SocialPub/PrivaPub/Federation/Controllers/PeasantsController.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.RateLimiting;

using MongoDB.Entities;

using PrivaPub.Models.Federation;
using PrivaPub.Models.Post;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using PostEntity = PrivaPub.Models.Post.Post;
using PrivaPub.Domain.Privacy;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Rendering;
using PrivaPub.Federation.Inbox;
using PrivaPub.Infrastructure;

namespace PrivaPub.Federation.Controllers
{
	[ApiController, Route("peasants")]
	public class PeasantsController : ControllerBase
	{
		const string ActivityContentType = "application/activity+json; charset=utf-8";
		const int OutboxSize = 20;

		readonly ILocalActorService _localActors;
		readonly IInboxReceiver _inbox;
		readonly DbEntities _dbEntities;
		readonly ILogger<PeasantsController> _logger;

		public PeasantsController(ILocalActorService localActors, IInboxReceiver inbox, DbEntities dbEntities,
			ILogger<PeasantsController> logger)
		{
			_localActors = localActors;
			_inbox = inbox;
			_dbEntities = dbEntities;
			_logger = logger;
		}

		[HttpGet, Route("{actor}")]
		public async Task<IActionResult> GetActor(string actor, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true })
				return NotFound();
			if (WantsHtml() && local.Kind != LocalActorKind.Application)
				return Redirect(local.HtmlUrl);
			return Activity(ActivityPubRenderer.Actor(local));
		}

		[HttpGet, Route("{actor}/anus")]
		public async Task<IActionResult> Outbox(string actor, [FromQuery] bool page, [FromQuery(Name = "max_id")] string maxId,
			CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true })
				return NotFound();

			if (!page)
			{
				var total = local.Kind == LocalActorKind.Group
					? await DB.Default.CountAsync<PostEntity>(f => f.Where(p => p.GroupId == local.Id) & f.Where(VisibilityPolicy.IsPublic), token)
					: await DB.Default.CountAsync<PostEntity>(f => f.Where(p => p.GroupUserId == local.Id && !p.IsFederatedCopy) & f.Where(VisibilityPolicy.IsPublic), token);
				return Activity(ActivityPubRenderer.OrderedCollection(local.Outbox, (int)total, default, $"{local.Outbox}?page=true"));
			}

			var query = local.Kind == LocalActorKind.Group
				? _dbEntities.Posts.Match(p => p.GroupId == local.Id).Match(VisibilityPolicy.IsPublic)
				: _dbEntities.Posts.Match(p => p.GroupUserId == local.Id && !p.IsFederatedCopy).Match(VisibilityPolicy.IsPublic);
			if (!string.IsNullOrEmpty(maxId))
				query.Match(f => f.Lt(p => p.ID, maxId));
			var latest = await query.Sort(p => p.ID, Order.Descending).Limit(OutboxSize).ExecuteAsync(token);

			var items = new List<JsonNode>();
			foreach (var post in latest)
			{
				if (local.Kind == LocalActorKind.Group)
				{
					items.Add(ActivityPubRenderer.Announce(local, post.ObjectURI, $"announce-{post.ID}"));
					continue;
				}
				if (post.ReblogOfPostId != default)
				{
					if (await AnnounceFor(post, token) is { } announce)
						items.Add(announce);
					continue;
				}
				items.Add(await CreateFor(post, local, token));
			}

			var pageId = string.IsNullOrEmpty(maxId) ? $"{local.Outbox}?page=true" : $"{local.Outbox}?page=true&max_id={maxId}";
			var next = latest.Count == OutboxSize ? $"{local.Outbox}?page=true&max_id={latest[^1].ID}" : default;
			return Activity(ActivityPubRenderer.OrderedCollectionPage(pageId, local.Outbox, items, next, default));
		}

		[HttpGet, Route("{actor}/groupies")]
		public async Task<IActionResult> Followers(string actor, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true })
				return NotFound();
			var count = await DB.Default.CountAsync<Follower>(
				f => f.LocalActorId == local.Id && f.LocalActorKind == local.Kind && f.IsAccepted, token);
			return Activity(ActivityPubRenderer.OrderedCollection(local.Followers, (int)count, default));
		}

		[HttpGet, Route("{actor}/stalking")]
		public async Task<IActionResult> Following(string actor, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			return local is not { IsFederated: true } ? NotFound() : Activity(ActivityPubRenderer.OrderedCollection(local.Following, 0, default));
		}

		[HttpGet, Route("{actor}/scribbles/{postId}")]
		public async Task<IActionResult> Post(string actor, string postId, CancellationToken token)
		{
			var (local, post) = await PublicPost(actor, postId, token);
			if (post == default)
				return await Tombstone(actor, postId, token) ?? NotFound();
			if (WantsHtml())
				return Redirect(local.PostHtmlUrl(post.ID));

			var group = string.IsNullOrEmpty(post.GroupId) ? default : await _localActors.FindById(LocalActorKind.Group, post.GroupId, token);
			var note = ActivityPubRenderer.Note(post, local, group, post.InReplyToURI);
			note["@context"] = ActivityPubRenderer.Context();
			return Activity(note);
		}

		[HttpGet, Route("{actor}/grunts/{activityId}")]
		public async Task<IActionResult> Grunt(string actor, string activityId, CancellationToken token)
		{
			if (activityId.StartsWith("announce-", StringComparison.Ordinal))
			{
				var booster = await _localActors.FindByUserName(actor, token);
				var uri = booster?.ActivityUri(activityId);
				var reblog = uri == default ? default : await _dbEntities.Posts.Match(p => p.ObjectURI == uri && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
				var rendered = reblog == default ? default : await AnnounceFor(reblog, token);
				return rendered == default ? NotFound() : Activity(rendered);
			}
			if (!activityId.StartsWith("create-", StringComparison.Ordinal))
				return NotFound();
			var (local, post) = await PublicPost(actor, activityId["create-".Length..], token);
			return post == default ? NotFound() : Activity(await CreateFor(post, local, token));
		}

		[HttpPost, Route("{actor}/mouth"), EnableRateLimiting(RateLimiting.Inbox)]
		public async Task<IActionResult> Inbox(string actor, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true })
				return NotFound();
			return Answer(await _inbox.Receive(Request, local, token));
		}

		[HttpPost, Route("{actor}/human-centipede"), EnableRateLimiting(RateLimiting.Inbox)]
		public async Task<IActionResult> ActorSharedInbox(string actor, CancellationToken token) =>
			Answer(await _inbox.Receive(Request, default, token));

		[HttpPost, Route("/human-centipede"), EnableRateLimiting(RateLimiting.Inbox)]
		public async Task<IActionResult> SharedInbox(CancellationToken token) =>
			Answer(await _inbox.Receive(Request, default, token));

		async Task<(LocalActor Actor, PostEntity Post)> PublicPost(string actor, string postId, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true, Kind: LocalActorKind.Person })
				return default;
			var post = await _dbEntities.Posts
				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && p.ReblogOfPostId == null)
				.Match(VisibilityPolicy.IsPublic)
				.ExecuteFirstAsync(token);
			return (local, post);
		}

		async Task<IActionResult> Tombstone(string actor, string postId, CancellationToken token)
		{
			var local = await _localActors.FindByUserName(actor, token);
			if (local is not { IsFederated: true, Kind: LocalActorKind.Person })
				return default;
			var deleted = await _dbEntities.Posts
				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && p.DeletedAt.HasValue
					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
				.ExecuteFirstAsync(token);
			if (deleted == default)
				return default;
			var tombstone = new JsonObject
			{
				["@context"] = ActivityPubRenderer.ActivityStreams,
				["id"] = local.PostUri(deleted.ID),
				["type"] = "Tombstone",
				["formerType"] = "Note",
				["deleted"] = ActivityPubRenderer.Timestamp(deleted.DeletedAt.Value)
			};
			return new ContentResult { Content = tombstone.ToJsonString(), ContentType = ActivityContentType, StatusCode = StatusCodes.Status410Gone };
		}

		async Task<JsonObject> AnnounceFor(PostEntity reblog, CancellationToken token)
		{
			var original = await _dbEntities.Posts.MatchID(reblog.ReblogOfPostId).ExecuteFirstAsync(token);
			if (original == default || original.DeletedAt.HasValue)
				return default;
			return new JsonObject
			{
				["@context"] = ActivityPubRenderer.ActivityStreams,
				["id"] = reblog.ObjectURI,
				["type"] = "Announce",
				["actor"] = reblog.ActorURI,
				["published"] = ActivityPubRenderer.Timestamp(reblog.CreationDate),
				["to"] = new JsonArray(reblog.To.Select(t => (JsonNode)t).ToArray()),
				["cc"] = new JsonArray(reblog.Cc.Select(c => (JsonNode)c).ToArray()),
				["object"] = original.ObjectURI
			};
		}

		async Task<JsonObject> CreateFor(PostEntity post, LocalActor author, CancellationToken token)
		{
			var group = string.IsNullOrEmpty(post.GroupId) ? default : await _localActors.FindById(LocalActorKind.Group, post.GroupId, token);
			var note = ActivityPubRenderer.Note(post, author, group, post.InReplyToURI);
			return ActivityPubRenderer.Create(author, note, $"create-{post.ID}");
		}

		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);
		}

		IActionResult Answer(InboxResult result)
		{
			if (result.Error != default)
				_logger.LogInformation("Inbox refused with {Status}: {Error}", result.StatusCode, result.Error);
			return result.Error == default ? StatusCode(result.StatusCode) : StatusCode(result.StatusCode, result.Error);
		}

		ContentResult Activity(JsonObject document) => new()
		{
			Content = document.ToJsonString(),
			ContentType = ActivityContentType,
			StatusCode = StatusCodes.Status200OK
		};
	}
}