// \file filesystem.cpp
//
// Copyright (C) 2014 MicroNeil Research Corporation.
//
// This program is part of the MicroNeil Research Open Library Project. For
// more information go to http://www.microneil.com/OpenLibrary/index.html
//
// 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 2 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, write to the Free Software Foundation, Inc., 59 Temple
// Place, Suite 330, Boston, MA 02111-1307 USA
//==============================================================================

#ifdef _WIN32

#include <windows.h>
#include <Shlwapi.h>

#else 

#include <dirent.h>
#include <unistd.h>
#include <sys/types.h>

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cerrno>

#endif

#include <sys/stat.h>

#include <stdexcept>

#include "filesystem.hpp"

namespace CodeDweller {

  void FileOps::moveFile(std::string const &from, std::string const &to) {

#ifdef _WIN32
    if (MoveFileEx(from.c_str(), to.c_str(), MOVEFILE_REPLACE_EXISTING) == 0) {
#else
    if (rename(from.c_str(), to.c_str()) != 0) {
#endif
      throw std::runtime_error("Error moving file \"" + from +
                               "\" to file \"" + to + "\":  " +
                               FileReference::getErrorText());
    }

  }


#ifdef _WIN32
  char const FilePath::DirectorySeparator = '\\';
#else
  char const FilePath::DirectorySeparator = '/';
#endif

  bool FilePath::isAbsolute(std::string const &path) {

#ifdef _WIN32
    return !PathIsRelative(path.c_str());
#else
    if (path.empty()) {
      return false;
    }
    return ('/' == path[0]);
#endif

  }

  std::string FilePath::join(std::initializer_list<std::string> components) {

    std::string path;

    for (auto &component : components) {

      if (!path.empty() &&
	  path.back() != FilePath::DirectorySeparator) {
	path += FilePath::DirectorySeparator;

        if (isAbsolute(component)) {
          throw std::invalid_argument("Attempted to use absolute path \"" +
                                      component + "\" where a relative path "
                                      "is required.");
        }

      }

      path += component;

    }

    if (!path.empty() &&
	path.back() == FilePath::DirectorySeparator) {
      path.pop_back();
    }

    return path;

  }

  FileReference::FileReference(std::string fileName) :
    name(fileName),
    modTimestamp(0),
    size_bytes(0),
    fileExists(false),
    fileIsDirectory(false) {

    refresh();

  }

  std::string FileReference::FileName() const {
    return name;
  }

  void FileReference::refresh() {

    reset();

    // Load info.
    struct stat statBuffer;

    int status = stat(name.c_str(), &statBuffer);

    if (-1 == status) {

      // File no longer exists.
      if (ENOENT == errno) {
        return;
      }

      // Something went wrong.
      throw std::runtime_error("Error updating status of file \"" +
                               name + "\":  " + getErrorText());

    }

    modTimestamp = statBuffer.st_mtime;
    size_bytes = statBuffer.st_size;
    fileExists = true;
    fileIsDirectory = S_ISDIR(statBuffer.st_mode);

  }

  void FileReference:: reset() {
    modTimestamp = 0;
    size_bytes = 0;
    fileExists = false;
    fileIsDirectory = false;
    path.clear();
  }

  time_t FileReference::ModTimestamp() const {
    return modTimestamp;
  }

  size_t FileReference::Size() const {
    return size_bytes;
  }

  std::string FileReference::FullPath() {

    if (!path.empty()) {
      return path;
    }

    if (!fileExists) {
      return "";
    }

#ifdef _WIN32
    // Get the size of the full path name.
    DWORD nTchars = GetFullPathName(name.c_str(), 0, NULL, NULL);

    if (0 == nTchars) {
      throw std::runtime_error("Error getting full path length for \"" + name
			       + "\":  " + getErrorText());
    }

    size_t bufSize = nTchars * sizeof(TCHAR);
    TCHAR fullPath[bufSize];
	
    nTchars = GetFullPathName(name.c_str(), bufSize, fullPath, NULL);

    if (0 == nTchars) {
      throw std::runtime_error("Error getting full path for \"" + name
			       + "\":  " + getErrorText());
    }

    path.assign(fullPath);
#else
    char *realPath = realpath(name.c_str(), NULL);

    if (NULL == realPath) {

      // Nothing to do if the file doesn't exist.
      if (ENOENT == errno) {
	reset();
        return "";
    }

    // Something went wrong.
    throw std::runtime_error("Error checking file \"" + name + "\":  " +
      getErrorText());
    }

    path.assign(realPath);
    free(realPath);
#endif
    return path;
  }

  bool FileReference::exists() const {
    return fileExists;
  }

  bool FileReference::isDirectory() const {
    return fileIsDirectory;
  }

  std::string FileReference::getErrorText() {

#ifdef _WIN32
    LPVOID winMsgBuf;
    DWORD lastError = GetLastError(); 

    FormatMessage(
		  FORMAT_MESSAGE_ALLOCATE_BUFFER | 
		  FORMAT_MESSAGE_FROM_SYSTEM |
		  FORMAT_MESSAGE_IGNORE_INSERTS,
		  NULL,
		  lastError,
		  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		  (char *) &winMsgBuf,
		  0, NULL );

    std::string errMsg((char *) winMsgBuf);

    LocalFree(winMsgBuf);
    return errMsg;
#else
    return strerror(errno);
#endif
  }

  DirectoryReference::DirectoryReference(std::string dirName,
                                         bool (*dirFilter)(std::string)) :
    name(dirName),
    filter(dirFilter) {

    refresh();
  }

  void DirectoryReference::refresh() {

    // Clear any entries in this object.
    this->clear();

#ifdef _WIN32

    HANDLE hDirList;
    WIN32_FIND_DATA dirListData;
    std::string searchString = FilePath::join({name, "*"});

    hDirList = FindFirstFile(searchString.c_str(), &dirListData);
    if (INVALID_HANDLE_VALUE == hDirList) {
      throw std::runtime_error("Error getting file list for \"" + name +
                               "\":  " + FileReference::getErrorText());
    }

    std::string tempName;

    while (INVALID_HANDLE_VALUE != hDirList) {

    tempName = FilePath::join({name, dirListData.cFileName});

      if ( (0 == filter) || (*filter)(dirListData.cFileName)) {
        emplace_back(tempName);
      }

      if (!FindNextFile(hDirList, &dirListData)) {
        FindClose(hDirList);
        hDirList = INVALID_HANDLE_VALUE;
      }

    }

#else
    // Get new list.
    struct dirent **entries;

    int nEntries = scandir(name.c_str(), &entries, 0, 0);

    if (nEntries < 0) {
      throw std::runtime_error("Error getting file list for \"" + name +
                               "\":  " + FileReference::getErrorText());
    }

    // Create the FileReference objects.
    while (nEntries--) {
      std::string tempName;

      tempName = FilePath::join({name, entries[nEntries]->d_name});
      if ( (0 == filter) || (*filter)(entries[nEntries]->d_name)) {
        emplace_back(tempName);
      }
      free(entries[nEntries]);
    }
    free(entries);

#endif

  }

}