backport of public nsfw module

src/NadekoBot/Modules/Nsfw/Common/Downloaders/DerpibooruImageDownloader.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Net.Http.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using NadekoBot.Extensions;
+
+namespace NadekoBot.Modules.Nsfw.Common
+{
+    public class DerpibooruImageDownloader : ImageDownloader<DerpiImageObject>
+    {
+        public DerpibooruImageDownloader(HttpClient http) : base(Booru.Derpibooru, http)
+        {
+        }
+
+        public override async Task<List<DerpiImageObject>> DownloadImagesAsync(string[] tags, int page, bool isExplicit = false, CancellationToken cancel = default)
+        {
+            var tagString = ImageDownloaderHelper.GetTagString(tags, isExplicit);
+            var uri = $"https://www.derpibooru.org/api/v1/json/search/images?q={tagString.Replace('+', ',')}&per_page=49&page={page}";
+            using var req = new HttpRequestMessage(HttpMethod.Get, uri);
+            req.Headers.AddFakeHeaders();
+            using var res = await _http.SendAsync(req, cancel).ConfigureAwait(false);
+            res.EnsureSuccessStatusCode();
+            
+            var container = await res.Content.ReadFromJsonAsync<DerpiContainer>(_serializerOptions, cancel).ConfigureAwait(false);
+            if (container?.Images is null)
+                return new();
+            
+            return container.Images
+                .Where(x => !string.IsNullOrWhiteSpace(x.ViewUrl))
+                .ToList();
+        }
+    }
+}