Added RelativeDirection for DownloadMessages

src/Discord.Net/API/Endpoints.cs

@@ -16,8 +16,8 @@
 		public static string ChannelInvites(string channelId) => $"channels/{channelId}/invites";
 		public static string ChannelMessages(string channelId) => $"channels/{channelId}/messages";
 		public static string ChannelMessages(string channelId, int limit) => $"channels/{channelId}/messages?limit={limit}";
-		public static string ChannelMessages(string channelId, int limit, string beforeId) => $"channels/{channelId}/messages?limit={limit}&before={beforeId}";
-		public static string ChannelMessage(string channelId, string msgId) => $"channels/{channelId}/messages/{msgId}";
+		public static string ChannelMessages(string channelId, int limit, string relativeId, string relativeDir) => $"channels/{channelId}/messages?limit={limit}&{relativeDir}={relativeId}";
+        public static string ChannelMessage(string channelId, string msgId) => $"channels/{channelId}/messages/{msgId}";
 		public static string ChannelMessageAck(string channelId, string msgId) => $"channels/{channelId}/messages/{msgId}/ack";
         public static string ChannelPermission(string channelId, string userOrRoleId) => $"channels/{channelId}/permissions/{userOrRoleId}";
 		public static string ChannelTyping(string channelId) => $"channels/{channelId}/typing";

src/Discord.Net/DiscordAPIClient.cs

@@ -1,5 +1,4 @@
 using Discord.API;
-using Discord.Net;
 using Discord.Net.Rest;
 using System;
 using System.Collections.Generic;
@@ -9,6 +8,8 @@ using System.Threading.Tasks;
 
 namespace Discord
 {
+	public enum RelativeDirection { Before, After }
+
 	/// <summary> A lightweight wrapper around the Discord API. </summary>
 	public class DiscordAPIClient
 	{
@@ -92,12 +93,12 @@ namespace Discord
 			var request = new ReorderChannelsRequest(channels);
 			return _rest.Patch(Endpoints.ServerChannels(serverId), request);
 		}
-		public Task<GetMessagesResponse> GetMessages(string channelId, int count, string beforeMessageId = null)
+		public Task<GetMessagesResponse> GetMessages(string channelId, int count, string relativeMessageId = null, RelativeDirection relativeDir = RelativeDirection.Before)
 		{
 			if (channelId == null) throw new ArgumentNullException(nameof(channelId));
 
-			if (beforeMessageId != null)
-				return _rest.Get<GetMessagesResponse>(Endpoints.ChannelMessages(channelId, count, beforeMessageId));
+			if (relativeMessageId != null)
+				return _rest.Get<GetMessagesResponse>(Endpoints.ChannelMessages(channelId, count, relativeMessageId, relativeDir == RelativeDirection.Before ? "before" : "after"));
 			else
 				return _rest.Get<GetMessagesResponse>(Endpoints.ChannelMessages(channelId, count));
 		}

src/Discord.Net/DiscordClient.Messages.cs

@@ -215,8 +215,9 @@ namespace Discord
 			catch (HttpException ex) when (ex.StatusCode == HttpStatusCode.NotFound) { }
 		}
 
-		/// <summary> Downloads last count messages from the server, starting at beforeMessageId if it's provided. </summary>
-		public async Task<Message[]> DownloadMessages(Channel channel, int count, string beforeMessageId = null, bool cache = true)
+
+		/// <summary> Downloads last count messages from the server, returning all messages before or after relativeMessageId, if it's provided. </summary>
+		public async Task<Message[]> DownloadMessages(Channel channel, int count, string relativeMessageId = null, RelativeDirection relativeDir = RelativeDirection.Before, bool cache = true)
 		{
 			if (channel == null) throw new ArgumentNullException(nameof(channel));
 			if (count < 0) throw new ArgumentNullException(nameof(count));
@@ -227,8 +228,8 @@ namespace Discord
 			{
 				try
 				{
-					var msgs = await _api.GetMessages(channel.Id, count, beforeMessageId).ConfigureAwait(false);
-					return msgs.Select(x =>
+					var msgs = await _api.GetMessages(channel.Id, count, relativeMessageId, relativeDir).ConfigureAwait(false);
+                    var result = msgs.Select(x =>
 					{
 						Message msg = null;
 						if (cache)