using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using Microsoft.Extensions.Logging;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.Session;
using MediaBrowser.Controller.Syncplay;
using MediaBrowser.Model.Configuration;
using MediaBrowser.Model.Syncplay;

namespace Emby.Server.Implementations.Syncplay
{
    /// <summary>
    /// Class SyncplayManager.
    /// </summary>
    public class SyncplayManager : ISyncplayManager, IDisposable
    {
        /// <summary>
        /// The logger.
        /// </summary>
        private readonly ILogger _logger;

        /// <summary>
        /// The user manager.
        /// </summary>
        private readonly IUserManager _userManager;

        /// <summary>
        /// The session manager.
        /// </summary>
        private readonly ISessionManager _sessionManager;

        /// <summary>
        /// The map between sessions and groups.
        /// </summary>
        private readonly ConcurrentDictionary<string, ISyncplayController> _sessionToGroupMap =
            new ConcurrentDictionary<string, ISyncplayController>(StringComparer.OrdinalIgnoreCase);

        /// <summary>
        /// The groups.
        /// </summary>
        private readonly ConcurrentDictionary<string, ISyncplayController> _groups =
        new ConcurrentDictionary<string, ISyncplayController>(StringComparer.OrdinalIgnoreCase);

        private bool _disposed = false;

        public SyncplayManager(
            ILogger<SyncplayManager> logger,
            IUserManager userManager,
            ISessionManager sessionManager)
        {
            _logger = logger;
            _userManager = userManager;
            _sessionManager = sessionManager;

            _sessionManager.SessionEnded += _sessionManager_SessionEnded;
            _sessionManager.PlaybackStopped += _sessionManager_PlaybackStopped;
        }

        /// <summary>
        /// Gets all groups.
        /// </summary>
        /// <value>All groups.</value>
        public IEnumerable<ISyncplayController> Groups => _groups.Values;

        /// <inheritdoc />
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and optionally managed resources.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (_disposed)
            {
                return;
            }

            _sessionManager.SessionEnded -= _sessionManager_SessionEnded;
            _sessionManager.PlaybackStopped -= _sessionManager_PlaybackStopped;

            _disposed = true;
        }

        private void CheckDisposed()
        {
            if (_disposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
        }

        void _sessionManager_SessionEnded(object sender, SessionEventArgs e)
        {
            var session = e.SessionInfo;
            if (!IsSessionInGroup(session)) return;
            LeaveGroup(session);
        }

        void _sessionManager_PlaybackStopped(object sender, PlaybackStopEventArgs e)
        {
            var session = e.Session;
            if (!IsSessionInGroup(session)) return;
            LeaveGroup(session);
        }

        private bool IsSessionInGroup(SessionInfo session)
        {
            return _sessionToGroupMap.ContainsKey(session.Id);
        }

        private Guid? GetSessionGroup(SessionInfo session)
        {
            ISyncplayController group;
            _sessionToGroupMap.TryGetValue(session.Id, out group);
            if (group != null)
            {
                return group.GetGroupId();
            }
            else
            {
                return null;
            }
        }

        /// <inheritdoc />
        public void NewGroup(SessionInfo session)
        {
            var user = _userManager.GetUserById(session.UserId);

            if (user.Policy.SyncplayAccess != SyncplayAccess.CreateAndJoinGroups)
            {
                // TODO: shall an error message be sent back to the client?
                return;
            }

            if (IsSessionInGroup(session))
            {
                LeaveGroup(session);
            }

            var group = new SyncplayController(_logger, _sessionManager, this);
            _groups[group.GetGroupId().ToString()] = group;

            group.InitGroup(session);
        }

        /// <inheritdoc />
        public void JoinGroup(SessionInfo session, string groupId)
        {
            var user = _userManager.GetUserById(session.UserId);

            if (user.Policy.SyncplayAccess == SyncplayAccess.None)
            {
                // TODO: shall an error message be sent back to the client?
                return;
            }

            if (IsSessionInGroup(session))
            {
                if (GetSessionGroup(session).Equals(groupId)) return;
                LeaveGroup(session);
            }

            ISyncplayController group;
            _groups.TryGetValue(groupId, out group);

            if (group == null)
            {
                _logger.LogError("Syncplaymanager JoinGroup: " + groupId + " does not exist.");

                var update = new SyncplayGroupUpdate<string>();
                update.Type = SyncplayGroupUpdateType.NotInGroup;
                _sessionManager.SendSyncplayGroupUpdate(session.Id.ToString(), update, CancellationToken.None);
                return;
            }
            group.SessionJoin(session);
        }

        /// <inheritdoc />
        public void LeaveGroup(SessionInfo session)
        {
            // TODO: what happens to users that are in a group and get their permissions revoked?

            ISyncplayController group;
            _sessionToGroupMap.TryGetValue(session.Id, out group);

            if (group == null)
            {
                _logger.LogWarning("Syncplaymanager HandleRequest: " + session.Id + " not in group.");

                var update = new SyncplayGroupUpdate<string>();
                update.Type = SyncplayGroupUpdateType.NotInGroup;
                _sessionManager.SendSyncplayGroupUpdate(session.Id.ToString(), update, CancellationToken.None);
                return;
            }
            group.SessionLeave(session);

            if (group.IsGroupEmpty())
            {
                _groups.Remove(group.GetGroupId().ToString(), out _);
            }
        }

        /// <inheritdoc />
        public List<GroupInfoView> ListGroups(SessionInfo session)
        {
            var user = _userManager.GetUserById(session.UserId);

            if (user.Policy.SyncplayAccess == SyncplayAccess.None)
            {
                return new List<GroupInfoView>();
            }

            // Filter by playing item if the user is viewing something already
            if (session.NowPlayingItem != null)
            {
                return _groups.Values.Where(
                    group => group.GetPlayingItemId().Equals(session.FullNowPlayingItem.Id)
                ).Select(
                    group => group.GetInfo()
                ).ToList();
            }
            // Otherwise show all available groups
            else
            {
                return _groups.Values.Select(
                    group => group.GetInfo()
                ).ToList();
            }
        }

        /// <inheritdoc />
        public void HandleRequest(SessionInfo session, SyncplayRequestInfo request)
        {
            var user = _userManager.GetUserById(session.UserId);

            if (user.Policy.SyncplayAccess == SyncplayAccess.None)
            {
                // TODO: same as LeaveGroup
                return;
            }

            ISyncplayController group;
            _sessionToGroupMap.TryGetValue(session.Id, out group);

            if (group == null)
            {
                _logger.LogWarning("Syncplaymanager HandleRequest: " + session.Id + " not in group.");

                var update = new SyncplayGroupUpdate<string>();
                update.Type = SyncplayGroupUpdateType.NotInGroup;
                _sessionManager.SendSyncplayGroupUpdate(session.Id.ToString(), update, CancellationToken.None);
                return;
            }
            group.HandleRequest(session, request);
        }
        
        /// <inheritdoc />
        public void MapSessionToGroup(SessionInfo session, ISyncplayController group)
        {
            if (IsSessionInGroup(session))
            {
                throw new InvalidOperationException("Session in other group already!");
            }
            _sessionToGroupMap[session.Id] = group;
        }

        /// <inheritdoc />
        public void UnmapSessionFromGroup(SessionInfo session, ISyncplayController group)
        {
            if (!IsSessionInGroup(session))
            {
                throw new InvalidOperationException("Session not in any group!");
            }

            ISyncplayController tempGroup;
            _sessionToGroupMap.Remove(session.Id, out tempGroup);

            if (!tempGroup.GetGroupId().Equals(group.GetGroupId()))
            {
                throw new InvalidOperationException("Session was in wrong group!");
            }
        }
    }
}