mode.c_str()))) {
    LOG(FATAL) << "fopen fail, path[" << path << "], mode[" << mode << "]";
  }
  return {fp, [path](FILE* fp) {
            if (shell_verbose()) {
              LOG(INFO) << "Closing file[" << path << "]";
            }
            if (0 != fclose(fp)) {
              LOG(FATAL) << "fclose fail, path[" << path << "]";
            }
          }};
#endif
}

// Close all open file descriptors
// The implementation is async signal safe
// Mostly copy from CPython code
static int close_open_fds_internal() {
#if defined _WIN32 || defined __APPLE__
  return 0;
#else
  struct linux_dirent {
    long d_ino = 0;  // NOLINT
    off_t d_off;
    unsigned short d_reclen = 0;  // NOLINT
    char d_name[256];
  };

  int dir_fd = -1;
  if ((dir_fd = open("/proc/self/fd", O_RDONLY)) < 0) {
    LOG(FATAL) << "proc/self/fd open fail";
    return -1;
  }
  char buffer[sizeof(linux_dirent)];

  for (;;) {
    int bytes = 0;
    if ((bytes = syscall(SYS_getdents, dir_fd,
                         reinterpret_cast<linux_dirent*>(buffer),
                         sizeof(buffer))) < 0) {
      LOG(FATAL) << "syscall fail";
      return -1;
    }

    if (bytes == 0) {
      break;
    }

    linux_dirent* entry = NULL;

    for (int offset = 0; offset < bytes; offset += entry->d_reclen) {
      entry = reinterpret_cast<linux_dirent*>(buffer + offset);
      int fd = 0;
      const char* s = entry->d_name;

      while (*s >= '0' && *s <= '9') {
        fd = fd * 10 + (*s - '0');
        s++;
      }

      if (s != entry->d_name && fd != dir_fd && fd >= 3) {
        close(fd);
      }
    }
  }

  close(dir_fd);
  return 0;
#endif
}

static int shell_popen_fork_internal(const char* real_cmd, bool do_read,
                                     int parent_end, int child_end) {
#if defined _WIN32 || defined __APPLE__
  return 0;
#else
  int child_pid = -1;
  // Too frequent calls to fork() makes openmpi very slow. Use vfork() instead.
  // But vfork() is very dangerous. Be careful.
  if ((child_pid = vfork()) < 0) {
    return -1;
  }

  // The following code is async signal safe (No memory allocation, no access to
  // global data, etc.)
  if (child_pid != 0) {
    return child_pid;
  }

  int child_std_end = do_read ? 1 : 0;
  close(parent_end);

  if (child_end != child_std_end) {
    if (dup2(child_end, child_std_end) != child_std_end) {
      return -1;
    }
    close(child_end);
  }

  close_open_fds_internal();
  if (execl("/bin/bash", "bash", "-c", real_cmd, NULL) < 0) {
    return -1;
  }
  exit(127);
#endif
}

std::shared_ptr<FILE> shell_popen(const std::string& cmd,
                                  const std::string& mode, int* err_no) {
#if defined _WIN32 || defined __APPLE__
  return nullptr;
#else
  bool do_read = mode == "r";
  bool do_write = mode == "w";
  if (!(do_read || do_write)) {
    *err_no = -1;
    return NULL;
  }

  if (shell_verbose()) {
    LOG(INFO) << "Opening pipe[" << cmd << "] with mode[" << mode << "]";
  }

  std::string real_cmd = "set -o pipefail; " + cmd;

  int pipe_fds[2];
  if (pipe(pipe_fds) != 0) {
    *err_no = -1;
    return NULL;
  }
  int parent_end = 0;
  int child_end = 0;

  if (do_read) {
    parent_end = pipe_fds[0];
    child_end = pipe_fds[1];
  } else if (do_write) {
    parent_end = pipe_fds[1];
    child_end = pipe_fds[0];
  }

  int child_pid = shell_popen_fork_internal(real_cmd.c_str(), do_read,
                                            parent_end, child_end);
  close(child_end);
  fcntl(parent_end, F_SETFD, FD_CLOEXEC);
  FILE* fp;
  if ((fp = fdopen(parent_end, mode.c_str())) == NULL) {
    *err_no = -1;
    return NULL;
  }
  return {fp, [child_pid, cmd, err_no](FILE* fp) {
            if (shell_verbose()) {
              LOG(INFO) << "Closing pipe[" << cmd << "]";
            }

            if (fclose(fp) != 0) {
              *err_no = -1;
            }
            int wstatus = -1;
            waitpid(child_pid, &wstatus, 0);
            if (wstatus == 0 || wstatus == (128 + SIGPIPE) * 256 ||
                (wstatus == -1 && errno == ECHILD)) {
            } else {
              *err_no = -1;
              LOG(WARNING) << "status[" << wstatus << "], cmd[" << cmd << "]"
                           << ", err_no[" << *err_no << "]";
            }
            if (wstatus == -1 && errno == ECHILD) {
              LOG(WARNING) << "errno is ECHILD";
            }
          }};
#endif
}

static int shell_p2open_fork_internal(const char* real_cmd, int pipein_fds[2],
                                      int pipeout_fds[2]) {
#if defined _WIN32 || defined __APPLE__
  return 0;
#else
  int child_pid = -1;
  if ((child_pid = fork()) < 0) {
    return -1;
  }

  if (child_pid != 0) {
    return child_pid;
  }

  close(pipein_fds[0]);
  close(pipeout_fds[1]);

  if (pipein_fds[1] != 1) {
    if (dup2(pipein_fds[1], 1) != 1) {
      return -1;
    }
    close(pipein_fds[1]);
  }

  if (pipeout_fds[0] != 0) {
    if (dup2(pipeout_fds[0], 0) != 0) {
      return -1;
    }
    close(pipeout_fds[0]);
  }

  close_open_fds_internal();
  if (execl("/bin/sh", "sh", "-c", real_cmd, NULL) < 0) {
    return -1;
  }
  exit(127);
#endif
}

std::pair<std::shared_ptr<FILE>, std::shared_ptr<FILE>> shell_p2open(
    const std::string& cmd) {
#if defined _WIN32 || defined __APPLE__
  return {};
#else
  if (shell_verbose()) {
    LOG(INFO) << "Opening bidirectional pipe[" << cmd << "]";
  }

  std::string real_cmd = "set -o pipefail; " + cmd;

  int pipein_fds[2];
  int pipeout_fds[2];
  if (pipe(pipein_fds) != 0) {
    return {NULL, NULL};
  }
  if (pipe(pipeout_fds) != 0) {
    return {NULL, NULL};
  }

  int child_pid =
      shell_p2open_fork_internal(real_cmd.c_str(), pipein_fds, pipeout_fds);

  close(pipein_fds[1]);
  close(pipeout_fds[0]);
  fcntl(pipein_fds[0], F_SETFD, FD_CLOEXEC);
  fcntl(pipeout_fds[1], F_SETFD, FD_CLOEXEC);

  std::shared_ptr<int> child_life = {
      NULL, [child_pid, cmd](void*) {
        if (shell_verbose()) {
          LOG(INFO) << "Closing bidirectional pipe[" << cmd << "]";
        }

        int wstatus, ret;

        do {
          PCHECK((ret = waitpid(child_pid, &wstatus, 0)) >= 0 ||
                 (ret == -1 && errno == EINTR));
        } while (ret == -1 && errno == EINTR);

        PCHECK(wstatus == 0 || wstatus == (128 + SIGPIPE) * 256 ||
               (wstatus == -1 && errno == ECHILD))
            << "status[" << wstatus << "], cmd[" << cmd << "]";

        if (wstatus == -1 && errno == ECHILD) {
          LOG(WARNING) << "errno is ECHILD";
        }
      }};

  FILE* in_fp;
  PCHECK((in_fp = fdopen(pipein_fds[0], "r")) != NULL);
  FILE* out_fp;
  PCHECK((out_fp = fdopen(pipeout_fds[1], "w")) != NULL);
  return {{in_fp, [child_life](FILE* fp) { PCHECK(fclose(fp) == 0); }},
          {out_fp, [child_life](FILE* fp) { PCHECK(fclose(fp) == 0); }}};
#endif
}

std::string shell_get_command_output(const std::string& cmd) {
#if defined _WIN32 || defined __APPLE__
  return "";
#else
  int err_no = 0;
  do {
    err_no = 0;
    std::shared_ptr<FILE> pipe = shell_popen(cmd, "r", &err_no);
    string::LineFileReader reader;

    if (reader.getdelim(&*pipe, 0)) {
      pipe = nullptr;
      if (err_no == 0) {
        return reader.get();
      }
    }
  } while (err_no == -1);
  return "";
#endif
}

}  // end namespace framework
}  // end namespace paddle
