using Microsoft.Extensions.Localization;

using MongoDB.Entities;

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

using System.Text.Json.Nodes;

using DmPostEntity = PrivaPub.Models.Post.DmPost;
using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Services
{
	public interface IPostsService
	{
		Task<WebResult> InsertPost(string rootUserId, InsertPostForm form, CancellationToken token);
		Task<WebResult> DeletePost(string rootUserId, DeletePostForm form, CancellationToken token);
		Task<WebResult> GetPosts(string rootUserId, string avatarId, string groupId, CancellationToken token);
		Task<WebResult> InsertDm(string rootUserId, InsertDmForm form, CancellationToken token);
		Task<WebResult> GetDms(string rootUserId, string avatarId, string dmGroupId, CancellationToken token);
	}

	public class PostsService : IPostsService
	{
		const int PageSize = 50;

		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IRemoteActorService _remoteActors;
		readonly IDeliveryService _delivery;
		readonly IStringLocalizer<GenericRes> _localizer;
		readonly ILogger<PostsService> _logger;

		public PostsService(DbEntities dbEntities,
			ILocalActorService localActors,
			IRemoteActorService remoteActors,
			IDeliveryService delivery,
			IStringLocalizer<GenericRes> localizer,
			ILogger<PostsService> logger)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
			_remoteActors = remoteActors;
			_delivery = delivery;
			_localizer = localizer;
			_logger = logger;
		}

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

				LocalActor group = default;
				if (!string.IsNullOrEmpty(form.GroupId))
				{
					var groupEntity = await _dbEntities.Groups.MatchID(form.GroupId).ExecuteFirstAsync(token);
					if (groupEntity == default || groupEntity.DeletionAt.HasValue
						|| !groupEntity.Members.Any(m => !m.IsForeign && m.AvatarId == form.AvatarId))
						return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);
					group = _localActors.FromGroup(groupEntity);
				}

				var post = new PostEntity
				{
					GroupUserId = author.Id,
					GroupId = group?.Id,
					Title = form.Title,
					Text = form.Text,
					HasContentWarning = form.HasContentWarning,
					AnsweringToPostId = form.AnsweringToPostId,
					ActorURI = author.Uri
				};
				post.ID = (string)post.GenerateNewID();
				post.ObjectURI = author.PostUri(post.ID);
				await DB.Default.SaveAsync(post, token);

				var inReplyTo = await ReplyTarget(form.AnsweringToPostId, token);
				var note = ActivityPubRenderer.Note(post, author, group, inReplyTo);
				var create = ActivityPubRenderer.Create(author, note, $"create-{post.ID}");
				await _delivery.EnqueueToFollowers(author, create, token);
				if (group != default)
					await _delivery.EnqueueToFollowers(group, ActivityPubRenderer.Announce(group, post.ObjectURI, $"announce-{post.ID}"), token);

				result.Data = ToView(post);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(PostsService)}.{nameof(InsertPost)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

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

				var post = await _dbEntities.Posts
					.Match(p => p.ID == form.PostId && p.GroupUserId == author.Id && !p.IsFederatedCopy)
					.ExecuteFirstAsync(token);
				if (post == default)
					return result.Invalidate(_localizer["Post not found."], StatusCodes.Status404NotFound);

				await DB.Default.DeleteAsync<PostEntity>(post.ID);

				var delete = ActivityPubRenderer.Delete(author, post.ObjectURI, $"delete-{post.ID}",
					new JsonArray(ActivityPubRenderer.Public), new JsonArray(author.Followers));
				var extraInboxes = Enumerable.Empty<string>();
				if (!string.IsNullOrEmpty(post.GroupId))
				{
					var group = await _localActors.FindById(LocalActorKind.Group, post.GroupId, token);
					if (group != default)
						extraInboxes = await _delivery.FollowerInboxes(group, token);
				}
				await _delivery.EnqueueToFollowers(author, delete, token, extraInboxes);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(PostsService)}.{nameof(DeletePost)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

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

				var query = _dbEntities.Posts;
				if (string.IsNullOrEmpty(groupId))
					query.Match(p => p.GroupUserId == avatar.Id);
				else
				{
					var isMember = await _dbEntities.Groups
						.Match(g => g.ID == groupId && g.Members.Any(m => !m.IsForeign && m.AvatarId == avatar.Id))
						.ExecuteAnyAsync(token);
					if (!isMember)
						return result.Invalidate(_localizer["Group not found."], StatusCodes.Status404NotFound);
					query.Match(p => p.GroupId == groupId);
				}

				var posts = await query.Sort(p => p.CreationDate, Order.Descending).Limit(PageSize).ExecuteAsync(token);
				result.Data = posts.Select(ToView).ToList();
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(PostsService)}.{nameof(GetPosts)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

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

				DmGroup dmGroup;
				if (!string.IsNullOrEmpty(form.DmGroupId))
				{
					dmGroup = await _dbEntities.DmGroups.MatchID(form.DmGroupId).ExecuteFirstAsync(token);
					if (dmGroup == default || !dmGroup.Members.Any(m => !m.IsForeign && m.AvatarId == author.Id))
						return result.Invalidate(_localizer["Conversation not found."], StatusCodes.Status404NotFound);
				}
				else
				{
					if (form.Recipients.Count == 0)
						return result.Invalidate(_localizer["At least one recipient is required."]);
					var members = new List<GroupMember> { new() { AvatarId = author.Id } };
					foreach (var recipient in form.Recipients.Distinct(StringComparer.OrdinalIgnoreCase))
					{
						var member = await ResolveRecipient(recipient, token);
						if (member == default)
							return result.Invalidate(_localizer["Recipient '{0}' not found.", recipient], StatusCodes.Status404NotFound);
						if (members.All(m => m.AvatarId != member.AvatarId))
							members.Add(member);
					}
					dmGroup = new DmGroup { Members = members };
					dmGroup.ID = (string)dmGroup.GenerateNewID();
					dmGroup.ConversationURI = $"{author.Uri}/conversations/{dmGroup.ID}";
					await DB.Default.SaveAsync(dmGroup, token);
				}

				var dm = new DmPostEntity
				{
					GroupUserId = author.Id,
					GroupId = dmGroup.ID,
					Text = form.Text,
					HasContentWarning = form.HasContentWarning,
					ActorURI = author.Uri
				};
				dm.ID = (string)dm.GenerateNewID();
				dm.ObjectURI = author.PostUri(dm.ID);
				await DB.Default.SaveAsync(dm, token);
				await DB.Default.Update<DmGroup>().MatchID(dmGroup.ID).Modify(g => g.UpdatedAt, DateTime.UtcNow).ExecuteAsync(token);

				var remote = new List<(string Uri, string Handle)>();
				var inboxes = new List<string>();
				foreach (var member in dmGroup.Members.Where(m => m.IsForeign))
				{
					var foreign = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == member.AvatarId).ExecuteFirstAsync(token);
					if (foreign == default)
						continue;
					remote.Add((foreign.ActorURI, $"{foreign.UserName}@{foreign.Domain}"));
					inboxes.Add(foreign.InboxURL);
				}
				foreach (var member in dmGroup.Members.Where(m => !m.IsForeign && m.AvatarId != author.Id))
				{
					var local = await _localActors.FindById(LocalActorKind.Person, member.AvatarId, token);
					if (local != default)
						remote.Add((local.Uri, local.Handle));
				}

				if (inboxes.Count > 0)
				{
					var note = ActivityPubRenderer.DirectNote(dm, author, remote, dmGroup.ConversationURI);
					var create = ActivityPubRenderer.Create(author, note, $"create-{dm.ID}");
					await _delivery.Enqueue(author, inboxes, create, token);
				}

				result.Data = ToView(dm);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(PostsService)}.{nameof(InsertDm)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

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

				if (string.IsNullOrEmpty(dmGroupId))
				{
					var groups = await _dbEntities.DmGroups
						.Match(g => !g.DeletionAt.HasValue && g.Members.Any(m => !m.IsForeign && m.AvatarId == avatar.Id))
						.Sort(g => g.UpdatedAt, Order.Descending)
						.ExecuteAsync(token);
					result.Data = groups.Select(g => new ViewDmGroup
					{
						Id = g.ID,
						Members = g.Members.Select(m => m.AvatarId).ToList(),
						UpdatedAt = g.UpdatedAt
					}).ToList();
					return result;
				}

				var isMember = await _dbEntities.DmGroups
					.Match(g => g.ID == dmGroupId && g.Members.Any(m => !m.IsForeign && m.AvatarId == avatar.Id))
					.ExecuteAnyAsync(token);
				if (!isMember)
					return result.Invalidate(_localizer["Conversation not found."], StatusCodes.Status404NotFound);

				var dms = await _dbEntities.DmPosts
					.Match(p => p.GroupId == dmGroupId)
					.Sort(p => p.CreationDate, Order.Descending)
					.Limit(PageSize)
					.ExecuteAsync(token);
				result.Data = dms.Select(ToView).ToList();
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(PostsService)}.{nameof(GetDms)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

		async Task<GroupMember> ResolveRecipient(string recipient, CancellationToken token)
		{
			var handle = recipient.Trim().TrimStart('@');
			if (!handle.Contains('@') || handle.EndsWith("@" + new Uri(_localActors.BaseAddress).Authority, StringComparison.OrdinalIgnoreCase))
			{
				var local = await _localActors.FindByUserName(handle.Split('@')[0], token);
				return local is { Kind: LocalActorKind.Person } ? new GroupMember { AvatarId = local.Id } : default;
			}

			var actorUri = await _remoteActors.ResolveHandle(handle, token);
			if (actorUri == default)
				return default;
			var foreign = await _remoteActors.GetActor(actorUri, await _localActors.GetInstanceActor(token), refresh: false, token);
			return foreign == default ? default : new GroupMember { AvatarId = foreign.ActorURI, IsForeign = true };
		}

		async Task<string> ReplyTarget(string answeringToPostId, CancellationToken token)
		{
			if (string.IsNullOrEmpty(answeringToPostId))
				return default;
			if (answeringToPostId.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
				return answeringToPostId;
			var parent = await _dbEntities.Posts.MatchID(answeringToPostId).ExecuteFirstAsync(token);
			return parent?.ObjectURI;
		}

		async Task<LocalActor> OwnedAvatar(string rootUserId, string avatarId, CancellationToken token)
		{
			if (string.IsNullOrEmpty(rootUserId) || string.IsNullOrEmpty(avatarId))
				return default;
			if (!await _dbEntities.RootToAvatars.Match(ra => ra.RootId == rootUserId && ra.AvatarId == avatarId).ExecuteAnyAsync(token))
				return default;
			return await _localActors.FindById(LocalActorKind.Person, avatarId, token);
		}

		static ViewPost ToView(PostEntity post) => new()
		{
			Id = post.ID,
			ObjectURI = post.ObjectURI,
			AuthorAvatarId = post.IsFederatedCopy ? default : post.GroupUserId,
			AuthorActorURI = post.ActorURI,
			GroupId = post.GroupId,
			AnsweringToPostId = post.AnsweringToPostId,
			Title = post.Title,
			Text = post.Text,
			HasContentWarning = post.HasContentWarning,
			IsFederatedCopy = post.IsFederatedCopy,
			CreationDate = post.CreationDate
		};

		static ViewPost ToView(DmPostEntity post) => new()
		{
			Id = post.ID,
			ObjectURI = post.ObjectURI,
			AuthorAvatarId = post.IsFederatedCopy ? default : post.GroupUserId,
			AuthorActorURI = post.ActorURI,
			DmGroupId = post.GroupId,
			AnsweringToPostId = post.AnsweringToPostId,
			Title = post.Title,
			Text = post.Text,
			HasContentWarning = post.HasContentWarning,
			IsFederatedCopy = post.IsFederatedCopy,
			CreationDate = post.CreationDate
		};
	}
}