Merge pull request #79 from ilopX/add-facade-pattern

Add facade pattern.

Author: ilopX

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.38.0
+- Add conceptual facade pattern.
+
 ## 0.37.0
 - Add iterator pattern: Word Iterator.
 

README.md

@@ -26,7 +26,7 @@ It contains **Dart** examples for all classic **GoF** design patterns.
     - [x] **Bridge** - [[Remote Device Control](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/bridge/devices_remote_control)] [[Clock](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/bridge/clock)] 
     - [x] **Composite** - [[Image Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/composite/image_editor)] [[Products and Boxes](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/composite/products_and_boxes)] 
     - [x] **Decorator** - [[Data Source Decoder](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/decorator/data_source_decoder)]
-    - [ ] **Facade**
+    - [ ] **Facade** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/facade/conceptul)]
     - [x] **Flyweight** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/flyweight/conceptual)]
     - [x] **Proxy** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/proxy/conceptual)]
 

patterns/facade/conceptual/README.md

@@ -0,0 +1,30 @@
+# Facade pattern
+Facade is a structural design pattern that provides a simplified interface to a library, a 
+framework, or any other complex set of classes.
+
+Tutorial: [here](https://refactoring.guru/design-patterns/facade).
+
+### About example.
+This the very conceptual example rewrite from original source code [java example](https://github.com/RefactoringGuru/design-patterns-java/tree/main/src/refactoring_guru/facade/example)
+
+### Diagram:
+![image](https://user-images.githubusercontent.com/8049534/183629745-a62d81be-f640-48e8-b70c-00d6cf59aa5f.png)
+
+### Client code:
+```dart
+void main() {
+  final converter = VideoConversionFacade();
+  final mp4Video = converter.convertVideo("youtubevideo.ogg", "mp4");
+  // ...;
+}
+```
+
+### Output:
+```
+VideoConversionFacade: conversion started.
+CodecFactory: extracting ogg audio...
+BitrateReader: reading file...
+BitrateReader: writing file...
+AudioMixer: fixing audio...
+VideoConversionFacade: conversion completed.
+```

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");
+  // ...;
+}

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;
+  }
+}

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');
+  }
+}

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;
+  }
+}

patterns/facade/conceptual/some_complex_media_library/codec.dart

@@ -0,0 +1 @@
+abstract class Codec {}

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();
+    }
+  }
+}

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';
+}

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';
+}

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);
+}

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.37.0
+version: 0.38.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue