/* Copyright 2015 The TensorFlow 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 <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include "tensorflow/core/lib/core/error_codes.pb.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/lib/strings/strcat.h"
#include "tensorflow/core/platform/env.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/platform/posix/error.h"
#include "tensorflow/core/platform/posix/posix_file_system.h"

namespace tensorflow {

// pread() based random-access
class PosixRandomAccessFile : public RandomAccessFile {
 private:
  string filename_;
  int fd_;

 public:
  PosixRandomAccessFile(const string& fname, int fd)
      : filename_(fname), fd_(fd) {}
  ~PosixRandomAccessFile() override { close(fd_); }

  Status Read(uint64 offset, size_t n, StringPiece* result,
              char* scratch) const override {
    Status s;
    char* dst = scratch;
    while (n > 0 && s.ok()) {
      ssize_t r = pread(fd_, dst, n, static_cast<off_t>(offset));
      if (r > 0) {
        dst += r;
        n -= r;
        offset += r;
      } else if (r == 0) {
        s = Status(error::OUT_OF_RANGE, "Read less bytes than requested");
      } else if (errno == EINTR || errno == EAGAIN) {
        // Retry
      } else {
        s = IOError(filename_, errno);
      }
    }
    *result = StringPiece(scratch, dst - scratch);
    return s;
  }
};

class PosixWritableFile : public WritableFile {
 private:
  string filename_;
  FILE* file_;

 public:
  PosixWritableFile(const string& fname, FILE* f)
      : filename_(fname), file_(f) {}

  ~PosixWritableFile() override {
    if (file_ != NULL) {
      // Ignoring any potential errors
      fclose(file_);
    }
  }

  Status Append(const StringPiece& data) override {
    size_t r = fwrite(data.data(), 1, data.size(), file_);
    if (r != data.size()) {
      return IOError(filename_, errno);
    }
    return Status::OK();
  }

  Status Close() override {
    Status result;
    if (fclose(file_) != 0) {
      result = IOError(filename_, errno);
    }
    file_ = NULL;
    return result;
  }

  Status Flush() override {
    if (fflush(file_) != 0) {
      return IOError(filename_, errno);
    }
    return Status::OK();
  }

  Status Sync() override {
    Status s;
    if (fflush(file_) != 0) {
      s = IOError(filename_, errno);
    }
    return s;
  }
};

class PosixReadOnlyMemoryRegion : public ReadOnlyMemoryRegion {
 public:
  PosixReadOnlyMemoryRegion(const void* address, uint64 length)
      : address_(address), length_(length) {}
  ~PosixReadOnlyMemoryRegion() { munmap(const_cast<void*>(address_), length_); }
  const void* data() override { return address_; }
  uint64 length() override { return length_; }

 private:
  const void* const address_;
  const uint64 length_;
};

Status PosixFileSystem::NewRandomAccessFile(
    const string& fname, std::unique_ptr<RandomAccessFile>* result) {
  string translated_fname = TranslateName(fname);
  Status s;
  int fd = open(translated_fname.c_str(), O_RDONLY);
  if (fd < 0) {
    s = IOError(fname, errno);
  } else {
    result->reset(new PosixRandomAccessFile(translated_fname, fd));
  }
  return s;
}

Status PosixFileSystem::NewWritableFile(const string& fname,
                                        std::unique_ptr<WritableFile>* result) {
  string translated_fname = TranslateName(fname);
  Status s;
  FILE* f = fopen(translated_fname.c_str(), "w");
  if (f == NULL) {
    s = IOError(fname, errno);
  } else {
    result->reset(new PosixWritableFile(translated_fname, f));
  }
  return s;
}

Status PosixFileSystem::NewAppendableFile(
    const string& fname, std::unique_ptr<WritableFile>* result) {
  string translated_fname = TranslateName(fname);
  Status s;
  FILE* f = fopen(translated_fname.c_str(), "a");
  if (f == NULL) {
    s = IOError(fname, errno);
  } else {
    result->reset(new PosixWritableFile(translated_fname, f));
  }
  return s;
}

Status PosixFileSystem::NewReadOnlyMemoryRegionFromFile(
    const string& fname, std::unique_ptr<ReadOnlyMemoryRegion>* result) {
  string translated_fname = TranslateName(fname);
  Status s = Status::OK();
  int fd = open(translated_fname.c_str(), O_RDONLY);
  if (fd < 0) {
    s = IOError(fname, errno);
  } else {
    struct stat st;
    ::fstat(fd, &st);
    const void* address =
        mmap(nullptr, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (address == MAP_FAILED) {
      s = IOError(fname, errno);
    } else {
      result->reset(new PosixReadOnlyMemoryRegion(address, st.st_size));
    }
    close(fd);
  }
  return s;
}

bool PosixFileSystem::FileExists(const string& fname) {
  return access(TranslateName(fname).c_str(), F_OK) == 0;
}

Status PosixFileSystem::GetChildren(const string& dir,
                                    std::vector<string>* result) {
  string translated_dir = TranslateName(dir);
  result->clear();
  DIR* d = opendir(translated_dir.c_str());
  if (d == NULL) {
    return IOError(dir, errno);
  }
  struct dirent* entry;
  while ((entry = readdir(d)) != NULL) {
    StringPiece basename = entry->d_name;
    if ((basename != ".") && (basename != "..")) {
      result->push_back(entry->d_name);
    }
  }
  closedir(d);
  return Status::OK();
}

Status PosixFileSystem::DeleteFile(const string& fname) {
  Status result;
  if (unlink(TranslateName(fname).c_str()) != 0) {
    result = IOError(fname, errno);
  }
  return result;
}

Status PosixFileSystem::CreateDir(const string& name) {
  Status result;
  if (mkdir(TranslateName(name).c_str(), 0755) != 0) {
    result = IOError(name, errno);
  }
  return result;
}

Status PosixFileSystem::DeleteDir(const string& name) {
  Status result;
  if (rmdir(TranslateName(name).c_str()) != 0) {
    result = IOError(name, errno);
  }
  return result;
}

Status PosixFileSystem::GetFileSize(const string& fname, uint64* size) {
  Status s;
  struct stat sbuf;
  if (stat(TranslateName(fname).c_str(), &sbuf) != 0) {
    *size = 0;
    s = IOError(fname, errno);
  } else {
    *size = sbuf.st_size;
  }
  return s;
}

Status PosixFileSystem::Stat(const string& fname, FileStatistics* stats) {
  Status s;
  struct stat sbuf;
  if (stat(TranslateName(fname).c_str(), &sbuf) != 0) {
    s = IOError(fname, errno);
  } else {
    stats->length = sbuf.st_size;
    stats->mtime_nsec = sbuf.st_mtime * 1e9;
    stats->is_directory = S_ISDIR(sbuf.st_mode);
  }
  return s;
}

Status PosixFileSystem::RenameFile(const string& src, const string& target) {
  Status result;
  if (rename(TranslateName(src).c_str(), TranslateName(target).c_str()) != 0) {
    result = IOError(src, errno);
  }
  return result;
}

}  // namespace tensorflow
