import UIKit
import SwiftUI
import UniformTypeIdentifiers

final class ShareViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .clear
        Task { await loadAttachment() }
    }

    private func loadAttachment() async {
        guard let item = (extensionContext?.inputItems as? [NSExtensionItem])?.first,
              let provider = item.attachments?.first(where: { $0.hasItemConformingToTypeIdentifier(UTType.image.identifier) })
        else {
            present(host: ShareSheetView(image: nil, onClose: { [weak self] in self?.complete() }))
            return
        }

        do {
            let data = try await loadImageData(from: provider)
            await MainActor.run {
                let image = data.flatMap { UIImage(data: $0) }
                let host = ShareSheetView(
                    image: image,
                    imageData: data,
                    onClose: { [weak self] in self?.complete() }
                )
                self.present(host: host)
            }
        } catch {
            await MainActor.run {
                present(host: ShareSheetView(image: nil, errorMessage: error.localizedDescription, onClose: { [weak self] in self?.complete() }))
            }
        }
    }

    private func loadImageData(from provider: NSItemProvider) async throws -> Data? {
        try await withCheckedThrowingContinuation { continuation in
            provider.loadItem(forTypeIdentifier: UTType.image.identifier, options: nil) { item, error in
                if let error { continuation.resume(throwing: error); return }
                if let data = item as? Data { continuation.resume(returning: data); return }
                if let url = item as? URL, let data = try? Data(contentsOf: url) { continuation.resume(returning: data); return }
                if let image = item as? UIImage, let data = image.pngData() { continuation.resume(returning: data); return }
                continuation.resume(returning: nil)
            }
        }
    }

    private func present(host: ShareSheetView) {
        let controller = UIHostingController(rootView: host)
        controller.modalPresentationStyle = .formSheet
        addChild(controller)
        controller.view.frame = view.bounds
        controller.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(controller.view)
        controller.didMove(toParent: self)
    }

    fileprivate func complete() {
        extensionContext?.completeRequest(returningItems: nil, completionHandler: nil)
    }

    fileprivate func cancel() {
        extensionContext?.cancelRequest(withError: NSError(domain: "GiteaIssueShare", code: 0))
    }
}