Implement file backend

lib/src/backend/file/file_descriptor.dart

@@ -0,0 +1,63 @@
+import 'dart:io';
+
+import 'package:async/async.dart';
+
+abstract class FileDescriptorInterface {
+  Stream<List<int>> open(String eTag);
+  String get etag;
+  dynamic decode(String line);
+  dynamic decodeKey(String line);
+}
+
+class FileDescriptor implements FileDescriptorInterface {
+  final File _file;
+  final Uri _uri;
+  final Decode _decode;
+  final DecodeKey _decodeKey;
+  String _eTag;
+
+  FileDescriptor.file(File file, {Decode decode, DecodeKey decodeKey})
+      : _file = file,
+        _uri = null,
+        _decode = decode,
+        _decodeKey = decodeKey;
+
+  FileDescriptor.uri(Uri uri, {Decode decode, DecodeKey decodeKey})
+      : _file = null,
+        _uri = uri,
+        _decode = decode,
+        _decodeKey = decodeKey;
+
+  Stream<List<int>> open(String eTag) {
+    if (_file != null) {
+      return LazyStream(() async {
+        _eTag = (await _file.lastModified()).millisecondsSinceEpoch.toString();
+        return _file.openRead();
+      });
+    }
+
+    if (_uri != null) {
+      return LazyStream(() async {
+        final request = await HttpClient().getUrl(_uri);
+        request.headers.set(HttpHeaders.ifNoneMatchHeader, eTag);
+
+        final response = await request.close();
+        _eTag = response.headers.value(HttpHeaders.etagHeader);
+        return response;
+      });
+    }
+
+    throw StateError('Invalid FileDescriptor');
+  }
+
+  String get etag {
+    if (_eTag != null) return _eTag;
+    throw StateError('etag must be called after open()');
+  }
+
+  dynamic decode(String line) => _decode(line);
+  dynamic decodeKey(String line) => _decodeKey(line);
+}
+
+typedef dynamic Decode(String line);
+typedef dynamic DecodeKey(String line);

lib/src/backend/file/file_mirror_manager.dart

@@ -0,0 +1,65 @@
+import 'dart:convert';
+
+import '../../handlers/dynamic_mirror_handler.dart';
+import '../../handlers/handler_holder.dart';
+import '../../hive_mirror.dart';
+import '../../metadata.dart';
+import '../mirror_manager.dart';
+import 'file_descriptor.dart';
+
+class FileMirrorManager implements MirrorManager {
+  final MirrorHandlerHolder _handler;
+  final Metadata _metadata;
+
+  FileMirrorManager(MirrorHandler handler, Metadata metadata)
+      : _handler = MirrorHandlerHolder(handler),
+        _metadata = metadata;
+
+  static FileMirrorManager withHandler<T>(
+      MirrorHandler<T> handler, Metadata metadata) {
+    return FileMirrorManager(DynamicMirrorHandler<T>(handler), metadata);
+  }
+
+  Future<void> mirror(dynamic fileDescriptor) => loadFile(fileDescriptor);
+
+  Future<void> loadFile(FileDescriptorInterface fileDescriptor) async {
+    final etag = _metadata.get(metaEtag);
+    final fileData = fileDescriptor.open(etag);
+
+    if (fileDescriptor.etag != etag) {
+      final lines = fileData.transform(Utf8Decoder()).transform(LineSplitter());
+
+      try {
+        await _applyLines(fileDescriptor.etag, await lines.toList(),
+            fileDescriptor.decode, fileDescriptor.decodeKey);
+      } finally {
+        await _handler.dispose();
+      }
+    }
+  }
+
+  Future<void> _applyLines(String etag, Iterable<String> lines, Decode decode,
+      DecodeKey decodeKey) async {
+    MapEntry decodeLine(String line) {
+      final key = decodeKey(line);
+      if (key != null) {
+        final object = decode(line);
+        return MapEntry(key, object);
+      }
+      return null;
+    }
+
+    final putEntries =
+        Map.fromEntries(lines.map(decodeLine).where((e) => e != null));
+
+    await (await _handler.use()).clear();
+
+    if (putEntries.isNotEmpty) {
+      await (await _handler.use()).putAll(putEntries);
+    }
+
+    await _metadata.put(metaEtag, etag);
+  }
+
+  static const metaEtag = 'etag';
+}

lib/src/backend/mirror_manager.dart

@@ -1,19 +1,26 @@
-import 'package:hive_mirror/src/handlers/handler_holder.dart';
-
 import '../hive_mirror.dart';
 import '../metadata.dart';
+import 'file/file_descriptor.dart';
+import 'file/file_mirror_manager.dart';
 import 'git/git_mirror_manager.dart';
 import 'git/git_patch.dart';
 
 abstract class MirrorManager {
   Future<void> mirror(dynamic source);
 
-  factory MirrorManager.fromSource(dynamic source,
-      {MirrorHandler handler, Metadata metadata}) {
+  factory MirrorManager.fromSource(
+    dynamic source, {
+    MirrorHandler handler,
+    Metadata metadata,
+  }) {
     if (source is GitPatchInterface) {
       return GitMirrorManager(handler, metadata);
     }
-    throw UnsupportedError('''source $source is not supported.
-         Use one of the supported sources [GitPatch]''');
+    if (source is FileDescriptorInterface) {
+      return FileMirrorManager(handler, metadata);
+    }
+    throw ArgumentError('''source $source is not supported.
+         Use one of the supported sources
+         [GitPatchInterface, FileDescriptorInterface]''');
   }
 }

lib/src/handlers/box_mirror_handler.dart

@@ -23,6 +23,9 @@ class BoxMirrorHandler<T> implements MirrorHandler<T> {
   @override
   Future<void> deleteAll(Iterable keys) => _box.deleteAll(keys);
 
+  @override
+  Future<void> clear() => _box.clear();
+
   @override
   Future<void> dispose() => _box.close();
 }

lib/src/handlers/dynamic_mirror_handler.dart

@@ -20,6 +20,9 @@ class DynamicMirrorHandler<T> implements MirrorHandler {
   @override
   Future<void> deleteAll(Iterable keys) => _delegate.deleteAll(keys);
 
+  @override
+  Future<void> clear() => _delegate.clear();
+
   @override
   Future<void> dispose() => _delegate.dispose();
 }

lib/src/hive_mirror.dart

@@ -11,5 +11,6 @@ abstract class MirrorHandler<T> {
   Future<void> init();
   Future<void> putAll(Map<dynamic, T> entries);
   Future<void> deleteAll(Iterable<dynamic> keys);
+  Future<void> clear();
   Future<void> dispose();
 }

test/assets/load2.yaml

@@ -0,0 +1,2 @@
+key1: value1
+key2: value2

test/file_descriptors.dart

@@ -0,0 +1,52 @@
+import 'dart:io';
+
+import 'package:hive_mirror/src/backend/file/file_descriptor.dart';
+
+import 'type.dart';
+
+abstract class TestFileDescriptorBase implements FileDescriptorInterface {
+  @override
+  final etag;
+
+  final String _filePath;
+  final Decode _decode;
+  final DecodeKey _decodeKey;
+
+  TestFileDescriptorBase._(
+      this.etag, this._filePath, this._decode, this._decodeKey);
+
+  @override
+  Stream<List<int>> open(String _) => File(_filePath).openRead();
+
+  @override
+  dynamic decode(String line) => _decode(line);
+
+  @override
+  dynamic decodeKey(String line) => _decodeKey(line);
+}
+
+class Load2FileDescriptor extends TestFileDescriptorBase {
+  Load2FileDescriptor.primitive()
+      : super._(etagValue, filePath, _decodePrimitive, _decodeKey);
+  Load2FileDescriptor.testType()
+      : super._(etagValue, filePath, _decodeTestType, _decodeKey);
+
+  static const filePath = 'test/assets/load2.yaml';
+  static const etagValue = 'etag_value';
+  static const loadMap = {'key1': 'value1', 'key2': 'value2'};
+}
+
+String _decodePrimitive(String line) {
+  final tupple = line.split(':');
+  return tupple[1].trim();
+}
+
+TestType _decodeTestType(String line) {
+  final tupple = line.split(':');
+  return TestType(tupple[0].trim(), tupple[1].trim());
+}
+
+String _decodeKey(String line) {
+  final tupple = line.split(':');
+  return tupple[0].trim();
+}

test/integration/mirror_test.dart

@@ -2,11 +2,12 @@ import 'package:hive/hive.dart';
 import 'package:hive_mirror/hive_mirror.dart';
 import 'package:test/test.dart';
 
+import '../file_descriptors.dart';
 import '../patches.dart';
 
 void main() {
   group('Mirror', () {
-    test('box', () async {
+    test('patch', () async {
       HiveMirror.init('.hive');
       await Hive.deleteBoxFromDisk('box');
 
@@ -17,5 +18,17 @@ void main() {
       expect(box.get('key1'), equals('value1'));
       expect(box.get('key2'), equals('value2'));
     });
+
+    test('file', () async {
+      HiveMirror.init('.hive');
+      await Hive.deleteBoxFromDisk('box');
+
+      final source = Load2FileDescriptor.primitive();
+      await HiveMirror.mirror(source, BoxMirrorHandler('box'));
+
+      final box = await Hive.openBox<String>('box');
+      expect(box.get('key1'), equals('value1'));
+      expect(box.get('key2'), equals('value2'));
+    });
   });
 }

test/unit/backend/file/file_mirror_manager_test.dart

@@ -0,0 +1,40 @@
+import 'package:hive_mirror/src/backend/file/file_mirror_manager.dart';
+import 'package:mockito/mockito.dart';
+import 'package:test/test.dart';
+
+import '../../../file_descriptors.dart';
+import '../../mocks.dart';
+
+const metaETag = FileMirrorManager.metaEtag;
+
+void main() {
+  group('FileMirrorManager load()', () {
+    test('file with new etag', () async {
+      final handler = MirrorHandlerMock();
+      final metadata = MetadataMock();
+      final manager = FileMirrorManager.withHandler(handler, metadata);
+
+      await manager.loadFile(Load2FileDescriptor.primitive());
+
+      verify(metadata.get(metaETag));
+      verify(handler.clear());
+      verify(handler.putAll(argThat(equals(Load2FileDescriptor.loadMap))));
+      verify(metadata.put(metaETag, Load2FileDescriptor.etagValue));
+    });
+
+    test('file with previous etag', () async {
+      final handler = MirrorHandlerMock();
+      final metadata = MetadataMock();
+      final manager = FileMirrorManager.withHandler(handler, metadata);
+
+      when(metadata.get(metaETag)).thenReturn(Load2FileDescriptor.etagValue);
+
+      await manager.loadFile(Load2FileDescriptor.primitive());
+
+      verify(metadata.get(metaETag));
+      verifyNever(handler.clear());
+      verifyNever(handler.putAll(any));
+      verifyNever(metadata.put(any, any));
+    });
+  });
+}