SocialPub/PrivaPub/Api/Mastodon/Mappers/MastodonMapper.cs

using MongoDB.Entities;

using PrivaPub.Api.Mastodon.Entities;
using PrivaPub.Api.Mastodon.Infrastructure;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Net;

using GroupEntity = PrivaPub.Models.Group.Group;
using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Api.Mastodon.Mappers
{
	public class MastodonMapper
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;

		public MastodonMapper(DbEntities dbEntities, ILocalActorService localActors)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
		}

		string MissingAvatar => $"{_localActors.BaseAddress}/media/missing-avatar.png";
		string MissingHeader => $"{_localActors.BaseAddress}/media/missing-header.png";

		public async Task<Account> Local(LocalActor actor, bool withSource, CancellationToken token)
		{
			var followers = await DB.Default.CountAsync<Follower>(f => f.LocalActorId == actor.Id && f.LocalActorKind == actor.Kind && f.IsAccepted, token);
			var following = actor.Kind == LocalActorKind.Person
				? await DB.Default.CountAsync<Following>(f => f.AvatarId == actor.Id && f.State == FollowState.Accepted, token)
				: 0;
			var latest = await _dbEntities.Posts
				.Match(p => (actor.Kind == LocalActorKind.Group ? p.GroupId == actor.Id : p.GroupUserId == actor.Id) && !p.IsFederatedCopy
					&& !p.DeletedAt.HasValue && p.Visibility != PostVisibility.Direct && p.ReblogOfPostId == null)
				.Sort(p => p.ID, Order.Descending)
				.Limit(1)
				.ExecuteFirstAsync(token);
			var statuses = latest == default
				? 0
				: await DB.Default.CountAsync<PostEntity>(p => (actor.Kind == LocalActorKind.Group ? p.GroupId == actor.Id : p.GroupUserId == actor.Id)
					&& !p.IsFederatedCopy && !p.DeletedAt.HasValue && p.Visibility != PostVisibility.Direct && p.ReblogOfPostId == null, token);

			var account = new Account
			{
				Id = actor.Id,
				Username = actor.UserName,
				Acct = actor.UserName,
				DisplayName = actor.Name ?? actor.UserName,
				Locked = actor.ManuallyApprovesFollowers,
				Bot = actor.IsBot,
				Discoverable = actor.Discoverable,
				Indexable = actor.Indexable,
				Noindex = !actor.Indexable,
				HideCollections = actor.Settings.HideCollections,
				Group = actor.Kind == LocalActorKind.Group,
				CreatedAt = MastodonJson.Day(actor.Published),
				Note = ActivityPubRenderer.Html(actor.Summary),
				Url = actor.HtmlUrl,
				Uri = actor.Uri,
				Avatar = actor.PictureURL ?? MissingAvatar,
				AvatarStatic = actor.PictureURL ?? MissingAvatar,
				Header = actor.ThumbnailURL ?? MissingHeader,
				HeaderStatic = actor.ThumbnailURL ?? MissingHeader,
				FollowersCount = (int)followers,
				FollowingCount = (int)following,
				StatusesCount = (int)statuses,
				LastStatusAt = latest == default ? default : latest.CreationDate.ToString("yyyy-MM-dd"),
				Fields = actor.Fields.Select(f => new Field { Name = f.Key, Value = ActivityPubRenderer.FieldValue(f.Value) }).ToList()
			};
			if (withSource)
				account.Source = new Source
				{
					Privacy = actor.Settings.DefaultVisibility ?? "public",
					Sensitive = actor.Settings.DefaultSensitive,
					Language = actor.Settings.DefaultLanguage,
					Note = actor.Summary ?? string.Empty,
					Fields = actor.Fields.Select(f => new Field { Name = f.Key, Value = f.Value }).ToList(),
					FollowRequestsCount = (int)await DB.Default.CountAsync<Follower>(f => f.LocalActorId == actor.Id && !f.IsAccepted, token)
				};
			return account;
		}

		public Account Foreign(ForeignAvatar foreign) => new()
		{
			Id = foreign.ID,
			Username = foreign.UserName,
			Acct = $"{foreign.UserName}@{foreign.Domain}",
			DisplayName = foreign.Name ?? foreign.UserName ?? string.Empty,
			Bot = foreign.AvatarType is AvatarType.Service or AvatarType.Application,
			Group = foreign.AvatarType == AvatarType.Group,
			Discoverable = foreign.IsDiscoverable,
			CreatedAt = MastodonJson.Day(foreign.CreatedAt),
			Note = foreign.Biography ?? string.Empty,
			Url = foreign.Url ?? foreign.ActorURI,
			Uri = foreign.ActorURI,
			Avatar = foreign.PictureURL ?? MissingAvatar,
			AvatarStatic = foreign.PictureURL ?? MissingAvatar,
			Header = foreign.ThumbnailURL ?? MissingHeader,
			HeaderStatic = foreign.ThumbnailURL ?? MissingHeader
		};

		public async Task<Account> Account(string id, CancellationToken token) =>
			(await Accounts(new[] { id }, token)).GetValueOrDefault(id);

		public async Task<Dictionary<string, Account>> Accounts(IEnumerable<string> ids, CancellationToken token)
		{
			var wanted = ids.Where(id => !string.IsNullOrEmpty(id)).Distinct().ToList();
			var accounts = new Dictionary<string, Account>();
			if (wanted.Count == 0)
				return accounts;

			foreach (var avatar in await _dbEntities.Avatars.Match(a => wanted.Contains(a.ID) && !a.DeletionAt.HasValue).ExecuteAsync(token))
				accounts[avatar.ID] = await Local(_localActors.FromAvatar(avatar), false, token);
			foreach (var group in await _dbEntities.Groups.Match(g => wanted.Contains(g.ID) && !g.DeletionAt.HasValue).ExecuteAsync(token))
				accounts[group.ID] = await Local(_localActors.FromGroup(group), false, token);
			foreach (var foreign in await _dbEntities.ForeignAvatars.Match(f => wanted.Contains(f.ID)).ExecuteAsync(token))
				accounts[foreign.ID] = Foreign(foreign);
			return accounts;
		}

		public async Task<Status> Status(PostEntity post, string viewerId, CancellationToken token) =>
			(await Statuses(new[] { post }, viewerId, token)).FirstOrDefault();

		public async Task<List<Status>> Statuses(IReadOnlyCollection<PostEntity> posts, string viewerId, CancellationToken token)
		{
			var originalIds = posts.Where(p => p.ReblogOfPostId != default).Select(p => p.ReblogOfPostId).Distinct().ToList();
			var originals = originalIds.Count == 0
				? new Dictionary<string, PostEntity>()
				: (await _dbEntities.Posts.Match(p => originalIds.Contains(p.ID) && !p.DeletedAt.HasValue).ExecuteAsync(token)).ToDictionary(p => p.ID);
			var all = posts.Concat(originals.Values).ToList();

			var mentionUris = all.SelectMany(p => p.Mentions).Where(m => !m.IsLocal).Select(m => m.ActorURI).Distinct().ToList();
			var mentionAccounts = mentionUris.Count == 0
				? new Dictionary<string, ForeignAvatar>()
				: (await _dbEntities.ForeignAvatars.Match(f => mentionUris.Contains(f.ActorURI)).ExecuteAsync(token)).ToDictionary(f => f.ActorURI);
			var accounts = await Accounts(all.Select(AuthorOf), token);

			var ids = all.Select(p => p.ID).ToList();
			var favourited = viewerId == default
				? new HashSet<string>()
				: (await _dbEntities.Favourites.Match(f => f.AccountId == viewerId && ids.Contains(f.PostId)).ExecuteAsync(token)).Select(f => f.PostId).ToHashSet();
			var reblogged = viewerId == default
				? new HashSet<string>()
				: (await _dbEntities.Posts.Match(p => p.AuthorAccountId == viewerId && ids.Contains(p.ReblogOfPostId) && !p.DeletedAt.HasValue).ExecuteAsync(token))
					.Select(p => p.ReblogOfPostId).ToHashSet();

			Status Map(PostEntity post)
			{
				if (!accounts.TryGetValue(AuthorOf(post), out var account))
					return default;
				var status = new Status
				{
					Id = post.ID,
					Uri = post.ObjectURI,
					Url = post.Url ?? post.ObjectURI,
					Account = account,
					InReplyToId = post.AnsweringToPostId,
					InReplyToAccountId = post.InReplyToAccountId,
					Content = Content(post),
					CreatedAt = MastodonJson.Time(post.CreationDate),
					EditedAt = post.EditedAt.HasValue ? MastodonJson.Time(post.EditedAt.Value) : default,
					RepliesCount = post.RepliesCount,
					ReblogsCount = post.ReblogsCount,
					FavouritesCount = post.FavouritesCount,
					Favourited = favourited.Contains(post.ID),
					Reblogged = reblogged.Contains(post.ID),
					Sensitive = post.HasContentWarning,
					SpoilerText = post.SpoilerText ?? (post.HasContentWarning ? post.Title ?? ActivityPubRenderer.ContentWarning : string.Empty),
					Visibility = Visibility(post.Visibility),
					Language = post.Language,
					MediaAttachments = post.Media.Select(Media).ToList(),
					Mentions = post.Mentions.Select(m => Mention(m, mentionAccounts)).Where(m => m != default).ToList(),
					Tags = post.Tags.Select(t => new StatusTag { Name = t, Url = ActivityPubRenderer.TagUrl(_localActors.BaseAddress, t) }).ToList()
				};
				return status;
			}

			var mapped = new List<Status>();
			foreach (var post in posts)
			{
				var status = Map(post);
				if (status == default)
					continue;
				if (post.ReblogOfPostId != default)
				{
					if (!originals.TryGetValue(post.ReblogOfPostId, out var original) || Map(original) is not { } inner)
						continue;
					status.Reblog = inner;
					status.Content = string.Empty;
					status.Reblogged = reblogged.Contains(original.ID);
				}
				mapped.Add(status);
			}
			return mapped;
		}

		public static string AuthorOf(PostEntity post) => post.AuthorAccountId ?? post.GroupUserId;

		public static string Content(PostEntity post)
		{
			var content = post.ContentHtml ?? ActivityPubRenderer.Html(post.Text);
			return string.IsNullOrEmpty(post.Title) || post.IsFederatedCopy
				? content ?? string.Empty
				: $"<p><strong>{WebUtility.HtmlEncode(post.Title)}</strong></p>{content}";
		}

		public static string Visibility(PostVisibility visibility) => visibility switch
		{
			PostVisibility.Unlisted => "unlisted",
			PostVisibility.FollowersOnly or PostVisibility.Circle => "private",
			PostVisibility.Direct => "direct",
			_ => "public"
		};

		StatusMention Mention(PostMention mention, IReadOnlyDictionary<string, ForeignAvatar> foreign)
		{
			if (mention.IsLocal)
			{
				var handle = mention.Handle?.TrimStart('@').Split('@')[0];
				return new StatusMention { Id = mention.AccountId, Username = handle, Acct = handle, Url = mention.ActorURI };
			}
			if (!foreign.TryGetValue(mention.ActorURI, out var account))
				return default;
			return new StatusMention { Id = account.ID, Username = account.UserName, Acct = $"{account.UserName}@{account.Domain}", Url = account.Url ?? account.ActorURI };
		}

		static MediaAttachment Media(PostMedia media) => new()
		{
			Id = media.Id.ToString("N"),
			Type = media.ContentType switch
			{
				{ } type when type.StartsWith("image/gif") => "gifv",
				{ } type when type.StartsWith("image/") => "image",
				{ } type when type.StartsWith("video/") => "video",
				{ } type when type.StartsWith("audio/") => "audio",
				_ => "unknown"
			},
			Url = media.URL ?? media.RemoteURL,
			PreviewUrl = media.URL ?? media.RemoteURL,
			RemoteUrl = media.RemoteURL,
			Description = media.Description,
			Blurhash = media.Blurhash,
			Meta = media.Width.HasValue && media.Height.HasValue
				? new { original = new { width = media.Width, height = media.Height, aspect = (double)media.Width / media.Height.Value } }
				: default
		};
	}
}