Implemented emoji endpoints (#835)

* Implemented emoji endpoints.

* Fixed: now using API entities for REST client.

* Removed emoji listing endpoint, as per @foxbot's request.

src/Discord.Net.Core/Entities/Emotes/EmoteProperties.cs

@@ -0,0 +1,10 @@
+using System.Collections.Generic;
+
+namespace Discord
+{
+    public class EmoteProperties
+    {
+        public Optional<string> Name { get; set; }
+        public Optional<IEnumerable<IRole>> Roles { get; set; }
+    }
+}

src/Discord.Net.Core/Entities/Guilds/IGuild.cs

@@ -117,5 +117,14 @@ namespace Discord
         Task DownloadUsersAsync();
         /// <summary> Removes all users from this guild if they have not logged on in a provided number of days or, if simulate is true, returns the number of users that would be removed. </summary>
         Task<int> PruneUsersAsync(int days = 30, bool simulate = false, RequestOptions options = null);
+
+        /// <summary> Gets a specific emote from this guild. </summary>
+        Task<GuildEmote> GetEmoteAsync(ulong id, RequestOptions options = null);
+        /// <summary> Creates a new emote in this guild. </summary>
+        Task<GuildEmote> CreateEmoteAsync(string name, Image image, Optional<IEnumerable<IRole>> roles = default(Optional<IEnumerable<IRole>>), RequestOptions options = null);
+        /// <summary> Modifies an existing emote in this guild. </summary>
+        Task<GuildEmote> ModifyEmoteAsync(GuildEmote emote, Action<EmoteProperties> func, RequestOptions options = null);
+        /// <summary> Deletes an existing emote from this guild. </summary>
+        Task DeleteEmoteAsync(GuildEmote emote, RequestOptions options = null);
     }
 }

src/Discord.Net.Rest/API/Rest/CreateGuildEmoteParams.cs

@@ -0,0 +1,16 @@
+#pragma warning disable CS1591
+using Newtonsoft.Json;
+
+namespace Discord.API.Rest
+{
+    [JsonObject(MemberSerialization = MemberSerialization.OptIn)]
+    internal class CreateGuildEmoteParams
+    {
+        [JsonProperty("name")]
+        public string Name { get; set; }
+        [JsonProperty("image")]
+        public Image Image { get; set; }
+        [JsonProperty("roles")]
+        public Optional<ulong[]> RoleIds { get; set; }
+    }
+}

src/Discord.Net.Rest/API/Rest/ModifyGuildEmoteParams.cs

@@ -0,0 +1,14 @@
+#pragma warning disable CS1591
+using Newtonsoft.Json;
+
+namespace Discord.API.Rest
+{
+    [JsonObject(MemberSerialization = MemberSerialization.OptIn)]
+    internal class ModifyGuildEmoteParams
+    {
+        [JsonProperty("name")]
+        public Optional<string> Name { get; set; }
+        [JsonProperty("roles")]
+        public Optional<ulong[]> RoleIds { get; set; }
+    }
+}

src/Discord.Net.Rest/DiscordRestApiClient.cs

@@ -1066,6 +1066,50 @@ namespace Discord.API
             return await SendJsonAsync<IReadOnlyCollection<Role>>("PATCH", () => $"guilds/{guildId}/roles", args, ids, options: options).ConfigureAwait(false);
         }
 
+        //Guild emoji
+        public async Task<Emoji> GetGuildEmoteAsync(ulong guildId, ulong emoteId, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(guildId, 0, nameof(guildId));
+            Preconditions.NotEqual(emoteId, 0, nameof(emoteId));
+            options = RequestOptions.CreateOrClone(options);
+
+            var ids = new BucketIds(guildId: guildId);
+            return await SendAsync<Emoji>("GET", () => $"guilds/{guildId}/emojis/{emoteId}", ids, options: options);
+        }
+
+        public async Task<Emoji> CreateGuildEmoteAsync(ulong guildId, Rest.CreateGuildEmoteParams args, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(guildId, 0, nameof(guildId));
+            Preconditions.NotNull(args, nameof(args));
+            Preconditions.NotNullOrWhitespace(args.Name, nameof(args.Name));
+            Preconditions.NotNull(args.Image.Stream, nameof(args.Image));
+            options = RequestOptions.CreateOrClone(options);
+
+            var ids = new BucketIds(guildId: guildId);
+            return await SendJsonAsync<Emoji>("POST", () => $"guilds/{guildId}/emojis", args, ids, options: options);
+        }
+
+        public async Task<Emoji> ModifyGuildEmoteAsync(ulong guildId, ulong emoteId, ModifyGuildEmoteParams args, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(guildId, 0, nameof(guildId));
+            Preconditions.NotEqual(emoteId, 0, nameof(emoteId));
+            Preconditions.NotNull(args, nameof(args));
+            options = RequestOptions.CreateOrClone(options);
+
+            var ids = new BucketIds(guildId: guildId);
+            return await SendJsonAsync<Emoji>("PATCH", () => $"guilds/{guildId}/emojis/{emoteId}", args, ids, options: options);
+        }
+
+        public async Task DeleteGuildEmoteAsync(ulong guildId, ulong emoteId, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(guildId, 0, nameof(guildId));
+            Preconditions.NotEqual(emoteId, 0, nameof(emoteId));
+            options = RequestOptions.CreateOrClone(options);
+
+            var ids = new BucketIds(guildId: guildId);
+            await SendAsync("DELETE", () => $"guilds/{guildId}/emojis/{emoteId}", ids, options: options);
+        }
+
         //Users
         public async Task<User> GetUserAsync(ulong userId, RequestOptions options = null)
         {

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -253,5 +253,46 @@ namespace Discord.Rest
                 model = await client.ApiClient.BeginGuildPruneAsync(guild.Id, args, options).ConfigureAwait(false);
             return model.Pruned;
         }
+
+        //Emotes
+        public static async Task<GuildEmote> GetEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, RequestOptions options)
+        {
+            var emote = await client.ApiClient.GetGuildEmoteAsync(guild.Id, id, options);
+            return emote.ToEntity();
+        }
+        public static async Task<GuildEmote> CreateEmoteAsync(IGuild guild, BaseDiscordClient client, string name, Image image, Optional<IEnumerable<IRole>> roles, 
+            RequestOptions options)
+        {
+            var apiargs = new CreateGuildEmoteParams
+            {
+                Name = name,
+                Image = image.ToModel()
+            };
+            if (roles.IsSpecified)
+                apiargs.RoleIds = roles.Value?.Select(xr => xr.Id)?.ToArray();
+
+            var emote = await client.ApiClient.CreateGuildEmoteAsync(guild.Id, apiargs, options);
+            return emote.ToEntity();
+        }
+        public static async Task<GuildEmote> ModifyEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, Action<EmoteProperties> func, 
+            RequestOptions options)
+        {
+            if (func == null) throw new ArgumentNullException(nameof(func));
+
+            var props = new EmoteProperties();
+            func(props);
+
+            var apiargs = new ModifyGuildEmoteParams
+            {
+                Name = props.Name
+            };
+            if (props.Roles.IsSpecified)
+                apiargs.RoleIds = props.Roles.Value?.Select(xr => xr.Id)?.ToArray();
+
+            var emote = await client.ApiClient.ModifyGuildEmoteAsync(guild.Id, id, apiargs, options);
+            return emote.ToEntity();
+        }
+        public static Task DeleteEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, RequestOptions options) 
+            => client.ApiClient.DeleteGuildEmoteAsync(guild.Id, id, options);
     }
 }

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -260,6 +260,16 @@ namespace Discord.Rest
         public override string ToString() => Name;
         private string DebuggerDisplay => $"{Name} ({Id})";
 
+        //Emotes
+        public Task<GuildEmote> GetEmoteAsync(ulong id, RequestOptions options = null)
+            => GuildHelper.GetEmoteAsync(this, Discord, id, options);
+        public Task<GuildEmote> CreateEmoteAsync(string name, Image image, Optional<IEnumerable<IRole>> roles = default(Optional<IEnumerable<IRole>>), RequestOptions options = null)
+            => GuildHelper.CreateEmoteAsync(this, Discord, name, image, roles, options);
+        public Task<GuildEmote> ModifyEmoteAsync(GuildEmote emote, Action<EmoteProperties> func, RequestOptions options = null)
+            => GuildHelper.ModifyEmoteAsync(this, Discord, emote.Id, func, options);
+        public Task DeleteEmoteAsync(GuildEmote emote, RequestOptions options = null)
+            => GuildHelper.DeleteEmoteAsync(this, Discord, emote.Id, options);
+
         //IGuild
         bool IGuild.Available => Available;
         IAudioClient IGuild.AudioClient => null;

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -433,6 +433,16 @@ namespace Discord.WebSocket
             _downloaderPromise.TrySetResultAsync(true);
         }
 
+        //Emotes
+        public Task<GuildEmote> GetEmoteAsync(ulong id, RequestOptions options = null)
+            => GuildHelper.GetEmoteAsync(this, Discord, id, options);
+        public Task<GuildEmote> CreateEmoteAsync(string name, Image image, Optional<IEnumerable<IRole>> roles = default(Optional<IEnumerable<IRole>>), RequestOptions options = null)
+            => GuildHelper.CreateEmoteAsync(this, Discord, name, image, roles, options);
+        public Task<GuildEmote> ModifyEmoteAsync(GuildEmote emote, Action<EmoteProperties> func, RequestOptions options = null)
+            => GuildHelper.ModifyEmoteAsync(this, Discord, emote.Id, func, options);
+        public Task DeleteEmoteAsync(GuildEmote emote, RequestOptions options = null)
+            => GuildHelper.DeleteEmoteAsync(this, Discord, emote.Id, options);
+
         //Voice States
         internal async Task<SocketVoiceState> AddOrUpdateVoiceStateAsync(ClientState state, VoiceStateModel model)
         {