Discord-History-Tracker/app/Server/Endpoints/GetAttachmentEndpoint.cs

using System.Net;
using System.Threading.Tasks;
using DHT.Server.Data;
using DHT.Server.Database;
using DHT.Server.Service;
using DHT.Utils.Http;
using Microsoft.AspNetCore.Http;

namespace DHT.Server.Endpoints {
	sealed class GetAttachmentEndpoint : BaseEndpoint {
		public GetAttachmentEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db, parameters) {}
		
		protected override Task<IHttpOutput> Respond(HttpContext ctx) {
			string attachmentUrl = WebUtility.UrlDecode((string) ctx.Request.RouteValues["url"]!);
			DownloadedAttachment? maybeDownloadedAttachment = Db.GetDownloadedAttachment(attachmentUrl);

			if (maybeDownloadedAttachment is {} downloadedAttachment) {
				return Task.FromResult<IHttpOutput>(new HttpOutput.File(downloadedAttachment.Type, downloadedAttachment.Data));
			}
			else {
				return Task.FromResult<IHttpOutput>(new HttpOutput.Redirect(attachmentUrl, permanent: false));
			}
		}
	}
}