import Foundation

/// dB ↔ linear gain helpers. -60 dB and below count as silence.
public enum Level {
    public static let floorDB: Float = -60

    public static func gain(fromDB db: Float) -> Float {
        db <= floorDB ? 0 : powf(10, db / 20)
    }

    public static func db(fromGain gain: Float) -> Float {
        gain <= 0 ? floorDB : max(floorDB, 20 * log10f(gain))
    }
}

/// Which part of a stereo source feeds a mono output channel.
public enum ChannelSelection: String, Codable, CaseIterable, Sendable {
    case left, right, mono

    @inline(__always)
    public func sample(left: Float, right: Float) -> Float {
        switch self {
        case .left: left
        case .right: right
        case .mono: 0.5 * (left + right)
        }
    }
}