/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file vertexDataSaveFile.cxx
 * @author drose
 * @date 2007-05-12
 */

#include "vertexDataSaveFile.h"
#include "mutexHolder.h"
#include "clockObject.h"
#include "config_gobj.h"

#ifndef _WIN32
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#endif  // _WIN32

/**
 *
 */
VertexDataSaveFile::
VertexDataSaveFile(const Filename &directory, const string &prefix,
                   size_t max_size) :
  SimpleAllocator(max_size, _lock)
{
  Filename dir;
  if (directory.empty()) {
    dir = Filename::get_temp_directory();
  } else {
    dir = directory;
  }

  _is_valid = false;
  _total_file_size = 0;

  // Try to open and lock a writable temporary filename.
  int index = 0;
  while (true) {
    ++index;
    ostringstream strm;
    strm << prefix << "_" << index << ".dat";

    string basename = strm.str();
    _filename = Filename(dir, basename);
    string os_specific = _filename.to_os_specific();

    if (gobj_cat.is_debug()) {
      gobj_cat.debug()
        << "Creating vertex data save file " << os_specific << "\n";
    }

#ifdef _WIN32
    // Windows case.
    DWORD flags = FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE | FILE_FLAG_RANDOM_ACCESS;
#if defined(HAVE_THREADS) && defined(SIMPLE_THREADS)
    // In SIMPLE_THREADS mode, we use "overlapped" IO.
    flags |= FILE_FLAG_OVERLAPPED | FILE_FLAG_NO_BUFFERING;
#endif
    _handle = CreateFile(os_specific.c_str(), GENERIC_READ | GENERIC_WRITE,
                         0, NULL, CREATE_ALWAYS, flags, NULL);
    if (_handle != INVALID_HANDLE_VALUE) {
      // The file was successfully opened and locked.
      break;

    } else {
      // Couldn't open the file.  Either the directory was bad, or the file
      // was already locked by another.
      DWORD err = GetLastError();

      if (err != ERROR_SHARING_VIOLATION) {
        // File couldn't be opened; permission problem or bogus directory.
        if (!dir.empty()) {
          // Try the current directory, once.
          dir = Filename();
        } else {
          gobj_cat.error()
            << "Couldn't open vertex data save file.\n";
          return;
        }
      }

      // Couldn't lock the file.  Try the next one.
    }

#else
    // Posix case.
    int flags = O_RDWR | O_CREAT;
#if defined(HAVE_THREADS) && defined(SIMPLE_THREADS)
    // In SIMPLE_THREADS mode, we use non-blocking IO.
    flags |= O_NONBLOCK;
#endif

    _fd = ::open(os_specific.c_str(), flags, 0666);
    while (_fd == -1 && errno == EAGAIN) {
      Thread::force_yield();
      _fd = ::open(os_specific.c_str(), flags, 0666);
    }

    if (_fd == -1) {
      // Couldn't open the file: permissions problem or bad directory.
      if (!_filename.exists()) {
        // It must be a bad directory.
        if (!dir.empty()) {
          // Try the current directory, once.
          dir = Filename();
        } else {
          gobj_cat.error()
            << "Couldn't open vertex data save file.\n";
          return;
        }
      }

      // If it's a permissions problem, it might be a user-level permissions
      // issue.  Continue to the next.
      continue;
    }

    // Now try to lock the file, so we can be sure that no other process is
    // simultaneously writing to the same save file.
#ifdef HAVE_LOCKF
    int result = lockf(_fd, F_TLOCK, 0);
#else
    int result = flock(_fd, LOCK_EX | LOCK_NB);
#endif
    if (result == 0) {
      // We've got the file.  Truncate it first, for good measure, in case
      // there's an old version of the file we picked up.
      if (ftruncate(_fd, 0) < 0) {
        gobj_cat.warning()
          << "Couldn't truncate vertex data save file.\n";
      }

      // On Unix, it's safe to unlink (delete) the temporary file after it's
      // been opened.  The file remains open, but disappears from the
      // directory.  This is kind of like DELETE_ON_CLOSE, to ensure the
      // temporary file won't accidentally get left behind, except it's a
      // little more proactive.
      unlink(os_specific.c_str());
      _filename = Filename();
      break;
    }

    // Try the next file.
    close(_fd);
#endif  // _WIN32
  }

  _is_valid = true;
}

/**
 *
 */
VertexDataSaveFile::
~VertexDataSaveFile() {
#ifdef _WIN32
  if (_handle != NULL) {
    CloseHandle(_handle);
  }
#else
  if (_fd != -1) {
    close(_fd);
  }
#endif  // _WIN32

  // No need to remove the file, since in both above cases we have already
  // removed it.  And removing it now, after we have closed and unlocked it,
  // might accidentally remove someone else's copy.
  /*
  if (!_filename.empty()) {
    _filename.unlink();
  }
  */
}

/**
 * Writes a block of data to the file, and returns a handle to the block
 * handle.  Returns NULL if the data cannot be written (e.g.  no remaining
 * space on the file).
 */
PT(VertexDataSaveBlock) VertexDataSaveFile::
write_data(const unsigned char *data, size_t size, bool compressed) {
  MutexHolder holder(_lock);

  if (!_is_valid) {
    return NULL;
  }

  PT(VertexDataSaveBlock) block = (VertexDataSaveBlock *)SimpleAllocator::do_alloc(size);
  if (block != (VertexDataSaveBlock *)NULL) {
    _total_file_size = max(_total_file_size, block->get_start() + size);
    block->set_compressed(compressed);

#ifdef _WIN32
    OVERLAPPED overlapped;
    memset(&overlapped, 0, sizeof(overlapped));
    overlapped.Offset = block->get_start();

    DWORD bytes_written = 0;
    double start_time = ClockObject::get_global_clock()->get_real_time();
    int num_passes = 0;
    BOOL success = WriteFile(_handle, data, size, &bytes_written, &overlapped);
    while (!success) {
      DWORD error = GetLastError();
      if (error == ERROR_IO_INCOMPLETE || error == ERROR_IO_PENDING) {
        // Wait for more later.
        Thread::force_yield();
        ++num_passes;
      } else {
        gobj_cat.error()
          << "Error writing " << size
          << " bytes to save file, windows error code 0x" << hex
          << error << dec << ".  Disk full?\n";
        return NULL;
      }
      success = GetOverlappedResult(_handle, &overlapped, &bytes_written, false);
    }
    nassertr(bytes_written == size, NULL);
    double finish_time = ClockObject::get_global_clock()->get_real_time();
    if (gobj_cat.is_debug()) {
      gobj_cat.debug()
        << "Wrote " << size << " bytes in " << *Thread::get_current_thread() << " over " << floor((finish_time - start_time) * 1000.0) << " ms and " << num_passes << " passes.\n";
    }
#else
    // Posix case.
    if (lseek(_fd, block->get_start(), SEEK_SET) == -1) {
      gobj_cat.error()
        << "Error seeking to position " << block->get_start() << " in save file.\n";
      return NULL;
    }

    while (size > 0) {
      ssize_t result = ::write(_fd, data, size);
      if (result < 0) {
        if (errno == EAGAIN) {
          Thread::force_yield();
        } else {
          gobj_cat.error()
            << "Error writing " << size << " bytes to save file.  Disk full?\n";
          return NULL;
        }
        continue;
      }

      Thread::consider_yield();
      data += result;
      size -= result;
    }
#endif  // _WIN32
  }

  return block;
}

/**
 * Reads a block of data from the file, and returns true on success, false on
 * failure.
 */
bool VertexDataSaveFile::
read_data(unsigned char *data, size_t size, VertexDataSaveBlock *block) {
  MutexHolder holder(_lock);

  if (!_is_valid) {
    return false;
  }

  nassertr(size == block->get_size(), false);

  /*
  static ConfigVariableBool allow_mainthread_read("allow-mainthread-read", 1);
  if (!allow_mainthread_read) {
    nassertr(Thread::get_current_thread() != Thread::get_main_thread(), false);
  }
  */

#ifdef _WIN32
  OVERLAPPED overlapped;
  memset(&overlapped, 0, sizeof(overlapped));
  overlapped.Offset = block->get_start();

  DWORD bytes_read = 0;
  double start_time = ClockObject::get_global_clock()->get_real_time();
  int num_passes = 0;
  BOOL success = ReadFile(_handle, data, size, &bytes_read, &overlapped);
  while (!success) {
    DWORD error = GetLastError();
    if (error == ERROR_IO_INCOMPLETE || error == ERROR_IO_PENDING) {
      // Wait for more later.
      Thread::force_yield();
      ++num_passes;
    } else {
      gobj_cat.error()
        << "Error reading " << size
        << " bytes from save file, windows error code 0x" << hex
        << error << dec << ".\n";
      return NULL;
    }
    success = GetOverlappedResult(_handle, &overlapped, &bytes_read, false);
  }
  nassertr(bytes_read == size, NULL);
  double finish_time = ClockObject::get_global_clock()->get_real_time();
  if (gobj_cat.is_debug()) {
    gobj_cat.debug()
      << "Read " << size << " bytes in " << *Thread::get_current_thread() << " over " << floor((finish_time - start_time) * 1000.0) << " ms and " << num_passes << " passes.\n";
  }

#else
  // Posix case.
  if (lseek(_fd, block->get_start(), SEEK_SET) == -1) {
    gobj_cat.error()
      << "Error seeking to position " << block->get_start() << " in save file.\n";
    return false;
  }
  while (size > 0) {
    ssize_t result = read(_fd, data, size);
    if (result == -1) {
      if (errno == EAGAIN) {
        Thread::force_yield();
      } else {
        gobj_cat.error()
          << "Error reading " << size << " bytes from save file.\n";
        return false;
      }
    }

    Thread::consider_yield();
    data += result;
    size -= result;
  }
#endif  // _WIN32

  return true;
}

/**
 * Creates a new SimpleAllocatorBlock object.  Override this function to
 * specialize the block type returned.
 */
SimpleAllocatorBlock *VertexDataSaveFile::
make_block(size_t start, size_t size) {
  return new VertexDataSaveBlock(this, start, size);
}