1 files changed, 50 insertions, 0 deletions
diff --git a/Timeline/Services/ImageValidator.cs b/Timeline/Services/ImageValidator.cs
new file mode 100644
index 00000000..897a37b8
--- /dev/null
+++ b/Timeline/Services/ImageValidator.cs
@@ -0,0 +1,50 @@
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Formats;
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Timeline.Services
+{
+    public class ImageValidator
+    {
+        private readonly bool _requireSquare;
+
+        public ImageValidator(bool requireSquare = false)
+        {
+            _requireSquare = requireSquare;
+        }
+
+        /// <summary>
+        /// Validate a image data.
+        /// </summary>
+        /// <param name="data">The data of the image. Can't be null.</param>
+        /// <param name="requestType">If not null, the real image format will be check against the requested format and throw if not match. If null, then do not check.</param>
+        /// <returns>The format.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="data"/> is null.</exception>
+        /// <exception cref="ImageException">Thrown when image data can't be decoded or real type does not match request type or image is not square when required.</exception>
+        public async Task<IImageFormat> Validate(byte[] data, string? requestType = null)
+        {
+            if (data == null)
+                throw new ArgumentNullException(nameof(data));
+
+            var format = await Task.Run(() =>
+            {
+                try
+                {
+                    using var image = Image.Load(data, out IImageFormat format);
+                    if (requestType != null && !format.MimeTypes.Contains(requestType))
+                        throw new ImageException(ImageException.ErrorReason.UnmatchedFormat, data, requestType, format.DefaultMimeType);
+                    if (_requireSquare && image.Width != image.Height)
+                        throw new ImageException(ImageException.ErrorReason.NotSquare, data, requestType, format.DefaultMimeType);
+                    return format;
+                }
+                catch (UnknownImageFormatException e)
+                {
+                    throw new ImageException(e, ImageException.ErrorReason.CantDecode, data, requestType, null);
+                }
+            });
+            return format;
+        }
+    }
+}