refactor user repo with helpers. better api validation etc.

backend-dart/lib/common/extensions.dart

@@ -0,0 +1,8 @@
+extension Let<T> on T? {
+  R? let<R>(R Function(T it) action) {
+    if (this != null) {
+      return action(this!);
+    }
+    return null;
+  }
+}

backend-dart/lib/common/request_helper.dart

@@ -0,0 +1,31 @@
+import 'dart:convert';
+import 'dart:core';
+
+import 'package:backend_dart/domain/errors/app_error.dart';
+import 'package:backend_dart/domain/interface/error.dart';
+import 'package:fpdart/fpdart.dart';
+import 'package:shelf/shelf.dart';
+
+TaskEither<IError, Map<String, dynamic>> requestToJson(Request request) {
+  return TaskEither.tryCatch(
+    () async {
+      final body = await request.readAsString();
+      return jsonDecode(body);
+    },
+    (error, stack) => AppError.inputError(
+      message: 'Failed to decode JSON: ${error.toString()}',
+    ),
+  );
+}
+
+TaskEither<IError, T> decodeJson<T>(
+    Map<String, dynamic> json, T Function(Map<String, dynamic>) fromJson) {
+  return TaskEither.tryCatch(
+    () async {
+      return fromJson(json);
+    },
+    (error, stack) => AppError.inputError(
+      message: 'Failed to decode JSON: ${error.toString()}',
+    ),
+  );
+}

backend-dart/lib/common/secure_hash.dart

@@ -0,0 +1,10 @@
+import 'dart:convert';
+
+import 'package:crypto/crypto.dart';
+
+String generateSecureHash(String input) {
+  final bytes = utf8.encode(input);
+  final hash = sha256.convert(bytes);
+  print(hash);
+  return hash.toString();
+}

backend-dart/lib/common/validation.dart

@@ -0,0 +1,22 @@
+import 'package:backend_dart/domain/errors/app_error.dart';
+import 'package:backend_dart/domain/interface/error.dart';
+import 'package:fpdart/fpdart.dart';
+
+TaskEither<IError, Map<String, dynamic>> validateJsonKeys(
+    Map<String, dynamic> json, List<String> requiredKeys) {
+  return TaskEither.tryCatch(
+    () async {
+      final missingKeys =
+          requiredKeys.where((key) => !json.containsKey(key)).toList();
+
+      if (missingKeys.isNotEmpty) {
+        throw Exception('Missing required keys: ${missingKeys.join(', ')}');
+      }
+
+      return json;
+    },
+    (error, _) => AppError.validationError(
+      message: 'Failed to validate JSON keys: ${error.toString()}',
+    ),
+  );
+}