Added new parameter scoring, support multiple matches

src/Discord.Net.Commands/Command.cs

@@ -1,7 +1,9 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Linq;
 using System.Reflection;
 using System.Threading.Tasks;
 
@@ -10,6 +12,9 @@ namespace Discord.Commands
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
     public class Command
     {
+        private static readonly MethodInfo _convertParamsMethod = typeof(Command).GetTypeInfo().GetDeclaredMethod(nameof(ConvertParamsList));
+        private static readonly ConcurrentDictionary<Type, Func<IEnumerable<object>, object>> _arrayConverters = new ConcurrentDictionary<Type, Func<IEnumerable<object>, object>>();
+
         private readonly object _instance;
         private readonly Func<IMessage, IReadOnlyList<object>, Task> _action;
 
@@ -19,6 +24,7 @@ namespace Discord.Commands
         public string Description { get; }
         public string Summary { get; }
         public string Text { get; }
+        public bool HasVarArgs { get; }
         public IReadOnlyList<CommandParameter> Parameters { get; }
         public IReadOnlyList<PreconditionAttribute> Preconditions { get; }
 
@@ -42,8 +48,9 @@ namespace Discord.Commands
             var summary = source.GetCustomAttribute<SummaryAttribute>();
             if (summary != null)
                 Summary = summary.Text;
-
+            
             Parameters = BuildParameters(source);
+            HasVarArgs = Parameters.Count > 0 ? Parameters[Parameters.Count - 1].IsMultiple : false;
             Preconditions = BuildPreconditions(source);
             _action = BuildAction(source);
         }
@@ -76,14 +83,38 @@ namespace Discord.Commands
 
             return await CommandParser.ParseArgs(this, msg, searchResult.Text.Substring(Text.Length), 0).ConfigureAwait(false);
         }
-        public async Task<ExecuteResult> Execute(IMessage msg, ParseResult parseResult)
+        public Task<ExecuteResult> Execute(IMessage msg, ParseResult parseResult)
         {
             if (!parseResult.IsSuccess)
-                return ExecuteResult.FromError(parseResult);
+                return Task.FromResult(ExecuteResult.FromError(parseResult));
 
+            var argList = new object[parseResult.ArgValues.Count];
+            for (int i = 0; i < parseResult.ArgValues.Count; i++)
+            {
+                if (!parseResult.ArgValues[i].IsSuccess)
+                    return Task.FromResult(ExecuteResult.FromError(parseResult.ArgValues[i]));
+                argList[i] = parseResult.ArgValues[i].Values.First().Value;
+            }
+
+            object[] paramList = null;
+            if (parseResult.ParamValues != null)
+            {
+                paramList = new object[parseResult.ParamValues.Count];
+                for (int i = 0; i < parseResult.ParamValues.Count; i++)
+                {
+                    if (!parseResult.ParamValues[i].IsSuccess)
+                        return Task.FromResult(ExecuteResult.FromError(parseResult.ParamValues[i]));
+                    paramList[i] = parseResult.ParamValues[i].Values.First().Value;
+                }
+            }
+
+            return Execute(msg, argList, paramList);
+        }
+        public async Task<ExecuteResult> Execute(IMessage msg, IEnumerable<object> argList, IEnumerable<object> paramList)
+        {
             try
             {
-                await _action.Invoke(msg, parseResult.Values);//Note: This code may need context
+                await _action.Invoke(msg, GenerateArgs(argList, paramList)).ConfigureAwait(false);//Note: This code may need context
                 return ExecuteResult.FromSuccess();
             }
             catch (Exception ex)
@@ -108,7 +139,7 @@ namespace Discord.Commands
             {
                 var parameter = parameters[i];
                 var type = parameter.ParameterType;
-                
+
                 //Detect 'params'
                 bool isMultiple = parameter.GetCustomAttribute<ParamArrayAttribute>() != null;
                 if (isMultiple)
@@ -156,6 +187,39 @@ namespace Discord.Commands
             };
         }
 
+        private object[] GenerateArgs(IEnumerable<object> argList, IEnumerable<object> paramsList)
+        {
+            int argCount = Parameters.Count;
+            var array = new object[Parameters.Count];
+            if (HasVarArgs)
+                argCount--;
+
+            int i = 0;
+            foreach (var arg in argList)
+            {
+                if (i == argCount)
+                    throw new InvalidOperationException("Command was invoked with too many parameters");
+                array[i++] = arg;
+            }
+            if (i < argCount)
+                throw new InvalidOperationException("Command was invoked with too few parameters");
+
+            if (HasVarArgs)
+            {
+                var func = _arrayConverters.GetOrAdd(Parameters[Parameters.Count - 1].ElementType, t =>
+                {
+                    var method = _convertParamsMethod.MakeGenericMethod(t);
+                    return (Func<IEnumerable<object>, object>)method.CreateDelegate(typeof(Func<IEnumerable<object>, object>));
+                });
+                array[i] = func(paramsList);
+            }
+
+            return array;
+        }
+
+        private static T[] ConvertParamsList<T>(IEnumerable<object> paramsList)
+            => paramsList.Cast<T>().ToArray();
+
         public override string ToString() => Name;
         private string DebuggerDisplay => $"{Module.Name}.{Name} ({Text})";
     }

src/Discord.Net.Commands/CommandError.cs

@@ -3,14 +3,14 @@
     public enum CommandError
     {
         //Search
-        UnknownCommand,
+        UnknownCommand = 1,
 
         //Parse
         ParseFailed,
         BadArgCount,
 
         //Parse (Type Reader)
-        CastFailed,
+        //CastFailed,
         ObjectNotFound,
         MultipleMatches,
 

src/Discord.Net.Commands/CommandParameter.cs

@@ -17,7 +17,7 @@ namespace Discord.Commands
         public bool IsRemainder { get; }
         public bool IsMultiple { get; }
         public Type ElementType { get; }
-        internal object DefaultValue { get; }
+        public object DefaultValue { get; }
 
         public CommandParameter(ParameterInfo source, string name, string summary, Type type, TypeReader reader, bool isOptional, bool isRemainder, bool isMultiple, object defaultValue)
         {

src/Discord.Net.Commands/CommandParser.cs

@@ -1,8 +1,5 @@
-using System;
-using System.Collections.Concurrent;
-using System.Collections.Generic;
+
 using System.Collections.Immutable;
-using System.Reflection;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -16,9 +13,6 @@ namespace Discord.Commands
             Parameter,
             QuotedParameter
         }
-
-        private static readonly MethodInfo _convertArrayMethod = typeof(CommandParser).GetTypeInfo().GetDeclaredMethod(nameof(ConvertParamsList));
-        private static readonly ConcurrentDictionary<Type, Func<List<object>, object>> _arrayConverters = new ConcurrentDictionary<Type, Func<List<object>, object>>();
         
         public static async Task<ParseResult> ParseArgs(Command command, IMessage context, string input, int startPos)
         {
@@ -27,9 +21,10 @@ namespace Discord.Commands
             int endPos = input.Length;
             var curPart = ParserPart.None;
             int lastArgEndPos = int.MinValue;
-            var argList = ImmutableArray.CreateBuilder<object>();
-            List<object> paramsList = null; // TODO: could we use a better type?
+            var argList = ImmutableArray.CreateBuilder<TypeReaderResult>();
+            ImmutableArray<TypeReaderResult>.Builder paramList = null;
             bool isEscaping = false;
+            bool hasMultipleMatches = false;
             char c;
 
             for (int curPos = startPos; curPos <= endPos; curPos++)
@@ -117,30 +112,28 @@ namespace Discord.Commands
 
                     var typeReaderResult = await curParam.Parse(context, argString).ConfigureAwait(false);
                     if (!typeReaderResult.IsSuccess)
-                        return ParseResult.FromError(typeReaderResult);
+                    {
+                        if (typeReaderResult.Error == CommandError.MultipleMatches)
+                            hasMultipleMatches = true;
+                        else
+                            return ParseResult.FromError(typeReaderResult);
+                    }
 
                     if (curParam.IsMultiple)
                     {
-                        if (paramsList == null)
-                            paramsList = new List<object>();
-                        paramsList.Add(typeReaderResult.Value);
+                        if (paramList == null)
+                            paramList = ImmutableArray.CreateBuilder<TypeReaderResult>();
+                        paramList.Add(typeReaderResult);
 
                         if (curPos == endPos)
                         {
-                            var func = _arrayConverters.GetOrAdd(curParam.ElementType, t =>
-                            {
-                                var method = _convertArrayMethod.MakeGenericMethod(t);
-                                return (Func<List<object>, object>)method.CreateDelegate(typeof(Func<List<object>, object>));
-                            });
-                            argList.Add(func.Invoke(paramsList));
-
                             curParam = null;
                             curPart = ParserPart.None;
                         }
                     }
                     else
                     {
-                        argList.Add(typeReaderResult.Value);
+                        argList.Add(typeReaderResult);
 
                         curParam = null;
                         curPart = ParserPart.None;
@@ -154,34 +147,24 @@ namespace Discord.Commands
                 var typeReaderResult = await curParam.Parse(context, argBuilder.ToString()).ConfigureAwait(false);
                 if (!typeReaderResult.IsSuccess)
                     return ParseResult.FromError(typeReaderResult);
-                argList.Add(typeReaderResult.Value);
+                argList.Add(typeReaderResult);
             }
 
             if (isEscaping)
                 return ParseResult.FromError(CommandError.ParseFailed, "Input text may not end on an incomplete escape.");
             if (curPart == ParserPart.QuotedParameter)
                 return ParseResult.FromError(CommandError.ParseFailed, "A quoted parameter is incomplete");
-
-            if (argList.Count < command.Parameters.Count)
+            
+            //Add missing optionals
+            for (int i = paramList.Count; i < command.Parameters.Count; i++)
             {
-                for (int i = argList.Count; i < command.Parameters.Count; i++)
-                {
-                    var param = command.Parameters[i];
-                    if (!param.IsOptional)
-                        return ParseResult.FromError(CommandError.BadArgCount, "The input text has too few parameters.");
-                    argList.Add(param.DefaultValue);
-                }
+                var param = command.Parameters[i];
+                if (!param.IsOptional)
+                    return ParseResult.FromError(CommandError.BadArgCount, "The input text has too few parameters.");
+                argList.Add(TypeReaderResult.FromSuccess(param.DefaultValue));
             }
-
-            return ParseResult.FromSuccess(argList.ToImmutable());
-        }
-
-        private static T[] ConvertParamsList<T>(List<object> paramsList)
-        {
-            var array = new T[paramsList.Count];
-            for (int i = 0; i < array.Length; i++)
-                array[i] = (T)paramsList[i];
-            return array;
+            
+            return ParseResult.FromSuccess(argList.ToImmutable(), paramList?.ToImmutable());
         }
     }
 }

src/Discord.Net.Commands/CommandService.cs

@@ -40,16 +40,8 @@ namespace Discord.Commands
                 [typeof(decimal)] = new SimpleTypeReader<decimal>(),
                 [typeof(DateTime)] = new SimpleTypeReader<DateTime>(),
                 [typeof(DateTimeOffset)] = new SimpleTypeReader<DateTimeOffset>(),
-
-                //TODO: Do we want to support any other interfaces?
-
-                //[typeof(IMentionable)] = new GeneralTypeReader(),
-                //[typeof(ISnowflakeEntity)] = new GeneralTypeReader(),
-                //[typeof(IEntity<ulong>)] = new GeneralTypeReader(),
-
+                
                 [typeof(IMessage)] = new MessageTypeReader(),
-                //[typeof(IAttachment)] = new xxx(),
-                //[typeof(IEmbed)] = new xxx(),
 
                 [typeof(IChannel)] = new ChannelTypeReader<IChannel>(),
                 [typeof(IDMChannel)] = new ChannelTypeReader<IDMChannel>(),
@@ -61,10 +53,8 @@ namespace Discord.Commands
                 [typeof(IVoiceChannel)] = new ChannelTypeReader<IVoiceChannel>(),
 
                 //[typeof(IGuild)] = new GuildTypeReader<IGuild>(),
-                //[typeof(IUserGuild)] = new GuildTypeReader<IUserGuild>(),
-                //[typeof(IGuildIntegration)] = new xxx(),
 
-                [typeof(IRole)] = new RoleTypeReader(),
+                [typeof(IRole)] = new RoleTypeReader<IRole>(),
 
                 //[typeof(IInvite)] = new InviteTypeReader<IInvite>(),
                 //[typeof(IInviteMetadata)] = new InviteTypeReader<IInviteMetadata>(),
@@ -72,10 +62,6 @@ namespace Discord.Commands
                 [typeof(IUser)] = new UserTypeReader<IUser>(),
                 [typeof(IGroupUser)] = new UserTypeReader<IGroupUser>(),
                 [typeof(IGuildUser)] = new UserTypeReader<IGuildUser>(),
-                //[typeof(ISelfUser)] = new UserTypeReader<ISelfUser>(),
-                //[typeof(IPresence)] = new UserTypeReader<IPresence>(),
-                //[typeof(IVoiceState)] = new UserTypeReader<IVoiceState>(),
-                //[typeof(IConnection)] = new xxx(),
             };
         }
 
@@ -201,8 +187,9 @@ namespace Discord.Commands
                 return SearchResult.FromError(CommandError.UnknownCommand, "Unknown command.");
         }
 
-        public Task<IResult> Execute(IMessage message, int argPos) => Execute(message, message.Content.Substring(argPos));
-        public async Task<IResult> Execute(IMessage message, string input)
+        public Task<IResult> Execute(IMessage message, int argPos, MultiMatchHandling multiMatchHandling = MultiMatchHandling.Exception) 
+            => Execute(message, message.Content.Substring(argPos), multiMatchHandling);
+        public async Task<IResult> Execute(IMessage message, string input, MultiMatchHandling multiMatchHandling = MultiMatchHandling.Exception)
         {
             var searchResult = Search(message, input);
             if (!searchResult.IsSuccess)
@@ -223,14 +210,29 @@ namespace Discord.Commands
                 var parseResult = await commands[i].Parse(message, searchResult, preconditionResult);
                 if (!parseResult.IsSuccess)
                 {
-                    if (commands.Count == 1)
-                        return parseResult;
-                    else
-                        continue;
+                    if (parseResult.Error == CommandError.MultipleMatches)
+                    {
+                        TypeReaderValue[] argList, paramList;
+                        switch (multiMatchHandling)
+                        {
+                            case MultiMatchHandling.Best:
+                                argList = parseResult.ArgValues.Select(x => x.Values.OrderByDescending(y => y.Score).First()).ToArray();
+                                paramList = parseResult.ParamValues?.Select(x => x.Values.OrderByDescending(y => y.Score).First()).ToArray();
+                                parseResult = ParseResult.FromSuccess(argList, paramList);
+                                break;
+                        }
+                    }
+
+                    if (!parseResult.IsSuccess)
+                    {
+                        if (commands.Count == 1)
+                            return parseResult;
+                        else
+                            continue;
+                    }
                 }
 
-                var executeResult = await commands[i].Execute(message, parseResult);
-                return executeResult;
+                return await commands[i].Execute(message, parseResult);
             }
             
             return SearchResult.FromError(CommandError.UnknownCommand, "This input does not match any overload.");

src/Discord.Net.Commands/MultiMatchHandling.cs

@@ -0,0 +1,8 @@
+namespace Discord.Commands
+{
+    public enum MultiMatchHandling
+    {
+        Exception,
+        Best
+    }
+}

src/Discord.Net.Commands/Readers/ChannelTypeReader.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
 
@@ -9,40 +11,37 @@ namespace Discord.Commands
     {
         public override async Task<TypeReaderResult> Read(IMessage context, string input)
         {
-            IGuildChannel guildChannel = context.Channel as IGuildChannel;
-            IChannel result = null;
+            var guild = (context.Channel as IGuildChannel)?.Guild;
 
-            if (guildChannel != null)
+            if (guild != null)
             {
-                //By Id
+                var results = new Dictionary<ulong, TypeReaderValue>();
+                var channels = await guild.GetChannelsAsync().ConfigureAwait(false);
                 ulong id;
-                if (MentionUtils.TryParseChannel(input, out id) || ulong.TryParse(input, out id))
-                {
-                    var channel = await guildChannel.Guild.GetChannelAsync(id).ConfigureAwait(false);
-                    if (channel != null)
-                        result = channel;
-                }
-
-                //By Name
-                if (result == null)
-                {
-                    var channels = await guildChannel.Guild.GetChannelsAsync().ConfigureAwait(false);
-                    var filteredChannels = channels.Where(x => string.Equals(input, x.Name, StringComparison.OrdinalIgnoreCase)).ToArray();
-                    if (filteredChannels.Length > 1)
-                        return TypeReaderResult.FromError(CommandError.MultipleMatches, "Multiple channels found.");
-                    else if (filteredChannels.Length == 1)
-                        result = filteredChannels[0];
-                }
+
+                //By Mention (1.0)
+                if (MentionUtils.TryParseChannel(input, out id))
+                    AddResult(results, await guild.GetUserAsync(id).ConfigureAwait(false) as T, 1.00f);
+
+                //By Id (0.9)
+                if (ulong.TryParse(input, NumberStyles.None, CultureInfo.InvariantCulture, out id))
+                    AddResult(results, await guild.GetChannelAsync(id).ConfigureAwait(false) as T, 0.90f);
+
+                //By Name (0.7-0.8)
+                foreach (var channel in channels.Where(x => string.Equals(input, x.Name, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, channel as T, channel.Name == input ? 0.80f : 0.70f);
+
+                if (results.Count > 0)
+                    return TypeReaderResult.FromSuccess(results.Values);
             }
 
-            if (result == null)
-                return TypeReaderResult.FromError(CommandError.ObjectNotFound, "Channel not found.");
+            return TypeReaderResult.FromError(CommandError.ObjectNotFound, "Channel not found.");
+        }
 
-            T castResult = result as T;
-            if (castResult == null)
-                return TypeReaderResult.FromError(CommandError.CastFailed, $"Channel is not a {typeof(T).Name}.");
-            else
-                return TypeReaderResult.FromSuccess(castResult);
+        private void AddResult(Dictionary<ulong, TypeReaderValue> results, T channel, float score)
+        {
+            if (channel != null && !results.ContainsKey(channel.Id))
+                results.Add(channel.Id, new TypeReaderValue(channel, score));
         }
     }
 }

src/Discord.Net.Commands/Readers/EnumTypeReader.cs

@@ -52,14 +52,14 @@ namespace Discord.Commands
                 if (_enumsByValue.TryGetValue(baseValue, out enumValue))
                     return Task.FromResult(TypeReaderResult.FromSuccess(enumValue));
                 else
-                    return Task.FromResult(TypeReaderResult.FromError(CommandError.CastFailed, $"Value is not a {_enumType.Name}"));
+                    return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, $"Value is not a {_enumType.Name}"));
             }
             else
             {
                 if (_enumsByName.TryGetValue(input.ToLower(), out enumValue))
                     return Task.FromResult(TypeReaderResult.FromSuccess(enumValue));
                 else
-                    return Task.FromResult(TypeReaderResult.FromError(CommandError.CastFailed, $"Value is not a {_enumType.Name}"));
+                    return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, $"Value is not a {_enumType.Name}"));
             }
         }
     }

src/Discord.Net.Commands/Readers/MessageTypeReader.cs

@@ -7,18 +7,17 @@ namespace Discord.Commands
     {
         public override Task<TypeReaderResult> Read(IMessage context, string input)
         {
-            //By Id
             ulong id;
+
+            //By Id (1.0)
             if (ulong.TryParse(input, NumberStyles.None, CultureInfo.InvariantCulture, out id))
             {
                 var msg = context.Channel.GetCachedMessage(id);
-                if (msg == null)
-                    return Task.FromResult(TypeReaderResult.FromError(CommandError.ObjectNotFound, "Message not found."));
-                else
+                if (msg != null)
                     return Task.FromResult(TypeReaderResult.FromSuccess(msg));
             }
 
-            return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, "Failed to parse Message Id."));
+            return Task.FromResult(TypeReaderResult.FromError(CommandError.ObjectNotFound, "Message not found."));
         }
     }
 }

src/Discord.Net.Commands/Readers/RoleTypeReader.cs

@@ -1,36 +1,46 @@
 using System;
+using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
 
 namespace Discord.Commands
 {
-    internal class RoleTypeReader : TypeReader
+    internal class RoleTypeReader<T> : TypeReader
+        where T : class, IRole
     {
         public override Task<TypeReaderResult> Read(IMessage context, string input)
         {
-            IGuildChannel guildChannel = context.Channel as IGuildChannel;
+            var guild = (context.Channel as IGuildChannel)?.Guild;
+            ulong id;
 
-            if (guildChannel != null)
+            if (guild != null)
             {
-                //By Id
-                ulong id;
-                if (MentionUtils.TryParseRole(input, out id) || ulong.TryParse(input, out id))
-                {
-                    var channel = guildChannel.Guild.GetRole(id);
-                    if (channel != null)
-                        return Task.FromResult(TypeReaderResult.FromSuccess(channel));
-                }
+                var results = new Dictionary<ulong, TypeReaderValue>();
+                var roles = guild.Roles;
 
-                //By Name
-                var roles = guildChannel.Guild.Roles;
-                var filteredRoles = roles.Where(x => string.Equals(input, x.Name, StringComparison.OrdinalIgnoreCase)).ToArray();
-                if (filteredRoles.Length > 1)
-                    return Task.FromResult(TypeReaderResult.FromError(CommandError.MultipleMatches, "Multiple roles found."));
-                else if (filteredRoles.Length == 1)
-                    return Task.FromResult(TypeReaderResult.FromSuccess(filteredRoles[0]));
+                //By Mention (1.0)
+                if (MentionUtils.TryParseRole(input, out id))
+                    AddResult(results, guild.GetRole(id) as T, 1.00f);
+
+                //By Id (0.9)
+                if (ulong.TryParse(input, NumberStyles.None, CultureInfo.InvariantCulture, out id))
+                     AddResult(results, guild.GetRole(id) as T, 0.90f);
+
+                //By Name (0.7-0.8)
+                foreach (var role in roles.Where(x => string.Equals(input, x.Name, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, role as T, role.Name == input ? 0.80f : 0.70f);
+
+                if (results.Count > 0)
+                    return Task.FromResult(TypeReaderResult.FromSuccess(results));
             }
-            
             return Task.FromResult(TypeReaderResult.FromError(CommandError.ObjectNotFound, "Role not found."));
         }
+
+        private void AddResult(Dictionary<ulong, TypeReaderValue> results, T role, float score)
+        {
+            if (role != null && !results.ContainsKey(role.Id))
+                results.Add(role.Id, new TypeReaderValue(role, score));
+        }
     }
 }

src/Discord.Net.Commands/Readers/SimpleTypeReader.cs

@@ -16,8 +16,7 @@ namespace Discord.Commands
             T value;
             if (_tryParse(input, out value))
                 return Task.FromResult(TypeReaderResult.FromSuccess(value));
-            else
-                return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, $"Failed to parse {typeof(T).Name}"));
+            return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, $"Failed to parse {typeof(T).Name}"));
         }
     }
 }

src/Discord.Net.Commands/Readers/UserTypeReader.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
 
@@ -9,54 +11,78 @@ namespace Discord.Commands
     {
         public override async Task<TypeReaderResult> Read(IMessage context, string input)
         {
-            IUser result = null;
-            
-            //By Id
+            var results = new Dictionary<ulong, TypeReaderValue>();
+            var guild = (context.Channel as IGuildChannel)?.Guild;
+            IReadOnlyCollection<IUser> channelUsers = await context.Channel.GetUsersAsync().ConfigureAwait(false);
+            IReadOnlyCollection<IGuildUser> guildUsers = null;
             ulong id;
-            if (MentionUtils.TryParseUser(input, out id) || ulong.TryParse(input, out id))
+
+            if (guild != null)
+                guildUsers = await guild.GetUsersAsync().ConfigureAwait(false);
+
+            //By Mention (1.0)
+            if (MentionUtils.TryParseUser(input, out id))
             {
-                var user = await context.Channel.GetUserAsync(id).ConfigureAwait(false);
-                if (user != null)
-                    result = user;
+                if (guild != null)
+                    AddResult(results, await guild.GetUserAsync(id).ConfigureAwait(false) as T, 1.00f);
+                else
+                    AddResult(results, await context.Channel.GetUserAsync(id).ConfigureAwait(false) as T, 1.00f);
             }
 
-            //By Username + Discriminator
-            if (result == null)
+            //By Id (0.9)
+            if (ulong.TryParse(input, NumberStyles.None, CultureInfo.InvariantCulture, out id))
             {
-                int index = input.LastIndexOf('#');
-                if (index >= 0)
+                if (guild != null)
+                    AddResult(results, await guild.GetUserAsync(id).ConfigureAwait(false) as T, 0.90f);
+                else
+                    AddResult(results, await context.Channel.GetUserAsync(id).ConfigureAwait(false) as T, 0.90f);
+            }
+
+            //By Username + Discriminator (0.7-0.85)
+            int index = input.LastIndexOf('#');
+            if (index >= 0)
+            {
+                string username = input.Substring(0, index);
+                ushort discriminator;
+                if (ushort.TryParse(input.Substring(index + 1), out discriminator))
                 {
-                    string username = input.Substring(0, index);
-                    ushort discriminator;
-                    if (ushort.TryParse(input.Substring(index + 1), out discriminator))
-                    {
-                        var users = await context.Channel.GetUsersAsync().ConfigureAwait(false);
-                        result = users.Where(x =>
-                            x.DiscriminatorValue == discriminator &&
-                            string.Equals(username, x.Username, StringComparison.OrdinalIgnoreCase)).FirstOrDefault();
-                    }
+                    var channelUser = channelUsers.Where(x => x.DiscriminatorValue == discriminator &&
+                        string.Equals(username, x.Username, StringComparison.OrdinalIgnoreCase)).FirstOrDefault();
+                    AddResult(results, channelUser as T, channelUser.Username == username ? 0.85f : 0.75f);
+
+                    var guildUser = channelUsers.Where(x => x.DiscriminatorValue == discriminator &&
+                        string.Equals(username, x.Username, StringComparison.OrdinalIgnoreCase)).FirstOrDefault();
+                    AddResult(results, guildUser as T, guildUser.Username == username ? 0.80f : 0.70f);
                 }
             }
 
-            //By Username
-            if (result == null)
+            //By Username (0.5-0.6)
             {
-                var users = await context.Channel.GetUsersAsync().ConfigureAwait(false);
-                var filteredUsers = users.Where(x => string.Equals(input, x.Username, StringComparison.OrdinalIgnoreCase)).ToArray();
-                if (filteredUsers.Length > 1)
-                    return TypeReaderResult.FromError(CommandError.MultipleMatches, "Multiple users found.");
-                else if (filteredUsers.Length == 1)
-                    result = filteredUsers[0];
+                foreach (var channelUser in channelUsers.Where(x => string.Equals(input, x.Username, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, channelUser as T, channelUser.Username == input ? 0.65f : 0.55f);
+
+                foreach (var guildUser in guildUsers.Where(x => string.Equals(input, x.Username, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, guildUser as T, guildUser.Username == input ? 0.60f : 0.50f);
             }
 
-            if (result == null)
-                return TypeReaderResult.FromError(CommandError.ObjectNotFound, "User not found.");
+            //By Nickname (0.5-0.6)
+            {
+                foreach (var channelUser in channelUsers.Where(x => string.Equals(input, (x as IGuildUser).Nickname, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, channelUser as T, (channelUser as IGuildUser).Nickname == input ? 0.65f : 0.55f);
+
+                foreach (var guildUser in guildUsers.Where(x => string.Equals(input, (x as IGuildUser).Nickname, StringComparison.OrdinalIgnoreCase)))
+                    AddResult(results, guildUser as T, (guildUser as IGuildUser).Nickname == input ? 0.60f : 0.50f);
+            }
 
-            T castResult = result as T;
-            if (castResult == null)
-                return TypeReaderResult.FromError(CommandError.CastFailed, $"User is not a {typeof(T).Name}.");
-            else
-                return TypeReaderResult.FromSuccess(castResult);
+            if (results.Count > 0)
+                return TypeReaderResult.FromSuccess(results.Values.ToArray());
+            return TypeReaderResult.FromError(CommandError.ObjectNotFound, "User not found.");
+        }
+
+        private void AddResult(Dictionary<ulong, TypeReaderValue> results, T user, float score)
+        {
+            if (user != null && !results.ContainsKey(user.Id))
+                results.Add(user.Id, new TypeReaderValue(user, score));
         }
     }
 }

src/Discord.Net.Commands/Results/ParseResult.cs

@@ -6,28 +6,53 @@ namespace Discord.Commands
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
     public struct ParseResult : IResult
     {
-        public IReadOnlyList<object> Values { get; }
+        public IReadOnlyList<TypeReaderResult> ArgValues { get; }
+        public IReadOnlyList<TypeReaderResult> ParamValues { get; }
 
         public CommandError? Error { get; }
         public string ErrorReason { get; }
 
         public bool IsSuccess => !Error.HasValue;
 
-        private ParseResult(IReadOnlyList<object> values, CommandError? error, string errorReason)
+        private ParseResult(IReadOnlyList<TypeReaderResult> argValues, IReadOnlyList<TypeReaderResult> paramValue, CommandError? error, string errorReason)
         {
-            Values = values;
+            ArgValues = argValues;
+            ParamValues = paramValue;
             Error = error;
             ErrorReason = errorReason;
         }
 
-        public static ParseResult FromSuccess(IReadOnlyList<object> values)
-            => new ParseResult(values, null, null);
+        public static ParseResult FromSuccess(IReadOnlyList<TypeReaderResult> argValues, IReadOnlyList<TypeReaderResult> paramValues)
+        {
+            for (int i = 0; i < argValues.Count; i++)
+            {
+                if (argValues[i].Values.Count > 1)
+                    return new ParseResult(argValues, paramValues, CommandError.MultipleMatches, "Multiple matches found.");
+            }
+            for (int i = 0; i < paramValues.Count; i++)
+            {
+                if (paramValues[i].Values.Count > 1)
+                    return new ParseResult(argValues, paramValues, CommandError.MultipleMatches, "Multiple matches found.");
+            }
+            return new ParseResult(argValues, paramValues, null, null);
+        }
+        public static ParseResult FromSuccess(IReadOnlyList<TypeReaderValue> argValues, IReadOnlyList<TypeReaderValue> paramValues)
+        {
+            var argList = new TypeReaderResult[argValues.Count];
+            for (int i = 0; i < argValues.Count; i++)
+                argList[i] = TypeReaderResult.FromSuccess(argValues[i]);
+            var paramList = new TypeReaderResult[paramValues.Count];
+            for (int i = 0; i < paramValues.Count; i++)
+                paramList[i] = TypeReaderResult.FromSuccess(paramValues[i]);
+            return new ParseResult(argList, paramList, null, null);
+        }
+
         public static ParseResult FromError(CommandError error, string reason)
-            => new ParseResult(null, error, reason);
+            => new ParseResult(null, null, error, reason);
         public static ParseResult FromError(IResult result)
-            => new ParseResult(null, result.Error, result.ErrorReason);
+            => new ParseResult(null, null, result.Error, result.ErrorReason);
 
         public override string ToString() => IsSuccess ? "Success" : $"{Error}: {ErrorReason}";
-        private string DebuggerDisplay => IsSuccess ? $"Success ({Values.Count} Values)" : $"{Error}: {ErrorReason}";
+        private string DebuggerDisplay => IsSuccess ? $"Success ({ArgValues.Count}{(ParamValues != null ? $" +{ParamValues.Count} Values" : "")})" : $"{Error}: {ErrorReason}";
     }
 }

src/Discord.Net.Commands/Results/TypeReaderResult.cs

@@ -1,32 +1,56 @@
-using System.Diagnostics;
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Discord.Commands
 {
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
-    public struct TypeReaderResult : IResult
+    public struct TypeReaderValue
     {
         public object Value { get; }
+        public float Score { get; }
+
+        public TypeReaderValue(object value, float score)
+        {
+            Value = value;
+            Score = score;
+        }
+
+        public override string ToString() => Value?.ToString();
+        private string DebuggerDisplay => $"[{Value}, {Math.Round(Score, 2)}]";
+    }
+
+    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
+    public struct TypeReaderResult : IResult
+    {
+        public IReadOnlyCollection<TypeReaderValue> Values { get; }
 
         public CommandError? Error { get; }
         public string ErrorReason { get; }
 
         public bool IsSuccess => !Error.HasValue;
 
-        private TypeReaderResult(object value, CommandError? error, string errorReason)
+        private TypeReaderResult(IReadOnlyCollection<TypeReaderValue> values, CommandError? error, string errorReason)
         {
-            Value = value;
+            Values = values;
             Error = error;
             ErrorReason = errorReason;
         }
 
         public static TypeReaderResult FromSuccess(object value)
-            => new TypeReaderResult(value, null, null);
+            => new TypeReaderResult(ImmutableArray.Create(new TypeReaderValue(value, 1.0f)), null, null);
+        public static TypeReaderResult FromSuccess(TypeReaderValue value)
+            => new TypeReaderResult(ImmutableArray.Create(value), null, null);
+        public static TypeReaderResult FromSuccess(IReadOnlyCollection<TypeReaderValue> values)
+            => new TypeReaderResult(values, null, null);
         public static TypeReaderResult FromError(CommandError error, string reason)
             => new TypeReaderResult(null, error, reason);
         public static TypeReaderResult FromError(IResult result)
             => new TypeReaderResult(null, result.Error, result.ErrorReason);
 
         public override string ToString() => IsSuccess ? "Success" : $"{Error}: {ErrorReason}";
-        private string DebuggerDisplay => IsSuccess ? $"Success ({Value})" : $"{Error}: {ErrorReason}";
+        private string DebuggerDisplay => IsSuccess ? $"Success ({string.Join(", ", Values)})" : $"{Error}: {ErrorReason}";
     }
 }