Add AddEntityTypeReader

src/Discord.Net.Commands/CommandService.cs

@@ -48,6 +48,7 @@ namespace Discord.Commands
         private readonly SemaphoreSlim _moduleLock;
         private readonly ConcurrentDictionary<Type, ModuleInfo> _typedModuleDefs;
         private readonly ConcurrentDictionary<Type, ConcurrentDictionary<Type, TypeReader>> _typeReaders;
+        private readonly ConcurrentDictionary<Type, ConcurrentQueue<Type>> _userEntityTypeReaders;
         private readonly ConcurrentDictionary<Type, TypeReader> _defaultTypeReaders;
         private readonly ConcurrentDictionary<Type, TypeReader> _overrideTypeReaders;
         private readonly ImmutableList<(Type EntityType, Type TypeReaderType)> _entityTypeReaders;
@@ -78,6 +79,15 @@ namespace Discord.Commands
         /// </summary>
         public ILookup<Type, TypeReader> TypeReaders => _typeReaders.SelectMany(x => x.Value.Select(y => new { y.Key, y.Value })).ToLookup(x => x.Key, x => x.Value);
 
+        /// <summary>
+        ///     Represents all entity type reader <see cref="Type" />s loaded within <see cref="CommandService"/>.
+        /// </summary>
+        /// <returns>
+        ///     A <see cref="ILookup{TKey, TElement}"/> that the key is the object type to be read by the <see cref="TypeReader"/>
+        ///     and the element is the type of the <see cref="TypeReader"/> generic definition.
+        /// </returns>
+        public ILookup<Type, Type> EntityTypeReaders => _userEntityTypeReaders.SelectMany(x => x.Value.Select(y => new { x.Key, TypeReaderType = y })).ToLookup(x => x.Key, y => y.TypeReaderType);
+
         /// <summary>
         ///     Initializes a new <see cref="CommandService"/> class.
         /// </summary>
@@ -110,6 +120,7 @@ namespace Discord.Commands
             _moduleDefs = new HashSet<ModuleInfo>();
             _map = new CommandMap(this);
             _typeReaders = new ConcurrentDictionary<Type, ConcurrentDictionary<Type, TypeReader>>();
+            _userEntityTypeReaders = new ConcurrentDictionary<Type, ConcurrentQueue<Type>>();
             _overrideTypeReaders = new ConcurrentDictionary<Type, TypeReader>();
 
             _defaultTypeReaders = new ConcurrentDictionary<Type, TypeReader>();
@@ -331,8 +342,6 @@ namespace Discord.Commands
         ///     type.
         ///     If <typeparamref name="T" /> is a <see cref="ValueType" />, a nullable <see cref="TypeReader" /> will
         ///     also be added.
-        ///     If a default <see cref="TypeReader" /> exists for <typeparamref name="T" />, a warning will be logged
-        ///     and the default <see cref="TypeReader" /> will be replaced.
         /// </summary>
         /// <typeparam name="T">The object type to be read by the <see cref="TypeReader"/>.</typeparam>
         /// <param name="reader">An instance of the <see cref="TypeReader" /> to be added.</param>
@@ -343,8 +352,6 @@ namespace Discord.Commands
         ///     type.
         ///     If <paramref name="type" /> is a <see cref="ValueType" />, a nullable <see cref="TypeReader" /> for the
         ///     value type will also be added.
-        ///     If a default <see cref="TypeReader" /> exists for <paramref name="type" />, a warning will be logged and
-        ///     the default <see cref="TypeReader" /> will be replaced.
         /// </summary>
         /// <param name="type">A <see cref="Type" /> instance for the type to be read.</param>
         /// <param name="reader">An instance of the <see cref="TypeReader" /> to be added.</param>
@@ -357,6 +364,40 @@ namespace Discord.Commands
                 AddNullableTypeReader(type, reader);
         }
         /// <summary>
+        ///     Adds a custom entity <see cref="TypeReader" /> to this <see cref="CommandService" /> for the supplied
+        ///     object type.
+        /// </summary>
+        /// <typeparam name="T">The object type to be read by the <see cref="TypeReader"/>.</typeparam>
+        /// <param name="typeReaderType">
+        ///     A <see cref="Type" /> that is a generic type definition with a single open argument
+        ///     of the <see cref="TypeReader" /> to be added.
+        /// </param>
+        public void AddEntityTypeReader<T>(Type typeReaderGenericType)
+            => AddEntityTypeReader(typeof(T), typeReaderGenericType);
+        /// <summary>
+        ///     Adds a custom entity <see cref="TypeReader" /> to this <see cref="CommandService" /> for the supplied
+        ///     object type.
+        /// </summary>
+        /// <param name="type">A <see cref="Type" /> instance for the type to be read.</param>
+        /// <param name="typeReaderType">
+        ///     A <see cref="Type" /> that is a generic type definition with a single open argument
+        ///     of the <see cref="TypeReader" /> to be added.
+        /// </param>
+        public void AddEntityTypeReader(Type type, Type typeReaderGenericType)
+        {
+            if (!typeReaderGenericType.IsGenericTypeDefinition)
+                throw new ArgumentException("TypeReader type must be a generic type definition.", nameof(typeReaderGenericType));
+            Type[] genericArgs = typeReaderGenericType.GetGenericArguments();
+            if (genericArgs.Length != 1)
+                throw new ArgumentException("TypeReader type must accept one and only one open generic argument.", nameof(typeReaderGenericType));
+            if (!genericArgs[0].IsGenericParameter)
+                throw new ArgumentException("TypeReader type must accept one and only one open generic argument.", nameof(typeReaderGenericType));
+            if (!genericArgs[0].GenericParameterAttributes.HasFlag(GenericParameterAttributes.ReferenceTypeConstraint))
+                throw new ArgumentException("TypeReader generic argument must have a reference type constraint.", nameof(typeReaderGenericType));
+            var readers = _userEntityTypeReaders.GetOrAdd(type, x => new ConcurrentQueue<Type>());
+            readers.Enqueue(typeReaderGenericType);
+        }
+        /// <summary>
         ///     Adds a custom <see cref="TypeReader" /> to this <see cref="CommandService" /> for the supplied object
         ///     type.
         ///     If <typeparamref name="T" /> is a <see cref="ValueType" />, a nullable <see cref="TypeReader" /> will
@@ -418,28 +459,35 @@ namespace Discord.Commands
             if (_typeReaders.TryGetValue(type, out var definedTypeReaders))
                 return definedTypeReaders;
 
-            var entityReaders = _typeReaders.Where(x => x.Key.IsAssignableFrom(type));
+            var assignableEntityReaders = _userEntityTypeReaders.Where(x => x.Key.IsAssignableFrom(type));
 
             int assignableTo = -1;
-            KeyValuePair<Type, ConcurrentDictionary<Type, TypeReader>>? typeReader = null;
-            foreach (var entityReader in entityReaders)
+            KeyValuePair<Type, ConcurrentQueue<Type>>? entityReaders = null;
+            foreach (var entityReader in assignableEntityReaders)
             {
-                int assignables = entityReaders.Sum(x => !x.Equals(entityReader) && x.Key.IsAssignableFrom(entityReader.Key) ? 1 : 0);
+                int assignables = assignableEntityReaders.Sum(x => !x.Equals(entityReader) && x.Key.IsAssignableFrom(entityReader.Key) ? 1 : 0);
                 if (assignableTo == -1)
                 {
                     // First time
                     assignableTo = assignables;
-                    typeReader = entityReader;
+                    entityReaders = entityReader;
                 }
-                // Try to get the "higher" interface. IMessageChannel is assignable to IChannel, but not the inverse
+                // Try to get the most specific type reader, i.e. IMessageChannel is assignable to IChannel, but not the inverse
                 else if (assignables > assignableTo)
                 {
                     assignableTo = assignables;
-                    typeReader = entityReader;
+                    entityReaders = entityReader;
                 }
             }
 
-            return typeReader?.Value;
+            if (entityReaders != null)
+            {
+                var entityTypeReaderType = entityReaders.Value.Value.First();
+                TypeReader reader = Activator.CreateInstance(entityTypeReaderType.MakeGenericType(type)) as TypeReader;
+                AddTypeReader(type, reader);
+                return GetTypeReaders(type);
+            }
+            return null;
         }
         internal TypeReader GetDefaultTypeReader(Type type)
         {