feat: JsonCacheHive class (#65)

* feat: JsonCacheHive class

Closes #64

* style: fix linter complain

Author: rafamizes

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- JsonCacheHive: an implementation on top of the Hive package —
+  [64](https://github.com/dartoos-dev/json_cache/issues/64).
+
 ## [1.1.2] - 2022-01-28
 
 ### Fixed

README.md

@@ -29,6 +29,7 @@ Rultor.com](https://www.rultor.com/b/dartoos-dev/json_cache)](https://www.rultor
   - [JsonCacheEncPrefs — EncryptedSharedPreferences](#jsoncacheencprefs)
   - [JsonCacheSecStorage — FlutterSecureStorage](#jsoncachesecstorage)
   - [JsonCacheLocalStorage — LocalStorage](#jsoncachelocalstorage)
+  - [JsonCacheHive — Hive](#jsoncachehive)
   - [JsonCacheCrossLocalStorage — CrossLocalStorage](#jsoncachecrosslocalstorage)
 - [Demo application](#demo-application)
 - [Contribute](#contribute)
@@ -79,7 +80,7 @@ abstract class JsonCache {
   Future<Map<String, dynamic>?> value(String key);
 
   /// It either updates data located at [key] with [value] or, if there is no
-  /// previous data at [key], creates a new cache row at [key] with [value].
+  /// data at [key], creates a new cache row at [key] with [value].
   ///
   /// **Note**: [value] must be json encodable.
   Future<void> refresh(String key, Map<String, dynamic> value);
@@ -127,7 +128,7 @@ the cache instance that persists data on the user's device.
 
 #### Typical Usage
 
-Due to the fact that `JsonCacheMem` is a decorator, you should always pass
+Due to the fact that `JsonCacheMem` is a decorator, you should normally pass
 another `JsonCache` instance to it whenever you instantiate a `JsonCacheMem`
 object. For example:
 
@@ -231,6 +232,20 @@ is an implementation on top of the
   …
 ```
 
+### JsonCacheHive
+
+[JsonCacheHive](https://pub.dev/documentation/json_cache/latest/json_cache/JsonCacheHive.html)
+is an implementation on top of the [hive](https://pub.dev/packages/hive)
+package.
+
+```dart
+  …
+  await Hive.initFlutter(); // mandatory initialization.
+  final box = await Hive.openBox<String>('appBox'); // it must be a Box<String>.
+  final JsonCache hiveCache = JsonCacheMem(JsonCacheHive(box));
+  …
+```
+
 ### JsonCacheCrossLocalStorage
 
 [JsonCacheLocalCrossStorage](https://pub.dev/documentation/json_cache/latest/json_cache/JsonCacheCrossLocalStorage-class.html)
@@ -270,7 +285,7 @@ Contributors are welcome!
    branch and make a Pull Request.
 3. After review and acceptance, the PR is merged and closed.
 
-Make sure the commands below **passes** before making a Pull Request.
+Make sure the command below **passes** before making a Pull Request.
 
 ```shell
   flutter analyze && flutter test

lib/json_cache.dart

@@ -5,6 +5,7 @@ export 'src/json_cache.dart';
 export 'src/json_cache_cross_local_storage.dart';
 export 'src/json_cache_enc_prefs.dart';
 export 'src/json_cache_fake.dart';
+export 'src/json_cache_hive.dart';
 export 'src/json_cache_hollow.dart';
 export 'src/json_cache_local_storage.dart';
 export 'src/json_cache_mem.dart';

lib/src/json_cache_hive.dart

@@ -0,0 +1,36 @@
+import 'dart:convert';
+
+import 'package:hive/hive.dart';
+import 'package:json_cache/json_cache.dart';
+
+/// Implementation on top of the Hive package.
+///
+/// See: [local storage](https://pub.dev/packages/hive)
+class JsonCacheHive implements JsonCache {
+  /// Sets the Hive [Box] instance.
+  const JsonCacheHive(this._box);
+
+  // final Box<String> _box;
+  final Box<String> _box;
+
+  @override
+  Future<void> clear() async {
+    await _box.clear();
+  }
+
+  @override
+  Future<void> refresh(String key, Map<String, dynamic> value) async {
+    await _box.put(key, json.encode(value));
+  }
+
+  @override
+  Future<void> remove(String key) async {
+    await _box.delete(key);
+  }
+
+  @override
+  Future<Map<String, dynamic>?> value(String key) async {
+    final data = _box.get(key);
+    return data == null ? null : json.decode(data) as Map<String, dynamic>;
+  }
+}

lib/src/json_cache_hollow.dart

@@ -31,7 +31,9 @@ class JsonCacheHollow implements JsonCache {
   @override
   Future<void> remove(String key) async {}
 
-  /// Does nothing.
+  /// Always returns null.
   @override
-  Future<Map<String, dynamic>?> value(String key) async {}
+  Future<Map<String, dynamic>?> value(String key) async {
+    return null;
+  }
 }