SocialPub/PrivaPub/Federation/Controllers/EmojisController.cs

using Microsoft.AspNetCore.Mvc;

using MongoDB.Entities;

using PrivaPub.Domain.Content;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Post;

using System.Text.Json.Nodes;

namespace PrivaPub.Federation.Controllers
{
	// Each of the server's custom emoji as an ActivityPub `Emoji` object at its id, /grimaces/{shortcode} (completion program
	// R7; the path is LocalEmojis.Path): the tag that posts, actors and reactions carry, with its @context. GoToSocial takes
	// an emoji only with an id, and may read it there. A disabled emoji is not served (404, it may come back); a deleted one
	// answers 410 with a Tombstone. An emoji tells nothing about anyone, so it is served unsigned under SecureMode too, as the
	// server's own actors are; a browser is sent to the picture.
	[ApiController]
	public class EmojisController : ControllerBase
	{
		const string ActivityContentType = "application/activity+json; charset=utf-8";

		readonly ILocalActorService _localActors;

		public EmojisController(ILocalActorService localActors)
		{
			_localActors = localActors;
		}

		[HttpGet, Route("/" + LocalEmojis.Path + "/{shortcode}")]
		public async Task<IActionResult> Get(string shortcode, CancellationToken token)
		{
			Response.Headers.Vary = "Accept";
			if (!LocalEmojis.IsShortcode(shortcode))
				return NotFound();
			var key = shortcode.ToLowerInvariant();
			var emoji = await DB.Default.Find<LocalEmoji>().Match(e => e.Key == key).ExecuteFirstAsync(token);
			if (emoji == default || emoji.Shortcode != shortcode)
				return NotFound();
			if (emoji.DeletedAt is { } deleted)
				return new ContentResult
				{
					Content = new JsonObject
					{
						["@context"] = ActivityPubRenderer.ActivityStreams,
						["id"] = LocalEmojis.Uri(_localActors.BaseAddress, emoji.Shortcode),
						["type"] = "Tombstone",
						["formerType"] = "Emoji",
						["deleted"] = ActivityPubRenderer.Timestamp(deleted)
					}.ToJsonString(),
					ContentType = ActivityContentType,
					StatusCode = StatusCodes.Status410Gone
				};
			if (emoji.Disabled || string.IsNullOrEmpty(emoji.Url))
				return NotFound();
			if (WantsHtml())
				return Redirect(emoji.Url);
			var live = new LocalEmojis.Live(emoji.ID, emoji.Shortcode, emoji.Url, emoji.StaticUrl ?? emoji.Url, emoji.ContentType ?? "image/png",
				emoji.ImageUpdatedAt, emoji.Category, emoji.VisibleInPicker);
			return new ContentResult
			{
				Content = LocalEmojis.Document(live, _localActors.BaseAddress).ToJsonString(),
				ContentType = ActivityContentType,
				StatusCode = StatusCodes.Status200OK
			};
		}

		bool WantsHtml()
		{
			var accept = Request.Headers.Accept.ToString();
			return accept.Contains("text/html", StringComparison.OrdinalIgnoreCase)
				&& !accept.Contains("activity+json", StringComparison.OrdinalIgnoreCase)
				&& !accept.Contains("ld+json", StringComparison.OrdinalIgnoreCase);
		}
	}
}