工单 优化 ，增加图片

OrderSupportTicket/ViewModels/ChatAttachmentViewModel.cs

@@ -0,0 +1,169 @@
+using OrderSupportTicket.Models.Api;
+using OrderSupportTicket.Services;
+using System;
+using System.Globalization;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Media;
+using WPFCommon.Models;
+
+namespace OrderSupportTicket.ViewModels;
+
+/// <summary>
+/// 留言气泡中的公开图片附件。
+/// </summary>
+public sealed class ChatAttachmentViewModel : BindableBaseEx
+{
+    private bool _isLoading;
+	private bool _isLoadFailed;
+    private ImageSource _image;
+
+    public ChatAttachmentViewModel(TicketAttachmentDto dto)
+    {
+        if (dto == null)
+            throw new ArgumentNullException(nameof(dto));
+        Id = dto.Id;
+        OriginalName = dto.OriginalName;
+        ContentType = dto.ContentType;
+        ByteSize = dto.ByteSize;
+        ReadUrl = dto.ReadUrl;
+    }
+
+    /// <summary>
+    /// 附件唯一 ID。
+    /// </summary>
+    public string Id { get; }
+
+    /// <summary>
+    /// 原始文件名。
+    /// </summary>
+    public string OriginalName { get; }
+
+    /// <summary>
+    /// 图片 MIME 类型。
+    /// </summary>
+    public string ContentType { get; }
+
+    /// <summary>
+    /// 图片字节数。
+    /// </summary>
+    public long ByteSize { get; }
+
+    /// <summary>
+    /// 服务端生成的短时读取地址。
+    /// </summary>
+    public string ReadUrl { get; }
+
+    /// <summary>
+    /// 已下载并解码的图片；加载完成前为空。
+    /// </summary>
+    public ImageSource Image
+    {
+        get => _image;
+        private set
+        {
+            if (SetValue(ref _image, value))
+                RaisePropertyChanged(nameof(HasImage));
+        }
+    }
+
+    /// <summary>
+    /// 是否已成功显示图片。
+    /// </summary>
+    public bool HasImage => Image != null;
+
+    /// <summary>
+    /// 图片是否已经确认加载失败。加载完成前保持为 false。
+    /// </summary>
+	public bool IsLoadFailed
+	{
+		get => _isLoadFailed;
+		private set
+		{
+			if (SetValue(ref _isLoadFailed, value))
+				RaisePropertyChanged(nameof(ToolTipText));
+		}
+	}
+
+    /// <summary>
+    /// 附件名称、大小与加载状态提示。
+    /// </summary>
+    public string ToolTipText
+    {
+        get
+        {
+            var name = string.IsNullOrWhiteSpace(OriginalName) ? "图片" : OriginalName;
+            var size = FormatSize(ByteSize);
+            if (string.IsNullOrWhiteSpace(ReadUrl))
+                return name + "（" + size + "，暂不可用）";
+            if (_isLoading)
+                return name + "（" + size + "，加载中…）";
+			if (IsLoadFailed)
+				return name + "（" + size + "，加载失败）";
+            return name + "（" + size + "）";
+        }
+    }
+
+    /// <summary>
+    /// 下载并解码短时读取地址。失败时保留占位提示，不阻断文字留言展示。
+    /// </summary>
+    public async Task LoadAsync()
+    {
+        if (Image != null || _isLoading)
+            return;
+        if (string.IsNullOrWhiteSpace(ReadUrl))
+        {
+			IsLoadFailed = true;
+            return;
+        }
+
+		IsLoadFailed = false;
+        _isLoading = true;
+        RaisePropertyChanged(nameof(ToolTipText));
+        try
+        {
+            var image = await ProductImageLoader.LoadAsync(ReadUrl);
+			if (image == null)
+				IsLoadFailed = true;
+			else
+				await SetImageAsync(image);
+        }
+        catch
+        {
+			IsLoadFailed = true;
+        }
+        finally
+        {
+            _isLoading = false;
+            RaisePropertyChanged(nameof(ToolTipText));
+        }
+    }
+
+    private async Task SetImageAsync(ImageSource image)
+    {
+        if (image == null)
+            return;
+
+        var dispatcher = Application.Current?.Dispatcher;
+        if (dispatcher == null || dispatcher.CheckAccess())
+        {
+            Image = image;
+			IsLoadFailed = false;
+            return;
+        }
+		await dispatcher.InvokeAsync(() =>
+		{
+			Image = image;
+			IsLoadFailed = false;
+		});
+    }
+
+    private static string FormatSize(long byteSize)
+    {
+        if (byteSize >= 1024 * 1024)
+            return (byteSize / 1024d / 1024d).ToString("0.0", CultureInfo.CurrentCulture) + " MB";
+        if (byteSize >= 1024)
+            return (byteSize / 1024d).ToString("0.0", CultureInfo.CurrentCulture) + " KB";
+        return byteSize.ToString(CultureInfo.CurrentCulture) + " B";
+    }
+}