Implement lazy image loading (copied from freefall reader)

Services/FileDownloader.cs

@@ -0,0 +1,32 @@
+namespace QuestReader.Services;
+
+public class FileDownloader
+{
+    public static async Task DownloadList(string basePath, Uri baseAssetsUrl, IEnumerable<string> files)
+    {
+        if (!Directory.Exists(Path.Join(basePath, "assets")))
+            Directory.CreateDirectory(Path.Join(basePath, "assets"));
+
+        var downloadTasks = new List<Task>();
+
+        using (var client = new HttpClient()) {
+            client.BaseAddress = baseAssetsUrl;
+            Console.Out.WriteLine($"Downloading missing files...");
+
+            await Task.WhenAll(
+                files
+                    .Where(file => !File.Exists(Path.Join(basePath, "assets", file)))
+                    .Select(file => client.GetStreamAsync(file).ContinueWith(async (stream) => {
+                            Console.Out.WriteLine($"Downloading {file}");
+                            using var fileWrite = File.OpenWrite(Path.Join(basePath, "assets", file));
+                            await (await stream).CopyToAsync(fileWrite);
+                            stream.Dispose();
+                            fileWrite.Dispose();
+                        })
+                    )
+                    .ToList()
+            );
+            Console.Out.WriteLine($"All files done");
+        }
+    }
+}

Services/PostsSource.cs

@@ -4,6 +4,7 @@ using System.Text.Json;
 using System.Text.Json.Serialization;
 using System.Text.RegularExpressions;
 using QuestReader.Models;
+using SixLabors.ImageSharp;
 
 public class PostsSource
 {
@@ -61,6 +62,20 @@ public class PostsSource
         Accepted.UnionWith(Posts.Where(p => referenced.Contains(p.Id)));
         Accepted = Accepted.OrderBy(p => p.Id).ToHashSet();
 
+        FileDownloader.DownloadList(BasePath, Metadata.AssetsBaseUrl, Accepted.Where(p => p.File is not null).Select(p => p.File!)).Wait();
+
+        foreach (var post in Accepted.Where(f => f.File is not null))
+        {
+            using var imageStream = File.OpenRead(Path.Combine(BasePath, "assets", post.File!));
+            IImageInfo imageInfo = Image.Identify(imageStream);
+            if (imageInfo is null) {
+                Console.Out.WriteLine($"Not a valid image: {post.File!}");
+                continue;
+            }
+            post.FileHeight = imageInfo.Height;
+            post.FileWidth = imageInfo.Width;
+        }
+
         Console.Out.WriteLine($"Done loading with {Accepted.Count} posts, referencing {Accepted.Where(a => a.File is not null).Count()} files");
     }
 }