import Foundation

public enum AudioLevel {
    /// Reported for empty or silent buffers (log of zero would be -infinity).
    public static let silenceFloorDbfs: Float = -120

    public static func rmsDbfs(_ samples: [Float]) -> Float {
        samples.withUnsafeBufferPointer { rmsDbfs($0) }
    }

    public static func rmsDbfs(_ samples: UnsafeBufferPointer<Float>) -> Float {
        guard !samples.isEmpty else { return silenceFloorDbfs }
        var sum: Float = 0
        for sample in samples { sum += sample * sample }
        let rms = (sum / Float(samples.count)).squareRoot()
        guard rms > 0 else { return silenceFloorDbfs }
        return max(silenceFloorDbfs, 20 * log10(rms))
    }

    /// VU reading for a dBFS level, where `referenceDbfs` is 0 VU.
    public static func vu(fromDbfs dbfs: Float, referenceDbfs: Float = -20) -> Float {
        dbfs - referenceDbfs
    }
}