//
//  SceneSignal.swift
//  Focale
//
//  Author: Simon-Pierre Boucher
//  Contact: contact@spboucher.ai
//
//  Cheap physical signals read off the capture device at shutter time.
//  No inference — these come straight from the sensor.
//

import Foundation

struct SceneSignal: Codable, Sendable {
    /// Estimated scene brightness in EV100 (log2 scale). Lower = darker.
    var luminanceEV: Double?
    /// Rough device/subject motion classification.
    var motion: MotionLevel
    /// Subject distance in meters when LiDAR/depth is available.
    var subjectDistance: Double?
    /// Convenience flag used by recipe scene triggers.
    var isLowLight: Bool

    static let unknown = SceneSignal(
        luminanceEV: nil, motion: .unknown, subjectDistance: nil, isLowLight: false
    )
}

enum MotionLevel: String, Codable, Sendable {
    case still
    case moving
    case unknown
}

extension SceneSignal {
    /// EV100 from the current exposure triplet: EV = log2(1 / (t * S/100)).
    /// Good enough to distinguish "sunlit" from "dim room" for scene triggers.
    static func estimateEV(iso: Float, shutterSeconds: Double) -> Double? {
        guard iso > 0, shutterSeconds > 0 else { return nil }
        return log2(1.0 / (shutterSeconds * Double(iso) / 100.0))
    }
}