import Messages
import SwiftUI
import UIKit

final class MessagesViewController: MSMessagesAppViewController {
	private let stickerBrowser = StickerBrowserViewController()
	private var addPackHostingController: UIHostingController<AddPackView>?

	override func viewDidLoad() {
		super.viewDidLoad()
		addStickerBrowser()
		stickerBrowser.reloadStickers()
	}

	override func willBecomeActive(with conversation: MSConversation) {
		stickerBrowser.reloadStickers()

		// Prompt user to add a pack on first launch
		if StickerStore.shared.savedPacks.isEmpty {
			requestPresentationStyle(.expanded)
		}
	}

	// MARK: - Presentation style transitions

	override func willTransition(to presentationStyle: MSMessagesAppPresentationStyle) {
		removeAddPackView()
	}

	override func didTransition(to presentationStyle: MSMessagesAppPresentationStyle) {
		switch presentationStyle {
		case .expanded:
			showAddPackView()
		case .compact:
			stickerBrowser.reloadStickers()
		default:
			break
		}
	}

	// MARK: - Child view controllers

	private func addStickerBrowser() {
		addChild(stickerBrowser)
		stickerBrowser.view.translatesAutoresizingMaskIntoConstraints = false
		view.addSubview(stickerBrowser.view)
		NSLayoutConstraint.activate([
			stickerBrowser.view.topAnchor.constraint(equalTo: view.topAnchor),
			stickerBrowser.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
			stickerBrowser.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
			stickerBrowser.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
		])
		stickerBrowser.didMove(toParent: self)
	}

	private func showAddPackView() {
		let addPackView = AddPackView { [weak self] in
			self?.stickerBrowser.reloadStickers()
		}
		let hostingController = UIHostingController(rootView: addPackView)
		addPackHostingController = hostingController

		addChild(hostingController)
		hostingController.view.translatesAutoresizingMaskIntoConstraints = false
		view.addSubview(hostingController.view)
		NSLayoutConstraint.activate([
			hostingController.view.topAnchor.constraint(equalTo: view.topAnchor),
			hostingController.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
			hostingController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
			hostingController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
		])
		hostingController.didMove(toParent: self)
	}

	private func removeAddPackView() {
		guard let hostingController = addPackHostingController else { return }
		hostingController.willMove(toParent: nil)
		hostingController.view.removeFromSuperview()
		hostingController.removeFromParent()
		addPackHostingController = nil
	}
}