CacheService example

.idea/runConfigurations/cache_service_dart.xml

@@ -0,0 +1,7 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="cache_service.dart" type="DartCommandLineRunConfigurationType" factoryName="Dart Command Line Application" singleton="true" nameIsGenerated="true">
+    <option name="filePath" value="$PROJECT_DIR$/example/cache_service.dart" />
+    <option name="workingDirectory" value="$PROJECT_DIR$" />
+    <method />
+  </configuration>
+</component>

.travis.yml

@@ -1 +1,3 @@
 language: dart
+dart:
+  - dev

example/cache_service.dart

@@ -0,0 +1,25 @@
+import 'package:angel_cache/angel_cache.dart';
+import 'package:angel_framework/angel_framework.dart';
+
+main() async {
+  var app = new Angel()..lazyParseBodies = true;
+
+  app.use(
+    '/api/todos',
+    new CacheService(
+      database: new AnonymousService(
+        index: ([params]) {
+          print('Fetched directly from the underlying service at ${new DateTime.now()}!');
+          return ['foo', 'bar', 'baz'];
+        },
+        read: (id, [params]) {
+          return {id: '$id at ${new DateTime.now()}'};
+        }
+      ),
+    ),
+  );
+
+  var http = new AngelHttp(app);
+  var server = await http.startServer('127.0.0.1', 3000);
+  print('Listening at http://${server.address.address}:${server.port}');
+}

lib/src/cache_service.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'package:collection/collection.dart';
 import 'package:angel_framework/angel_framework.dart';
 import 'package:meta/meta.dart';
 
@@ -15,28 +16,118 @@ class CacheService extends Service {
   /// If not provided, this defaults to a [MapService].
   final Service cache;
 
-  CacheService({@required this.database, Service cache})
+  final bool ignoreQuery;
+
+  final Duration timeout;
+
+  final Map<dynamic, _CachedItem> _cache = {};
+  _CachedItem _indexed;
+
+  CacheService(
+      {@required this.database,
+      Service cache,
+      this.ignoreQuery: false,
+      this.timeout})
       : this.cache = cache ?? new MapService() {
     assert(database != null);
   }
 
+  Future _getCached(Map params, _CachedItem get(), Future getFresh(),
+      Future getCached(), Future save(data, DateTime now)) async {
+    var cached = get();
+    //print('$params => $cached');
+    var now = new DateTime.now().toUtc();
+
+    if (cached != null) {
+      // If the entry has expired, don't send from the cache
+      var expired =
+          timeout != null && now.difference(cached.timestamp) >= timeout;
+
+      if (timeout == null || !expired) {
+        // Read from the cache if necessary
+        var queryEqual = ignoreQuery == true ||
+            (params != null &&
+                cached.params != null &&
+                const MapEquality()
+                    .equals(params['query'], cached.params['query']));
+        if (queryEqual) {
+          return await getCached();
+        }
+      }
+    }
+
+    // If we haven't fetched from the cache by this point,
+    // let's fetch from the database.
+    var data = await getFresh();
+    await save(data, now);
+    return data;
+  }
+
+  @override
+  Future index([Map params]) {
+    return _getCached(
+      params,
+      () => _indexed,
+      () => database.index(params),
+      () => _indexed.data,
+      (data, now) async {
+        _indexed = new _CachedItem(params, now, data);
+        return data;
+      },
+    );
+  }
+
+  @override
+  Future read(id, [Map params]) async {
+    return _getCached(
+      params,
+      () => _cache[id],
+      () => database.read(id, params),
+      () => cache.read(id),
+      (data, now) async {
+        _cache[id] = new _CachedItem(params, now);
+        return await cache.modify(id, data);
+      },
+    );
+  }
+
   @override
   Future create(data, [Map params]) {
+    _indexed = null;
     return database.create(data, params);
   }
 
   @override
   Future modify(id, data, [Map params]) {
+    _indexed = null;
+    _cache.remove(id);
     return database.modify(id, data, params);
   }
 
   @override
   Future update(id, data, [Map params]) {
+    _indexed = null;
+    _cache.remove(id);
     return database.modify(id, data, params);
   }
 
   @override
   Future remove(id, [Map params]) {
+    _indexed = null;
+    _cache.remove(id);
     return database.remove(id, params);
   }
 }
+
+class _CachedItem {
+  final params;
+  final DateTime timestamp;
+  final data;
+
+  _CachedItem(this.params, this.timestamp, [this.data]);
+
+  @override
+  String toString() {
+    return '$timestamp:$params:$data';
+  }
+}