ANTOOZA-BACKEND/Application/Features/Api/ChannelTitle/UploadIcon/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Donations.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;
using SharedKernel.Storage;

namespace Application.Features.Api.ChannelTitle.UploadIcon;

internal sealed class Handler(IAppDbContext db, IFileStorage fileStorage) : ICommandHandler<Command, Result<string>>
{
    private static readonly string[] AllowedExtensions = [".gif", ".jpg", ".jpeg", ".png", ".webp"];
    private static readonly string[] AllowedContentTypes = ["image/gif", "image/jpeg", "image/png", "image/webp"];

    public async Task<Result<string>> Handle(Command r, CancellationToken ct)
    {
        if (r.File is null || r.File.Length == 0)
        {
            return Result.Failure<string>(Error.Problem("ChannelTitle.UploadIcon.Empty", "파일이 비어 있습니다."));
        }

        var maxSizeBytes = (long)DonationConstants.Title.MaxIconFileSizeMB * 1024 * 1024;
        if (r.File.Length > maxSizeBytes)
        {
            return Result.Failure<string>(Error.Problem("ChannelTitle.UploadIcon.FileTooLarge", $"파일 크기는 {DonationConstants.Title.MaxIconFileSizeMB}MB 이하여야 합니다."));
        }

        if (!string.IsNullOrEmpty(r.File.ContentType) && !AllowedContentTypes.Contains(r.File.ContentType.ToLowerInvariant()))
        {
            return Result.Failure<string>(Error.Problem("ChannelTitle.UploadIcon.InvalidType", "이미지 파일(gif, jpeg, png, webp)만 업로드할 수 있습니다."));
        }

        var channel = await db.Channel.AsNoTracking().FirstOrDefaultAsync(c => c.ID == r.ChannelID, ct);
        if (channel is null)
        {
            return Result.Failure<string>(Error.NotFound("ChannelTitle.UploadIcon.ChannelNotFound", "채널을 찾을 수 없습니다."));
        }

        if (channel.MemberID != r.MemberID)
        {
            return Result.Failure<string>(Error.Forbidden("ChannelTitle.UploadIcon.Forbidden", "본인 채널만 업로드할 수 있습니다."));
        }

        var path = new FileStoragePath(UploadTarget.Upload, UploadFolder.ChannelTitle, r.ChannelID);
        var result = await fileStorage.SaveFileAsync(r.File, path, AllowedExtensions, ct);

        if (result is null)
        {
            return Result.Failure<string>(Error.Problem("ChannelTitle.UploadIcon.Failed", "파일 업로드에 실패했습니다. 허용된 확장자(gif, jpeg, png, webp)인지 확인하세요."));
        }

        return Result.Success(result.Url);
    }
}