using Steamworks;

namespace ytLive.Services.Entitlement;

/// <summary>
/// The lifetime SKU: a Steam **DLC** on the free app, read locally from the Steam client.
///
/// <para><b>This is the whole purchase story.</b> There is no key, no server and no lease — the
/// customer buys the DLC on the store page and Steam already knows. The app asks once and caches
/// the answer; a refunded DLC stops reporting ownership the next time the app starts.</para>
///
/// <para><b>⛔ Never sell the monthly plan through this.</b> Steamworks requires in-app purchases
/// to use the Steam Wallet, so anything sold from inside the app would be a policy violation. The
/// monthly lives on the website and is billed by Polar (<see cref="PolarEntitlement"/> when it
/// lands); this class only ever reads what Valve already sold.</para>
///
/// <para><b>Steam absent is normal, not exceptional.</b> A copied folder, a shortcut run without
/// the client, or a CI machine has no Steam — <see cref="SteamAPI.Init"/> returns false and the
/// app runs as the free tier. It must never refuse to start over an entitlement lookup.</para>
/// </summary>
public sealed class SteamEntitlement : IEntitlement
{
    /// <summary>The DLC's own app id, not the base app's. Zero = not configured yet, which reads
    /// as "no entitlement" rather than "try anyway".</summary>
    private readonly uint _dlcAppId;

    private bool _initAttempted;
    private bool _available;
    private bool? _cached;

    public SteamEntitlement(uint dlcAppId) => _dlcAppId = dlcAppId;

    /// <summary>Configured with no product id — the state before the Steamworks app exists.</summary>
    public static SteamEntitlement NotConfigured() => new(0);

    public bool IsPro
    {
        get
        {
            if (_dlcAppId == 0) return false;
            if (_cached is { } known) return known;

            if (!_initAttempted)
            {
                _initAttempted = true;
                try
                {
                    // No steam_appid.txt and no client → false. That is the documented free path.
                    _available = SteamAPI.Init();
                }
                catch (Exception)
                {
                    // A missing steam_api64.dll throws on first touch. Free tier, never a crash.
                    _available = false;
                }
            }

            if (!_available) { _cached = false; return false; }

            try
            {
                var owned = SteamApps.BIsDlcInstalled(new AppId_t(_dlcAppId));
                _cached = owned;
                return owned;
            }
            catch (Exception)
            {
                return false;
            }
        }
    }

    /// <summary>Matches Steam's own lifecycle callbacks; called from the frame pump's pump thread
    /// would be wrong, so nothing here schedules it automatically.</summary>
    public void Shutdown()
    {
        if (_available) SteamAPI.Shutdown();
        _available = false;
        _cached = null;
        _initAttempted = false;
    }
}