using System;
using System.Collections.Generic;
using Unity.Netcode;
using Unity.Services.Authentication;
using Unity.Services.Core;
using Unity.Services.Multiplayer;
using UnityEngine;

/// <summary>
/// Online hosting/joining over Unity Gaming Services so players can connect across the internet
/// without port forwarding. Uses the unified Multiplayer Services "Sessions" API, which bundles
/// Relay (NAT-free messaging via Unity's relay servers) + Lobby (the public server list) + anonymous
/// Authentication behind single calls, and configures + starts the NGO transport itself - so we do
/// NOT call <see cref="NetworkManager.StartHost"/>/<c>StartClient</c> here; CreateSessionAsync starts
/// the host and JoinSession* starts the client.
///
/// Terminology: the UGS "session" is the entry in the public server list (network layer). It is a
/// different thing from the in-game "Lobby" scene (the pre-match staging area that <see cref="MatchManager"/>
/// loads after the connection is up). This component does not touch the match flow at all - the usual
/// NetworkManager callbacks fire exactly as they do for loopback hosting, so MatchManager, spawning and
/// authority are unaffected.
///
/// This is a quick IMGUI server browser for clone testing; replace with proper uGUI later. The loopback
/// dev path (see <see cref="NetworkBootstrap"/>, H/C/J/K) stays for fast local testing - online is additive.
/// Requires the project to be linked to a UGS cloud project (Project Settings > Services) with Relay,
/// Lobby and Authentication (Anonymous) enabled; otherwise sign-in fails with a clear status message.
/// Attach to the same GameObject as the NetworkManager.
/// </summary>
[RequireComponent(typeof(NetworkManager))]
[DisallowMultipleComponent]
public class OnlineSessionManager : MonoBehaviour
{
    [Tooltip("Maximum players per hosted session (host included).")]
    public int maxPlayers = 8;

    [Tooltip("Draw the on-screen online server-browser panel (below the dev panel).")]
    public bool showGui = true;

    private NetworkManager _net;
    private ISession _session;                 // active session (host or client); null when not in one
    private IList<ISessionInfo> _browse = new List<ISessionInfo>();
    private string _hostName = "";
    private string _status = "Idle";
    private bool _busy;
    private bool _leaving;                      // suppress the defensive leave while an explicit leave is in flight
    private Vector2 _scroll;

    private void Awake()
    {
        _net = GetComponent<NetworkManager>();
        _hostName = $"{SystemInfo.deviceName} game";
    }

    private void OnEnable()
    {
        if (!_net) return;
        _net.OnServerStopped += OnNetworkStopped;
        _net.OnClientStopped += OnNetworkStopped;
    }

    private void OnDisable()
    {
        if (!_net) return;
        _net.OnServerStopped -= OnNetworkStopped;
        _net.OnClientStopped -= OnNetworkStopped;
    }

    // The match-end / disconnect / Shutdown paths stop the NetworkManager without telling UGS. Leave the
    // session here too so the Relay allocation and the public lobby entry are released.
    private void OnNetworkStopped(bool _)
    {
        var stale = _session;
        _session = null;
        if (stale != null && !_leaving) LeaveSilently(stale);
    }

    private async void LeaveSilently(ISession session)
    {
        try { await session.LeaveAsync(); }
        catch (Exception e) { Debug.LogWarning($"[OnlineSession] leave-on-stop failed: {e.Message}"); }
    }

    private async System.Threading.Tasks.Task EnsureSignedInAsync()
    {
        if (UnityServices.State != ServicesInitializationState.Initialized)
        {
            // Anonymous tokens are cached per machine under company/product, NOT per project path - so
            // junction-mirror clones (shared ProjectSettings) would otherwise resolve to one UGS player id
            // and collide on join (409 LobbyConflict). Namespacing the auth cache by a hash of this install's
            // path gives each clone a stable, distinct identity. Harmless in production - separate machines
            // already have separate caches; this only matters for same-machine clone testing.
            var options = new InitializationOptions();
            options.SetProfile(ProfileForThisInstall());
            await UnityServices.InitializeAsync(options);
        }
        if (!AuthenticationService.Instance.IsSignedIn)
            await AuthenticationService.Instance.SignInAnonymouslyAsync();
    }

    // Deterministic, regex-safe (^[a-zA-Z0-9_-]{1,30}$) profile derived from the install path, so the same
    // clone is always the same UGS player across restarts - no random per-launch identity, no orphaned ghost
    // players/lobbies piling up. SHA1 over dataPath -> "mirror_" + 12 hex chars = 19 chars (fits the limit).
    private static string ProfileForThisInstall()
    {
        using (var sha1 = System.Security.Cryptography.SHA1.Create())
        {
            var bytes = sha1.ComputeHash(System.Text.Encoding.UTF8.GetBytes(Application.dataPath));
            var name = new System.Text.StringBuilder("mirror_", 19);
            for (int i = 0; i < 6; i++) name.Append(bytes[i].ToString("x2"));
            return name.ToString();
        }
    }

    private async void HostAsync()
    {
        if (_busy) return;
        _busy = true;
        try
        {
            _status = "Signing in…";
            await EnsureSignedInAsync();
            _status = "Creating session…";
            var options = new SessionOptions
            {
                Name = string.IsNullOrWhiteSpace(_hostName) ? "Chameleon game" : _hostName.Trim(),
                MaxPlayers = Mathf.Max(2, maxPlayers)
            }.WithRelayNetwork();
            _session = await MultiplayerService.Instance.CreateSessionAsync(options);
            _status = $"Hosting \"{_session.Name}\" (code {_session.Code})";
        }
        catch (Exception e)
        {
            _status = $"Host failed: {e.Message}";
            Debug.LogException(e);
        }
        finally { _busy = false; }
    }

    private async void RefreshAsync()
    {
        if (_busy) return;
        _busy = true;
        try
        {
            _status = "Signing in…";
            await EnsureSignedInAsync();
            _status = "Querying sessions…";
            var results = await MultiplayerService.Instance.QuerySessionsAsync(new QuerySessionsOptions());
            _browse = results.Sessions;
            _status = $"{_browse.Count} session(s) found";
        }
        catch (Exception e)
        {
            _status = $"Refresh failed: {e.Message}";
            Debug.LogException(e);
        }
        finally { _busy = false; }
    }

    private async void JoinAsync(string sessionId)
    {
        if (_busy) return;
        _busy = true;
        try
        {
            _status = "Signing in…";
            await EnsureSignedInAsync();
            _status = "Joining session…";
            _session = await MultiplayerService.Instance.JoinSessionByIdAsync(sessionId);
            _status = $"Joined \"{_session.Name}\"";
        }
        catch (Exception e)
        {
            _status = $"Join failed: {e.Message}";
            Debug.LogException(e);
        }
        finally { _busy = false; }
    }

    private async void LeaveAsync()
    {
        if (_busy || _session == null) return;
        _busy = true;
        _leaving = true;
        try
        {
            _status = "Leaving…";
            await _session.LeaveAsync();   // also tears down the NGO connection
            _status = "Left session";
        }
        catch (Exception e)
        {
            _status = $"Leave failed: {e.Message}";
            Debug.LogException(e);
        }
        finally { _session = null; _leaving = false; _busy = false; }
    }

    private void OnGUI()
    {
        if (!showGui || !_net) return;

        GUILayout.BeginArea(new Rect(10, 180, 340, 360), GUI.skin.box);
        GUILayout.Label("Online (UGS Relay + Lobby)");
        GUILayout.Label(_status);

        GUI.enabled = !_busy;
        if (!_net.IsListening)
        {
            GUILayout.Label("Session name:");
            _hostName = GUILayout.TextField(_hostName);
            if (GUILayout.Button("Host Online")) HostAsync();

            GUILayout.Space(6);
            if (GUILayout.Button("Refresh List")) RefreshAsync();

            _scroll = GUILayout.BeginScrollView(_scroll, GUILayout.Height(180));
            if (_browse.Count == 0)
                GUILayout.Label("No sessions. Click Refresh.");
            foreach (var s in _browse)
            {
                GUILayout.BeginHorizontal();
                int taken = Mathf.Max(0, s.MaxPlayers - s.AvailableSlots);
                GUILayout.Label($"{s.Name}  ({taken}/{s.MaxPlayers})");
                if (GUILayout.Button("Join", GUILayout.Width(60))) JoinAsync(s.Id);
                GUILayout.EndHorizontal();
            }
            GUILayout.EndScrollView();
        }
        else if (_session != null)
        {
            GUILayout.Label($"In session: {_session.Name}");
            if (GUILayout.Button("Leave Session")) LeaveAsync();
        }
        else
        {
            GUILayout.Label("Local (loopback) session active.");
        }
        GUI.enabled = true;

        GUILayout.EndArea();
    }
}