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";
    }
}