공유 확장: 제안되고, 불러오고, 쓰고, 절대 조용하지 않게

  SparkShare:
    type: app-extension
    platform: iOS
    info:
      path: ShareExtension/Info.plist
      properties:
        NSExtension:
          NSExtensionPointIdentifier: com.apple.share-services
          NSExtensionPrincipalClass: $(PRODUCT_MODULE_NAME).ShareViewController
          NSExtensionAttributes:
            # The dictionary form (NSExtensionActivationSupportsFileWithMaxCount...) was never
            # offered for a PDF from Safari or Mail. A predicate says what it means.
            # Never TRUEPREDICATE: Apple rejects an app whose extension contains it.
            NSExtensionActivationRule: >-
              SUBQUERY(extensionItems, $extensionItem,
                $extensionItem.attachments.@count >= 1 AND $extensionItem.attachments.@count <= 8 AND
                SUBQUERY($extensionItem.attachments, $attachment,
                  ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "public.image" OR
                  ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "com.adobe.pdf" OR
                  ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "public.url" OR
                  ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "public.plain-text"
                ).@count == $extensionItem.attachments.@count
              ).@count >= 1

import Foundation
import UniformTypeIdentifiers

enum ShareKind: Int, Comparable, Sendable {
    case image, pdf, file, link, text      // a RANKING: the first match wins
    static func < (a: ShareKind, b: ShareKind) -> Bool { a.rawValue < b.rawValue }
}

/// Decide what a provider IS before loading anything. Every file-borne share also conforms to
/// public.url (because public.file-url does), so "is it a link?" must never be asked first.
func shareKind(ofTypes identifiers: [String]) -> ShareKind? {
    let types = identifiers.compactMap(UTType.init)
    func has(_ type: UTType) -> Bool { types.contains { $0.conforms(to: type) } }
    let isFile = has(.fileURL)
    let candidates: [ShareKind?] = [
        has(.image) ? .image : nil,
        has(.pdf) ? .pdf : nil,
        isFile ? .file : nil,                    // a zip or a .docx: still a file the app may take
        has(.url) && !isFile ? .link : nil,      // a web link is the only url WITHOUT file-url
        has(.plainText) ? .text : nil,
    ]
    return candidates.compactMap { $0 }.min()
}

// Measured on macOS with NSItemProvider(contentsOf:) and a web link object:
//   photo.jpg    [public.jpeg, public.file-url, public.url]      -> image
//   doc.pdf      [com.adobe.pdf, public.file-url, public.url]    -> pdf
//   archive.zip  [public.zip-archive, public.file-url, public.url] -> file
//   web link     [public.url]                                    -> link