harmonia/Harmonia.WinUI/Caching/AudioBitmapImageCache.cs

using Harmonia.Core.Caching;
using Harmonia.Core.Imaging;
using Harmonia.Core.Models;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.UI.Xaml.Media.Imaging;
using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace Harmonia.WinUI.Caching;

public class AudioBitmapImageCache(IAudioImageExtractor audioImageExtractor) : MemoryCache<Song, BitmapImage>, IAudioBitmapImageCache
{
    protected override MemoryCacheOptions Options => new()
    {
        SizeLimit = 200_000_000,
        CompactionPercentage = 0.2,
    };

    protected override TimeSpan SlidingExpiration => TimeSpan.FromSeconds(600);
    protected override int MaxConcurrentRequests => 8;
    protected virtual int MaxImageWidthOrHeight => 1000;

    protected override object? GetKey(Song key)
    {
        if (string.IsNullOrWhiteSpace(key.ImageHash) == false)
        {
            return key.ImageHash;
        }
        else if (string.IsNullOrWhiteSpace(key.ImageName) == false)
        {
            return key.ImageName;
        }

        return "Default";
    }

    protected override async ValueTask<BitmapImage?> FetchAsync(Song key, CancellationToken cancellationToken)
    {
        SongPictureInfo? songPictureInfo = await audioImageExtractor.ExtractImageAsync(key.FileName, cancellationToken);

        if (songPictureInfo == null)
            return GetDefaultBitmapImage();

        using MemoryStream stream = new(songPictureInfo.Data);

        BitmapImage bitmapImage = new();

        await bitmapImage.SetSourceAsync(stream.AsRandomAccessStream());

        bitmapImage.DecodePixelWidth = GetDecodePixelWidth(bitmapImage);
        bitmapImage.DecodePixelHeight = GetDecodePixelHeight(bitmapImage);

        return bitmapImage;
    }

    private BitmapImage GetDefaultBitmapImage()
    {
        Uri uri = new("ms-appx:///Assets/Default.png", UriKind.Absolute);

        BitmapImage bitmapImage = new();
        bitmapImage.DecodePixelWidth = GetDecodePixelWidth(bitmapImage);
        bitmapImage.DecodePixelHeight = GetDecodePixelHeight(bitmapImage);
        bitmapImage.UriSource = uri;

        return bitmapImage;
    }

    private int GetDecodePixelWidth(BitmapImage bitmapImage)
    {
        int originalImageWidth = bitmapImage.PixelWidth;
        int orignalImageHeight = bitmapImage.PixelHeight;

        if (originalImageWidth <= MaxImageWidthOrHeight && orignalImageHeight <= MaxImageWidthOrHeight)
            return 0;

        if (orignalImageHeight > originalImageWidth)
            return 0;

        return MaxImageWidthOrHeight;
    }

    private int GetDecodePixelHeight(BitmapImage bitmapImage)
    {
        int originalImageWidth = bitmapImage.PixelWidth;
        int orignalImageHeight = bitmapImage.PixelHeight;

        if (originalImageWidth <= MaxImageWidthOrHeight && orignalImageHeight <= MaxImageWidthOrHeight)
            return 0;

        if (originalImageWidth > orignalImageHeight)
            return 0;

        return MaxImageWidthOrHeight;
    }

    protected override long GetEntrySize(BitmapImage entry)
    {
        return entry.DecodePixelWidth * entry.DecodePixelHeight;
    }
}