#61 - task(firestore service): add service interface for firestore API

Sadly the converter solution was a dead end, due to dart not being able to invoke interface methods via generic types.

However, a similar solution is utilizing a middleware service for each requested entity, that fetched the required json data from the firestore and calls the corresponding toJson/fromJson method to map json data to entity model.

lib/core/interfaces/json_serializable.dart

@@ -1 +1,11 @@
-abstract class JsonSerializable {}
+import 'package:lifting_progress_tracker/firebase/firestore_json.dart';
+
+abstract class JsonSerializable<T> {
+  // Usage of named constructors can't be enforced, however the usage of
+  // both methods is heavily encouraged.
+  JsonSerializable.fromJson();
+
+  FirestoreJson toJson() {
+    return {};
+  }
+}

lib/firebase/services/firestore_service.dart

@@ -1,7 +1,7 @@
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:get_it/get_it.dart';
+import 'package:lifting_progress_tracker/firebase/firestore_json.dart';
 import 'package:lifting_progress_tracker/firebase/services/firebase_service.dart';
-import 'package:lifting_progress_tracker/training_plan/models/training_plan_list.dart';
 import 'package:logging/logging.dart';
 
 class FirestoreService {
@@ -43,19 +43,12 @@ class FirestoreService {
         .set(documentData);
   }
 
-  Future<TrainingPlanList> get(
+  Future<FirestoreJson> get(
     String collectionName,
     String documentId,
   ) async {
-    final DocumentSnapshot<TrainingPlanList> documentSnapshot = await _firestore
-        .collection(collectionName)
-        .doc(documentId)
-        .withConverter(
-          fromFirestore: (snapshot, _) =>
-              TrainingPlanList.fromJson(snapshot.data()!),
-          toFirestore: (trainingPlanList, _) => trainingPlanList.toJson(),
-        )
-        .get();
+    final DocumentSnapshot<FirestoreJson> documentSnapshot =
+        await _firestore.collection(collectionName).doc(documentId).get();
 
     if (!documentSnapshot.exists) {
       _logger.severe(

lib/pages/home.dart

@@ -3,49 +3,28 @@ import 'package:get_it/get_it.dart';
 import 'package:lifting_progress_tracker/core/models/app_user.dart';
 import 'package:lifting_progress_tracker/core/services/user_service.dart';
 import 'package:lifting_progress_tracker/core/widgets/error_message.dart';
-import 'package:lifting_progress_tracker/firebase/services/firestore_service.dart';
 import 'package:lifting_progress_tracker/pages/starting/widgets/welcome_message.dart';
 import 'package:logging/logging.dart';
 
 class HomePage extends StatelessWidget {
   final Logger _logger = Logger("StartingPage");
 
+  final UserService _userService = GetIt.I.get<UserService>();
+
   @override
   Widget build(BuildContext context) {
-    final UserService userService = GetIt.I.get<UserService>();
-    final FirestoreService firestoreService = GetIt.I.get<FirestoreService>();
-
     return Scaffold(
       body: Center(
         child: FutureBuilder(
-          future: userService.user$,
+          future: _userService.user$,
           builder: (BuildContext context, AsyncSnapshot<AppUser> snapshot) {
             if (snapshot.connectionState == ConnectionState.waiting) {
               return const CircularProgressIndicator();
             }
 
             if (snapshot.connectionState == ConnectionState.done) {
-              return Column(
-                children: [
-                  WelcomeMessage(
-                    username: snapshot.data?.email ?? "",
-                  ),
-                  ElevatedButton(
-                    onPressed: () => {
-                      firestoreService.get(
-                        "plan-entries",
-                        snapshot.data?.uid ?? "",
-                      ),
-                      //     .then(
-                      //   (value) {
-                      //     final plans = value;
-                      //     print(plans);
-                      //   },
-                      // ),
-                    },
-                    child: const Text("press to fetch!"),
-                  ),
-                ],
+              return WelcomeMessage(
+                username: snapshot.data?.email ?? "",
               );
             }
 

lib/training_plan/models/training_plan.dart

@@ -1,16 +1,22 @@
+import 'package:lifting_progress_tracker/core/interfaces/json_serializable.dart';
 import 'package:lifting_progress_tracker/firebase/firestore_json.dart';
 import 'package:lifting_progress_tracker/training_plan/models/training_plan_entry.dart';
 
-class TrainingPlan {
+class TrainingPlan implements JsonSerializable<TrainingPlan> {
   Map<String, TrainingPlanEntry> planEntries;
 
-  TrainingPlan({required this.planEntries});
-
   TrainingPlan.fromJson(FirestoreJson json)
       : planEntries = json.map(
           (key, value) => MapEntry(
             key,
             TrainingPlanEntry.fromJson(value as FirestoreJson),
           ),
         );
+
+  @override
+  FirestoreJson toJson() {
+    return {
+      "planEntries": planEntries,
+    };
+  }
 }

lib/training_plan/models/training_plan_entry.dart

@@ -1,21 +1,17 @@
+import 'package:lifting_progress_tracker/core/interfaces/json_serializable.dart';
 import 'package:lifting_progress_tracker/firebase/firestore_json.dart';
 
-class TrainingPlanEntry {
+class TrainingPlanEntry implements JsonSerializable<TrainingPlanEntry> {
   String repeats;
   String exerciseName;
   String weight;
 
-  TrainingPlanEntry({
-    required this.repeats,
-    required this.exerciseName,
-    required this.weight,
-  });
-
   TrainingPlanEntry.fromJson(FirestoreJson json)
       : repeats = json["repeats"] as String,
         exerciseName = json["exerciseName"] as String,
         weight = json["weight"] as String;
 
+  @override
   FirestoreJson toJson() {
     return {
       "repeats": repeats,

lib/training_plan/models/training_plan_list.dart

@@ -1,10 +1,11 @@
+import 'package:lifting_progress_tracker/core/interfaces/json_serializable.dart';
 import 'package:lifting_progress_tracker/firebase/firestore_json.dart';
 import 'package:lifting_progress_tracker/training_plan/models/training_plan.dart';
 
-class TrainingPlanList {
+class TrainingPlanList implements JsonSerializable<TrainingPlanList> {
   Map<String, TrainingPlan> trainingPlanList;
 
-  TrainingPlanList({required this.trainingPlanList});
+  TrainingPlanList(this.trainingPlanList);
 
   TrainingPlanList.fromJson(FirestoreJson json)
       : trainingPlanList = json.map(
@@ -14,6 +15,7 @@ class TrainingPlanList {
           ),
         );
 
+  @override
   FirestoreJson toJson() {
     return {
       "trainingPlanList": trainingPlanList,

lib/training_plan/training_plan_service.ts.dart

@@ -0,0 +1,16 @@
+import 'package:get_it/get_it.dart';
+import 'package:lifting_progress_tracker/firebase/services/firestore_service.dart';
+import 'package:lifting_progress_tracker/training_plan/models/training_plan_list.dart';
+
+class TrainingPlanService {
+  final FirestoreService _firestoreService = GetIt.I.get<FirestoreService>();
+
+  Future<TrainingPlanList> getPlanList(
+    String collectionName,
+    String documentId,
+  ) async {
+    return TrainingPlanList.fromJson(
+      await _firestoreService.get(collectionName, documentId),
+    );
+  }
+}