using System;

namespace ytLive.Helpers;

/// <summary>The accessible mono fold: average each stereo pair into both channels.
///
/// <para>Creator context (2026-10-30): profoundly deaf on the right. Hard-panned content is not
/// quieter to them, it is ABSENT, so a single-sided game or clip is unusable. Folding to mono puts
/// everything on both sides — the loudness cost is honest (a one-sided signal arrives at half
/// amplitude) and speech is unaffected because the mic is already centred.</para></summary>
public static class AudioFold
{
    /// <summary>Folds an interleaved buffer in place. Mono buffers are left untouched: there is
    /// nothing to combine, and rewriting them would be a silent no-op that hides a caller's bug.</summary>
    public static void ToMono(Span<float> interleaved, int channels)
    {
        if (channels < 2) return;
        var frames = interleaved.Length / channels;
        for (var frame = 0; frame < frames; frame++)
        {
            var offset = frame * channels;
            var mono = (interleaved[offset] + interleaved[offset + 1]) * 0.5f;
            interleaved[offset] = mono;
            interleaved[offset + 1] = mono;
        }
    }
}