SocialPub/PrivaPub/Services/GroupUsersService.cs

using Microsoft.Extensions.Localization;

using MongoDB.Entities;

using PrivaPub.ClientModels;
using PrivaPub.ClientModels.Group;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Group;
using PrivaPub.Resources;
using PrivaPub.StaticServices;

using GroupEntity = PrivaPub.Models.Group.Group;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Rendering;
using PrivaPub.Federation.Outbox;

namespace PrivaPub.Services
{
	public interface IGroupUsersService
	{
		Task<WebResult> GetGroup(string actor, CancellationToken token);
		Task<WebResult> GetGroups(string rootUserId, string avatarId, CancellationToken token);
		Task<WebResult> InsertGroup(string rootUserId, InsertGroupForm form, CancellationToken token);
		Task<WebResult> UpdateGroup(string rootUserId, UpdateGroupForm form, CancellationToken token);
		Task<WebResult> JoinGroup(string rootUserId, JoinGroupForm form, CancellationToken token);
		Task<WebResult> LeaveGroup(string rootUserId, GroupMembershipForm form, CancellationToken token);
		Task<WebResult> ApproveMember(string rootUserId, GroupMembershipForm form, CancellationToken token);
		Task<WebResult> GetMembers(string rootUserId, string avatarId, string groupId, CancellationToken token);
		Task<WebResult> RejectMember(string rootUserId, GroupMembershipForm form, CancellationToken token);
		Task<WebResult> RemoveMember(string rootUserId, GroupMembershipForm form, CancellationToken token);
		Task<WebResult> GetInvitation(string invitationCode, string invitationPassword, CancellationToken token);
	}

	public class GroupUsersService : IGroupUsersService
	{
		readonly DbEntities _dbEntities;
		readonly IPasswordHasher _passwordHasher;
		readonly ILocalActorService _localActors;
		readonly IDeliveryService _delivery;
		readonly Domain.Media.IMediaProxy _proxy;
		readonly IStringLocalizer<GenericRes> _localizer;
		readonly ILogger<GroupUsersService> _logger;

		public GroupUsersService(DbEntities dbEntities,
			IPasswordHasher passwordHasher,
			ILocalActorService localActors,
			IDeliveryService delivery,
			IStringLocalizer<GenericRes> localizer,
			ILogger<GroupUsersService> logger,
			Domain.Media.IMediaProxy proxy)
		{
			_proxy = proxy;
			_dbEntities = dbEntities;
			_passwordHasher = passwordHasher;
			_localActors = localActors;
			_delivery = delivery;
			_localizer = localizer;
			_logger = logger;
		}

		public async Task<WebResult> GetGroup(string actor, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var userName = actor?.ToLowerInvariant();
				var group = await _dbEntities.Groups
					.Match(g => g.UserName == userName && !g.DeletionAt.HasValue)
					.ExecuteFirstAsync(token);
				if (group == default)
					return result.Invalidate(_localizer["Group '{0}' not found.", actor], StatusCodes.Status404NotFound);
				result.Data = group;
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(GetGroup)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> GetGroups(string rootUserId, string avatarId, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				if (!await OwnsAvatar(rootUserId, avatarId, token))
					return result.Invalidate(_localizer["Avatar not found."], StatusCodes.Status404NotFound);

				var groups = await _dbEntities.Groups
					.Match(g => !g.DeletionAt.HasValue && g.Members.Any(m => !m.IsForeign && m.AvatarId == avatarId))
					.ExecuteAsync(token);
				result.Data = groups.Select(g => ToView(g, avatarId)).ToList();
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(GetGroups)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> InsertGroup(string rootUserId, InsertGroupForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				if (!await OwnsAvatar(rootUserId, form.AvatarId, token))
					return result.Invalidate(_localizer["Avatar not found."], StatusCodes.Status404NotFound);

				var userName = form.UserName.ToLowerInvariant();
				if (await _localActors.IsUserNameTaken(userName, token))
					return result.Invalidate(_localizer["The username '{0}' is already taken.", userName]);

				var (privateKey, publicKey) = Keys.NewKeyPair();
				var group = new GroupEntity
				{
					UserName = userName,
					Name = form.Name,
					Description = form.Description,
					Domain = _localActors.BaseAddress,
					PrivateKey = privateKey,
					PublicKey = publicKey,
					Kind = form.IsCommunity ? GroupKind.Community : GroupKind.Circle,
					PostingPolicy = Policy(form.PostingPolicy) ?? PostingPolicy.Followers,
					IsDiscoverable = form.IsDiscoverable,
					ManuallyApprovesMembers = form.ManuallyApprovesMembers,
					OwnerAvatarId = form.AvatarId,
					InvitationCode = NewInvitationCode(),
					HashedInvitationPassword = string.IsNullOrEmpty(form.InvitationPassword) ? default : _passwordHasher.Hash(form.InvitationPassword),
					Members = new() { new GroupMember { AvatarId = form.AvatarId, Role = GroupRole.Owner } }
				};
				group.ID = (string)group.GenerateNewID();
				if (!await _localActors.TryReserveUserName(userName, LocalActorKind.Group, group.ID, token))
					return result.Invalidate(_localizer["The username '{0}' is already taken.", userName]);
				var actor = _localActors.FromGroup(group);
				group.Url = actor.Uri;
				group.InboxURL = actor.Inbox;
				group.OutboxURL = actor.Outbox;
				await DB.Default.SaveAsync(group, token);

				result.Data = ToView(group, form.AvatarId);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(InsertGroup)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> UpdateGroup(string rootUserId, UpdateGroupForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var group = await ManagedGroup(rootUserId, form.AvatarId, form.GroupId, token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);

				if (form.Name != default)
					group.Name = form.Name;
				if (form.Description != default)
					group.Description = form.Description;
				if (form.IsDiscoverable.HasValue)
					group.IsDiscoverable = form.IsDiscoverable.Value;
				if (Policy(form.PostingPolicy) is { } policy)
					group.PostingPolicy = policy;
				if (form.ManuallyApprovesMembers.HasValue)
					group.ManuallyApprovesMembers = form.ManuallyApprovesMembers.Value;
				if (form.RemoveInvitationPassword)
					group.HashedInvitationPassword = default;
				else if (!string.IsNullOrEmpty(form.InvitationPassword))
					group.HashedInvitationPassword = _passwordHasher.Hash(form.InvitationPassword);
				if (form.RegenerateInvitationCode)
					group.InvitationCode = NewInvitationCode();
				group.UpdatedAt = DateTime.UtcNow;
				await DB.Default.SaveAsync(group, token);

				result.Data = ToView(group, form.AvatarId);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(UpdateGroup)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> JoinGroup(string rootUserId, JoinGroupForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				if (!await OwnsAvatar(rootUserId, form.AvatarId, token))
					return result.Invalidate(_localizer["Avatar not found."], StatusCodes.Status404NotFound);

				var group = await _dbEntities.Groups
					.Match(g => g.InvitationCode == form.InvitationCode && !g.DeletionAt.HasValue)
					.ExecuteFirstAsync(token);
				if (group == default)
					return result.Invalidate(_localizer["Invalid invitation."], StatusCodes.Status404NotFound);

				if (!string.IsNullOrEmpty(group.HashedInvitationPassword))
				{
					var (verified, _) = string.IsNullOrEmpty(form.InvitationPassword)
						? (false, false)
						: _passwordHasher.Check(group.HashedInvitationPassword, form.InvitationPassword);
					if (!verified)
						return result.Invalidate(_localizer["Invalid password."], StatusCodes.Status406NotAcceptable);
				}

				if (!group.Members.Any(m => !m.IsForeign && m.AvatarId == form.AvatarId))
				{
					group.Members.Add(new GroupMember { AvatarId = form.AvatarId });
					group.UpdatedAt = DateTime.UtcNow;
					await DB.Default.SaveAsync(group, token);
				}
				await FollowAsMember(group, form.AvatarId, token);

				result.Data = ToView(group, form.AvatarId);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(JoinGroup)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		// Joining by invitation is following, as a local follow of the group would be: the member counts among its
		// followers (so /groupies and /flock agree) and gets its posts in the home timeline.
		async Task FollowAsMember(GroupEntity group, string avatarId, CancellationToken token)
		{
			var persona = await _localActors.FindById(LocalActorKind.Person, avatarId, token);
			var target = _localActors.FromGroup(group);
			if (persona == default)
				return;
			await DB.Default.Update<Follower>()
				.Match(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == persona.Uri)
				.Modify(f => f.InboxURL, persona.Inbox)
				.Modify(f => f.SharedInboxURL, persona.SharedInbox)
				.Modify(f => f.IsAccepted, true)
				.Modify(b => b.SetOnInsert(f => f.CreationDate, DateTime.UtcNow))
				.Option(o => o.IsUpsert = true)
				.ExecuteAsync(token);
			await DB.Default.Update<Models.Social.Following>()
				.Match(f => f.AvatarId == persona.Id && f.TargetActorURI == target.Uri)
				.Modify(f => f.TargetAccountId, group.ID)
				.Modify(f => f.TargetIsLocal, true)
				.Modify(f => f.TargetInboxURL, target.Inbox)
				.Modify(f => f.State, Models.Social.FollowState.Accepted)
				.Modify(b => b.SetOnInsert(f => f.CreatedAt, DateTime.UtcNow))
				.Option(o => o.IsUpsert = true)
				.ExecuteAsync(token);
		}

		public async Task<WebResult> LeaveGroup(string rootUserId, GroupMembershipForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				if (!await OwnsAvatar(rootUserId, form.AvatarId, token))
					return result.Invalidate(_localizer["Avatar not found."], StatusCodes.Status404NotFound);

				var group = await _dbEntities.Groups.MatchID(form.GroupId).ExecuteFirstAsync(token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);
				if (group.OwnerAvatarId == form.AvatarId)
					return result.Invalidate(_localizer["The owner cannot leave the group."]);

				group.Members.RemoveAll(m => !m.IsForeign && m.AvatarId == form.AvatarId);
				group.UpdatedAt = DateTime.UtcNow;
				await DB.Default.SaveAsync(group, token);
				// leaving is unfollowing, as joining was following
				var groupUri = _localActors.FromGroup(group).Uri;
				var personaUri = (await _localActors.FindById(LocalActorKind.Person, form.AvatarId, token))?.Uri;
				await DB.Default.DeleteAsync<Models.Social.Following>(f => f.AvatarId == form.AvatarId && f.TargetActorURI == groupUri);
				if (personaUri != default)
					await DB.Default.DeleteAsync<Follower>(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == personaUri);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(LeaveGroup)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> ApproveMember(string rootUserId, GroupMembershipForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var group = await ManagedGroup(rootUserId, form.AvatarId, form.GroupId, token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);

				var follower = await _dbEntities.Followers
					.Match(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == form.MemberActorURI)
					.ExecuteFirstAsync(token);
				if (follower == default)
					return result.Invalidate(_localizer["Request not found."], StatusCodes.Status404NotFound);

				follower.IsAccepted = true;
				await DB.Default.SaveAsync(follower, token);
				if (!group.Members.Any(m => m.IsForeign && m.AvatarId == follower.ActorURI))
				{
					group.Members.Add(new GroupMember { AvatarId = follower.ActorURI, IsForeign = true });
					await DB.Default.SaveAsync(group, token);
				}

				var actor = _localActors.FromGroup(group);
				var follow = new System.Text.Json.Nodes.JsonObject
				{
					["id"] = follower.FollowActivityURI,
					["type"] = "Follow",
					["actor"] = follower.ActorURI,
					["object"] = actor.Uri
				};
				var accept = ActivityPubRenderer.Accept(actor, follow, $"accept-{follower.ID}-{DateTime.UtcNow.Ticks}");
				await _delivery.Enqueue(actor, new[] { follower.InboxURL }, accept, token);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(ApproveMember)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		public async Task<WebResult> GetInvitation(string invitationCode, string invitationPassword, CancellationToken token)
		{
			var result = new WebResult();
			var group = string.IsNullOrEmpty(invitationCode)
				? default
				: await _dbEntities.Groups.Match(g => g.InvitationCode == invitationCode && !g.DeletionAt.HasValue).ExecuteFirstAsync(token);
			if (group == default)
				return result.Invalidate(_localizer["Invalid invitation."], StatusCodes.Status404NotFound);
			if (!string.IsNullOrEmpty(group.HashedInvitationPassword)
				&& (string.IsNullOrEmpty(invitationPassword) || !_passwordHasher.Check(group.HashedInvitationPassword, invitationPassword).verified))
				return result.Invalidate(_localizer["Invalid password."], StatusCodes.Status406NotAcceptable);
			result.Data = group;
			return result;
		}

		// the group's members and the requests to join it, for its owner and moderators only: members are never shown to
		// anyone else (FEDERATION.md, followers' members are never public)
		public async Task<WebResult> GetMembers(string rootUserId, string avatarId, string groupId, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var group = await ManagedGroup(rootUserId, avatarId, groupId, token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);

				var members = new List<ViewGroupMember>();
				foreach (var member in group.Members)
				{
					if (member.IsForeign)
					{
						var foreign = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == member.AvatarId).ExecuteFirstAsync(token);
						members.Add(Remote(member.AvatarId, foreign, member.Role, member.JoinedAt, pending: false));
						continue;
					}
					if (await _localActors.FindById(LocalActorKind.Person, member.AvatarId, token) is { } local)
						members.Add(new ViewGroupMember
						{
							ActorUri = local.Uri, Handle = local.Handle, Name = local.Name ?? local.UserName, PictureUrl = local.PictureURL,
							IsLocal = true, Role = member.Role.ToString().ToLowerInvariant(), Since = member.JoinedAt
						});
				}
				var asking = await _dbEntities.Followers
					.Match(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && !f.IsAccepted)
					.Sort(f => f.CreationDate, Order.Ascending)
					.ExecuteAsync(token);
				foreach (var request in asking.Where(r => members.All(m => m.ActorUri != r.ActorURI)))
				{
					var foreign = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == request.ActorURI).ExecuteFirstAsync(token);
					members.Add(Remote(request.ActorURI, foreign, GroupRole.Member, request.CreationDate, pending: true));
				}
				result.Data = members;
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(GetMembers)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		// a remote member's picture through the media proxy, as everywhere else a client sees remote media
		ViewGroupMember Remote(string actorUri, Models.User.ForeignAvatar foreign, GroupRole role, DateTime since, bool pending) => new()
		{
			ActorUri = actorUri,
			Handle = foreign == default ? actorUri : $"{foreign.UserName}@{foreign.Domain}",
			Name = foreign?.Name ?? foreign?.UserName,
			PictureUrl = _proxy.Wrap(foreign?.PictureURL),
			IsPending = pending,
			Role = role.ToString().ToLowerInvariant(),
			Since = since
		};

		// a request to join declined: the asker's server is told with a Reject of its Follow
		public async Task<WebResult> RejectMember(string rootUserId, GroupMembershipForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var group = await ManagedGroup(rootUserId, form.AvatarId, form.GroupId, token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);
				var request = await _dbEntities.Followers
					.Match(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == form.MemberActorURI && !f.IsAccepted)
					.ExecuteFirstAsync(token);
				if (request == default)
					return result.Invalidate(_localizer["Request not found."], StatusCodes.Status404NotFound);
				await DB.Default.DeleteAsync<Follower>(request.ID);
				await RejectFollow(group, request, token);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(RejectMember)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		// a member taken out of the group: a persona here stops following it, someone elsewhere is told with a Reject of
		// their Follow (as Mastodon removes a follower). The owner stays.
		public async Task<WebResult> RemoveMember(string rootUserId, GroupMembershipForm form, CancellationToken token)
		{
			var result = new WebResult();
			try
			{
				var group = await ManagedGroup(rootUserId, form.AvatarId, form.GroupId, token);
				if (group == default)
					return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);
				var localMember = await _localActors.FindByUri(form.MemberActorURI, token);
				var member = group.Members.FirstOrDefault(m => localMember is { Kind: LocalActorKind.Person }
					? !m.IsForeign && m.AvatarId == localMember.Id
					: m.IsForeign && m.AvatarId == form.MemberActorURI);
				if (member == default)
					return result.Invalidate(_localizer["Member not found."], StatusCodes.Status404NotFound);
				if (member.Role == GroupRole.Owner)
					return result.Invalidate(_localizer["The owner cannot leave the group."]);

				group.Members.Remove(member);
				group.UpdatedAt = DateTime.UtcNow;
				await DB.Default.SaveAsync(group, token);
				var follower = await _dbEntities.Followers
					.Match(f => f.LocalActorId == group.ID && f.LocalActorKind == LocalActorKind.Group && f.ActorURI == form.MemberActorURI)
					.ExecuteFirstAsync(token);
				if (follower != default)
					await DB.Default.DeleteAsync<Follower>(follower.ID);
				if (localMember is { Kind: LocalActorKind.Person })
				{
					var groupUri = _localActors.FromGroup(group).Uri;
					await DB.Default.DeleteAsync<Models.Social.Following>(f => f.AvatarId == localMember.Id && f.TargetActorURI == groupUri);
				}
				else if (follower != default)
					await RejectFollow(group, follower, token);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(RemoveMember)}");
				return result.Invalidate(_localizer["Something went wrong."], exception: ex);
			}
		}

		async Task RejectFollow(GroupEntity group, Follower follower, CancellationToken token)
		{
			if (string.IsNullOrEmpty(follower.InboxURL))
				return;
			var actor = _localActors.FromGroup(group);
			var follow = new System.Text.Json.Nodes.JsonObject
			{
				["id"] = follower.FollowActivityURI,
				["type"] = "Follow",
				["actor"] = follower.ActorURI,
				["object"] = actor.Uri
			};
			var reject = ActivityPubRenderer.Accept(actor, follow, $"reject-{follower.ID}-{DateTime.UtcNow.Ticks}");
			reject["type"] = "Reject";
			await _delivery.Enqueue(actor, new[] { follower.InboxURL }, reject, token);
		}

		async Task<GroupEntity> ManagedGroup(string rootUserId, string avatarId, string groupId, CancellationToken token)
		{
			if (!await OwnsAvatar(rootUserId, avatarId, token))
				return default;
			var group = await _dbEntities.Groups.MatchID(groupId).ExecuteFirstAsync(token);
			if (group == default || group.DeletionAt.HasValue)
				return default;
			var role = group.Members.FirstOrDefault(m => !m.IsForeign && m.AvatarId == avatarId)?.Role;
			return role is GroupRole.Owner or GroupRole.Moderator ? group : default;
		}

		async Task<bool> OwnsAvatar(string rootUserId, string avatarId, CancellationToken token) =>
			!string.IsNullOrEmpty(rootUserId) && !string.IsNullOrEmpty(avatarId)
			&& await _dbEntities.RootToAvatars.Match(ra => ra.RootId == rootUserId && ra.AvatarId == avatarId).ExecuteAnyAsync(token);

		static PostingPolicy? Policy(string value) => value?.ToLowerInvariant() switch
		{
			"anyone" => PostingPolicy.Anyone,
			"moderators" => PostingPolicy.Moderators,
			"followers" => PostingPolicy.Followers,
			_ => (PostingPolicy?)null
		};

		static string NewInvitationCode() => $"{Guid.NewGuid():N}{Guid.NewGuid():N}";

		ViewGroup ToView(GroupEntity group, string avatarId)
		{
			var actor = _localActors.FromGroup(group);
			var isManager = group.Members.Any(m => !m.IsForeign && m.AvatarId == avatarId && m.Role is GroupRole.Owner or GroupRole.Moderator);
			return new ViewGroup
			{
				Id = group.ID,
				UserName = group.UserName,
				Name = group.Name,
				Description = group.Description,
				Url = actor.Uri,
				Handle = actor.Handle,
				IsCommunity = group.Kind == GroupKind.Community,
				PostingPolicy = group.PostingPolicy.ToString().ToLowerInvariant(),
				IsDiscoverable = group.IsDiscoverable,
				ManuallyApprovesMembers = group.ManuallyApprovesMembers,
				IsOwner = group.OwnerAvatarId == avatarId,
				InvitationCode = isManager ? group.InvitationCode : default,
				IsPasswordRequired = !string.IsNullOrEmpty(group.HashedInvitationPassword),
				MembersCount = group.Members.Count,
				CreationDate = group.CreationDate
			};
		}
	}
}