Add project files.

Database/schema_v1.sql

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+-- This file is a part of Music Turret project.
+-- 
+-- Copyright 2018 Emzi0767
+-- 
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+-- 
+-- http://www.apache.org/licenses/LICENSE-2.0
+-- 
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+-- 
+-- ----------------------------------------------------------------------------
+-- 
+-- Turret's PostgreSQL database schema
+-- 
+-- Version:                  1
+-- Bot version:              v1.0.0
+-- Timestamp:                2018-07-20 08:24 +02:00
+-- Author:                   Emzi0767
+-- Project:                  Music Turret
+-- License:                  Apache License 2.0
+-- PostgreSQL version:       9.6 or above
+-- 
+-- ----------------------------------------------------------------------------
+-- 
+-- Types
+
+-- entity_type
+-- Determines entity type of the attached ID.
+create type entity_kind as enum('user', 'channel', 'guild');
+
+-- ----------------------------------------------------------------------------
+-- 
+-- Tables
+
+-- metadata
+-- This table holds a key-value pairs, which hold various metadata about the 
+-- database schema. This table is pre-populated.
+create table metadata(
+  meta_key text not null,
+  meta_value text not null,
+  primary key(meta_key)
+);
+insert into metadata(meta_key, meta_value) values
+  ('schema_version', '1'),
+  ('timestamp', '2018-07-20T08:24+02:00'),
+  ('author', 'Emzi0767'),
+  ('project', 'Music Turret'),
+  ('license', 'Apache License 2.0');
+
+-- prefixes
+-- Holds information about prefixes set in various guilds and channels.
+create table prefixes(
+  guild_id bigint, -- snowflake
+  prefixes text[] not null,
+  enable_default boolean not null default true,
+  primary key(guild_id)
+);
+
+-- blocked_entities
+-- Holds information about blocked users, channels, and guilds, along with 
+-- information about block reason.
+create table blocked_entities(
+  id bigint not null, -- snowflake
+  kind entity_kind not null,
+  reason text,
+  since timestamp with time zone not null,
+  primary key(id, kind)
+);

Emzi0767.MusicTurret.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.27703.2035
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Emzi0767.MusicTurret", "Emzi0767.MusicTurret\Emzi0767.MusicTurret.csproj", "{9040B8E2-057E-40CF-949D-9F7D9D0BEA04}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{E1AE4D00-A5E7-4BDB-A427-C20AA0D16B30}"
+	ProjectSection(SolutionItems) = preProject
+		license.txt = license.txt
+		notice.txt = notice.txt
+		readme.md = readme.md
+	EndProjectSection
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Database", "Database", "{FBF4A86B-4C48-48A4-B94A-EC436D0600B8}"
+	ProjectSection(SolutionItems) = preProject
+		Database\schema_v1.sql = Database\schema_v1.sql
+	EndProjectSection
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Scripts", "Scripts", "{06C9B896-03DC-456F-81F5-43329B7A018A}"
+	ProjectSection(SolutionItems) = preProject
+		Scripts\bot.sh = Scripts\bot.sh
+		Scripts\lavalink.sh = Scripts\lavalink.sh
+	EndProjectSection
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{9040B8E2-057E-40CF-949D-9F7D9D0BEA04}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9040B8E2-057E-40CF-949D-9F7D9D0BEA04}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9040B8E2-057E-40CF-949D-9F7D9D0BEA04}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9040B8E2-057E-40CF-949D-9F7D9D0BEA04}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {0B23A7AB-E37F-46FE-8B40-F931EAE40A02}
+	EndGlobalSection
+EndGlobal

Emzi0767.MusicTurret/.gitignore

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+config.json

Emzi0767.MusicTurret/AsyncExecutor.cs

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+// This file is a part of Music Turret project.
+// 
+// Copyright 2018 Emzi0767
+// 
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Emzi0767.MusicTurret
+{
+    /// <summary>
+    /// Provides a simplified way of executing asynchronous code synchronously.
+    /// </summary>
+    public class AsyncExecutor
+    {
+        // this is used to wait for tasks to finish executing.
+        private SemaphoreSlim Semaphore { get; }
+
+        /// <summary>
+        /// Creates a new instance of asynchronous executor.
+        /// </summary>
+        public AsyncExecutor()
+        {
+            this.Semaphore = new SemaphoreSlim(1, 1);
+        }
+
+        /// <summary>
+        /// Executes a specified task in an asynchronous manner, waiting for its completion.
+        /// </summary>
+        /// <param name="task">Task to execute.</param>
+        public void Execute(Task task)
+        {
+            // wait for execution slot
+            this.Semaphore.Wait();
+
+            // this is used to capture task execution exception
+            Exception taskex = null;
+
+            // queue a task and wait for it to finish executing
+            var are = new AutoResetEvent(false);
+            _ = Task.Run(Executor);
+            are.WaitOne();
+
+            // release execution slot
+            this.Semaphore.Release();
+
+            // check for and rethrow any exceptions
+            if (taskex != null)
+                throw new Exception("Exception occured while executing asynchronous code.", taskex);
+
+            // executor method
+            async Task Executor()
+            {
+                try
+                {
+                    // try and execute the supplied task
+                    await task;
+                }
+                catch (Exception ex)
+                {
+                    // capture any exceptions
+                    taskex = ex;
+                }
+
+                // signal that the execution is done
+                are.Set();
+            }
+        }
+
+        /// <summary>
+        /// Executes a specified task in an asynchronous manner, waiting for its completion, and returning the result.
+        /// </summary>
+        /// <typeparam name="T">Type of the Task's return value.</typeparam>
+        /// <param name="task">Task to execute.</param>
+        /// <returns>Task's result.</returns>
+        public T Execute<T>(Task<T> task)
+        {
+            // wait for execution slot
+            this.Semaphore.Wait();
+
+            // this is used to capture task execution exception and result
+            Exception taskex = null;
+            T result = default;
+
+            // queue a task and wait for it to finish executing
+            var are = new AutoResetEvent(false);
+            _ = Task.Run(Executor);
+            are.WaitOne();
+
+            // release execution slot
+            this.Semaphore.Release();
+
+            // check for and rethrow any exceptions
+            if (taskex != null)
+                throw new Exception("Exception occured while executing asynchronous code.", taskex);
+
+            // return the execution result
+            return result;
+
+            // executor method
+            async Task Executor()
+            {
+                try
+                {
+                    // try and execute the supplied task
+                    result = await task;
+                }
+                catch (Exception ex)
+                {
+                    // capture any exceptions
+                    taskex = ex;
+                }
+
+                // signal that the execution is done
+                are.Set();
+            }
+        }
+    }
+}

Emzi0767.MusicTurret/Attributes/NotBlockedAttribute.cs

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+// This file is a part of Music Turret project.
+// 
+// Copyright 2018 Emzi0767
+// 
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System.Linq;
+using System.Threading.Tasks;
+using DSharpPlus.CommandsNext;
+using DSharpPlus.CommandsNext.Attributes;
+using Emzi0767.MusicTurret.Data;
+using Emzi0767.MusicTurret.Services;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Emzi0767.MusicTurret.Attributes
+{
+    /// <summary>
+    /// Verifies that the user is not blocked for the purpose of the command usage.
+    /// </summary>
+    public sealed class NotBlockedAttribute : CheckBaseAttribute
+    {
+        public override Task<bool> ExecuteCheckAsync(CommandContext ctx, bool help)
+        {
+            if (ctx.Guild == null)
+                return Task.FromResult(false);
+
+            if (help)
+                return Task.FromResult(true);
+
+            if (ctx.User == ctx.Client.CurrentApplication.Owner)
+                return Task.FromResult(true);
+
+            var uid = (long)ctx.User.Id;
+            var cid = (long)ctx.Channel.Id;
+            var gid = (long)ctx.Guild.Id;
+
+            var db = ctx.Services.GetService<DatabaseContext>();
+            var blocked = db.BlockedEntities.Any(x => (x.Id == uid && x.Kind == DatabaseEntityKind.User) || (x.Id == cid && x.Kind == DatabaseEntityKind.Channel) || (x.Id == gid && x.Kind == DatabaseEntityKind.Channel));
+            return Task.FromResult(blocked);
+        }
+    }
+}

Emzi0767.MusicTurret/Data/DatabaseBlockedEntity.cs

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+// This file is a part of Music Turret project.
+// 
+// Copyright 2018 Emzi0767
+// 
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Emzi0767.MusicTurret.Data
+{
+    /// <summary>
+    /// Represents a collection of entities blocked from using the bot.
+    /// </summary>
+    [Table("blocked_entities")]
+    public partial class DatabaseBlockedEntity
+    {
+        /// <summary>
+        /// Gets or sets the entity's ID.
+        /// </summary>
+        [Column("id")]
+        public long Id { get; set; }
+
+        /// <summary>
+        /// Gets or sets the entity's kind.
+        /// </summary>
+        [Column("kind")]
+        public DatabaseEntityKind Kind { get; set; }
+
+        /// <summary>
+        /// Gets or sets the reason why the entity was blocked.
+        /// </summary>
+        [Column("reason")]
+        public string Reason { get; set; }
+
+        /// <summary>
+        /// Gets or sets when the entity was blocked.
+        /// </summary>
+        [Column("since", TypeName = "timestamp with time zone")]
+        public DateTime Since { get; set; }
+    }
+}

Emzi0767.MusicTurret/Data/DatabaseEntityKind.cs

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+// This file is a part of Music Turret project.
+// 
+// Copyright 2018 Emzi0767
+// 
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+// http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+namespace Emzi0767.MusicTurret.Data
+{
+    /// <summary>
+    /// Represents kind of an entity with associated ID.
+    /// </summary>
+    public enum DatabaseEntityKind
+    {
+        /// <summary>
+        /// Defines that the entity is a user.
+        /// </summary>
+        User,
+
+        /// <summary>
+        /// Defines that the entity is a channel.
+        /// </summary>
+        Channel,
+
+        /// <summary>
+        /// Defines that the entity is a guild.
+        /// </summary>
+        Guild
+    }
+}