add web_dashboard API (#333)

* add web_dashboard sample

* add docs

* address code review comments

* restructure web_dashboard

* set up provider and mock service

* add copyright headers, use relative imports

* add API class, add tests

* fmt

* rename services -> API, remove data library

* use new API in app

* add stream to items api

* convert from StreamBuilder to StreamProvider

* add subscription to Entry API

* rename API classes

* address comments

* Update README.md

* update README

* remove routing_demo

experimental/web_dashboard/lib/src/api/api.dart

@@ -0,0 +1,45 @@
+// Copyright 2020, the Flutter project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Manipulates app data,
+abstract class DashboardApi {
+  ItemApi get items;
+  EntryApi get entries;
+}
+
+/// Manipulates [Item] data.
+abstract class ItemApi {
+  Future<Item> delete(String id);
+  Future<Item> get(String id);
+  Future<Item> insert(Item item);
+  Future<List<Item>> list();
+  Future<Item> update(Item item, String id);
+  Stream<List<Item>> allItemsStream();
+}
+
+/// Something being tracked.
+class Item {
+  final String name;
+  String id;
+
+  Item(this.name);
+}
+
+/// Manipulates [Entry] data.
+abstract class EntryApi {
+  Future<Entry> delete(String itemId, String id);
+  Future<Entry> insert(String itemId, Entry entry);
+  Future<List<Entry>> list(String itemId);
+  Future<Entry> update(String itemId, String id, Entry entry);
+  Stream<List<Entry>> allEntriesStream(String itemId);
+}
+
+/// A number tracked at a point in time.
+class Entry {
+  final int value;
+  final DateTime time;
+  String id;
+
+  Entry(this.value, this.time);
+}

experimental/web_dashboard/lib/src/api/firebase.dart

@@ -0,0 +1,3 @@
+// Copyright 2020, the Flutter project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.

experimental/web_dashboard/lib/src/api/mock.dart

@@ -0,0 +1,106 @@
+// Copyright 2020, the Flutter project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:uuid/uuid.dart' as uuid;
+
+import 'api.dart';
+
+class MockDashboardApi implements DashboardApi {
+  @override
+  final EntryApi entries = MockEntryApi();
+
+  @override
+  final ItemApi items = MockItemApi();
+}
+
+class MockItemApi implements ItemApi {
+  Map<String, Item> _storage = {};
+  StreamController<List<Item>> _streamController =
+      StreamController<List<Item>>.broadcast();
+
+  @override
+  Future<Item> delete(String id) async {
+    _emit();
+    return _storage.remove(id);
+  }
+
+  @override
+  Future<Item> get(String id) async {
+    return _storage[id];
+  }
+
+  @override
+  Future<Item> insert(Item item) async {
+    var id = uuid.Uuid().v4();
+    var newItem = Item(item.name)..id = id;
+    _storage[id] = newItem;
+    _emit();
+    return newItem;
+  }
+
+  @override
+  Future<List<Item>> list() async {
+    return _storage.values.toList();
+  }
+
+  @override
+  Future<Item> update(Item item, String id) async {
+    _storage[id] = item;
+    return item..id = id;
+  }
+
+  Stream<List<Item>> allItemsStream() {
+    return _streamController.stream;
+  }
+
+  void _emit() {
+    _streamController.add(_storage.values.toList());
+  }
+}
+
+class MockEntryApi implements EntryApi {
+  Map<String, Entry> _storage = {};
+  StreamController<List<Entry>> _streamController =
+      StreamController<List<Entry>>.broadcast();
+
+  @override
+  Future<Entry> delete(String itemId, String id) async {
+    _emit();
+    return _storage.remove('$itemId-$id');
+  }
+
+  @override
+  Future<Entry> insert(String itemId, Entry entry) async {
+    var id = uuid.Uuid().v4();
+    var newEntry = Entry(entry.value, entry.time)..id = id;
+    _storage['$itemId-$id'] = newEntry;
+    _emit();
+    return newEntry;
+  }
+
+  @override
+  Future<List<Entry>> list(String itemId) async {
+    return _storage.keys
+        .where((k) => k.startsWith(itemId))
+        .map((k) => _storage[k])
+        .toList();
+  }
+
+  @override
+  Future<Entry> update(String itemId, String id, Entry entry) async {
+    _storage['$itemId-$id'] = entry;
+    return entry..id = id;
+  }
+
+  @override
+  Stream<List<Entry>> allEntriesStream(String itemId) {
+    return _streamController.stream;
+  }
+
+  void _emit() {
+    _streamController.add(_storage.values.toList());
+  }
+}