✨ New feature github device flow

lib/src/common.dart

@@ -5,6 +5,7 @@ library;
 export 'package:github_flutter/src/common/github.dart';
 export 'package:github_flutter/src/common/util/auth.dart';
 export 'package:github_flutter/src/common/util/crawler.dart';
+export 'package:github_flutter/src/common/util/device_flow.dart';
 export 'package:github_flutter/src/common/util/errors.dart';
 export 'package:github_flutter/src/common/util/json.dart';
 export 'package:github_flutter/src/common/util/oauth2.dart';

lib/src/common/util/device_flow.dart

@@ -0,0 +1,126 @@
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:github_flutter/src/common.dart';
+import 'package:http/http.dart' as http;
+
+/// Device Flow Helper
+///
+/// **Example**:
+///
+///
+class DeviceFlow {
+  /// Client ID
+  final String clientId;
+
+  /// Requested Scopes
+  final List<String> scopes;
+
+  /// Grant type
+  final String? grantType;
+
+  /// Device flow Base URL
+  final String baseUrl;
+
+  /// GitHub instance
+  GitHub? github;
+
+  Map<String, dynamic> _response = {};
+
+  DeviceFlow(
+    this.clientId, {
+    this.scopes = const [],
+    this.baseUrl = 'https://github.com',
+    this.grantType = "urn:ietf:params:oauth:grant-type:device_code",
+  });
+
+  Future<String> fetchUserCode() async {
+    final headers = <String, String>{
+      'Accept': 'application/json',
+      'content-type': 'application/json',
+    };
+
+    final body = GitHubJson.encode(<String, dynamic>{
+      'client_id': clientId,
+      'scope': scopes.join(','),
+    });
+
+    final response = await (github == null ? http.Client() : github!.client)
+        .post(
+          Uri.parse("$baseUrl/login/device/code"),
+          body: body,
+          headers: headers,
+        );
+
+    final json = jsonDecode(response.body) as Map<String, dynamic>;
+
+    _response = json;
+
+    if (json['error'] != null) {
+      throw Exception(json['error']);
+    }
+    return json['user_code'];
+  }
+
+  /// Generates an Authorization URL
+  ///
+  /// This should be displayed to the user.
+  String createAuthorizeUrl() {
+    if (_response['verification_uri'] == null) {
+      throw Error();
+    }
+    return '${_response['verification_uri']}?user_code=${_response['user_code']}';
+  }
+
+  /// Exchange `device code` after user verified for token
+  Future<DeviceFlowExchangeResponse> exchange() {
+    if (!_response.containsKey("device_code")) {
+      throw Exception("Device code not found");
+    }
+
+    final headers = <String, String>{
+      'Accept': 'application/json',
+      'content-type': 'application/json',
+    };
+
+    final body = GitHubJson.encode(<String, dynamic>{
+      'client_id': clientId,
+      'device_code': _response['device_code'],
+      'grant_type': grantType,
+    });
+
+    return (github == null ? http.Client() : github!.client)
+        .post(
+          Uri.parse('$baseUrl/login/oauth/access_token'),
+          body: body,
+          headers: headers,
+        )
+        .then((response) {
+          final json = jsonDecode(response.body) as Map<String, dynamic>;
+          if (json['error'] != null) {
+            throw Exception(json['error'] ?? "Unknown error");
+          }
+          return DeviceFlowExchangeResponse(
+            json['access_token'],
+            json['token_type'],
+            (json['scope'] as String).split(','),
+            json['interval'] ?? 0,
+          );
+        });
+  }
+}
+
+/// Represents a response for exchanging a code for a token.
+class DeviceFlowExchangeResponse {
+  final String? token;
+  final List<String> scopes;
+  final String? tokenType;
+  final int interval;
+
+  DeviceFlowExchangeResponse(
+    this.token,
+    this.tokenType,
+    this.scopes,
+    this.interval,
+  );
+}