ModuleViewController.swift

import SwiftUI
import UIKit

/// Контроллер модуля: собирает живой экран по описанию `ViewBody`
/// и приводит его к новому описанию, когда менеджер пересчитал `view.body`.
///
/// В монорепозитории контроллер строит UIKit-иерархию напрямую:
/// навигационная панель и список — свои надстройки над UIKit,
/// обновление контента идёт через дифф коллекции. Здесь каждый слот
/// отдаётся своему `UIHostingController` — базовый слой остаётся
/// на UIKit, компоненты пишутся на SwiftUI, как и в проде.
@MainActor
public final class ModuleViewController<View: ModuleView>: UIViewController {

    private var manager: ModuleViewManager<View>?

    private let navigationBarController = UIHostingController(rootView: AnyView(EmptyView()))
    private let contentController = UIHostingController(rootView: AnyView(EmptyView()))
    private let accessoryBoxController = UIHostingController(rootView: AnyView(EmptyView()))

    private var accessoryKeyboardConstraint: NSLayoutConstraint?
    private var accessoryBottomConstraint: NSLayoutConstraint?

    private var isFirstAppearance = true

    public func associate(with view: View) {
        manager = ModuleViewManager(view: view) { [weak self] viewBody in
            self?.update(with: viewBody)
        }
    }

    public override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .systemBackground

        embedSlotControllers()

        manager?.updateViewBodyWithObservation()
    }

    public override func viewIsAppearing(_ animated: Bool) {
        super.viewIsAppearing(animated)

        if isFirstAppearance {
            isFirstAppearance = false

            (manager?.view.model as? ModuleViewObserver)?.onFirstViewAppear()
        }
    }

    private func embedSlotControllers() {
        for controller in [navigationBarController, contentController, accessoryBoxController] {
            addChild(controller)
            view.addSubview(controller.view)
            controller.view.translatesAutoresizingMaskIntoConstraints = false
            controller.view.backgroundColor = .clear
            controller.didMove(toParent: self)
        }

        navigationBarController.sizingOptions = .intrinsicContentSize
        accessoryBoxController.sizingOptions = .intrinsicContentSize

        NSLayoutConstraint.activate([
            navigationBarController.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            navigationBarController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            navigationBarController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),

            contentController.view.topAnchor.constraint(equalTo: navigationBarController.view.bottomAnchor),
            contentController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            contentController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            contentController.view.bottomAnchor.constraint(equalTo: accessoryBoxController.view.topAnchor),

            accessoryBoxController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            accessoryBoxController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor)
        ])

        // Плашка либо прилипает к клавиатуре (без клавиатуры направляющая
        // лежит на нижней границе экрана), либо остаётся у нижней границы —
        // выбор делает `AccessoryBox.followsKeyboard` при каждом обновлении
        accessoryKeyboardConstraint = accessoryBoxController.view.bottomAnchor.constraint(
            equalTo: view.keyboardLayoutGuide.topAnchor
        )

        accessoryBottomConstraint = accessoryBoxController.view.bottomAnchor.constraint(
            equalTo: view.safeAreaLayoutGuide.bottomAnchor
        )
    }

    private func update(with viewBody: View.Body) {
        if let navigationBar = viewBody.navigationBar {
            navigationBarController.rootView = AnyView(NavigationBarView(navigationBar: navigationBar))
        } else {
            navigationBarController.rootView = AnyView(EmptyView())
        }

        contentController.rootView = viewBody.content

        if let accessoryBox = viewBody.accessoryBox {
            accessoryBoxController.rootView = accessoryBox.content
            accessoryBoxController.view.isHidden = false
        } else {
            accessoryBoxController.rootView = AnyView(EmptyView())
            accessoryBoxController.view.isHidden = true
        }

        let followsKeyboard = viewBody.accessoryBox?.followsKeyboard ?? false

        accessoryKeyboardConstraint?.isActive = followsKeyboard
        accessoryBottomConstraint?.isActive = !followsKeyboard

        if let accessibilityKey = viewBody.accessibilityKey {
            view.accessibilityIdentifier = String(describing: accessibilityKey)
        }

        applyBottomSheetSettings(viewBody.bottomSheetSettings)
    }

    private func applyBottomSheetSettings(_ settings: BottomSheetSettings) {
        sheetPresentationController?.detents = settings.detents.map { detent in
            switch detent {
            case .medium:
                .medium()

            case .large:
                .large()
            }
        }
    }
}