SocialPub/PrivaPub/Api/Mastodon/Controllers/TimelinesController.cs

using Microsoft.AspNetCore.Mvc;

using MongoDB.Driver;
using MongoDB.Entities;

using PrivaPub.Api.Mastodon.Entities;
using PrivaPub.Api.Mastodon.Infrastructure;
using PrivaPub.Api.Mastodon.Mappers;
using PrivaPub.Domain.Privacy;
using PrivaPub.Domain.Statuses;
using PrivaPub.Models.Group;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.StaticServices;

using PostEntity = PrivaPub.Models.Post.Post;
using NotificationEntity = PrivaPub.Models.Social.Notification;
using MarkerEntity = PrivaPub.Models.Social.Marker;

namespace PrivaPub.Api.Mastodon.Controllers
{
	public class TimelinesController : MastodonController
	{
		readonly MastodonMapper _mapper;
		readonly DbEntities _dbEntities;

		public TimelinesController(MastodonMapper mapper, DbEntities dbEntities)
		{
			_mapper = mapper;
			_dbEntities = dbEntities;
		}

		[HttpGet("/api/v1/timelines/home"), Scope("read:statuses")]
		public async Task<IActionResult> Home(CancellationToken token)
		{
			//an exclusive list's members are read in that list, not at home
			var exclusive = (await DB.Default.Find<PersonaList>().Match(l => l.AvatarId == MyId && l.Exclusive).ExecuteAsync(token)).Select(l => l.ID).ToList();
			var apart = exclusive.Count == 0
				? new List<string>()
				: (await DB.Default.Find<PersonaListMember>().Match(m => exclusive.Contains(m.ListId)).ExecuteAsync(token)).Select(m => m.AccountId).Distinct().ToList();
			var home = _dbEntities.TimelineEntries.Match(e => e.AvatarId == MyId);
			if (apart.Count > 0)
				home.Match(e => !apart.Contains(e.AuthorAccountId));
			var entries = await Page.From(Params, Limit()).Fetch(home, e => e.PostId, token);
			var ids = entries.Select(e => e.PostId).ToList();
			// (located posts once reached their author's home: the entries left from then are passed over)
			var posts = (await _dbEntities.Posts.Match(p => ids.Contains(p.ID) && p.Visibility != PostVisibility.LocalGeo).Match(VisibilityPolicy.IsShown)
				.ExecuteAsync(token)).ToDictionary(p => p.ID);
			var statuses = await _mapper.Statuses(ids.Where(posts.ContainsKey).Select(id => posts[id]).ToList(), MyId, token);
			Link("/api/v1/timelines/home", entries.LastOrDefault()?.PostId, entries.FirstOrDefault()?.PostId);
			return Json(statuses);
		}

		[HttpGet("/api/v1/timelines/public"), Scope("read:statuses", requiresUser: false), Microsoft.AspNetCore.Authorization.AllowAnonymous]
		public async Task<IActionResult> Public(CancellationToken token)
		{
			var query = _dbEntities.Posts.Match(p => p.Visibility == PostVisibility.Public && p.ReblogOfPostId == null).Match(VisibilityPolicy.IsPublic);
			if (Params.Bool("local") == true)
				query.Match(p => !p.IsFederatedCopy);
			if (Params.Bool("remote") == true)
				query.Match(p => p.IsFederatedCopy);
			if (Params.Bool("only_media") == true)
				query.Match(p => p.Media.Count > 0);
			return await Respond(query, "/api/v1/timelines/public", token);
		}

		[HttpGet("/api/v1/timelines/tag/{hashtag}"), Scope("read:statuses", requiresUser: false), Microsoft.AspNetCore.Authorization.AllowAnonymous]
		public async Task<IActionResult> Tag(string hashtag, CancellationToken token)
		{
			var tag = hashtag.TrimStart('#').ToLowerInvariant();
			var query = _dbEntities.Posts.Match(p => p.Tags.Contains(tag) && p.Visibility == PostVisibility.Public && p.ReblogOfPostId == null).Match(VisibilityPolicy.IsPublic);
			if (Params.Bool("local") == true)
				query.Match(p => !p.IsFederatedCopy);
			return await Respond(query, $"/api/v1/timelines/tag/{hashtag}", token);
		}

		[HttpGet("/api/v1/favourites"), Scope("read:favourites")]
		public async Task<IActionResult> Favourites(CancellationToken token)
		{
			var favourites = await Page.From(Params, Limit()).Fetch(_dbEntities.Favourites.Match(f => f.AccountId == MyId), f => f.ID, token);
			var ids = favourites.Select(f => f.PostId).ToList();
			var posts = (await _dbEntities.Posts.Match(p => ids.Contains(p.ID) && !p.DeletedAt.HasValue).ExecuteAsync(token)).ToDictionary(p => p.ID);
			var visible = new List<PostEntity>();
			foreach (var id in ids.Where(posts.ContainsKey))
				if (await VisibilityPolicy.CanSee(posts[id], MyId, token))
					visible.Add(posts[id]);
			Link("/api/v1/favourites", favourites.LastOrDefault()?.ID, favourites.FirstOrDefault()?.ID);
			return Json(await _mapper.Statuses(visible, MyId, token));
		}

		// the persona's direct conversations, by their newest post (paged like Mastodon's by that post's id), each with its
		// other members and whether its newest post, someone else's, is newer than what the persona read; the ones it took
		// off its list stay off until a newer message
		[HttpGet("/api/v1/conversations"), Scope("read:statuses")]
		public async Task<IActionResult> Conversations(CancellationToken token)
		{
			var groups = await Page.From(Params, Limit(20, 40)).Fetch(
				_dbEntities.DmGroups.Match(g => !g.DeletionAt.HasValue && g.LastPostId != null && g.Members.Any(m => !m.IsForeign && m.AvatarId == MyId)),
				g => g.LastPostId, token);
			Link("/api/v1/conversations", groups.LastOrDefault()?.LastPostId, groups.FirstOrDefault()?.LastPostId);
			return Json(await ConversationsOf(groups, token));
		}

		async Task<List<Conversation>> ConversationsOf(List<DmGroup> groups, CancellationToken token)
		{
			var ids = groups.Select(g => g.ID).ToList();
			var states = (await DB.Default.Find<ConversationState>().Match(s => s.AvatarId == MyId && ids.Contains(s.ConversationId)).ExecuteAsync(token))
				.ToDictionary(s => s.ConversationId);
			groups = groups.Where(g => !ConversationStates.IsHidden(states.GetValueOrDefault(g.ID), g.LastPostId)).ToList();

			// the newest post each conversation still shows: usually its LastPostId, else (deleted) the one before
			var newestIds = groups.Select(g => g.LastPostId).ToList();
			var newest = (await _dbEntities.Posts.Match(p => newestIds.Contains(p.ID)).Match(VisibilityPolicy.IsShown).ExecuteAsync(token))
				.ToDictionary(p => p.ConversationId);
			foreach (var group in groups.Where(g => !newest.ContainsKey(g.ID)))
				if (await _dbEntities.Posts.Match(p => p.ConversationId == group.ID).Match(VisibilityPolicy.IsShown).Sort(p => p.ID, Order.Descending)
					.ExecuteFirstAsync(token) is { } shown)
					newest[group.ID] = shown;

			var foreignUris = groups.SelectMany(g => g.Members).Where(m => m.IsForeign).Select(m => m.AvatarId).Distinct().ToList();
			var foreignIds = (await _dbEntities.ForeignAvatars.Match(f => foreignUris.Contains(f.ActorURI)).ExecuteAsync(token))
				.GroupBy(f => f.ActorURI).ToDictionary(g => g.Key, g => g.First().ID);
			List<string> Others(DmGroup group) => group.Members.Where(m => !(m.AvatarId == MyId && !m.IsForeign))
				.Select(m => m.IsForeign ? foreignIds.GetValueOrDefault(m.AvatarId) : m.AvatarId).Where(id => id != default).ToList();
			var accounts = await _mapper.Accounts(groups.SelectMany(Others).Distinct(), token);
			var statuses = (await _mapper.Statuses(newest.Values.ToList(), MyId, token)).ToDictionary(s => s.Id);

			return groups.Where(g => newest.ContainsKey(g.ID) && statuses.ContainsKey(newest[g.ID].ID))
				.Select(g => new Conversation
				{
					Id = g.ID,
					Unread = ConversationStates.IsUnread(states.GetValueOrDefault(g.ID), newest[g.ID].ID, newest[g.ID].AuthorAccountId, MyId),
					Accounts = Others(g).Select(id => accounts.GetValueOrDefault(id)).Where(a => a != default).ToList(),
					LastStatus = statuses[newest[g.ID].ID]
				})
				.ToList();
		}

		async Task<DmGroup> MyConversation(string id, CancellationToken token) =>
			await _dbEntities.DmGroups.Match(g => g.ID == id && !g.DeletionAt.HasValue && g.Members.Any(m => !m.IsForeign && m.AvatarId == MyId))
				.ExecuteFirstAsync(token);

		[HttpPost("/api/v1/conversations/{id}/read"), Scope("write:conversations")]
		public async Task<IActionResult> ReadConversation(string id, CancellationToken token)
		{
			var group = await MyConversation(id, token);
			if (group == default)
				return NotFoundError();
			await ConversationStates.Read(MyId, group.ID, group.LastPostId, token);
			var conversation = (await ConversationsOf(new List<DmGroup> { group }, token)).FirstOrDefault();
			return Json(conversation ?? new Conversation { Id = group.ID });
		}

		// off the persona's list until a newer message; the messages themselves stay
		[HttpDelete("/api/v1/conversations/{id}"), Scope("write:conversations")]
		public async Task<IActionResult> RemoveConversation(string id, CancellationToken token)
		{
			var group = await MyConversation(id, token);
			if (group == default)
				return NotFoundError();
			await ConversationStates.Hide(MyId, group.ID, group.LastPostId, token);
			await ConversationStates.Read(MyId, group.ID, group.LastPostId, token);
			return Json(new { });
		}

		[HttpGet("/api/v1/markers"), Scope("read:statuses")]
		public async Task<IActionResult> Markers(CancellationToken token)
		{
			var wanted = Params.List("timeline");
			var markers = await DB.Default.Find<MarkerEntity>().Match(m => m.AvatarId == MyId).ExecuteAsync(token);
			return Json(markers.Where(m => wanted.Count == 0 || wanted.Contains(m.Timeline))
				.ToDictionary(m => m.Timeline, m => new Entities.Marker { LastReadId = m.LastReadId, Version = m.Version, UpdatedAt = MastodonJson.Time(m.UpdatedAt) }));
		}

		[HttpPost("/api/v1/markers"), Scope("write:statuses")]
		public async Task<IActionResult> SaveMarkers(CancellationToken token)
		{
			var result = new Dictionary<string, Entities.Marker>();
			foreach (var timeline in new[] { "home", "notifications" })
			{
				var lastRead = Params.Get($"{timeline}[last_read_id]");
				if (string.IsNullOrEmpty(lastRead))
					continue;
				var marker = await DB.Default.UpdateAndGet<MarkerEntity>()
					.Match(m => m.AvatarId == MyId && m.Timeline == timeline)
					.Modify(m => m.LastReadId, lastRead)
					.Modify(m => m.UpdatedAt, DateTime.UtcNow)
					.Modify(b => b.Inc(m => m.Version, 1))
					.Option(o => o.IsUpsert = true)
					.ExecuteAsync(token);
				result[timeline] = new Entities.Marker { LastReadId = marker.LastReadId, Version = marker.Version, UpdatedAt = MastodonJson.Time(marker.UpdatedAt) };
				// what the marker passes is read: the unread count (v1 and v2) counts only what is newer
				if (timeline == "notifications")
					await DB.Default.Update<NotificationEntity>().Match(n => n.AvatarId == MyId && !n.IsRead)
						.Match(f => f.Lte(n => n.ID, lastRead)).Modify(n => n.IsRead, true).ExecuteAsync(token);
			}
			return Json(result);
		}

		async Task<IActionResult> Respond(Find<PostEntity, PostEntity> query, string path, CancellationToken token)
		{
			var posts = await Page.From(Params, Limit()).Fetch(query, p => p.ID, token);
			Link(path, posts.LastOrDefault()?.ID, posts.FirstOrDefault()?.ID);
			return Json(await _mapper.Statuses(posts, MyId, token));
		}
	}

	public class NotificationsController : MastodonController
	{
		internal static readonly Dictionary<NotificationType, string> Names = new()
		{
			[NotificationType.Mention] = "mention",
			[NotificationType.Follow] = "follow",
			[NotificationType.FollowRequest] = "follow_request",
			[NotificationType.Favourite] = "favourite",
			[NotificationType.Reblog] = "reblog",
			[NotificationType.Update] = "update",
			[NotificationType.Poll] = "poll",
			[NotificationType.Reaction] = "pleroma:emoji_reaction",
			[NotificationType.Quote] = "quote",
			[NotificationType.ModerationWarning] = "moderation_warning"
		};

		readonly MastodonMapper _mapper;
		readonly DbEntities _dbEntities;

		public NotificationsController(MastodonMapper mapper, DbEntities dbEntities)
		{
			_mapper = mapper;
			_dbEntities = dbEntities;
		}

		Find<NotificationEntity, NotificationEntity> Filtered()
		{
			var types = Params.List("types").Select(Parse).Where(t => t.HasValue).Select(t => t.Value).ToList();
			var excluded = Params.List("exclude_types").Select(Parse).Where(t => t.HasValue).Select(t => t.Value).ToList();
			var query = _dbEntities.Notifications.Match(n => n.AvatarId == MyId);
			// what the persona's notification policy filtered stays in its requests, unless asked for (a request's own page)
			if (Params.Bool("include_filtered") != true)
				query.Match(NotFiltered);
			if (types.Count > 0)
				query.Match(n => types.Contains(n.Type));
			if (excluded.Count > 0)
				query.Match(n => !excluded.Contains(n.Type));
			if (Params.Get("account_id") is { } accountId)
				query.Match(n => n.FromAccountId == accountId);
			return query;
		}

		// (notifications made before the policy have no Filtered at all)
		static readonly FilterDefinition<NotificationEntity> NotFiltered = Builders<NotificationEntity>.Filter.Ne(n => n.Filtered, true);

		[HttpGet("/api/v1/notifications"), Scope("read:notifications")]
		public async Task<IActionResult> List(CancellationToken token)
		{
			var notifications = await Page.From(Params, Limit(15, 30)).Fetch(Filtered(), n => n.ID, token);
			Link("/api/v1/notifications", notifications.LastOrDefault()?.ID, notifications.FirstOrDefault()?.ID);
			return Json(await Map(notifications, token));
		}

		// Grouped notifications (Mastodon 4.3): api_versions.mastodon says we speak that API, so clients call it. Likes and
		// boosts of one post group together, as do follows within an hour; everything else stands alone.
		internal static readonly HashSet<string> DefaultGrouped = new() { "favourite", "reblog", "follow" };

		HashSet<string> Grouped() => Params.List("grouped_types") is { Count: > 0 } chosen ? chosen.ToHashSet() : DefaultGrouped;

		internal static string GroupKey(NotificationEntity n, ISet<string> grouped) =>
			!grouped.Contains(Names[n.Type]) ? $"ungrouped-{n.ID}"
			: n.Type == NotificationType.Follow ? $"grouped-follow-{n.CreatedAt:yyyyMMddHH}"
			: string.IsNullOrEmpty(n.PostId) ? $"ungrouped-{n.ID}"
			: $"grouped-{Names[n.Type]}-{n.PostId}";

		// the notifications a group key stands for
		System.Linq.Expressions.Expression<Func<NotificationEntity, bool>> InGroup(string key)
		{
			var me = MyId;
			if (key.StartsWith("ungrouped-", StringComparison.Ordinal))
			{
				var id = key["ungrouped-".Length..];
				return n => n.AvatarId == me && n.ID == id;
			}
			if (key.StartsWith("grouped-follow-", StringComparison.Ordinal)
				&& DateTime.TryParseExact(key["grouped-follow-".Length..], "yyyyMMddHH", System.Globalization.CultureInfo.InvariantCulture,
					System.Globalization.DateTimeStyles.AdjustToUniversal | System.Globalization.DateTimeStyles.AssumeUniversal, out var hour))
			{
				var end = hour.AddHours(1);
				return n => n.AvatarId == me && n.Type == NotificationType.Follow && n.CreatedAt >= hour && n.CreatedAt < end;
			}
			if (key.Split('-') is ["grouped", var name, var postId] && Parse(name) is { } type)
				return n => n.AvatarId == me && n.Type == type && n.PostId == postId;
			return default;
		}

		async Task<List<NotificationEntity>> Members(string key, CancellationToken token) =>
			InGroup(key) is { } filter
				? await _dbEntities.Notifications.Match(filter).Match(NotFiltered).Sort(n => n.ID, Order.Descending).Limit(80).ExecuteAsync(token)
				: new List<NotificationEntity>();

		async Task<object> Groups(List<NotificationEntity> page, ISet<string> grouped, CancellationToken token)
		{
			var mapped = (await Map(page, token)).ToDictionary(n => n.Id);
			var shown = page.Where(n => mapped.ContainsKey(n.ID)).ToList();
			var groups = new List<object>();
			foreach (var group in shown.GroupBy(n => GroupKey(n, grouped)))
			{
				var newest = mapped[group.First().ID];
				var total = group.Key.StartsWith("ungrouped-", StringComparison.Ordinal) ? 1
					: await DB.Default.CountAsync(Builders<NotificationEntity>.Filter.And(Builders<NotificationEntity>.Filter.Where(InGroup(group.Key)), NotFiltered), token);
				groups.Add(new
				{
					group_key = group.Key,
					notifications_count = Math.Max(total, group.Count()),
					type = newest.Type,
					most_recent_notification_id = newest.Id,
					page_min_id = group.Last().ID,
					page_max_id = group.First().ID,
					latest_page_notification_at = newest.CreatedAt,
					sample_account_ids = group.Select(n => mapped[n.ID].Account.Id).Distinct().Take(8).ToList(),
					status_id = newest.Status?.Id,
					emoji = newest.Emoji,
					emoji_url = newest.EmojiUrl,
					moderation_warning = newest.ModerationWarning
				});
			}
			return new
			{
				accounts = mapped.Values.Select(n => n.Account).DistinctBy(a => a.Id).ToList(),
				statuses = mapped.Values.Where(n => n.Status != default).Select(n => n.Status).DistinctBy(s => s.Id).ToList(),
				notification_groups = groups
			};
		}

		[HttpGet("/api/v2/notifications"), Scope("read:notifications")]
		public async Task<IActionResult> GroupedList(CancellationToken token)
		{
			var notifications = await Page.From(Params, Limit(40, 80)).Fetch(Filtered(), n => n.ID, token);
			Link("/api/v2/notifications", notifications.LastOrDefault()?.ID, notifications.FirstOrDefault()?.ID);
			return Json(await Groups(notifications, Grouped(), token));
		}

		[HttpGet("/api/v2/notifications/unread_count"), Scope("read:notifications")]
		public async Task<IActionResult> GroupedUnreadCount(CancellationToken token)
		{
			var unread = await Filtered().Match(n => !n.IsRead).Sort(n => n.ID, Order.Descending)
				.Limit(Math.Clamp(Params.Int("limit") ?? 100, 1, 1000)).ExecuteAsync(token);
			var shown = (await Map(unread, token)).Select(n => n.Id).ToHashSet();
			var grouped = Grouped();
			return Json(new { count = unread.Where(n => shown.Contains(n.ID)).Select(n => GroupKey(n, grouped)).Distinct().Count() });
		}

		[HttpGet("/api/v2/notifications/{groupKey}"), Scope("read:notifications")]
		public async Task<IActionResult> Group(string groupKey, CancellationToken token)
		{
			var members = await Members(groupKey, token);
			if (members.Count == 0)
				return NotFoundError();
			return Json(await Groups(members, new HashSet<string>(DefaultGrouped.Append(Names[members[0].Type])), token));
		}

		[HttpGet("/api/v2/notifications/{groupKey}/accounts"), Scope("read:notifications")]
		public async Task<IActionResult> GroupAccounts(string groupKey, CancellationToken token)
		{
			var members = await Members(groupKey, token);
			if (members.Count == 0)
				return NotFoundError();
			return Json((await Map(members, token)).Select(n => n.Account).DistinctBy(a => a.Id).ToList());
		}

		[HttpPost("/api/v2/notifications/{groupKey}/dismiss"), Scope("write:notifications")]
		public async Task<IActionResult> DismissGroup(string groupKey, CancellationToken token)
		{
			if (InGroup(groupKey) is not { } filter)
				return NotFoundError();
			await DB.Default.DeleteAsync(filter);
			return Json(new { });
		}

		[HttpGet("/api/v1/notifications/{id}"), Scope("read:notifications")]
		public async Task<IActionResult> Get(string id, CancellationToken token)
		{
			var notification = await _dbEntities.Notifications.Match(n => n.ID == id && n.AvatarId == MyId).ExecuteFirstAsync(token);
			var mapped = notification == default ? default : (await Map(new List<NotificationEntity> { notification }, token)).FirstOrDefault();
			return mapped == default ? NotFoundError() : Json(mapped);
		}

		[HttpPost("/api/v1/notifications/clear"), Scope("write:notifications")]
		public async Task<IActionResult> Clear(CancellationToken token)
		{
			await DB.Default.DeleteAsync<NotificationEntity>(n => n.AvatarId == MyId);
			return Json(new { });
		}

		[HttpPost("/api/v1/notifications/{id}/dismiss"), Scope("write:notifications")]
		public async Task<IActionResult> Dismiss(string id, CancellationToken token)
		{
			await DB.Default.DeleteAsync<NotificationEntity>(n => n.ID == id && n.AvatarId == MyId);
			return Json(new { });
		}

		// counts what the list would show (Map drops notifications from gone accounts and about hidden posts), at most
		// `limit` of them, as Mastodon does
		[HttpGet("/api/v1/notifications/unread_count"), Scope("read:notifications")]
		public async Task<IActionResult> UnreadCount(CancellationToken token)
		{
			var unread = await DB.Default.Find<NotificationEntity>().Match(n => n.AvatarId == MyId && !n.IsRead).Match(NotFiltered)
				.Sort(n => n.ID, Order.Descending).Limit(Math.Clamp(Params.Int("limit") ?? 100, 1, 1000)).ExecuteAsync(token);
			return Json(new { count = (await Map(unread, token)).Count });
		}

		Task<List<Entities.Notification>> Map(List<NotificationEntity> notifications, CancellationToken token) =>
			_mapper.Notifications(notifications, MyId, token);

		static NotificationType? Parse(string name) => Names.FirstOrDefault(n => n.Value == name) is { Value: not null } pair ? pair.Key : (NotificationType?)null;
	}
}