import UIKit
import SwiftUI
import UniformTypeIdentifiers

@objc(ShareViewController)
class ShareViewController: UIViewController {
    private let supportedTypeIdentifiers = [
        UTType.url.identifier,
        UTType.html.identifier,
        UTType.rtf.identifier,
        UTType.plainText.identifier,
        UTType.text.identifier
    ]

    override func viewDidLoad() {
        super.viewDidLoad()
        let blur = UIVisualEffectView(effect: UIBlurEffect(style: .systemMaterial))
        blur.frame = view.bounds
        blur.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(blur)
        extractPayload()
    }

    private func extractPayload() {
        guard let item = extensionContext?.inputItems.first as? NSExtensionItem,
              let attachments = item.attachments else {
            present(payload: nil)
            return
        }

        let candidates = attachments.flatMap { attachment in
            supportedTypeIdentifiers
                .filter { attachment.hasItemConformingToTypeIdentifier($0) }
                .map { (attachment, $0) }
        }

        loadNext(candidates, index: 0)
    }

    private func loadNext(_ candidates: [(NSItemProvider, String)], index: Int) {
        guard index < candidates.count else {
            present(payload: nil)
            return
        }

        let (attachment, typeIdentifier) = candidates[index]
        attachment.loadItem(forTypeIdentifier: typeIdentifier, options: nil) { [weak self] item, _ in
            guard let self else { return }
            if let payload = IngestPayloadParser.parse(item: item, typeIdentifier: typeIdentifier) {
                DispatchQueue.main.async { self.present(payload: payload) }
            } else {
                DispatchQueue.main.async { self.loadNext(candidates, index: index + 1) }
            }
        }
    }

    /// Hosts the SwiftUI save card. A nil URL surfaces an error state in the card.
    private func present(payload: IngestPayload?) {
        let root = ShareView(
            url: payload?.url ?? "",
            initialTitle: payload?.title,
            initialNotes: payload?.notes ?? ""
        ) { [weak self] _ in
            self?.close()
        }
        let host = UIHostingController(rootView: root)
        host.view.backgroundColor = .clear
        addChild(host)
        host.view.frame = view.bounds
        host.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(host.view)
        host.didMove(toParent: self)

        if payload == nil {
            // No URL to work with — let the card render its failure state briefly.
            DispatchQueue.main.asyncAfter(deadline: .now() + 1.6) { [weak self] in self?.close() }
        }
    }

    private func close() {
        extensionContext?.completeRequest(returningItems: [], completionHandler: nil)
    }
}