backport of public nsfw module

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

@@ -0,0 +1,40 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace NadekoBot.Modules.Nsfw.Common
+{
+    public abstract class ImageDownloader<T> : IImageDownloader
+        where T : IImageData
+    {
+        protected readonly HttpClient _http;
+
+        protected JsonSerializerOptions _serializerOptions = new JsonSerializerOptions()
+        {
+            PropertyNameCaseInsensitive = true,
+            NumberHandling = JsonNumberHandling.WriteAsString | JsonNumberHandling.AllowReadingFromString,
+            
+        };
+        
+        public Booru Booru { get; }
+
+        public ImageDownloader(Booru booru, HttpClient http)
+        {
+            _http = http;
+            this.Booru = booru;
+        }
+
+        public abstract Task<List<T>> DownloadImagesAsync(string[] tags, int page, bool isExplicit = false, CancellationToken cancel = default);
+
+        public async Task<List<ImageData>> DownloadImageDataAsync(string[] tags, int page, bool isExplicit = false,
+            CancellationToken cancel = default)
+        {
+            var images = await DownloadImagesAsync(tags, page, isExplicit, cancel).ConfigureAwait(false);
+            return images.Select(x => x.ToCachedImageData(Booru)).ToList();
+        }
+    }
+}