IYmtg/IYmtg_App_iOS/Services/CoreML/FoilEngine.swift

import Vision
import CoreML
import CoreGraphics

// MARK: - FOIL ENGINE
actor FoilEngine {
    private var frameCounter = 0
    private var lowConfidenceStreak = 0

    static var model: VNCoreMLModel? = {
        guard AppConfig.enableFoilDetection else { return nil }
        return ModelManager.shared.getModel(name: "IYmtgFoilClassifier")
    }()

    private lazy var request: VNCoreMLRequest? = {
        guard let model = FoilEngine.model else { return nil }
        let req = VNCoreMLRequest(model: model)
        req.imageCropAndScaleOption = .scaleFill
        return req
    }()

    func addFrame(_ image: CGImage, orientation: CGImagePropertyOrientation = .up) -> String? {
        frameCounter += 1
        // SAFETY: Prevent integer overflow in long-running sessions
        if frameCounter > 1000 { frameCounter = 0 }
        if frameCounter % 5 != 0 { return nil }
        guard let request = self.request else { return AppConfig.Defaults.defaultFoil }

        let handler = VNImageRequestHandler(cgImage: image, orientation: orientation, options: [:])

        do {
            try handler.perform([request])
            guard let results = request.results as? [VNClassificationObservation], let top = results.first else { return AppConfig.Defaults.defaultFoil }

            if top.confidence > 0.85 {
                lowConfidenceStreak = 0
                return top.identifier
            } else {
                lowConfidenceStreak += 1
                if lowConfidenceStreak >= 3 {
                    return AppConfig.Defaults.defaultFoil
                } else {
                    return nil
                }
            }
        } catch { return AppConfig.Defaults.defaultFoil }
    }
}