//
//  DeviceManagementContentView.swift
//  MullvadVPN
//
//  Created by pronebird on 19/07/2022.
//  Copyright © 2025 Mullvad VPN AB. All rights reserved.
//

import UIKit

class DeviceManagementContentView: UIView {
    private let scrollView: UIScrollView = {
        let scrollView = UIScrollView()
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        return scrollView
    }()

    let scrollContentView: UIView = {
        let view = UIView()
        view.directionalLayoutMargins = UIMetrics.contentLayoutMargins
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    let statusImageView: StatusImageView = {
        let imageView = StatusImageView(style: .failure)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        return imageView
    }()

    let titleLabel: UILabel = {
        let textLabel = UILabel()
        textLabel.font = .mullvadLarge
        textLabel.adjustsFontForContentSizeCategory = true
        textLabel.textColor = .white
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        return textLabel
    }()

    let messageLabel: UILabel = {
        let textLabel = UILabel()
        textLabel.font = .mullvadSmall
        textLabel.adjustsFontForContentSizeCategory = true
        textLabel.textColor = .white
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        textLabel.numberOfLines = 0
        textLabel.lineBreakStrategy = []
        return textLabel
    }()

    let deviceStackView: UIStackView = {
        let stackView = UIStackView(arrangedSubviews: [])
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        stackView.spacing = 1
        stackView.clipsToBounds = true
        stackView.distribution = .fillEqually
        return stackView
    }()

    let continueButton: AppButton = {
        let button = AppButton(style: .success)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.setTitle(
            NSLocalizedString("Continue with login", comment: ""),
            for: .normal
        )
        button.isEnabled = false
        button.setAccessibilityIdentifier(.continueWithLoginButton)
        return button
    }()

    let cancelButton: AppButton = {
        let button = AppButton(style: .default)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.setTitle(
            NSLocalizedString("Cancel", comment: ""),
            for: .normal
        )
        return button
    }()

    private lazy var buttonStackView: UIStackView = {
        let stackView = UIStackView(arrangedSubviews: [continueButton, cancelButton])
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        stackView.distribution = .fillEqually
        stackView.spacing = UIMetrics.interButtonSpacing
        return stackView
    }()

    var handleDeviceDeletion: (@Sendable (DeviceViewModel, @escaping @Sendable () -> Void) -> Void)?

    private var currentDeviceModels = [DeviceViewModel]()

    var canContinue = false {
        didSet {
            updateView()
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)

        addViews()
        constraintViews()
        updateView()

        setAccessibilityIdentifier(.deviceManagementView)
    }

    private func addViews() {
        try? [scrollView, buttonStackView].forEach(addSubview)

        scrollView.addSubview(scrollContentView)

        try? [statusImageView, titleLabel, messageLabel, deviceStackView]
            .forEach(scrollContentView.addSubview)
    }

    private func constraintViews() {
        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint(equalTo: topAnchor, constant: 16),
            scrollView.leadingAnchor.constraint(equalTo: leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: trailingAnchor),

            buttonStackView.topAnchor.constraint(
                equalTo: scrollView.bottomAnchor,
                constant: UIMetrics.contentLayoutMargins.top
            ),
            buttonStackView.leadingAnchor.constraint(
                equalTo: leadingAnchor,
                constant: UIMetrics.contentLayoutMargins.leading
            ),
            buttonStackView.trailingAnchor.constraint(
                equalTo: trailingAnchor,
                constant: -UIMetrics.contentLayoutMargins.trailing
            ),
            buttonStackView.bottomAnchor.constraint(
                equalTo: safeAreaLayoutGuide.bottomAnchor,
                constant: -UIMetrics.contentLayoutMargins.bottom
            ),

            scrollContentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
            scrollContentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
            scrollContentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
            scrollContentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
            scrollContentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor),

            statusImageView.topAnchor
                .constraint(equalTo: scrollContentView.topAnchor),
            statusImageView.centerXAnchor.constraint(equalTo: scrollContentView.centerXAnchor),

            titleLabel.topAnchor.constraint(equalTo: statusImageView.bottomAnchor, constant: 22),
            titleLabel.leadingAnchor
                .constraint(equalTo: scrollContentView.layoutMarginsGuide.leadingAnchor),
            titleLabel.trailingAnchor
                .constraint(equalTo: scrollContentView.layoutMarginsGuide.trailingAnchor),

            messageLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 8),
            messageLabel.leadingAnchor
                .constraint(equalTo: scrollContentView.layoutMarginsGuide.leadingAnchor),
            messageLabel.trailingAnchor
                .constraint(equalTo: scrollContentView.layoutMarginsGuide.trailingAnchor),

            deviceStackView.topAnchor.constraint(
                equalTo: messageLabel.bottomAnchor,
                constant: UIMetrics.TableView.sectionSpacing
            ),
            deviceStackView.leadingAnchor.constraint(equalTo: scrollContentView.leadingAnchor),
            deviceStackView.trailingAnchor.constraint(equalTo: scrollContentView.trailingAnchor),
            deviceStackView.bottomAnchor.constraint(equalTo: scrollContentView.bottomAnchor),
        ])
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setDeviceViewModels(_ newModels: [DeviceViewModel], animated: Bool) {
        let difference = newModels.difference(from: currentDeviceModels) { newModel, model in
            newModel.id == model.id
        }

        currentDeviceModels = newModels

        var viewsToAdd: [(view: UIView, offset: Int)] = []
        var viewsToRemove: [UIView] = []

        difference.forEach { change in
            switch change {
            case let .insert(offset, model, _):
                viewsToAdd.append((createDeviceRowView(from: model), offset))
            case let .remove(offset, _, _):
                viewsToRemove.append(deviceStackView.arrangedSubviews[offset])
            }
        }

        viewsToAdd.forEach { item in
            deviceStackView.insertArrangedSubview(item.view, at: item.offset)
        }

        // Layout inserted subviews before running animations to achieve a folding effect.
        if animated {
            UIView.performWithoutAnimation {
                deviceStackView.layoutIfNeeded()
            }
        }

        if animated {
            UIView.animate(
                withDuration: 0.25,
                delay: 0,
                options: [.curveEaseInOut],
                animations: { [weak self] in
                    self?.showHideViews(viewsToAdd: viewsToAdd, viewsToRemove: viewsToRemove)
                    self?.deviceStackView.layoutIfNeeded()
                },
                completion: { [weak self] _ in
                    self?.removeViews(viewsToRemove: viewsToRemove)
                }
            )
        } else {
            showHideViews(viewsToAdd: viewsToAdd, viewsToRemove: viewsToRemove)
            removeViews(viewsToRemove: viewsToRemove)
        }
    }

    private func showHideViews(viewsToAdd: [(view: UIView, offset: Int)], viewsToRemove: [UIView]) {
        viewsToRemove.forEach { view in
            view.alpha = 0
            view.isHidden = true
        }

        viewsToAdd.forEach { item in
            item.view.alpha = 1
            item.view.isHidden = false
        }
    }

    private func removeViews(viewsToRemove: [UIView]) {
        viewsToRemove.forEach { view in
            view.removeFromSuperview()
        }
    }

    private func createDeviceRowView(from model: DeviceViewModel) -> DeviceRowView {
        let view = DeviceRowView(viewModel: model)

        view.isHidden = true
        view.alpha = 0

        view.deleteHandler = { [weak self] _ in
            view.showsActivityIndicator = true

            self?.handleDeviceDeletion?(view.viewModel) {
                Task { @MainActor in
                    view.showsActivityIndicator = false
                }
            }
        }

        return view
    }

    private func updateView() {
        titleLabel.text = titleText
        messageLabel.text = messageText
        continueButton.isEnabled = canContinue
        statusImageView.style = canContinue ? .success : .failure
    }

    private var titleText: String {
        if canContinue {
            return NSLocalizedString("Super!", comment: "")
        } else {
            return NSLocalizedString("Too many devices", comment: "")
        }
    }

    private var messageText: String {
        if canContinue {
            return NSLocalizedString("You can now continue logging in on this device.", comment: "")
        } else {
            return NSLocalizedString(
                """
                Please log out of at least one by removing it from the list below. You can find \
                the corresponding device name under the device’s Account settings.
                """, comment: "")
        }
    }
}