NadekoBot/NadekoBot.Core/_Extensions/Extensions.cs

using Discord;
using Discord.Commands;
using Discord.WebSocket;
using ImageSharp;
using Newtonsoft.Json;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using NadekoBot.Common.Collections;
using SixLabors.Primitives;
using NadekoBot.Common;
using NadekoBot.Services;

namespace NadekoBot.Extensions
{
    public static class Extensions
    {
        public static string RedisKey(this IBotCredentials bc)
        {
            return bc.Token.Substring(0, 10);
        }

        public static async Task<string> ReplaceAsync(this Regex regex, string input, Func<Match, Task<string>> replacementFn)
        {
            var sb = new StringBuilder();
            var lastIndex = 0;

            foreach (Match match in regex.Matches(input))
            {
                sb.Append(input, lastIndex, match.Index - lastIndex)
                  .Append(await replacementFn(match).ConfigureAwait(false));

                lastIndex = match.Index + match.Length;
            }

            sb.Append(input, lastIndex, input.Length - lastIndex);
            return sb.ToString();
        }

        public static void ThrowIfNull<T>(this T obj, string name) where T : class
        {
            if (obj == null)
                throw new ArgumentNullException(nameof(name));
        }

        public static ConcurrentDictionary<TKey, TValue> ToConcurrent<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> dict)
            => new ConcurrentDictionary<TKey, TValue>(dict);

        public static bool IsAuthor(this IMessage msg, IDiscordClient client) =>
            msg.Author?.Id == client.CurrentUser.Id;

        public static string RealSummary(this CommandInfo cmd, string prefix) => string.Format(cmd.Summary, prefix);
        public static string RealRemarks(this CommandInfo cmd, string prefix) => string.Format(cmd.Remarks, prefix);

        public static EmbedBuilder AddPaginatedFooter(this EmbedBuilder embed, int curPage, int? lastPage)
        {
            if (lastPage != null)
                return embed.WithFooter(efb => efb.WithText($"{curPage + 1} / {lastPage + 1}"));
            else
                return embed.WithFooter(efb => efb.WithText(curPage.ToString()));
        }

        public static EmbedBuilder WithOkColor(this EmbedBuilder eb) =>
            eb.WithColor(NadekoBot.OkColor);

        public static EmbedBuilder WithErrorColor(this EmbedBuilder eb) =>
            eb.WithColor(NadekoBot.ErrorColor);

        public static ReactionEventWrapper OnReaction(this IUserMessage msg, DiscordSocketClient client, Action<SocketReaction> reactionAdded, Action<SocketReaction> reactionRemoved = null)
        {
            if (reactionRemoved == null)
                reactionRemoved = delegate { };

            var wrap = new ReactionEventWrapper(client, msg);
            wrap.OnReactionAdded += (r) => { var _ = Task.Run(() => reactionAdded(r)); };
            wrap.OnReactionRemoved += (r) => { var _ = Task.Run(() => reactionRemoved(r)); };
            return wrap;
        }

        public static void AddFakeHeaders(this HttpClient http)
        {
            http.DefaultRequestHeaders.Clear();
            http.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.202 Safari/535.1");
            http.DefaultRequestHeaders.Add("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
        }

        public static IMessage DeleteAfter(this IUserMessage msg, int seconds)
        {
            Task.Run(async () =>
            {
                await Task.Delay(seconds * 1000);
                try { await msg.DeleteAsync().ConfigureAwait(false); }
                catch { }
            });
            return msg;
        }

        public static ModuleInfo GetTopLevelModule(this ModuleInfo module)
        {
            while (module.Parent != null)
            {
                module = module.Parent;
            }
            return module;
        }

        //public static async Task<IEnumerable<IGuildUser>> MentionedUsers(this IUserMessage msg) =>


        public static void AddRange<T>(this HashSet<T> target, IEnumerable<T> elements) where T : class
        {
            foreach (var item in elements)
            {
                target.Add(item);
            }
        }

        public static void AddRange<T>(this ConcurrentHashSet<T> target, IEnumerable<T> elements) where T : class
        {
            foreach (var item in elements)
            {
                target.Add(item);
            }
        }

        public static double UnixTimestamp(this DateTime dt) => dt.ToUniversalTime().Subtract(new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds;

        public static async Task<IEnumerable<IGuildUser>> GetMembersAsync(this IRole role) =>
            (await role.Guild.GetUsersAsync(CacheMode.CacheOnly)).Where(u => u.RoleIds.Contains(role.Id)) ?? Enumerable.Empty<IGuildUser>();
        
        public static string ToJson<T>(this T any, Formatting formatting = Formatting.Indented) =>
            JsonConvert.SerializeObject(any, formatting);

        public static MemoryStream ToStream(this ImageSharp.Image<Rgba32> img)
        {
            var imageStream = new MemoryStream();
            img.SaveAsPng(imageStream, new ImageSharp.Formats.PngEncoder() { CompressionLevel = 9});
            imageStream.Position = 0;
            return imageStream;
        }

        /// <summary>
        /// returns an IEnumerable with randomized element order
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> items)
        {
            // Thanks to @Joe4Evr for finding a bug in the old version of the shuffle
            using (var provider = RandomNumberGenerator.Create())
            {
                var list = items.ToList();
                var n = list.Count;
                while (n > 1)
                {
                    var box = new byte[(n / Byte.MaxValue) + 1];
                    int boxSum;
                    do
                    {
                        provider.GetBytes(box);
                        boxSum = box.Sum(b => b);
                    }
                    while (!(boxSum < n * ((Byte.MaxValue * box.Length) / n)));
                    var k = (boxSum % n);
                    n--;
                    var value = list[k];
                    list[k] = list[n];
                    list[n] = value;
                }
                return list;
            }
        }

        public static IEnumerable<T> ForEach<T>(this IEnumerable<T> elems, Action<T> exec)
        {
            foreach (var elem in elems)
            {
                exec(elem);
            }
            return elems;
        }

        public static Stream ToStream(this IEnumerable<byte> bytes, bool canWrite = false)
        {
            var ms = new MemoryStream(bytes as byte[] ?? bytes.ToArray(), canWrite);
            ms.Seek(0, SeekOrigin.Begin);
            return ms;
        }

        public static IEnumerable<IRole> GetRoles(this IGuildUser user) =>
            user.RoleIds.Select(r => user.Guild.GetRole(r)).Where(r => r != null);

        public static async Task<IMessage> SendMessageToOwnerAsync(this IGuild guild, string message)
        {
            var ownerPrivate = await (await guild.GetOwnerAsync().ConfigureAwait(false)).GetOrCreateDMChannelAsync()
                                .ConfigureAwait(false);

            return await ownerPrivate.SendMessageAsync(message).ConfigureAwait(false);
        }

        public static Image<Rgba32> Merge(this IEnumerable<Image<Rgba32>> images)
        {
            var imgs = images.ToArray();

            var canvas = new Image<Rgba32>(imgs.Sum(img => img.Width), imgs.Max(img => img.Height));

            var xOffset = 0;
            for (int i = 0; i < imgs.Length; i++)
            {
                canvas.DrawImage(imgs[i], 100, default, new Point(xOffset, 0));
                xOffset += imgs[i].Bounds.Width;
            }

            return canvas;
        }
    }
}