Custom PDF page labels in the sharing UI in Swift for iOS

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//
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//  Copyright © 2021-2026 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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class PageLabelsInSharingExample: Example {
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    override init() {
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        super.init()
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        title = "Show Page Labels in the Sharing UI"
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        contentDescription = "Shows how to display page labels instead of page numbers in the sharing UI."
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        category = .sharing
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        priority = 900
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.document(for: .welcome)
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        let pdfViewController = PDFViewController(document: document) { mainConfiguration in
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            mainConfiguration.sharingConfigurations = mainConfiguration.sharingConfigurations.map { sharingConfiguration in
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                sharingConfiguration.configurationUpdated { sharingConfigurationBuilder in
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                    /*
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                     By default Nutrient displays page numbers in the sharing UI for picking a page range and
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                     showing the selected pages. This ensures the UI is easy to understand for any document.
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                     You can use `pageDescriptionProvider` and `selectedPagesDescriptionProvider` to customize
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                     these strings. This example shows how to display the page labels set in the PDF instead.
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                     */
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                    sharingConfigurationBuilder.pageDescriptionProvider = { pageIndex, document in
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                        document.pageLabelForPage(at: pageIndex, substituteWithPlainLabel: true)!
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                    }
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                    let originalSelectedPagesDescriptionProvider = sharingConfigurationBuilder.selectedPagesDescriptionProvider
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                    sharingConfigurationBuilder.selectedPagesDescriptionProvider = { selectedPages in
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                        switch selectedPages {
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                        case .all, .annotated:
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                            // Use the default Nutrient implementation.
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                            return originalSelectedPagesDescriptionProvider(selectedPages)
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                        case .current(let currentPageIndex, let document):
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                            // Show the page label instead of the page number.
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                            // Not shown here, but you should localize this string using NSLocalizedString.
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                            return String.localizedStringWithFormat("Current Page (%@)", document.pageLabelForPage(at: currentPageIndex, substituteWithPlainLabel: true)!)
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                        case .range(let selectedPageIndexes, let document):
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                            // Show the page labels instead of the page numbers.
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                            // Not shown here, but you should localize this string using NSLocalizedString.
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                            // This only shows supporting a single range in the index set. In practice,
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                            // the Nutrient UI only allows setting a single range for now so this is fine.
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                            return String.localizedStringWithFormat(
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                                "Pages %@–%@",
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                                document.pageLabelForPage(at: PageIndex(selectedPageIndexes.first!), substituteWithPlainLabel: true)!,
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                                document.pageLabelForPage(at: PageIndex(selectedPageIndexes.last!), substituteWithPlainLabel: true)!
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                            )
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                        }
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                    }
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                }
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            }
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        }
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        return pdfViewController
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    }
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}