namespace AcDream.App.Net;

/// <summary>
/// Tracks retail's stamina-exhaustion notification edge for one live-session
/// generation.
/// </summary>
internal sealed class StaminaExhaustionEdgeTracker
{
    private bool? _wasExhausted;

    /// <summary>
    /// Observes the current stamina value and returns <see langword="true"/>
    /// only when a previously initialized state changes between exhausted and
    /// non-exhausted.
    /// </summary>
    public bool Observe(int currentStamina)
    {
        bool exhausted = currentStamina == 0;
        if (_wasExhausted == exhausted)
            return false;

        bool isEdge = _wasExhausted.HasValue;
        _wasExhausted = exhausted;
        return isEdge;
    }

    /// <summary>
    /// Forgets the retiring character/session sample. The first sample in the
    /// next generation establishes a baseline and must not synthesize an edge.
    /// </summary>
    public void Reset() => _wasExhausted = null;
}