using System.Diagnostics;

namespace LibMMD.Unity3D
{
    /// <summary>Owns frame-budget accounting for incremental Unity object construction.</summary>
    internal sealed class MmdLoadTimeSlicer
    {
        private readonly long _budgetTicks;
        private long _sliceStarted;
        private bool _resumingAfterYield;

        internal MmdLoadTimeSlicer(MmdModelOptions options)
        {
            _budgetTicks = (long)(options.LoadingFrameBudgetMilliseconds * Stopwatch.Frequency / 1000d);
            _sliceStarted = Stopwatch.GetTimestamp();
        }

        internal bool ShouldYield()
        {
            var now = Stopwatch.GetTimestamp();
            if (_resumingAfterYield)
            {
                _resumingAfterYield = false;
                _sliceStarted = now;
                return false;
            }
            if (_budgetTicks > 0 && now - _sliceStarted < _budgetTicks) return false;
            _resumingAfterYield = true;
            return true;
        }
    }
}