using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Data;
using System.Windows.Media.Imaging;
using Work;

namespace _29WxOrderWpf.Converters
{
    public class ImageUrlToBitmapImageConverter : IValueConverter
    {
        /// <summary> 缓存上限，防止大量缩略图重复下载导致内存膨胀 </summary>
        private const int MaxCacheCount = 200;

        private readonly ConcurrentDictionary<string, BitmapImage> _imageCache = new ConcurrentDictionary<string, BitmapImage>();

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value is string url && Uri.IsWellFormedUriString(url, UriKind.Absolute))
            {
                if (_imageCache.TryGetValue(url, out BitmapImage cached))
                {
                    return cached;
                }

                try
                {
                    // 直接加载绑定如果遇到有问题的网络图片会直接崩溃。
                    BitmapImage bitMap = AllBase.ImageBuild.LoadBitmipImageFromUrl(url);
                    if (bitMap != null)
                    {
                        if (_imageCache.Count >= MaxCacheCount)
                        {
                            _imageCache.Clear();
                        }
                        _imageCache[url] = bitMap;
                    }
                    return bitMap;
                }
                catch
                {

                }
            }
            return null;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException(); // 不需要反向转换，所以不实现。
        }
    }
}