Implemented the base64 image encoding

app/MindWork AI Studio/Chat/ContentImage.cs

@@ -49,4 +49,62 @@ public sealed class ContentImage : IContent
     /// The image source.
     /// </summary>
     public required string Source { get; set; }
+
+    /// <summary>
+    /// Read the image content as a base64 string.
+    /// </summary>
+    /// <remarks>
+    /// The images are directly converted to base64 strings. The maximum
+    /// size of the image is around 10 MB. If the image is larger, the method
+    /// returns an empty string.
+    ///
+    /// As of now, this method does no sort of image processing. LLMs usually
+    /// do not work with arbitrary image sizes. In the future, we might have
+    /// to resize the images before sending them to the model.
+    /// </remarks>
+    /// <param name="token">The cancellation token.</param>
+    /// <returns>The image content as a base64 string; might be empty.</returns>
+    public async Task<string> AsBase64(CancellationToken token = default)
+    {
+        switch (this.SourceType)
+        {
+            case ContentImageSource.BASE64:
+                return this.Source;
+            
+            case ContentImageSource.URL:
+            {
+                using var httpClient = new HttpClient();
+                using var response = await httpClient.GetAsync(this.Source, HttpCompletionOption.ResponseHeadersRead, token);
+                if(response.IsSuccessStatusCode)
+                {
+                    // Read the length of the content:
+                    var lengthBytes = response.Content.Headers.ContentLength;
+                    if(lengthBytes > 10_000_000)
+                        return string.Empty;
+                    
+                    var bytes = await response.Content.ReadAsByteArrayAsync(token);
+                    return Convert.ToBase64String(bytes);
+                }
+
+                return string.Empty;
+            }
+
+            case ContentImageSource.LOCAL_PATH:
+                if(File.Exists(this.Source))
+                {
+                    // Read the content length:
+                    var length = new FileInfo(this.Source).Length;
+                    if(length > 10_000_000)
+                        return string.Empty;
+                    
+                    var bytes = await File.ReadAllBytesAsync(this.Source, token);
+                    return Convert.ToBase64String(bytes);
+                }
+
+                return string.Empty;
+            
+            default:
+                return string.Empty;
+        }
+    }
 }