/// <summary>
/// Creates a new randomly-named backup directory in the given directory. Creates the given directory too, if
/// required.
/// </summary>
/// <param name="targetPath">The path of the directory in which to create the backup directory.</param>
/// <returns>The name of the new backup directory.</returns>
/// <exception cref="BackupDirectoryCreateException">If the new directory could not be created, due to I/O
/// errors, permission errors, etc.</exception>
public static string CreateBackupDirectory(string targetPath)
{
var retries = BACKUP_DIRECTORY_CREATION_RETRIES;
List <string> attemptedDirectoryNames = new();
while (true)
{
var name = Utility.RandomAlphaNumericString(BACKUP_DIRECTORY_NAME_LENGTH);
attemptedDirectoryNames.Add(name);
var path = BackupPath(targetPath, name);
FilesystemException?exception = null;
// Non-atomicity :|
if (!Directory.Exists(path) && !File.Exists(path))
{
try {
FilesystemException.ConvertSystemException(() => Directory.CreateDirectory(path), () => path);
return(name);
}
catch (FilesystemException e) {
exception = e;
}
}
if (retries <= 0)
{
throw new BackupDirectoryCreateException(targetPath, attemptedDirectoryNames, exception);
}
retries--;
}
}
/// <summary>
/// Parses and validates the application's command line arguments.
/// </summary>
/// <remarks>
/// Note that the filesystem paths in the returned <see cref="AppConfig"/> are not guaranteed to be valid, as
/// this is unfortunately not really possible to check without actually doing the desired I/O operation. <br/>
/// However, some invalid paths are detected by this method.
/// </remarks>
/// <param name="args">The command line arguments.</param>
/// <returns>The <see cref="AppConfig"/> parsed from the arguments.</returns>
/// <exception cref="InvalidCmdArgsError">If the command line arguments are invalid.</exception>
/// <exception cref="ApplicationRuntimeError">If the config paths can't be resolved.</exception>
private AppConfig ParseCmdArgs(string[] args)
{
if (args.Length < 2)
{
throw new InvalidCmdArgsError();
}
var sourcePath = args[0];
var targetPath = args[1];
var excludePaths = args.Skip(2);
try {
sourcePath = FilesystemException.ConvertSystemException(() => Path.GetFullPath(sourcePath),
() => sourcePath);
}
catch (FilesystemException e) {
throw new ApplicationRuntimeError($"Failed to resolve source directory: {e.Reason}");
}
if (File.Exists(sourcePath))
{
throw new ApplicationRuntimeError("Source directory is not a directory");
}
if (!Directory.Exists(sourcePath))
{
throw new ApplicationRuntimeError("Source directory not found");
}
try {
targetPath = FilesystemException.ConvertSystemException(() => Path.GetFullPath(targetPath),
() => targetPath);
}
catch (FilesystemException e) {
throw new ApplicationRuntimeError($"Failed to resolve target directory: {e.Reason}");
}
if (File.Exists(targetPath))
{
throw new ApplicationRuntimeError("Target directory exists and is not a directory.");
}
List <string> parsedExcludePaths = new();
foreach (var path in excludePaths)
{
string fullPath;
try {
fullPath = FilesystemException.ConvertSystemException(
() => Path.GetFullPath(path, sourcePath), () => path);
}
catch (FilesystemException e) {
Logger.Warning($"Failed to resolve exclude path \"{path}\" ({e.Reason}); discarding.");
continue;
}
parsedExcludePaths.Add(fullPath);
}
return(new(sourcePath, targetPath, parsedExcludePaths));
}
/// <summary>
/// Opens a backup index file for reading.
/// </summary>
/// <param name="filePath">The path to the index file.</param>
/// <returns>A new <see cref="StreamReader"/> associated with the file.</returns>
/// <exception cref="BackupIndexFileIOException">If the file could not be opened.</exception>
private static StreamReader OpenFile(string filePath)
{
try {
return(FilesystemException.ConvertSystemException(
() => new StreamReader(filePath, new UTF8Encoding(false, true)), () => filePath));
}
catch (FilesystemException e) {
throw new BackupIndexFileIOException(filePath, e);
}
}
/// <summary>
/// Creates a handler that logs to a file at the given path. <br/>
/// The file is created new or overwritten if it exists.
/// </summary>
/// <param name="path">The file to log messages to.</param>
/// <exception cref="LoggingException">If the file could not be opened.</exception>
public FileLogHandler(string path)
{
try {
Stream = FilesystemException.ConvertSystemException(() => File.CreateText(path), () => path);
}
catch (FilesystemException e) {
throw new LoggingException($"Failed to create/open log file \"{path}\": {e.Reason}", e);
}
FilePath = path;
}
/// <summary>
/// Logs a message to the associated file.
/// </summary>
/// <param name="level">The level of the message.</param>
/// <param name="message">The message to log.</param>
/// <exception cref="LoggingException">If the message could not be written to the file due to I/O errors.
/// </exception>
public void Log(LogLevel level, string message)
{
var formattedMessage = LogFormatter.FormatMessage(level, message);
try {
FilesystemException.ConvertSystemException(() => {
Stream.Write(formattedMessage);
Stream.Flush();
}, () => FilePath);
}
catch (FilesystemException e) {
throw new LoggingException($"Failed to log to file \"{FilePath}\": {e.Reason}", e);
}
}
/// <summary>
/// Reads a backup index from file.
/// </summary>
/// <param name="filePath">The path to the index file.</param>
/// <returns>The read backup index.</returns>
/// <exception cref="BackupIndexFileIOException">If a filesystem error occurs during reading.</exception>
/// <exception cref="BackupIndexFileParseException">If the file is not a valid backup index.</exception>
public static BackupIndex Read(string filePath)
{
using var stream = OpenFile(filePath);
BackupIndex index = new();
long lineNum = 0;
while (true)
{
string?line;
try {
line = FilesystemException.ConvertSystemException(() => stream.ReadLine(), () => filePath);
}
catch (FilesystemException e) {
throw new BackupIndexFileIOException(filePath, e);
}
if (line is null)
{
break;
}
lineNum++;
// Empty line ok, just skip it.
if (line.Length == 0)
{
continue;
}
// Split on first separator (should be exactly 1).
var parts = line.Split(BackupIndexFileConstants.SEPARATOR, 2);
if (parts.Length != 2)
{
throw new BackupIndexFileParseException(filePath, lineNum);
}
// Note that empty values are valid, even though that shouldn't happen in practice.
var backupDirectory = parts[0];
var backupSourcePath = Utility.NewlineDecode(parts[1]);
index.Backups[backupDirectory] = backupSourcePath;
}
return(index);
}
/// <summary>
/// Performs the back up. <br/>
/// Should not be called more than once per instance.
/// </summary>
/// <returns>The results of the backup.</returns>
/// <exception cref="BackupServiceException">If the source directory can't be accessed.</exception>
private BackupResults Run()
{
// Explore directories in a depth-first manner, on the basis that files/directories within the same branch
// of the filesystem are likely to be modified together, so we want to back them up as close together in
// time as possible. It's also probably more useful to have some directories fully backed up rather than
// all directories partially backed up (if using breadth-first), in the case the backup is stopped early.
SearchState searchState = new(true, new(1000), new(20));
try {
var root = FilesystemException.ConvertSystemException(() => new DirectoryInfo(SourcePath),
() => SourcePath);
searchState.NodeStack.Add(state => VisitDirectory(state, root));
}
catch (FilesystemException e) {
throw new BackupServiceException($"Failed to enumerate source directory \"{SourcePath}\": {e.Reason}", e);
}
do
{
var currentNode = searchState.NodeStack[^ 1];
/// <summary>
/// Writes a new backup entry to a backup index file.
/// </summary>
/// <param name="indexFilePath">The path of the index file to write to. May be a nonexistent file, in which
/// case it will be created.</param>
/// <param name="backupName">The name of the backup directory. Must not contain
/// <see cref="BackupIndexFileConstants.SEPARATOR"/> or newline characters.</param>
/// <param name="backupSourcePath">The path of the source directory for the backup.</param>
/// <exception cref="ArgumentException">If <paramref name="backupName"/> contains invalid characters.
/// </exception>
/// <exception cref="BackupIndexFileIOException">Failed to write to the index file due to filesystem-related
/// errors.</exception>
public static void AddEntry(string indexFilePath, string backupName, string backupSourcePath)
{
if (backupName.Contains(BackupIndexFileConstants.SEPARATOR))
{
throw new ArgumentException(
$"{nameof(backupName)} must not contain {BackupIndexFileConstants.SEPARATOR}", nameof(backupName));
}
if (Utility.ContainsNewlines(backupName))
{
throw new ArgumentException($"{nameof(backupName)} must not contain newlines.", nameof(backupName));
}
var entry = $"{backupName}{BackupIndexFileConstants.SEPARATOR}{Utility.NewlineEncode(backupSourcePath)}\n";
try {
FilesystemException.ConvertSystemException(
() => File.AppendAllText(indexFilePath, entry, new UTF8Encoding(false, true)),
() => indexFilePath);
}
catch (FilesystemException e) {
throw new BackupIndexFileIOException(indexFilePath, e);
}
}