using System;
using System.Threading;

namespace ytLive.Services;

/// <summary>
/// An atomic "publish only if strictly newer" gate for the capture's latest-wins
/// hand-out. Screen capture conversions may now overlap (slice 17), so two
/// conversions can finish briefly out of order; without a monotonic gate the slower
/// (older) completion would overwrite the faster (newer) one's LatestFrame and the
/// compositor would render STALE content — a time hole in the other direction.
/// Sequence must be a strictly increasing per-source counter
/// (<c>Interlocked.Increment</c> in <c>ScreenCaptureFrameSource</c>).
/// </summary>
internal sealed class MonotonicGate
{
    private long _last;

    /// <summary>Returns true iff <paramref name="seq"/> is strictly newer than every
    /// seq accepted so far (and records it).</summary>
    public bool TryPublish(long seq)
    {
        while (true)
        {
            var current = Interlocked.Read(ref _last);
            if (seq <= current) return false;
            if (Interlocked.CompareExchange(ref _last, seq, current) == current) return true;
        }
    }
}