Impl facade pattern.

ilopX · ilopX · commit caea3caa6dca · 2022-08-09T13:49:12.000+03:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 0.37.0
+- Add iterator pattern: Word Iterator.
+
 ## 0.36.0
 - Add iterator pattern: Github Commit.
 
diff --git a/README.md b/README.md
@@ -13,7 +13,7 @@ It contains **Dart** examples for all classic **GoF** design patterns.
     - [x] **Chain of Responsibility** - [[Server Middleware](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/chain_of_responsibility/server_middleware)]
     - [x] **Command** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/command/conceptual)] [[Text Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/command/text_editor)] 
     - [x] **Interpreter**  - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/interpreter/conceptual)]
-    - [x] **Iterator** - [[Github Commit](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/iterator/github_commit)]
+    - [x] **Iterator** - [[Word Iterator](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/iterator/word_iterator)] [[Github Commit](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/iterator/github_commit)]
     - [x] **Mediator** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/mediator/conceptual)]
     - [x] **Memento** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/memento/conceptual)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Memento Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/memento/memento_editor)] 
     - [x] **Observer** - [[Open-Close Editor Events](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/open_close_editor_events)] [[AppObserver](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/app_observer)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Subscriber Flutter Widget](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/subscriber_flutter_widget)]
diff --git a/patterns/facade/conceptual/main.dart b/patterns/facade/conceptual/main.dart
@@ -0,0 +1,9 @@
+// ignore_for_file: unused_local_variable
+
+import 'pattern/video_conversion_facade.dart';
+
+void main() {
+  final converter = VideoConversionFacade();
+  final mp4Video = converter.convertVideo("youtubevideo.ogg", "mp4");
+  // ...;
+}
diff --git a/patterns/facade/conceptual/pattern/video_conversion_facade.dart b/patterns/facade/conceptual/pattern/video_conversion_facade.dart
@@ -0,0 +1,31 @@
+import 'dart:io';
+
+import '../some_complex_media_library/audio_mixer.dart';
+import '../some_complex_media_library/bitrate_reader.dart';
+import '../some_complex_media_library/codec.dart';
+import '../some_complex_media_library/codec_factory.dart';
+import '../some_complex_media_library/mpeg4_compression_codec.dart';
+import '../some_complex_media_library/ogg_compression_codec.dart';
+import '../some_complex_media_library/video_file.dart';
+
+class VideoConversionFacade {
+  File convertVideo(String fileName, String format) {
+    print('VideoConversionFacade: conversion started.');
+    final file = VideoFile(fileName);
+    final sourceCodec = CodecFactory.extract(file);
+    late final Codec destinationCodec;
+
+    if (format == "mp4") {
+      destinationCodec = MPEG4CompressionCodec();
+    } else {
+      destinationCodec = OggCompressionCodec();
+    }
+
+    final buffer = BitrateReader.read(file, sourceCodec);
+    final intermediateResult = BitrateReader.convert(buffer, destinationCodec);
+    final result = AudioMixer().fix(intermediateResult);
+    print('VideoConversionFacade: conversion completed.');
+
+    return result;
+  }
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/audio_mixer.dart b/patterns/facade/conceptual/some_complex_media_library/audio_mixer.dart
@@ -0,0 +1,10 @@
+import 'dart:io';
+
+import 'video_file.dart';
+
+class AudioMixer {
+  File fix(VideoFile result) {
+    print('AudioMixer: fixing audio...');
+    return File('tmp');
+  }
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/bitrate_reader.dart b/patterns/facade/conceptual/some_complex_media_library/bitrate_reader.dart
@@ -0,0 +1,14 @@
+import 'codec.dart';
+import 'video_file.dart';
+
+class BitrateReader {
+  static VideoFile read(VideoFile file, Codec codec) {
+    print('BitrateReader: reading file...');
+    return file;
+  }
+
+  static VideoFile convert(VideoFile buffer, Codec codec) {
+    print('BitrateReader: writing file...');
+    return buffer;
+  }
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/codec.dart b/patterns/facade/conceptual/some_complex_media_library/codec.dart
@@ -0,0 +1 @@
+abstract class Codec {}
diff --git a/patterns/facade/conceptual/some_complex_media_library/codec_factory.dart b/patterns/facade/conceptual/some_complex_media_library/codec_factory.dart
@@ -0,0 +1,17 @@
+import 'codec.dart';
+import 'mpeg4_compression_codec.dart';
+import 'ogg_compression_codec.dart';
+import 'video_file.dart';
+
+class CodecFactory {
+  static Codec extract(VideoFile file) {
+    String type = file.codecType;
+    if (type == 'mp4') {
+      print('CodecFactory: extracting mpeg audio...');
+      return MPEG4CompressionCodec();
+    } else {
+      print('CodecFactory: extracting ogg audio...');
+      return OggCompressionCodec();
+    }
+  }
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/mpeg4_compression_codec.dart b/patterns/facade/conceptual/some_complex_media_library/mpeg4_compression_codec.dart
@@ -0,0 +1,5 @@
+import 'codec.dart';
+
+class MPEG4CompressionCodec implements Codec {
+  String type = 'mp4';
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/ogg_compression_codec.dart b/patterns/facade/conceptual/some_complex_media_library/ogg_compression_codec.dart
@@ -0,0 +1,5 @@
+import 'codec.dart';
+
+class OggCompressionCodec implements Codec {
+  final type = 'ogg';
+}
diff --git a/patterns/facade/conceptual/some_complex_media_library/video_file.dart b/patterns/facade/conceptual/some_complex_media_library/video_file.dart
@@ -0,0 +1,6 @@
+class VideoFile {
+  final String name;
+  final String codecType;
+
+  VideoFile(this.name) : codecType = name.substring(name.indexOf('.') + 1);
+}
diff --git a/patterns/iterator/word_iterator/README.md b/patterns/iterator/word_iterator/README.md
@@ -0,0 +1,47 @@
+# Iterator pattern
+Iterator is a behavioral design pattern that lets you traverse elements of a collection without
+exposing its underlying representation (list, stack, tree, etc.).
+
+Tutorial: [here](https://refactoring.guru/design-patterns/iterator).
+
+### Client code:
+```dart
+void main() {
+  final text = Text(
+    'Iterator is a behavioral design pattern that lets you traverse elements '
+        'of a collection without exposing its underlying representation '
+        '(list, stack, tree, etc.).',
+  );
+
+  for (final s in text) {
+    print(s);
+  }
+}
+```
+
+**Output:**
+```
+Iterator
+is
+a
+behavioral
+design
+pattern
+that
+lets
+you
+traverse
+elements
+of
+a
+collection
+without
+exposing
+its
+underlying
+representation
+list
+stack
+tree
+etc
+```
diff --git a/patterns/iterator/word_iterator/main.dart b/patterns/iterator/word_iterator/main.dart
@@ -0,0 +1,13 @@
+import 'text/text.dart';
+
+void main() {
+  final text = Text(
+    'Iterator is a behavioral design pattern that lets you traverse elements '
+    'of a collection without exposing its underlying representation '
+    '(list, stack, tree, etc.).',
+  );
+
+  for (final s in text) {
+    print(s);
+  }
+}
diff --git a/patterns/iterator/word_iterator/pattern/word_iterator.dart b/patterns/iterator/word_iterator/pattern/word_iterator.dart
@@ -0,0 +1,48 @@
+import '../text/text.dart';
+
+class WordIterator extends Iterator<String> {
+  WordIterator(this._text);
+
+  @override
+  String get current => _currWord!;
+
+  @override
+  bool moveNext() {
+    final start = _lastIndex;
+
+    while (_searchNextSpaceChar(' ')) {
+      // ++
+    }
+
+    _currWord = _getWord(start, _lastIndex);
+    return _currWord!.isNotEmpty;
+  }
+
+  final Text _text;
+  int _lastIndex = 0;
+  String? _currWord;
+
+  bool _searchNextSpaceChar(String char) {
+    final isTextEnd = _lastIndex >= _text.text.length;
+
+    if (isTextEnd) {
+      return false;
+    }
+
+    final isNotSpaceChar = _text.text[_lastIndex++] != char;
+    return isNotSpaceChar;
+  }
+
+  String _getWord(int start, int end) {
+    final noWordChars = RegExp(r'\W');
+    return _text.text
+        .substring(
+          start,
+          _lastIndex,
+        )
+        .replaceAll(
+          noWordChars,
+          '',
+        );
+  }
+}
diff --git a/patterns/iterator/word_iterator/text/text.dart b/patterns/iterator/word_iterator/text/text.dart
@@ -0,0 +1,10 @@
+import '../pattern/word_iterator.dart';
+
+class Text extends Iterable<String> {
+  final String text;
+
+  Text(this.text);
+
+  @override
+  Iterator<String> get iterator => WordIterator(this);
+}
diff --git a/pubspec.yaml b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.36.0
+version: 0.37.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue
