Merge pull request #364 from FiniteReality/feature/parameter-tweaks

Parameter preconditions and typereader overriding

src/Discord.Net.Commands/Attributes/OverrideTypeReaderAttribute.cs

@@ -0,0 +1,22 @@
+using System;
+
+using System.Reflection;
+
+namespace Discord.Commands
+{
+    [AttributeUsage(AttributeTargets.Parameter)]
+    public class OverrideTypeReaderAttribute : Attribute
+    {
+        private static readonly TypeInfo _typeReaderTypeInfo = typeof(TypeReader).GetTypeInfo();
+
+        public Type TypeReader { get; }
+
+        public OverrideTypeReaderAttribute(Type overridenTypeReader)
+        {
+            if (!_typeReaderTypeInfo.IsAssignableFrom(overridenTypeReader.GetTypeInfo()))
+                throw new ArgumentException($"{nameof(overridenTypeReader)} must inherit from {nameof(TypeReader)}");
+            
+            TypeReader = overridenTypeReader;
+        }
+    } 
+}

src/Discord.Net.Commands/Attributes/ParameterPreconditionAttribute.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Discord.Commands
+{
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = true, Inherited = true)]
+    public abstract class ParameterPreconditionAttribute : Attribute
+    {
+        public abstract Task<PreconditionResult> CheckPermissions(CommandContext context, ParameterInfo parameter, object value, IDependencyMap map);
+    }
+}

src/Discord.Net.Commands/Builders/ModuleClassBuilder.cs

@@ -182,6 +182,10 @@ namespace Discord.Commands
                 // TODO: C#7 type switch
                 if (attribute is SummaryAttribute)
                     builder.Summary = (attribute as SummaryAttribute).Text;
+                else if (attribute is OverrideTypeReaderAttribute)
+                    builder.TypeReader = GetTypeReader(service, paramType, (attribute as OverrideTypeReaderAttribute).TypeReader);
+                else if (attribute is ParameterPreconditionAttribute)
+                    builder.AddPrecondition(attribute as ParameterPreconditionAttribute);
                 else if (attribute is ParamArrayAttribute)
                 {
                     builder.IsMultiple = true;
@@ -196,23 +200,42 @@ namespace Discord.Commands
                 }
             }
 
-            var reader = service.GetTypeReader(paramType);
-            if (reader == null)
+            if (builder.TypeReader == null)
             {
-                var paramTypeInfo = paramType.GetTypeInfo();
-                if (paramTypeInfo.IsEnum)
-                {
-                    reader = EnumTypeReader.GetReader(paramType);
-                    service.AddTypeReader(paramType, reader);
-                }
-                else
+                var reader = service.GetDefaultTypeReader(paramType);
+
+                if (reader == null)
                 {
-                    throw new InvalidOperationException($"{paramType.FullName} is not supported as a command parameter, are you missing a TypeReader?");
+                    var paramTypeInfo = paramType.GetTypeInfo();
+                    if (paramTypeInfo.IsEnum)
+                    {
+                        reader = EnumTypeReader.GetReader(paramType);
+                        service.AddTypeReader(paramType, reader);
+                    }
+                    else
+                    {
+                        throw new InvalidOperationException($"{paramType.FullName} is not supported as a command parameter, are you missing a TypeReader?");
+                    }
                 }
+
+                builder.ParameterType = paramType;
+                builder.TypeReader = reader;
             }
+        }
+
+        private static TypeReader GetTypeReader(CommandService service, Type paramType, Type typeReaderType)
+        {
+            var readers = service.GetTypeReaders(paramType);
+            TypeReader reader = null;
+            if (readers != null)
+                if (readers.TryGetValue(typeReaderType, out reader))
+                    return reader;
+
+            //could not find any registered type reader: try to create one
+            reader = ReflectionUtils.CreateObject<TypeReader>(typeReaderType.GetTypeInfo(), service, DependencyMap.Empty);
+            service.AddTypeReader(paramType, reader);
 
-            builder.ParameterType = paramType;
-            builder.TypeReader = reader;
+            return reader;
         }
 
         private static bool IsValidModuleDefinition(TypeInfo typeInfo)

src/Discord.Net.Commands/Builders/ParameterBuilder.cs

@@ -1,10 +1,15 @@
 using System;
+using System.Linq;
 using System.Reflection;
 
+using System.Collections.Generic;
+
 namespace Discord.Commands.Builders
 {
     public class ParameterBuilder
     {
+        private readonly List<ParameterPreconditionAttribute> _preconditions; 
+
         public CommandBuilder Command { get; }
         public string Name { get; internal set; }
         public Type ParameterType { get; internal set; }
@@ -16,16 +21,20 @@ namespace Discord.Commands.Builders
         public object DefaultValue { get; set; }
         public string Summary { get; set; }
 
+        public IReadOnlyList<ParameterPreconditionAttribute> Preconditions => _preconditions;
+
         //Automatic
         internal ParameterBuilder(CommandBuilder command)
         {
+            _preconditions = new List<ParameterPreconditionAttribute>();
+
             Command = command;
         }
         //User-defined
         internal ParameterBuilder(CommandBuilder command, string name, Type type)
             : this(command)
         {
-            Preconditions.NotNull(name, nameof(name));
+            Discord.Preconditions.NotNull(name, nameof(name));
 
             Name = name;
             SetType(type);
@@ -33,7 +42,11 @@ namespace Discord.Commands.Builders
 
         internal void SetType(Type type)
         {
-            TypeReader = Command.Module.Service.GetTypeReader(type);
+            var readers = Command.Module.Service.GetTypeReaders(type);
+            if (readers == null)
+                throw new InvalidOperationException($"{type} does not have a TypeReader registered for it");
+            
+            TypeReader = readers.FirstOrDefault().Value;
 
             if (type.GetTypeInfo().IsValueType)
                 DefaultValue = Activator.CreateInstance(type);
@@ -49,7 +62,7 @@ namespace Discord.Commands.Builders
         }
         public ParameterBuilder WithDefault(object defaultValue)
         {
-            DefaultValue = defaultValue;            
+            DefaultValue = defaultValue;
             return this;
         }
         public ParameterBuilder WithIsOptional(bool isOptional)
@@ -68,6 +81,12 @@ namespace Discord.Commands.Builders
             return this;
         }
 
+        public ParameterBuilder AddPrecondition(ParameterPreconditionAttribute precondition)
+        {
+            _preconditions.Add(precondition);
+            return this;
+        }
+
         internal ParameterInfo Build(CommandInfo info)
         {
             if (TypeReader == null)

src/Discord.Net.Commands/CommandService.cs

@@ -15,7 +15,8 @@ namespace Discord.Commands
     {
         private readonly SemaphoreSlim _moduleLock;
         private readonly ConcurrentDictionary<Type, ModuleInfo> _typedModuleDefs;
-        private readonly ConcurrentDictionary<Type, TypeReader> _typeReaders;
+        private readonly ConcurrentDictionary<Type, ConcurrentDictionary<Type, TypeReader>> _typeReaders;
+        private readonly ConcurrentDictionary<Type, TypeReader> _defaultTypeReaders;
         private readonly ConcurrentBag<ModuleInfo> _moduleDefs;
         private readonly CommandMap _map;
 
@@ -24,6 +25,7 @@ namespace Discord.Commands
 
         public IEnumerable<ModuleInfo> Modules => _moduleDefs.Select(x => x);
         public IEnumerable<CommandInfo> Commands => _moduleDefs.SelectMany(x => x.Commands);
+        public ILookup<Type, TypeReader> TypeReaders => _typeReaders.SelectMany(x => x.Value.Select(y => new {y.Key, y.Value})).ToLookup(x => x.Key, x => x.Value);
 
         public CommandService() : this(new CommandServiceConfig()) { }
         public CommandService(CommandServiceConfig config)
@@ -32,7 +34,9 @@ namespace Discord.Commands
             _typedModuleDefs = new ConcurrentDictionary<Type, ModuleInfo>();
             _moduleDefs = new ConcurrentBag<ModuleInfo>();
             _map = new CommandMap();
-            _typeReaders = new ConcurrentDictionary<Type, TypeReader>
+            _typeReaders = new ConcurrentDictionary<Type, ConcurrentDictionary<Type, TypeReader>>();
+
+            _defaultTypeReaders = new ConcurrentDictionary<Type, TypeReader>
             {
                 [typeof(bool)] = new SimpleTypeReader<bool>(),
                 [typeof(char)] = new SimpleTypeReader<char>(),
@@ -50,7 +54,7 @@ namespace Discord.Commands
                 [typeof(decimal)] = new SimpleTypeReader<decimal>(),
                 [typeof(DateTime)] = new SimpleTypeReader<DateTime>(),
                 [typeof(DateTimeOffset)] = new SimpleTypeReader<DateTimeOffset>(),
-                [typeof(TimeSpan)] = new SimpleTypeReader<TimeSpan>(),
+                
                 [typeof(IMessage)] = new MessageTypeReader<IMessage>(),
                 [typeof(IUserMessage)] = new MessageTypeReader<IUserMessage>(),
                 [typeof(IChannel)] = new ChannelTypeReader<IChannel>(),
@@ -196,16 +200,25 @@ namespace Discord.Commands
         //Type Readers
         public void AddTypeReader<T>(TypeReader reader)
         {
-            _typeReaders[typeof(T)] = reader;
+            var readers = _typeReaders.GetOrAdd(typeof(T), x => new ConcurrentDictionary<Type, TypeReader>());
+            readers[reader.GetType()] = reader;
         }
         public void AddTypeReader(Type type, TypeReader reader)
         {
-            _typeReaders[type] = reader;
+            var readers = _typeReaders.GetOrAdd(type, x=> new ConcurrentDictionary<Type, TypeReader>());
+            readers[reader.GetType()] = reader;
+        }
+        internal IDictionary<Type, TypeReader> GetTypeReaders(Type type)
+        {
+            ConcurrentDictionary<Type, TypeReader> definedTypeReaders;
+            if (_typeReaders.TryGetValue(type, out definedTypeReaders))
+                return definedTypeReaders;
+            return null;
         }
-        internal TypeReader GetTypeReader(Type type)
+        internal TypeReader GetDefaultTypeReader(Type type)
         {
             TypeReader reader;
-            if (_typeReaders.TryGetValue(type, out reader))
+            if (_defaultTypeReaders.TryGetValue(type, out reader))
                 return reader;
             return null;
         }

src/Discord.Net.Commands/Info/CommandInfo.cs

@@ -137,7 +137,15 @@ namespace Discord.Commands
 
             try
             {
-                var args = GenerateArgs(argList, paramList);
+                object[] args = GenerateArgs(argList, paramList);
+
+                foreach (var parameter in Parameters)
+                {
+                    var result = await parameter.CheckPreconditionsAsync(context, args, map).ConfigureAwait(false);
+                    if (!result.IsSuccess)
+                        return ExecuteResult.FromError(result);
+                }
+
                 switch (RunMode)
                 {
                     case RunMode.Sync: //Always sync

src/Discord.Net.Commands/Info/ParameterInfo.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Linq;
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Threading.Tasks;
 
 using Discord.Commands.Builders;
@@ -10,6 +12,17 @@ namespace Discord.Commands
     {
         private readonly TypeReader _reader;
 
+        public CommandInfo Command { get; }
+        public string Name { get; }
+        public string Summary { get; }
+        public bool IsOptional { get; }
+        public bool IsRemainder { get; }
+        public bool IsMultiple { get; }
+        public Type Type { get; }
+        public object DefaultValue { get; }
+
+        public IReadOnlyList<ParameterPreconditionAttribute> Preconditions { get; }
+
         internal ParameterInfo(ParameterBuilder builder, CommandInfo command, CommandService service)
         {
             Command = command;
@@ -23,17 +36,30 @@ namespace Discord.Commands
             Type = builder.ParameterType;
             DefaultValue = builder.DefaultValue;
 
+            Preconditions = builder.Preconditions.ToImmutableArray();
+
             _reader = builder.TypeReader;
         }
 
-        public CommandInfo Command { get; }
-        public string Name { get; }
-        public string Summary { get; }
-        public bool IsOptional { get; }
-        public bool IsRemainder { get; }
-        public bool IsMultiple { get; }
-        public Type Type { get; }
-        public object DefaultValue { get; }
+        public async Task<PreconditionResult> CheckPreconditionsAsync(CommandContext context, object[] args, IDependencyMap map = null)
+        {
+            if (map == null)
+                map = DependencyMap.Empty;
+
+            int position = 0;
+            for(position = 0; position < Command.Parameters.Count; position++)
+                if (Command.Parameters[position] == this)
+                    break;
+
+            foreach (var precondition in Preconditions)
+            {
+                var result = await precondition.CheckPermissions(context, this, args[position], map).ConfigureAwait(false);
+                if (!result.IsSuccess)
+                    return result;
+            }
+
+            return PreconditionResult.FromSuccess();
+        }
 
         public async Task<TypeReaderResult> Parse(CommandContext context, string input)
         {