import SwiftUI
import PDFKit

struct LeadPDFView: UIViewRepresentable {
    let url: URL
    var signaturePlacement: PDFSignaturePlacement?
    var fitsWholePage = false
    var onPageChanged: ((Int, Int) -> Void)?

    func makeUIView(context: Context) -> PDFView {
        let view = PDFView()
        view.displayMode = fitsWholePage ? .singlePage : .singlePageContinuous
        if fitsWholePage {
            view.displayDirection = .horizontal
            view.usePageViewController(true)
        }
        view.autoScales = true
        view.backgroundColor = .secondarySystemGroupedBackground
        context.coordinator.observe(view)
        return view
    }

    func updateUIView(_ view: PDFView, context: Context) {
        context.coordinator.onPageChanged = onPageChanged
        guard view.document?.documentURL != url else { return }
        view.document = PDFDocument(url: url)
        view.autoScales = true
        if let signaturePlacement,
           let page = view.document?.page(at: signaturePlacement.pageIndex) {
            // The marker exists only in the preview; the signing service reads the original file.
            let marker = PDFAnnotation(bounds: signaturePlacement.bounds, forType: .square, withProperties: nil)
            marker.color = .systemOrange
            marker.interiorColor = UIColor.systemOrange.withAlphaComponent(0.08)
            marker.contents = "Unterschrift Kunde"
            let border = PDFBorder()
            border.lineWidth = 1
            border.style = .dashed
            border.dashPattern = [3, 2]
            marker.border = border
            page.addAnnotation(marker)
            view.go(to: page)
        }
        context.coordinator.report(view)
    }

    func makeCoordinator() -> Coordinator { Coordinator() }

    final class Coordinator: NSObject {
        var onPageChanged: ((Int, Int) -> Void)?

        func observe(_ view: PDFView) {
            NotificationCenter.default.addObserver(
                self, selector: #selector(pageChanged(_:)), name: .PDFViewPageChanged, object: view
            )
        }

        @objc private func pageChanged(_ notification: Notification) {
            guard let view = notification.object as? PDFView else { return }
            report(view)
        }

        func report(_ view: PDFView) {
            guard let document = view.document, let page = view.currentPage else { return }
            let number = document.index(for: page) + 1
            let count = document.pageCount
            // Avoid changing SwiftUI state while the representable is updating.
            Task { @MainActor [weak self] in self?.onPageChanged?(number, count) }
        }

        deinit { NotificationCenter.default.removeObserver(self) }
    }
}