SocialPub/PrivaPub/Domain/Statuses/QuoteService.cs

using MongoDB.Entities;

using PrivaPub.Domain.Social;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Inbox;
using PrivaPub.Federation.Objects;
using PrivaPub.Federation.Outbox;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Federation;
using PrivaPub.Models.User;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using static PrivaPub.Federation.Objects.ActivityJson;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Domain.Statuses
{
	public interface IQuoteService
	{
		Task Resolve(PostEntity post, NoteDocument note, CancellationToken token);
		Task Revoke(string stampUri, CancellationToken token);
		Task<bool> Verified(string stampUri, string quotingUri, PostEntity quoted, CancellationToken token);
		Task<QuotePermission> Permission(PostEntity quoted, LocalActor author, CancellationToken token);
		Task<string> Grant(LocalActor author, PostEntity quoted, string quotingUri, string quoterUri, CancellationToken token);
		Task ReceiveRequest(JsonNode request, ForeignAvatar actor, CancellationToken token);
		Task<bool> RevokeLicence(PostEntity quoted, PostEntity quoting, CancellationToken token);
		Task Request(LocalActor author, PostEntity post, PostEntity quoted, JsonObject note, CancellationToken token);
		Task<bool> Answered(JsonNode answer, ForeignAvatar actor, bool accepted, CancellationToken token);
	}

	public enum QuotePermission
	{
		Denied,
		Granted,
		AskFirst
	}

	public class QuoteService : IQuoteService
	{
		readonly DbEntities _dbEntities;
		readonly IRemoteActorService _remoteActors;
		readonly IRemotePosts _remotePosts;
		readonly ILocalActorService _localActors;
		readonly IDeliveryService _delivery;
		readonly IOutboxPublisher _outbox;

		public QuoteService(DbEntities dbEntities, IRemoteActorService remoteActors, IRemotePosts remotePosts, ILocalActorService localActors,
			IDeliveryService delivery, IOutboxPublisher outbox)
		{
			_dbEntities = dbEntities;
			_remoteActors = remoteActors;
			_remotePosts = remotePosts;
			_localActors = localActors;
			_delivery = delivery;
			_outbox = outbox;
		}

		const string RequestPrefix = "quote-request-";

		const string LicencePath = "/parrot-licences/";

		public static string LicenceUri(LocalActor author, string licenceId) => author.Uri + LicencePath + licenceId;

		async Task<bool> MayQuote(PostEntity quoted, string quoterUri, CancellationToken token)
		{
			var author = await _localActors.FindById(LocalActorKind.Person, quoted.GroupUserId, token);
			if (author == default)
				return false;
			if (quoterUri == author.Uri)
				return quoted.Visibility is PostVisibility.Public or PostVisibility.Unlisted;
			return ActivityPubRenderer.QuotableBy(quoted) switch
			{
				QuotePolicies.Public => true,
				QuotePolicies.Followers => await Follows(quoterUri, author, token),
				_ => false
			};
		}

		async Task<bool> Follows(string followerUri, LocalActor author, CancellationToken token)
		{
			if (await _dbEntities.Followers.Match(f => f.LocalActorId == author.Id && f.ActorURI == followerUri && f.IsAccepted).ExecuteAnyAsync(token))
				return true;
			var local = await _localActors.FindByUri(followerUri, token);
			return local != default
				&& await _dbEntities.Followings.Match(f => f.AvatarId == local.Id && f.TargetActorURI == author.Uri && f.State == FollowState.Accepted).ExecuteAnyAsync(token);
		}

		public async Task<string> Grant(LocalActor author, PostEntity quoted, string quotingUri, string quoterUri, CancellationToken token)
		{
			var existing = await DB.Default.Find<QuoteLicence>().Match(l => l.PostId == quoted.ID && l.QuotingObjectURI == quotingUri && l.RevokedAt == null).ExecuteFirstAsync(token);
			if (existing != default)
				return LicenceUri(author, existing.ID);
			var licence = new QuoteLicence { PostId = quoted.ID, AuthorAvatarId = author.Id, QuotingObjectURI = quotingUri, QuoterActorURI = quoterUri };
			await DB.Default.SaveAsync(licence, token);
			return LicenceUri(author, licence.ID);
		}

		public async Task ReceiveRequest(JsonNode request, ForeignAvatar actor, CancellationToken token)
		{
			var objectUri = Id(request["object"]);
			var instrument = request["instrument"];
			var quotingUri = Id(instrument);
			if (objectUri == default || quotingUri == default || !Origin.Same(quotingUri, actor.ActorURI)
				|| instrument is JsonObject embedded && Id(embedded["attributedTo"]) is { } by && by != actor.ActorURI)
			{
				Arrival.Drop("misattributed");
				return;
			}
			var quoted = await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri && !p.IsFederatedCopy && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
			var author = quoted == default ? default : await _localActors.FindById(LocalActorKind.Person, quoted.GroupUserId, token);
			if (author == default || string.IsNullOrEmpty(actor.InboxURL))
			{
				Arrival.Drop("unknown-object");
				return;
			}
			Arrival.About("Note", quoted.Visibility, quoted.CreationDate);
			var answer = new JsonObject
			{
				["@context"] = ActivityPubRenderer.Context(),
				["actor"] = author.Uri,
				["object"] = Id(request),
				["to"] = new JsonArray(actor.ActorURI)
			};
			if (await MayQuote(quoted, actor.ActorURI, token))
			{
				Arrival.Accept("quote-granted");
				answer["type"] = "Accept";
				answer["result"] = await Grant(author, quoted, quotingUri, actor.ActorURI, token);
				answer["id"] = author.ActivityUri($"accept-quote-{Guid.NewGuid():N}");
			}
			else
			{
				Arrival.Reject("quote-refused");
				answer["type"] = "Reject";
				answer["id"] = author.ActivityUri($"reject-quote-{Guid.NewGuid():N}");
			}
			await _delivery.Enqueue(author, new[] { actor.InboxURL }, answer, token);
		}

		public async Task<bool> RevokeLicence(PostEntity quoted, PostEntity quoting, CancellationToken token)
		{
			var licence = await DB.Default.Find<QuoteLicence>().Match(l => l.PostId == quoted.ID && l.QuotingObjectURI == quoting.ObjectURI && l.RevokedAt == null).ExecuteFirstAsync(token);
			var author = licence == default ? default : await _localActors.FindById(LocalActorKind.Person, quoted.GroupUserId, token);
			if (author == default)
				return false;
			await DB.Default.Update<QuoteLicence>().MatchID(licence.ID).Modify(l => l.RevokedAt, DateTime.UtcNow).ExecuteAsync(token);
			var uri = LicenceUri(author, licence.ID);
			await Revoke(uri, token);
			var quoter = quoting.IsFederatedCopy ? await _dbEntities.ForeignAvatars.Match(f => f.ActorURI == quoting.ActorURI).ExecuteFirstAsync(token) : default;
			var inboxes = (await _delivery.FollowerInboxes(author, token)).Append(quoter?.InboxURL).Where(i => !string.IsNullOrEmpty(i)).Distinct().ToList();
			if (inboxes.Count > 0)
				await _delivery.Enqueue(author, inboxes, new JsonObject
				{
					["@context"] = ActivityPubRenderer.Context(),
					["id"] = author.ActivityUri($"revoke-quote-{licence.ID}"),
					["type"] = "Delete",
					["actor"] = author.Uri,
					["object"] = uri,
					["to"] = new JsonArray(Addressing.Public)
				}, token);
			return true;
		}

		async Task<bool> OurLicence(string stampUri, PostEntity quoting, PostEntity quoted, CancellationToken token)
		{
			var marker = stampUri?.LastIndexOf(LicencePath, StringComparison.Ordinal) ?? -1;
			if (marker < 0 || !stampUri.StartsWith(_localActors.BaseAddress + "/", StringComparison.OrdinalIgnoreCase))
				return false;
			var id = stampUri[(marker + LicencePath.Length)..];
			return await DB.Default.Find<QuoteLicence>().Match(l => l.ID == id && l.PostId == quoted.ID && l.QuotingObjectURI == quoting.ObjectURI && l.RevokedAt == null)
				.ExecuteAnyAsync(token);
		}

		public async Task<QuotePermission> Permission(PostEntity quoted, LocalActor author, CancellationToken token)
		{
			if (!quoted.IsFederatedCopy)
				return await MayQuote(quoted, author.Uri, token) ? QuotePermission.Granted : QuotePermission.Denied;
			if (quoted.Visibility is not (PostVisibility.Public or PostVisibility.Unlisted))
				return QuotePermission.Denied;
			if (quoted.QuotePolicy is not { } policy)
				return QuotePermission.Granted;
			return policy.Automatic.Concat(policy.Manual).Any(Addressing.IsPublic) || policy.Automatic.Concat(policy.Manual).Contains(author.Uri)
				? QuotePermission.AskFirst
				: QuotePermission.Denied;
		}

		public async Task Request(LocalActor author, PostEntity post, PostEntity quoted, JsonObject note, CancellationToken token)
		{
			var owner = await _dbEntities.ForeignAvatars.Match(f => f.ActorURI == quoted.ActorURI).ExecuteFirstAsync(token);
			if (string.IsNullOrEmpty(owner?.InboxURL))
				return;
			await _delivery.Enqueue(author, new[] { owner.InboxURL }, new JsonObject
			{
				["@context"] = ActivityPubRenderer.Context(),
				["id"] = author.ActivityUri(RequestPrefix + post.ID),
				["type"] = "QuoteRequest",
				["actor"] = author.Uri,
				["object"] = quoted.ObjectURI,
				["instrument"] = note.DeepClone(),
				["to"] = new JsonArray(quoted.ActorURI)
			}, token);
		}

		public async Task<bool> Answered(JsonNode answer, ForeignAvatar actor, bool accepted, CancellationToken token)
		{
			var request = answer["object"];
			var requestId = Id(request);
			var marker = requestId?.LastIndexOf("/grunts/" + RequestPrefix, StringComparison.Ordinal) ?? -1;
			if (marker < 0 && !(request is JsonObject && Value(request, "type") == "QuoteRequest"))
				return false;
			if (marker < 0)
				return true;
			var postId = requestId[(marker + "/grunts/".Length + RequestPrefix.Length)..];
			var post = await _dbEntities.Posts.Match(p => p.ID == postId && !p.IsFederatedCopy && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
			var author = post == default ? default : await _localActors.FindById(LocalActorKind.Person, post.GroupUserId, token);
			if (author == default || author.ActivityUri(RequestPrefix + post.ID) != requestId || post.QuoteState != QuoteState.Pending)
				return true;
			var quoted = await _dbEntities.Posts.MatchID(post.QuotedPostId).ExecuteFirstAsync(token);
			if (quoted?.ActorURI != actor.ActorURI)
				return true;
			if (!accepted)
			{
				await DB.Default.Update<PostEntity>().MatchID(post.ID).Modify(p => p.QuoteState, QuoteState.Rejected).ExecuteAsync(token);
				return true;
			}
			var stamp = Id(answer["result"]);
			if (stamp == default || !await Verified(stamp, post.ObjectURI, quoted, token))
				return true;
			post.QuoteAuthorizationURI = stamp;
			post.QuoteState = QuoteState.Accepted;
			await DB.Default.Update<PostEntity>().MatchID(post.ID)
				.Modify(p => p.QuoteAuthorizationURI, stamp)
				.Modify(p => p.QuoteState, QuoteState.Accepted)
				.ExecuteAsync(token);
			await DB.Default.Update<PostEntity>().MatchID(quoted.ID).Modify(b => b.Inc(p => p.QuotesCount, 1)).ExecuteAsync(token);
			if (!post.IsLocalOnly)
				await _outbox.Publish(author, post, ActivityPubRenderer.UpdateOf(post, author, "quote-approved"), token);
			return true;
		}

		public async Task Resolve(PostEntity post, NoteDocument note, CancellationToken token)
		{
			if (note.QuoteUri == default && !note.QuoteDeleted)
				return;
			var quoted = note.QuoteUri == default
				? default
				: await _dbEntities.Posts.Match(p => p.ObjectURI == note.QuoteUri && !p.DeletedAt.HasValue).ExecuteFirstAsync(token)
					?? await _remotePosts.StoreContext(note.QuoteUri, RemotePosts.MaxDepth, token);

			var state = note.QuoteDeleted ? QuoteState.Deleted
				: quoted == default ? QuoteState.Pending
				: note.QuoteAuthorization != default
					? (quoted.IsFederatedCopy ? await Verified(note.QuoteAuthorization, post.ObjectURI, quoted, token) : await OurLicence(note.QuoteAuthorization, post, quoted, token))
						? QuoteState.Accepted
						: QuoteState.Unauthorized
				: note.QuotesByConsent ? QuoteState.Pending
				: quoted.Visibility is PostVisibility.Public or PostVisibility.Unlisted ? QuoteState.Accepted
				: QuoteState.Unauthorized;

			var wasCounted = post.QuoteState == QuoteState.Accepted ? post.QuotedPostId : default;
			await DB.Default.Update<PostEntity>().MatchID(post.ID)
				.Modify(p => p.QuoteURI, note.QuoteUri)
				.Modify(p => p.QuotedPostId, quoted?.ID)
				.Modify(p => p.QuoteState, state)
				.Modify(p => p.QuoteAuthorizationURI, state == QuoteState.Accepted ? note.QuoteAuthorization : default)
				.ExecuteAsync(token);
			post.QuotedPostId = quoted?.ID;
			post.QuoteState = state;

			var nowCounted = state == QuoteState.Accepted ? quoted?.ID : default;
			if (wasCounted == nowCounted)
				return;
			if (wasCounted != default)
				await DB.Default.Update<PostEntity>().MatchID(wasCounted).Modify(b => b.Inc(p => p.QuotesCount, -1)).ExecuteAsync(token);
			if (nowCounted != default)
			{
				await DB.Default.Update<PostEntity>().MatchID(nowCounted).Modify(b => b.Inc(p => p.QuotesCount, 1)).ExecuteAsync(token);
				if (!quoted.IsFederatedCopy)
					await Notifications.Add(quoted.GroupUserId, NotificationType.Quote, post.AuthorAccountId, post.ActorURI, post.ID, token);
			}
		}

		public async Task Revoke(string stampUri, CancellationToken token)
		{
			var revoked = await _dbEntities.Posts.Match(p => p.QuoteAuthorizationURI == stampUri && p.QuoteState == QuoteState.Accepted).ExecuteAsync(token);
			foreach (var post in revoked)
			{
				await DB.Default.Update<PostEntity>().MatchID(post.ID).Modify(p => p.QuoteState, QuoteState.Revoked).ExecuteAsync(token);
				if (post.QuotedPostId != default)
					await DB.Default.Update<PostEntity>().MatchID(post.QuotedPostId).Modify(b => b.Inc(p => p.QuotesCount, -1)).ExecuteAsync(token);
			}
		}

		public async Task<bool> Verified(string stampUri, string quotingUri, PostEntity quoted, CancellationToken token)
		{
			if (!Origin.Same(stampUri, quoted.ActorURI))
				return false;
			using var fetched = await _remoteActors.FetchObject(stampUri, token);
			if (fetched == default)
				return false;
			var stamp = JsonNode.Parse(fetched.Root.GetRawText());
			return Value(stamp, "type") == "QuoteAuthorization"
				&& Id(stamp["attributedTo"]) == quoted.ActorURI
				&& Id(stamp["interactingObject"]) == quotingUri
				&& Id(stamp["interactionTarget"]) == quoted.ObjectURI;
		}
	}
}