added %img:YOUR_TAG% custom reactions placeholder to pull imgur images with that tag.

src/NadekoBot/Services/CustomReactions/Extensions.cs

@@ -1,10 +1,13 @@
-using Discord;
+using AngleSharp;
+using AngleSharp.Dom.Html;
+using Discord;
 using Discord.WebSocket;
 using NadekoBot.DataStructures;
 using NadekoBot.Extensions;
 using NadekoBot.Services.Database.Models;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
@@ -14,13 +17,7 @@ namespace NadekoBot.Services.CustomReactions
     {
         public static Dictionary<string, Func<IUserMessage, string, string>> responsePlaceholders = new Dictionary<string, Func<IUserMessage, string, string>>()
         {
-            {"%target%", (ctx, trigger) => { return ctx.Content.Substring(trigger.Length).Trim().SanitizeMentions(); } }
+            {"%target%", (ctx, trigger) => { return ctx.Content.Substring(trigger.Length).Trim().SanitizeMentions(); } },
-        };
-
-        public static Dictionary<string, Func<IUserMessage, DiscordShardedClient, string>> placeholders = new Dictionary<string, Func<IUserMessage, DiscordShardedClient, string>>()
-        {
-            {"%mention%", (ctx, client) => { return $"<@{client.CurrentUser.Id}>"; } },
-            {"%user%", (ctx, client) => { return ctx.Author.Mention; } },
             {"%rnduser%", (ctx, client) => {
                 //var ch = ctx.Channel as ITextChannel;
                 //if(ch == null)
@@ -40,15 +37,22 @@ namespace NadekoBot.Services.CustomReactions
                 //var users = g.Users.ToArray();
 
                 //return users[new NadekoRandom().Next(0, users.Length-1)].Mention;
-            } }
+            } },
+        };
+
+        public static Dictionary<string, Func<IUserMessage, DiscordShardedClient, string>> placeholders = new Dictionary<string, Func<IUserMessage, DiscordShardedClient, string>>()
+        {
+            {"%mention%", (ctx, client) => { return $"<@{client.CurrentUser.Id}>"; } },
+            {"%user%", (ctx, client) => { return ctx.Author.Mention; } },
             //{"%rng%", (ctx) => { return new NadekoRandom().Next(0,10).ToString(); } }
         };
 
         private static readonly Regex rngRegex = new Regex("%rng(?:(?<from>(?:-)?\\d+)-(?<to>(?:-)?\\d+))?%", RegexOptions.Compiled);
+        private static readonly Regex imgRegex = new Regex("%(img|image):(?<tag>.*?)%", RegexOptions.Compiled);
 
         private static readonly NadekoRandom rng = new NadekoRandom();
 
-        public static Dictionary<Regex, MatchEvaluator> regexPlaceholders = new Dictionary<Regex, MatchEvaluator>()
+        public static Dictionary<Regex, Func<Match, Task<string>>> regexPlaceholders = new Dictionary<Regex, Func<Match, Task<string>>>()
         {
             { rngRegex, (match) => {
                 int from = 0;
@@ -59,13 +63,34 @@ namespace NadekoBot.Services.CustomReactions
 
                 if(from == 0 && to == 0)
                 {
-                    return rng.Next(0, 11).ToString();
+                    return Task.FromResult(rng.Next(0, 11).ToString());
                 }
 
                 if(from >= to)
+                    return Task.FromResult(string.Empty);
+
+                return Task.FromResult(rng.Next(from,to+1).ToString());
+            } },
+            { imgRegex, async (match) => {
+                var tag = match.Groups["tag"].ToString();
+                if(string.IsNullOrWhiteSpace(tag))
                     return "";
 
-                return rng.Next(from,to+1).ToString();
+                var fullQueryLink = $"http://imgur.com/search?q={ tag }";
+                var config = Configuration.Default.WithDefaultLoader();
+                var document = await BrowsingContext.New(config).OpenAsync(fullQueryLink);
+
+                var elems = document.QuerySelectorAll("a.image-list-link").ToArray();
+
+                if (!elems.Any())
+                    return "";
+
+                var img = (elems.ElementAtOrDefault(new NadekoRandom().Next(0, elems.Length))?.Children?.FirstOrDefault() as IHtmlImageElement);
+
+                if (img?.Source == null)
+                    return "";
+
+                return " "+img.Source.Replace("b.", ".") + " ";
             } }
         };
 
@@ -73,26 +98,31 @@ namespace NadekoBot.Services.CustomReactions
         {
             foreach (var ph in placeholders)
             {
-                str = str.ToLowerInvariant().Replace(ph.Key, ph.Value(ctx, client));
+                if (str.Contains(ph.Key))
+                    str = str.ToLowerInvariant().Replace(ph.Key, ph.Value(ctx, client));
             }
             return str;
         }
 
-        private static string ResolveResponseString(this string str, IUserMessage ctx, DiscordShardedClient client, string resolvedTrigger)
+        private static async Task<string> ResolveResponseStringAsync(this string str, IUserMessage ctx, DiscordShardedClient client, string resolvedTrigger)
         {
             foreach (var ph in placeholders)
             {
-                str = str.Replace(ph.Key.ToLowerInvariant(), ph.Value(ctx, client));
+                var lowerKey = ph.Key.ToLowerInvariant();
+                if (str.Contains(lowerKey))
+                    str = str.Replace(lowerKey, ph.Value(ctx, client));
             }
 
             foreach (var ph in responsePlaceholders)
             {
-                str = str.Replace(ph.Key.ToLowerInvariant(), ph.Value(ctx, resolvedTrigger));
+                var lowerKey = ph.Key.ToLowerInvariant();
+                if (str.Contains(lowerKey))
+                    str = str.Replace(lowerKey, ph.Value(ctx, resolvedTrigger));
             }
 
             foreach (var ph in regexPlaceholders)
             {
-                str = ph.Key.Replace(str, ph.Value);
+                str = await ph.Key.ReplaceAsync(str, ph.Value);
             }
             return str;
         }
@@ -100,8 +130,8 @@ namespace NadekoBot.Services.CustomReactions
         public static string TriggerWithContext(this CustomReaction cr, IUserMessage ctx, DiscordShardedClient client)
             => cr.Trigger.ResolveTriggerString(ctx, client);
 
-        public static string ResponseWithContext(this CustomReaction cr, IUserMessage ctx, DiscordShardedClient client)
+        public static Task<string > ResponseWithContextAsync(this CustomReaction cr, IUserMessage ctx, DiscordShardedClient client)
-            => cr.Response.ResolveResponseString(ctx, client, cr.Trigger.ResolveTriggerString(ctx, client));
+            => cr.Response.ResolveResponseStringAsync(ctx, client, cr.Trigger.ResolveTriggerString(ctx, client));
 
         public static async Task<IUserMessage> Send(this CustomReaction cr, IUserMessage context, DiscordShardedClient client, CustomReactionsService crs)
         {
@@ -113,7 +143,7 @@ namespace NadekoBot.Services.CustomReactions
             {
                 return await channel.EmbedAsync(crembed.ToEmbed(), crembed.PlainText ?? "");
             }
-            return await channel.SendMessageAsync(cr.ResponseWithContext(context, client).SanitizeMentions());
+            return await channel.SendMessageAsync((await cr.ResponseWithContextAsync(context, client)).SanitizeMentions());
         }
     }
 }

src/NadekoBot/_Extensions/Extensions.cs

@@ -11,6 +11,7 @@ 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;
 
@@ -18,6 +19,23 @@ namespace NadekoBot.Extensions
 {
     public static class Extensions
     {
+        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)