using System.Security.Claims;
using System.Text.Json;
using System.Text.Json.Serialization;
using ChessCubing.App.Models;
using ChessCubing.App.Models.Social;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.AspNetCore.SignalR.Client;

namespace ChessCubing.App.Services;

public sealed class SocialRealtimeService(
    NavigationManager navigation,
    AuthenticationStateProvider authenticationStateProvider) : IAsyncDisposable
{
    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
    };

    private readonly NavigationManager _navigation = navigation;
    private readonly AuthenticationStateProvider _authenticationStateProvider = authenticationStateProvider;
    private readonly SemaphoreSlim _gate = new(1, 1);

    private HubConnection? _hubConnection;
    private string? _currentSubject;
    private string? _joinedPlaySessionId;
    private HashSet<string> _knownPresenceSubjects = new(StringComparer.Ordinal);
    private HashSet<string> _onlineSubjects = new(StringComparer.Ordinal);
    private PlayInviteMessage? _incomingPlayInvite;
    private PlayInviteMessage? _outgoingPlayInvite;
    private PlaySessionResponse? _activePlaySession;
    private CollaborativeMatchSnapshot? _collaborativeSnapshot;
    private string? _lastInviteNotice;
    private int _socialVersion;
    private bool _started;

    public event Action? Changed;

    public PlayInviteMessage? IncomingPlayInvite => _incomingPlayInvite;

    public PlayInviteMessage? OutgoingPlayInvite => _outgoingPlayInvite;

    public PlaySessionResponse? ActivePlaySession => _activePlaySession;

    public CollaborativeMatchSnapshot? CollaborativeSnapshot => _collaborativeSnapshot;

    public string? LastInviteNotice => _lastInviteNotice;

    public int SocialVersion => _socialVersion;

    public async Task EnsureStartedAsync()
    {
        if (_started)
        {
            await SyncConnectionAsync();
            return;
        }

        _started = true;
        _authenticationStateProvider.AuthenticationStateChanged += HandleAuthenticationStateChanged;
        await SyncConnectionAsync();
    }

    public bool IsUserOnline(string subject)
        => _onlineSubjects.Contains(subject);

    public bool? GetKnownOnlineStatus(string subject)
    {
        if (_onlineSubjects.Contains(subject))
        {
            return true;
        }

        return _knownPresenceSubjects.Contains(subject)
            ? false
            : null;
    }

    public async Task EnsureJoinedPlaySessionAsync(string? sessionId)
    {
        var normalizedSessionId = sessionId?.Trim();
        if (string.IsNullOrWhiteSpace(normalizedSessionId))
        {
            return;
        }

        await EnsureStartedAsync();
        await JoinPlaySessionCoreAsync(normalizedSessionId);
    }

    public async Task PublishMatchStateAsync(MatchState? match, string route)
    {
        var sessionId = match?.CollaborationSessionId
            ?? _activePlaySession?.SessionId
            ?? _joinedPlaySessionId;

        if (string.IsNullOrWhiteSpace(sessionId))
        {
            return;
        }

        await EnsureJoinedPlaySessionAsync(sessionId);

        if (_hubConnection is null || _hubConnection.State != HubConnectionState.Connected)
        {
            throw new InvalidOperationException("La connexion temps reel n'est pas prete.");
        }

        var payload = match is null
            ? null
            : JsonSerializer.Serialize(match, JsonOptions);

        await _hubConnection.InvokeAsync("PublishMatchState", sessionId, payload, route);
    }

    public async Task SendPlayInviteAsync(string recipientSubject, string recipientColor)
    {
        _lastInviteNotice = null;

        if (_hubConnection is null)
        {
            throw new InvalidOperationException("La connexion temps reel n'est pas prete.");
        }

        var invite = await _hubConnection.InvokeAsync<PlayInviteMessage>("SendPlayInvite", recipientSubject, recipientColor);
        ApplyInvite(invite);
        RaiseChanged();
    }

    public async Task RespondToIncomingPlayInviteAsync(bool accept)
    {
        if (_hubConnection is null || _incomingPlayInvite is null)
        {
            return;
        }

        var inviteId = _incomingPlayInvite.InviteId;
        await _hubConnection.InvokeAsync("RespondToPlayInvite", inviteId, accept);

        if (!accept)
        {
            _incomingPlayInvite = null;
            RaiseChanged();
        }
    }

    public async Task CancelOutgoingPlayInviteAsync()
    {
        if (_hubConnection is null || _outgoingPlayInvite is null)
        {
            return;
        }

        var inviteId = _outgoingPlayInvite.InviteId;
        await _hubConnection.InvokeAsync("CancelPlayInvite", inviteId);
    }

    public void ClearInviteNotice()
    {
        if (string.IsNullOrWhiteSpace(_lastInviteNotice))
        {
            return;
        }

        _lastInviteNotice = null;
        RaiseChanged();
    }

    public async ValueTask DisposeAsync()
    {
        _authenticationStateProvider.AuthenticationStateChanged -= HandleAuthenticationStateChanged;

        await _gate.WaitAsync();
        try
        {
            if (_hubConnection is not null)
            {
                await _hubConnection.DisposeAsync();
                _hubConnection = null;
            }
        }
        finally
        {
            _gate.Release();
            _gate.Dispose();
        }
    }

    private void HandleAuthenticationStateChanged(Task<AuthenticationState> authenticationStateTask)
        => _ = SyncConnectionAsync();

    private async Task SyncConnectionAsync()
    {
        await _gate.WaitAsync();
        try
        {
            var authState = await _authenticationStateProvider.GetAuthenticationStateAsync();
            var user = authState.User;
            var subject = ResolveSubject(user);
            var preserveSessionState = string.Equals(subject, _currentSubject, StringComparison.Ordinal);

            if (string.IsNullOrWhiteSpace(subject))
            {
                await DisconnectUnsafeAsync(clearSessionState: true);
                return;
            }

            if (_hubConnection is not null &&
                string.Equals(subject, _currentSubject, StringComparison.Ordinal) &&
                _hubConnection.State is HubConnectionState.Connected or HubConnectionState.Connecting or HubConnectionState.Reconnecting)
            {
                return;
            }

            await DisconnectUnsafeAsync(clearSessionState: !preserveSessionState);

            _currentSubject = subject;
            _hubConnection = BuildHubConnection();
            RegisterHandlers(_hubConnection);
            await _hubConnection.StartAsync();

            if (!string.IsNullOrWhiteSpace(_joinedPlaySessionId))
            {
                await JoinPlaySessionCoreAsync(_joinedPlaySessionId);
            }
        }
        finally
        {
            _gate.Release();
        }
    }

    private HubConnection BuildHubConnection()
        => new HubConnectionBuilder()
            .WithUrl(_navigation.ToAbsoluteUri("/hubs/social"))
            .WithAutomaticReconnect()
            .Build();

    private void RegisterHandlers(HubConnection connection)
    {
        connection.On<PresenceSnapshotMessage>("PresenceSnapshot", message =>
        {
            _knownPresenceSubjects = message.OnlineSubjects.ToHashSet(StringComparer.Ordinal);
            _onlineSubjects = message.OnlineSubjects.ToHashSet(StringComparer.Ordinal);
            RaiseChanged();
        });

        connection.On<PresenceChangedMessage>("PresenceChanged", message =>
        {
            _knownPresenceSubjects.Add(message.Subject);

            if (message.IsOnline)
            {
                _onlineSubjects.Add(message.Subject);
            }
            else
            {
                _onlineSubjects.Remove(message.Subject);
            }

            RaiseChanged();
        });

        connection.On("SocialChanged", async () =>
        {
            Interlocked.Increment(ref _socialVersion);
            await RequestPresenceSnapshotAsync();
            RaiseChanged();
        });

        connection.On<PlayInviteMessage>("PlayInviteUpdated", message =>
        {
            ApplyInvite(message);
            RaiseChanged();
        });

        connection.On<PlayInviteClosedMessage>("PlayInviteClosed", message =>
        {
            if (_incomingPlayInvite?.InviteId == message.InviteId)
            {
                _incomingPlayInvite = null;
            }

            if (_outgoingPlayInvite?.InviteId == message.InviteId)
            {
                _outgoingPlayInvite = null;
            }

            _lastInviteNotice = message.Message;
            RaiseChanged();
        });

        connection.On<CollaborativeMatchStateMessage>("CollaborativeMatchStateUpdated", message =>
        {
            ApplyCollaborativeState(message);
            RaiseChanged();
        });

        connection.On<PlaySessionResponse>("PlayInviteAccepted", async session =>
        {
            _incomingPlayInvite = null;
            _outgoingPlayInvite = null;
            _activePlaySession = session;
            _lastInviteNotice = "La partie est confirmee. Les deux ecrans resteront synchronises pendant le match.";
            await JoinPlaySessionCoreAsync(session.SessionId);
            RaiseChanged();
        });

        connection.Reconnected += async _ =>
        {
            await RequestPresenceSnapshotAsync();

            if (!string.IsNullOrWhiteSpace(_joinedPlaySessionId))
            {
                await JoinPlaySessionCoreAsync(_joinedPlaySessionId);
            }

            RaiseChanged();
        };

        connection.Closed += async _ =>
        {
            if (!string.IsNullOrWhiteSpace(_currentSubject))
            {
                await SyncConnectionAsync();
            }
        };
    }

    private async Task RequestPresenceSnapshotAsync()
    {
        if (_hubConnection is null || _hubConnection.State != HubConnectionState.Connected)
        {
            return;
        }

        try
        {
            await _hubConnection.InvokeAsync("RequestPresenceSnapshot");
        }
        catch
        {
            // La vue peut continuer avec le dernier etat connu si le snapshot echoue ponctuellement.
        }
    }

    private async Task JoinPlaySessionCoreAsync(string sessionId)
    {
        if (_hubConnection is null || _hubConnection.State != HubConnectionState.Connected)
        {
            return;
        }

        if (!string.IsNullOrWhiteSpace(_joinedPlaySessionId) &&
            !string.Equals(_joinedPlaySessionId, sessionId, StringComparison.Ordinal))
        {
            try
            {
                await _hubConnection.InvokeAsync("LeavePlaySession", _joinedPlaySessionId);
            }
            catch
            {
                // La prochaine connexion recreera les groupes si besoin.
            }
        }

        var latestState = await _hubConnection.InvokeAsync<CollaborativeMatchStateMessage?>("JoinPlaySession", sessionId);
        _joinedPlaySessionId = sessionId;

        if (latestState is not null)
        {
            ApplyCollaborativeState(latestState);
        }
        else if (_collaborativeSnapshot?.SessionId != sessionId)
        {
            _collaborativeSnapshot = null;
        }
    }

    private void ApplyInvite(PlayInviteMessage invite)
    {
        if (string.IsNullOrWhiteSpace(_currentSubject))
        {
            return;
        }

        if (string.Equals(invite.RecipientSubject, _currentSubject, StringComparison.Ordinal))
        {
            _incomingPlayInvite = invite;
        }

        if (string.Equals(invite.SenderSubject, _currentSubject, StringComparison.Ordinal))
        {
            _outgoingPlayInvite = invite;
        }
    }

    private void ApplyCollaborativeState(CollaborativeMatchStateMessage message)
    {
        if (_collaborativeSnapshot is not null &&
            string.Equals(_collaborativeSnapshot.SessionId, message.SessionId, StringComparison.Ordinal) &&
            message.Revision <= _collaborativeSnapshot.Revision)
        {
            return;
        }

        MatchState? match = null;
        if (!string.IsNullOrWhiteSpace(message.MatchJson))
        {
            try
            {
                match = JsonSerializer.Deserialize<MatchState>(message.MatchJson, JsonOptions);
                if (match is not null)
                {
                    match.CollaborationSessionId = message.SessionId;
                    MatchEngine.NormalizeRecoveredMatch(match);
                }
            }
            catch
            {
                match = null;
            }
        }

        _collaborativeSnapshot = new CollaborativeMatchSnapshot
        {
            SessionId = message.SessionId,
            Match = match,
            Route = string.IsNullOrWhiteSpace(message.Route) ? "/application.html" : message.Route,
            SenderSubject = message.SenderSubject,
            Revision = message.Revision,
            UpdatedUtc = message.UpdatedUtc,
        };
    }

    private async Task DisconnectUnsafeAsync(bool clearSessionState)
    {
        _currentSubject = clearSessionState ? null : _currentSubject;
        _knownPresenceSubjects.Clear();
        _onlineSubjects.Clear();
        _incomingPlayInvite = null;
        _outgoingPlayInvite = null;

        if (clearSessionState)
        {
            _activePlaySession = null;
            _joinedPlaySessionId = null;
            _collaborativeSnapshot = null;
            _lastInviteNotice = null;
        }

        if (_hubConnection is not null)
        {
            await _hubConnection.DisposeAsync();
            _hubConnection = null;
        }

        RaiseChanged();
    }

    private void RaiseChanged()
        => Changed?.Invoke();

    private static string? ResolveSubject(ClaimsPrincipal user)
        => user.Identity?.IsAuthenticated == true
            ? user.FindFirst("sub")?.Value ?? user.FindFirst(ClaimTypes.NameIdentifier)?.Value
            : null;
}