Improve performance (#162)

DiscordChatExporter.Core.Models/Attachment.cs

@@ -0,0 +1,50 @@
+using System;
+using System.IO;
+using System.Linq;
+
+namespace DiscordChatExporter.Core.Models
+{
+    // https://discordapp.com/developers/docs/resources/channel#attachment-object
+
+    public partial class Attachment
+    {
+        public string Id { get; }
+
+        public string Url { get; }
+
+        public int? Width { get; }
+
+        public int? Height { get; }
+
+        public string FileName { get; }
+
+        public bool IsImage { get; }
+
+        public FileSize FileSize { get; }
+
+        public Attachment(string id, int? width, int? height, string url, string fileName, FileSize fileSize)
+        {
+            Id = id;
+            Url = url;
+            Width = width;
+            Height = height;
+            FileName = fileName;
+            FileSize = fileSize;
+
+            IsImage = GetIsImage(fileName);
+        }
+
+        public override string ToString() => FileName;
+    }
+
+    public partial class Attachment
+    {
+        private static readonly string[] ImageFileExtensions = { ".jpg", ".jpeg", ".png", ".gif", ".bmp" };
+
+        public static bool GetIsImage(string fileName)
+        {
+            var fileExtension = Path.GetExtension(fileName);
+            return ImageFileExtensions.Contains(fileExtension, StringComparer.OrdinalIgnoreCase);
+        }
+    }
+}