Login page checks URL and credentials

lib/api/api.dart

@@ -34,6 +34,29 @@ class FeverAPI {
     return md5.convert(bytes).toString();
   }
 
+  /// Checks whether the given API URL is a valid Fever API endpoint
+  static Future<bool> isValidAPI(String url) async {
+    try {
+      final response = jsonDecode((await http.post(Uri.parse(url))).body);
+      return response['api_version'] == 3;
+    } catch(e) {
+      print(e);
+      return false;
+    }
+  }
+
+  /// Checks whether the given API URL is a valid Fever API endpoint and the given API key is authorized to access it
+  static Future<bool> isAuthenticated(String url, String key) async {
+    try {
+      final response = jsonDecode((await http.post(Uri.parse(url), body: { 'api_key': key })).body);
+      return response['api_version'] == 3 && response['auth'] == 1;
+    } catch(e) {
+      print(e);
+      return false;
+    }
+  }
+
+  /// Whether we have an API URL and API key set
   bool loggedIn() {
     return apiKey != null && apiUrl != null;
   }

lib/main.dart

@@ -35,9 +35,9 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({ super.key, required this.title, required this.api });
   final String title;
   final FeverAPI api;
+  const MyHomePage({ super.key, required this.title, required this.api });
 
   @override
   State<MyHomePage> createState() => _MyHomePageState();
@@ -52,7 +52,7 @@ class _MyHomePageState extends State<MyHomePage> {
       ),
       body: widget.api.loggedIn()
         ? const Center(child: Text('Meep'))
-        : const Center(child: LoginPrompt()),
+        : Center(child: LoginPrompt(api: widget.api)),
     );
   }
 }

lib/pages/login.dart

@@ -1,13 +1,55 @@
+import 'package:feet/api/api.dart';
 import 'package:flutter/material.dart';
 
 class LoginPage extends StatefulWidget {
-  LoginPage({ super.key });
+  final FeverAPI api;
+  const LoginPage({ super.key, required this.api });
 
   @override
   State<LoginPage> createState() => _LoginPageState();
 }
 
 class _LoginPageState extends State<LoginPage> {
+  bool? _validAPI;
+
+  final _urlController = TextEditingController();
+  final _usernameController = TextEditingController();
+  final _passwordController = TextEditingController();
+
+  final _urlFocus = FocusNode();
+
+  Future<bool> checkUrl() async {
+    if (_urlController.text.isNotEmpty) {
+      var value = await FeverAPI.isValidAPI(_urlController.text);
+      setState(() {
+        _validAPI = value;
+      });
+
+      return value;
+    }
+
+    return false;
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    _urlFocus.addListener(() {
+      if (!_urlFocus.hasFocus) {
+        checkUrl();
+      }
+    });
+  }
+
+  @override
+  void dispose() {
+    _urlController.dispose();
+    _usernameController.dispose();
+    _passwordController.dispose();
+    _urlFocus.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -20,18 +62,88 @@ class _LoginPageState extends State<LoginPage> {
             padding: const EdgeInsets.all(8.0),
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
-              children: const [
-                Text("Fever compatible API URL"),
+              children: [
+                const Text("Fever compatible API URL"),
                 TextField(
+                  controller: _urlController,
+                  focusNode: _urlFocus,
                   decoration: InputDecoration(
-                    border: OutlineInputBorder(),
-                    contentPadding: EdgeInsets.all(8.0),
+                    border: const OutlineInputBorder(),
+                    contentPadding: const EdgeInsets.all(8.0),
                     hintText: 'https://among-us.morbius.sus/api/fever.php',
+                    errorText: _validAPI == false ? 'Invalid or unsupported API' : null,
                   )
-                )
+                ),
               ],
             ),
-          )
+          ),
+          Container(
+            padding: const EdgeInsets.all(8.0),
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                const Text("Authentication"),
+                Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+                  children: [
+                    Flexible(child: TextField(
+                      controller: _usernameController,
+                      decoration: const InputDecoration(
+                        border: OutlineInputBorder(),
+                        contentPadding: EdgeInsets.all(8.0),
+                        hintText: 'Username',
+                      ),
+                    )),
+                    const SizedBox(width: 8),
+                    Flexible(child: TextField(
+                      controller: _passwordController,
+                      decoration: const InputDecoration(
+                        border: OutlineInputBorder(),
+                        contentPadding: EdgeInsets.all(8.0),
+                        hintText: 'Password',
+                      ),
+                      obscureText: true,
+                    )),
+                  ],
+                ),
+              ],
+            ),
+          ),
+          ElevatedButton(
+            onPressed: () async {
+              if (_urlController.text.isEmpty) return;
+              _validAPI ??= await checkUrl();
+              if (_validAPI != true || _usernameController.text.isEmpty || _passwordController.text.isEmpty) return;
+
+              var apiKey = FeverAPI.generateApiKey(_usernameController.text, _passwordController.text);
+              var isAuthenticated = await FeverAPI.isAuthenticated(_urlController.text, apiKey);
+
+              if (!isAuthenticated) {
+                // ignore: use_build_context_synchronously
+                showDialog(
+                  context: context,
+                  builder: (BuildContext context) {
+                    return AlertDialog(
+                      title: const Text('Authentication failed'),
+                      content: const Text('The API URL seems to be valid, but the provided credentials appear to be incorrect.'),
+                      actions: [
+                        TextButton(onPressed: () => Navigator.of(context).pop(), child: const Text('Got it!')),
+                      ],
+                    );
+                  }
+                );
+
+                return;
+              }
+
+              widget.api.apiUrl = _urlController.text;
+              widget.api.apiKey = apiKey;
+
+              // ignore: use_build_context_synchronously
+              Navigator.of(context).pop();
+            },
+            child: const Text('Continue'),
+          ),
         ],
       ),
     );

lib/widgets/login_prompt.dart

@@ -1,8 +1,10 @@
 import 'package:flutter/material.dart';
 import 'package:feet/pages/login.dart';
+import '../api/api.dart';
 
 class LoginPrompt extends StatelessWidget {
-  const LoginPrompt({ super.key });
+  final FeverAPI api;
+  const LoginPrompt({ super.key, required this.api });
 
   @override
   Widget build(BuildContext context) {
@@ -11,9 +13,9 @@ class LoginPrompt extends StatelessWidget {
         const Text('Please log in'),
         ElevatedButton(
           onPressed: () {
-            Navigator.push(context, MaterialPageRoute(builder: (context) => LoginPage()));
+            Navigator.push(context, MaterialPageRoute(builder: (context) => LoginPage(api: api)));
           },
-          child: const Text('Log in')
+          child: const Text('Log in'),
         ),
       ],
     );