Improve plugin interface and errors (#565)

lib/nyxx.dart

@@ -315,3 +315,4 @@ export 'package:http/http.dart'
         BaseResponse,
         StreamedResponse;
 export 'package:logging/logging.dart' show Logger, Level;
+export 'package:runtime_type/runtime_type.dart' show RuntimeType;

lib/src/client.dart

@@ -2,6 +2,7 @@ import 'package:logging/logging.dart';
 import 'package:nyxx/src/builders/presence.dart';
 import 'package:nyxx/src/builders/voice.dart';
 import 'package:nyxx/src/client_options.dart';
+import 'package:nyxx/src/errors.dart';
 import 'package:nyxx/src/event_mixin.dart';
 import 'package:nyxx/src/gateway/gateway.dart';
 import 'package:nyxx/src/http/handler.dart';
@@ -16,12 +17,21 @@ import 'package:nyxx/src/models/user/user.dart';
 import 'package:nyxx/src/plugin/plugin.dart';
 import 'package:nyxx/src/utils/flags.dart';
 import 'package:oauth2/oauth2.dart';
+import 'package:runtime_type/runtime_type.dart';
 
 /// A helper function to nest and execute calls to plugin connect methods.
 Future<T> _doConnect<T extends Nyxx>(ApiOptions apiOptions, ClientOptions clientOptions, Future<T> Function() connect, List<NyxxPlugin> plugins) {
+  final actualClientType = RuntimeType<T>();
+
+  for (final plugin in plugins) {
+    if (!actualClientType.isSubtypeOf(plugin.clientType)) {
+      throw PluginError('Unsupported client type: plugin needs ${plugin.clientType.internalType}, client was ${actualClientType.internalType}');
+    }
+  }
+
   connect = plugins.fold(
     connect,
-    (previousConnect, plugin) => () async => (await plugin.doConnect(apiOptions, clientOptions, previousConnect)) as T,
+    (previousConnect, plugin) => () async => actualClientType.castInstance(await plugin.doConnect(apiOptions, clientOptions, previousConnect)),
   );
   return connect();
 }

lib/src/errors.dart

@@ -127,3 +127,15 @@ class AlreadyRespondedError extends AlreadyAcknowledgedError {
   @override
   String toString() => 'Interaction has already been responded to';
 }
+
+/// An error thrown when an issue with a client's plugin is encountered.
+class PluginError extends Error {
+  /// The message for this [PluginError].
+  final String message;
+
+  /// Create a new [PluginError].
+  PluginError(this.message);
+
+  @override
+  String toString() => message;
+}

lib/src/models/channel/thread.dart

@@ -97,7 +97,7 @@ class PartialThreadMember {
 
 /// {@template thread_member}
 /// Additional information associated with a [Member] in a [Thread].
-/// {@endtemplate thread_member}
+/// {@endtemplate}
 class ThreadMember extends PartialThreadMember {
   /// The manager for this [ThreadMember].
   final ChannelManager manager;

lib/src/plugin/plugin.dart

@@ -1,14 +1,22 @@
 import 'dart:async';
 
+import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 import 'package:nyxx/src/api_options.dart';
 import 'package:nyxx/src/client.dart';
 import 'package:nyxx/src/client_options.dart';
+import 'package:runtime_type/runtime_type.dart';
 
 /// Provides access to the connection and closing process for implementing plugins.
 abstract class NyxxPlugin<ClientType extends Nyxx> {
   /// The name of this plugin.
-  String get name;
+  String get name => runtimeType.toString();
+
+  /// A logger that can be used to log messages from this plugin.
+  Logger get logger => Logger(name);
+
+  /// The type of client this plugin requires.
+  RuntimeType<ClientType> get clientType => RuntimeType<ClientType>();
 
   late final Expando<NyxxPluginState<ClientType, NyxxPlugin<ClientType>>> _states = Expando('$name plugin states');
 
@@ -64,6 +72,9 @@ class NyxxPluginState<ClientType extends Nyxx, PluginType extends NyxxPlugin<Cli
   /// The plugin this state belongs to.
   final PluginType plugin;
 
+  /// A logger that can be used to log messages from this plugin.
+  Logger get logger => plugin.logger;
+
   /// Create a new plugin state.
   NyxxPluginState(this.plugin);