// ----------------------------------------------------------------------
// File: DirectoryIterator.cc
// Author: Georgios Bitzes - CERN
// ----------------------------------------------------------------------

/************************************************************************
 * quarkdb - a redis-like highly available key-value store              *
 * Copyright (C) 2016 CERN/Switzerland                                  *
 *                                                                      *
 * This program is free software: you can redistribute it and/or modify *
 * it under the terms of the GNU General Public License as published by *
 * the Free Software Foundation, either version 3 of the License, or    *
 * (at your option) any later version.                                  *
 *                                                                      *
 * This program is distributed in the hope that it will be useful,      *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of       *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
 * GNU General Public License for more details.                         *
 *                                                                      *
 * You should have received a copy of the GNU General Public License    *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.*
 ************************************************************************/

#include "DirectoryIterator.hh"
#include "Macros.hh"
#include <string.h>
#include <sys/stat.h>

using namespace quarkdb;

//------------------------------------------------------------------------------
// Construct iterator object on the given path - must be a directory.
//------------------------------------------------------------------------------
DirectoryIterator::DirectoryIterator(std::string_view mypath)
: path(mypath), reachedEnd(false), dir(nullptr) {

  if (*path.rbegin() != '/') {
    path += '/';
  }

  dir = opendir(path.c_str());
  if(!dir) {
    error = SSTR("Unable to opendir: " << path);
    return;
  }
}

//------------------------------------------------------------------------------
// Destructor
//------------------------------------------------------------------------------
DirectoryIterator::~DirectoryIterator() {
  if(dir) {
    if(closedir(dir) != 0) {
      qdb_critical("Unable to close DIR* for " << path);
    }
    dir = nullptr;
  }
}

//------------------------------------------------------------------------------
// Retrieve next directory entry.
// This object retains ownership on the given pointer, never call free on it.
//
// If the iterator is in an error state, next() will only ever return nullptr.
//------------------------------------------------------------------------------
struct dirent* DirectoryIterator::next() {
  if(!ok()) return nullptr;
  if(reachedEnd) return nullptr;

  errno = 0;
  nextEntry = readdir(dir);

  if(!nextEntry && errno == 0) {
    reachedEnd = true;
  }
  else if(!nextEntry) {
    error = SSTR("Error when calling readdir: " << strerror(errno));
  }

  // Fallback to stat if readdir does not provide the d_type for the entries
  if (nextEntry && (nextEntry->d_type == DT_UNKNOWN)) {
    struct stat buf;
    const std::string full_path = path + nextEntry->d_name;

    if (stat(full_path.c_str(), &buf)) {
      nextEntry = nullptr;
    } else {
      nextEntry->d_type = S_ISDIR(buf.st_mode) ? DT_DIR : DT_REG;
    }
  }

  return nextEntry;
}

//------------------------------------------------------------------------------
// Checks if the iterator is in an error state. EOF is not an error state!
//------------------------------------------------------------------------------
bool DirectoryIterator::ok() {
  return error.empty();
}

//------------------------------------------------------------------------------
// Checks whether we have reached the end.
//------------------------------------------------------------------------------
bool DirectoryIterator::eof() {
  return reachedEnd;
}

//------------------------------------------------------------------------------
// Retrieve the error message if the iterator object is in an error state.
// If no error state, returns an empty string.
//------------------------------------------------------------------------------
std::string DirectoryIterator::err() {
  return error;
}