import CoreImage
import CoreImage.CIFilterBuiltins
import SwiftUI

/// Printed Kasztelan cards contain an arbitrary 13-digit account number.
/// Code 128 preserves all 13 digits exactly. EAN-13 cannot, because its final
/// digit is always a mandatory checksum.
struct CardBarcodeView: View {
    let digits: String
    @Environment(\.displayScale) private var displayScale

    var body: some View {
        GeometryReader { geometry in
            if let image = barcodeImage(
                targetWidth: geometry.size.width,
                targetHeight: geometry.size.height,
                displayScale: displayScale
            ) {
                Image(decorative: image, scale: displayScale)
                    .interpolation(.none)
                    .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .center)
            }
        }
        .background(.white)
        .accessibilityElement()
        .accessibilityLabel("Barcode \(digits)")
    }

    private func barcodeImage(targetWidth: CGFloat, targetHeight: CGFloat, displayScale: CGFloat) -> CGImage? {
        let clean = String(digits.filter(\.isNumber))
        guard clean.count == 13, let data = clean.data(using: .ascii) else { return nil }

        let generator = CIFilter.code128BarcodeGenerator()
        generator.message = data
        generator.quietSpace = 12
        guard let output = generator.outputImage else { return nil }

        let pixelWidth = floor(targetWidth * displayScale)
        let pixelHeight = floor(targetHeight * displayScale)
        let horizontalScale = max(1, floor(pixelWidth / output.extent.width))
        let verticalScale = max(1, floor(pixelHeight / output.extent.height))
        let scaled = output.transformed(
            by: CGAffineTransform(scaleX: horizontalScale, y: verticalScale)
        )
        return CIContext(options: [.useSoftwareRenderer: false]).createCGImage(scaled, from: scaled.extent)
    }
}