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.Services.Federation;
using PrivaPub.StaticServices;

using GroupEntity = PrivaPub.Models.Group.Group;

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> GetInvitation(string invitationCode, string invitationPassword, CancellationToken token);
	}

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

		public GroupUsersService(DbEntities dbEntities,
			IPasswordHasher passwordHasher,
			ILocalActorService localActors,
			IDeliveryService delivery,
			IStringLocalizer<GenericRes> localizer,
			ILogger<GroupUsersService> logger)
		{
			_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["Error: {0}", ex.Message], 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["Error: {0}", ex.Message], 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 take.", 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,
					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 } }
				};
				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["Error: {0}", ex.Message], 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 (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["Error: {0}", ex.Message], 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);
				}

				result.Data = ToView(group, form.AvatarId);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(JoinGroup)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], exception: ex);
			}
		}

		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);
				return result;
			}
			catch (Exception ex)
			{
				_logger.LogError(ex, $"{nameof(GroupUsersService)}.{nameof(LeaveGroup)}");
				return result.Invalidate(_localizer["Error: {0}", ex.Message], 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["Error: {0}", ex.Message], 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;
		}

		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 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,
				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
			};
		}
	}
}