Foxnouns.NET/Foxnouns.Backend/Extensions/AvatarObjectExtensions.cs

using System.Security.Cryptography;
using Foxnouns.Backend.Database;
using Foxnouns.Backend.Jobs;
using Foxnouns.Backend.Services;
using Foxnouns.Backend.Utils;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Webp;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.Processing.Processors.Transforms;

namespace Foxnouns.Backend.Extensions;

public static class AvatarObjectExtensions
{
    private static readonly string[] ValidContentTypes = ["image/png", "image/webp", "image/jpeg"];

    public static async Task
        DeleteMemberAvatarAsync(this ObjectStorageService objectStorageService, Snowflake id, string hash,
            CancellationToken ct = default) =>
        await objectStorageService.RemoveObjectAsync(MemberAvatarUpdateInvocable.Path(id, hash), ct);

    public static async Task
        DeleteUserAvatarAsync(this ObjectStorageService objectStorageService, Snowflake id, string hash,
            CancellationToken ct = default) =>
        await objectStorageService.RemoveObjectAsync(UserAvatarUpdateInvocable.Path(id, hash), ct);

    public static async Task<(string Hash, Stream Image)> ConvertBase64UriToImage(this string uri, int size, bool crop)
    {
        if (!uri.StartsWith("data:image/"))
            throw new ArgumentException("Not a data URI", nameof(uri));

        var split = uri.Remove(0, "data:".Length).Split(";base64,");
        var contentType = split[0];
        var encoded = split[1];
        if (!ValidContentTypes.Contains(contentType))
            throw new ArgumentException("Invalid content type for image", nameof(uri));

        if (!AuthUtils.TryFromBase64String(encoded, out var rawImage))
            throw new ArgumentException("Invalid base64 string", nameof(uri));

        var image = Image.Load(rawImage);

        var processor = new ResizeProcessor(
            new ResizeOptions
            {
                Size = new Size(size),
                Mode = crop ? ResizeMode.Crop : ResizeMode.Max,
                Position = AnchorPositionMode.Center
            },
            image.Size
        );

        image.Mutate(x => x.ApplyProcessor(processor));

        var stream = new MemoryStream(64 * 1024);
        await image.SaveAsync(stream, new WebpEncoder { Quality = 95, NearLossless = false });

        stream.Seek(0, SeekOrigin.Begin);
        var hash = Convert.ToHexString(await SHA256.HashDataAsync(stream)).ToLower();
        stream.Seek(0, SeekOrigin.Begin);

        return (hash, stream);
    }
}