using System;
using Unity.Services.Authentication;
using UnityEngine;

/// <summary>
/// A stable, per-install unique player id that survives application restarts, so the server can recognise a
/// returning client across sessions (the NGO clientId is ephemeral and reused).
///
/// Primary source is the UGS anonymous <see cref="AuthenticationService"/> PlayerId, which is already cached
/// per machine AND namespaced per install via the auth profile (see OnlineSessionManager.ProfileForThisInstall),
/// so it is restart-stable and stays distinct even for same-machine clone tests. When there was no UGS sign-in
/// (pure loopback / offline play) it falls back to a locally generated GUID persisted in PlayerPrefs.
/// </summary>
public static class PersistentPlayerId
{
    private const string PrefKey = "chameleon.persistentPlayerId";

    private static string _ugsId;        // authoritative once signed in; cached permanently
    private static string _localFallback; // loopback/offline only

    /// <summary>The persistent id for THIS install. Stable across restarts, never null/empty. Prefers the
    /// signed-in UGS id (the send path runs after sign-in, so online clients always report that); only pure
    /// loopback play resolves the local fallback.</summary>
    public static string Value
    {
        get
        {
            if (!string.IsNullOrEmpty(_ugsId)) return _ugsId;

            // AuthenticationService.Instance throws if UGS was never initialised (loopback) - guard it.
            try
            {
                var auth = AuthenticationService.Instance;
                if (auth != null && auth.IsSignedIn && !string.IsNullOrEmpty(auth.PlayerId))
                    return _ugsId = auth.PlayerId;
            }
            catch (Exception) { /* services not initialised - use the local fallback */ }

            return LocalFallback();
        }
    }

    // NOT cached into _ugsId: a later signed-in read must be able to upgrade to the authoritative UGS id.
    // The fallback itself is restart-stable (PlayerPrefs), which is all offline play needs.
    private static string LocalFallback()
    {
        if (!string.IsNullOrEmpty(_localFallback)) return _localFallback;

        _localFallback = PlayerPrefs.GetString(PrefKey, "");
        if (string.IsNullOrEmpty(_localFallback))
        {
            _localFallback = Guid.NewGuid().ToString("N");
            PlayerPrefs.SetString(PrefKey, _localFallback);
            PlayerPrefs.Save();
        }
        return _localFallback;
    }
}