service: Make [XmppState] and [PreferencesState] migratable

test/migrations.dart

@@ -0,0 +1,187 @@
+import "package:moxxyv2/shared/migrator.dart";
+
+import "package:test/test.dart";
+
+class Greeting {
+  final String action;
+  final String entity;
+  final bool beNice;
+
+  Greeting(this.entity, this.action, this.beNice);
+}
+
+class TestMigrator extends Migrator<Greeting> {
+  final void Function(int, Greeting) onCommited;
+  TestMigrator(this.onCommited) : super(
+    2, // Latest version
+    [
+      Migration<Greeting>(
+        1,
+        (data) => Greeting(
+          data["name"]!,
+          data["action"]!,
+          true
+        )
+      )
+    ]
+  );
+
+  @override
+  Future<Map<String, dynamic>?> loadRawData() async {
+    return {
+      "name": "Welt",
+      "action": "welcome"
+    };
+  }
+
+  @override
+  Future<int?> loadVersion() async => 1;
+
+  @override
+  Greeting fromData(Map<String, dynamic> data) => Greeting(
+    data["name"],
+    data["action"],
+    data["beNice"]
+  );
+
+  @override
+  Greeting fromDefault() => Greeting(
+    "Moxxy",
+    "hug",
+    true
+  );
+
+  Future<void> commit(int version, Greeting data) async {
+    onCommited(version, data);
+  }
+}
+
+class NoDataMigrator extends Migrator<Greeting> {
+  final void Function(int, Greeting) onCommited;
+  NoDataMigrator(this.onCommited) : super(
+    2, // Latest version
+    [
+      Migration<Greeting>(
+        1,
+        (data) => Greeting(
+          data["name"]!,
+          data["action"]!,
+          true
+        )
+      )
+    ]
+  );
+
+  @override
+  Future<Map<String, dynamic>?> loadRawData() async => null;
+
+  @override
+  Future<int?> loadVersion() async => null;
+
+  @override
+  Greeting fromData(Map<String, dynamic> data) => Greeting(
+    data["name"],
+    data["action"],
+    data["beNice"]
+  );
+
+  @override
+  Greeting fromDefault() => Greeting(
+    "Moxxyv2",
+    "hug_more",
+    true
+  );
+
+  Future<void> commit(int version, Greeting data) async {
+    onCommited(version, data);
+  }
+}
+
+class MultipleStagedMigrator extends Migrator<Greeting> {
+  final void Function(int, Greeting) onCommited;
+  MultipleStagedMigrator(this.onCommited) : super(
+    3, // Latest version
+    [
+      Migration<Greeting>(
+        1,
+        (data) => Greeting(
+          data["name"]!,
+          "hug1",
+          true
+        )
+      ),
+      Migration<Greeting>(
+        2,
+        (data) => Greeting(
+          data["name"]!,
+          "hug2",
+          true
+        )
+      )
+    ]
+  );
+  
+  @override
+  Future<Map<String, dynamic>?> loadRawData() async {
+    return {
+      "name": "Welt",
+      "action": "welcome"
+    };
+  }
+
+  @override
+  Future<int?> loadVersion() async => 2;
+
+  @override
+  Greeting fromData(Map<String, dynamic> data) => Greeting(
+    data["name"],
+    data["action"],
+    data["beNice"]
+  );
+
+  @override
+  Greeting fromDefault() => Greeting(
+    "Moxxyv2",
+    "hug_more",
+    true
+  );
+
+  Future<void> commit(int version, Greeting data) async {
+    onCommited(version, data);
+  }
+}
+
+void main() {
+  test("Test a simple migration", () async {
+      final mig = TestMigrator((v, g) {
+          expect(v, 2);
+      });
+      final greeting = await mig.load();
+
+      expect(greeting.entity, "Welt");
+      expect(greeting.action, "welcome");
+      expect(greeting.beNice, true);
+  });
+
+  test("Test loading data where there was none", () async {
+      final mig = NoDataMigrator((v, g) {
+          expect(v, 2);
+      });
+      final greeting = await mig.load();
+
+      expect(greeting.entity, "Moxxyv2");
+      expect(greeting.action, "hug_more");
+      expect(greeting.beNice, true);
+  });
+
+  test("Test that only the correct stage is ran", () async {
+      final mig = MultipleStagedMigrator((v, g) {
+          expect(v, 3);
+      });
+      final greeting = await mig.load();
+
+      expect(greeting.entity, "Welt");
+      expect(greeting.action, "hug2");
+      expect(greeting.beNice, true);
+  });
+}