Additional tools for gardening.

tools/gardening/lib/src/logger.dart

Index: tools/gardening/lib/src/logger.dart
diff --git a/tools/gardening/lib/src/logger.dart b/tools/gardening/lib/src/logger.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3701f2f2c82836f23167e7c1b5ff0a8cb9a71ed0
--- /dev/null
+++ b/tools/gardening/lib/src/logger.dart
@@ -0,0 +1,117 @@
+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+import 'package:path/path.dart' as path;
+
+enum Level { debug, info, warning, error }
+
+abstract class Logger {
+  Level level;
+
+  Logger(this.level);
+
+  void info(String msg, [Error, StackTrace]);
+  void warning(String msg, [Error, StackTrace]);
+  void error(String msg, [Error, StackTrace]);
+  void debug(String msg, [Error, StackTrace]);
+
+  void destroy();
+}
+
+String _formatErrorMessage(String msg, Exception error,
+    [StackTrace stackTrace]) {
+  if (error == null) return msg;
+  if (stackTrace == null) return msg + ": $error";
+  return msg + ": $error\n$stackTrace";
+}
+
+class StdOutLogger extends Logger {
+  StdOutLogger(Level level) : super(level);
+
+  @override
+  void info(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.info, "$_datetime Info: $msg");
+  }
+
+  @override
+  void warning(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.warning, "$_datetime Warning: $msg");
+  }
+
+  @override
+  void error(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.error, "$_datetime Error: $msg");
+  }
+
+  @override
+  void debug(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.debug, "$_datetime Debug: $msg");
+  }
+
+  void _print(Level logLevel, String msg) {
+    if (logLevel.index >= level.index) {
+      print(msg);
+    }
+  }
+
+  @override
+  void destroy() {
+    // nothing to do
+  }
+
+  String get _datetime => "${new DateTime.now()}";
+}
+
+class FileLogger extends Logger {
+  IOSink _sink;
+
+  FileLogger(String fileName, Level level, {bool append: false})
+      : super(level) {
+    var mode = append ? FileMode.APPEND : FileMode.WRITE;
+    _sink = new File(path.absolute(fileName)).openWrite(mode: mode);
+  }
+
+  @override
+  void destroy() {
+    if (_sink != null) {
+      _sink.close();
+      _sink = null;
+    }
+  }
+
+  @override
+  void info(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.info, "$_datetime Info: $msg");
+  }
+
+  @override
+  void warning(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.warning, "$_datetime Warning: $msg");
+  }
+
+  @override
+  void error(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.error, "$_datetime Error: $msg");
+  }
+
+  @override
+  void debug(String msg, [error, stackTrace]) {
+    msg = _formatErrorMessage(msg, error, stackTrace);
+    _print(Level.debug, "$_datetime Debug: $msg");
+  }
+
+  void _print(Level logLevel, String msg) {
+    if (logLevel.index >= level.index && _sink != null) _sink.writeln(msg);
+  }
+
+  static String get _datetime => "${new DateTime.now()}";
+}