namespace DeepDrftContent.Processors;

/// <summary>
/// Derives the bucket count for a track's high-resolution loudness datum from the audio's duration, so
/// the stored profile captures at a constant <em>time</em> resolution instead of a fixed bucket count.
/// Applies to every track (Mix, Session, Cut) — the release is just the host (phase-12 §5).
///
/// Rationale (phase-9 Mix Visualizer redesign spec §F): the max-zoom window shows one quarter note
/// at 180 BPM = 333 ms of audio, and a smooth glassy curve wants ~100+ sample points across that
/// window. A fixed 2048-bucket datum gives fractions of a sample per 333 ms window on any real-length
/// audio (a 30-minute mix gets ~0.38 buckets), so long content is badly under-sampled. Capturing at a
/// constant ≈333 samples/sec (≈3 ms/sample) makes a 333 ms window hold ~111 samples regardless of
/// length — the direct expression of "high enough resolution regardless of content length."
///
/// This is the orchestration-side derivation (duration → bucket count); the actual compute/store stays
/// in <see cref="WaveformProfileService"/>, which is content-agnostic and parameterized by bucket count.
/// </summary>
public static class WaveformResolution
{
    /// <summary>≈333 samples/sec (≈3 ms/sample): one quarter note at 180 BPM (333 ms) holds ~111 samples.</summary>
    public const int SamplesPerSecond = 333;

    /// <summary>
    /// Upper cap on bucket count (~2,000,000 samples ≈ a 100-minute track at 333/s). Past this length we
    /// accept slightly-below-target density rather than an unbounded datum (spec §F mitigation #1).
    /// </summary>
    public const int MaxBucketCount = 2_000_000;

    /// <summary>
    /// Floor on bucket count. Keeps the historical 2048-bucket density as the minimum so a degenerate
    /// near-zero or very-short track still yields a usable profile rather than zero/handful of buckets.
    /// </summary>
    public const int MinBucketCount = 2048;

    /// <summary>
    /// Maps a track's duration (seconds) to a bucket count of <c>ceil(durationSeconds × 333)</c>,
    /// clamped to [<see cref="MinBucketCount"/>, <see cref="MaxBucketCount"/>]. Non-finite or negative
    /// durations fall to the floor. A 60-minute track → ~1.2M buckets; a 3-minute track → ~60k.
    /// </summary>
    public static int BucketCountForDuration(double durationSeconds)
    {
        if (double.IsNaN(durationSeconds) || durationSeconds <= 0)
            return MinBucketCount;

        // Guard against overflow before the cast: anything at/above the cap clamps anyway.
        var raw = Math.Ceiling(durationSeconds * SamplesPerSecond);
        if (raw >= MaxBucketCount)
            return MaxBucketCount;

        var buckets = (int)raw;
        return buckets < MinBucketCount ? MinBucketCount : buckets;
    }
}
