//
//  LoginContentView.swift
//  MullvadVPN
//
//  Created by pronebird on 22/03/2021.
//  Copyright © 2021 Mullvad VPN AB. All rights reserved.
//

import UIKit

class LoginContentView: UIView {

    lazy var titleLabel: UILabel = {
        let textLabel = UILabel()
        textLabel.font = UIFont.systemFont(ofSize: 32)
        textLabel.textColor = .white
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        return textLabel
    }()

    let messageLabel: UILabel = {
        let textLabel = UILabel()
        textLabel.font = UIFont.systemFont(ofSize: 17)
        textLabel.textColor = UIColor.white.withAlphaComponent(0.6)
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        return textLabel
    }()

    let accountInputGroup: AccountInputGroupView = {
        let inputGroup = AccountInputGroupView()
        inputGroup.translatesAutoresizingMaskIntoConstraints = false
        return inputGroup
    }()

    var accountTextField: AccountTextField {
        return accountInputGroup.textField
    }

    let statusImageView: StatusImageView = {
        let imageView = StatusImageView(style: .failure)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.alpha = 0
        return imageView
    }()

    let contentContainer: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.layoutMargins = UIMetrics.contentLayoutMargins
        return view
    }()

    let formContainer: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.layoutMargins = UIMetrics.contentLayoutMargins
        return view
    }()

    let footerContainer: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.layoutMargins = UIMetrics.contentLayoutMargins
        view.backgroundColor = .secondaryColor
        return view
    }()

    let footerLabel: UILabel = {
        let textLabel = UILabel()
        textLabel.font = UIFont.systemFont(ofSize: 17)
        textLabel.textColor = UIColor.white.withAlphaComponent(0.6)
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        textLabel.text = NSLocalizedString("Don't have an account number?", comment: "")
        return textLabel
    }()

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

    let activityIndicator: SpinnerActivityIndicatorView = {
        let view = SpinnerActivityIndicatorView(style: .large)
        view.tintColor = .white
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    private var isStatusImageVisible = false
    private var contentContainerBottomConstraint: NSLayoutConstraint?

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

        backgroundColor = .primaryColor
        layoutMargins = UIMetrics.contentLayoutMargins

        addSubviews()
        addKeyboardHandlers()
    }

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

    func setStatusImage(style: StatusImageView.Style?, visible: Bool, animated: Bool) {
        if let style = style {
            statusImageView.style = style
        }

        isStatusImageVisible = visible
        updateStatusImageVisibility(animated: animated)
    }

    private func updateStatusImageVisibility(animated: Bool) {
        let statusImageFrame = statusImageView.convert(statusImageView.bounds, to: self)
        let shouldShow = isStatusImageVisible && safeAreaLayoutGuide.layoutFrame.contains(statusImageFrame)

        let actions = {
            // Only display the status image if it doesn't overlap the safe area layout guide.
            if shouldShow {
                self.statusImageView.alpha = 1
            } else {
                self.statusImageView.alpha = 0
            }
        }

        if animated {
            UIView.animate(withDuration: 0.25) {
                actions()
            }
        } else {
            actions()
        }
    }

    private func addSubviews() {
        formContainer.addSubview(titleLabel)
        formContainer.addSubview(messageLabel)
        formContainer.addSubview(accountInputGroup)

        contentContainer.addSubview(activityIndicator)
        contentContainer.addSubview(statusImageView)
        contentContainer.addSubview(formContainer)

        footerContainer.addSubview(footerLabel)
        footerContainer.addSubview(createAccountButton)

        addSubview(contentContainer)
        addSubview(footerContainer)

        let contentContainerBottomConstraint = bottomAnchor.constraint(equalTo: contentContainer.bottomAnchor)
        self.contentContainerBottomConstraint = contentContainerBottomConstraint

        NSLayoutConstraint.activate([
            contentContainer.topAnchor.constraint(equalTo: safeAreaLayoutGuide.topAnchor),
            contentContainer.leadingAnchor.constraint(equalTo: leadingAnchor),
            contentContainer.trailingAnchor.constraint(equalTo: trailingAnchor),
            contentContainerBottomConstraint,

            footerContainer.leadingAnchor.constraint(equalTo: leadingAnchor),
            footerContainer.trailingAnchor.constraint(equalTo: trailingAnchor),
            footerContainer.bottomAnchor.constraint(equalTo: bottomAnchor),

            footerLabel.topAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.topAnchor),
            footerLabel.leadingAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.leadingAnchor),
            footerLabel.trailingAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.trailingAnchor),

            createAccountButton.topAnchor.constraint(equalToSystemSpacingBelow: footerLabel.bottomAnchor, multiplier: 1),
            createAccountButton.leadingAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.leadingAnchor),
            createAccountButton.trailingAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.trailingAnchor),
            createAccountButton.bottomAnchor.constraint(equalTo: footerContainer.layoutMarginsGuide.bottomAnchor),

            statusImageView.centerXAnchor.constraint(equalTo: contentContainer.centerXAnchor),
            formContainer.topAnchor.constraint(equalTo: statusImageView.bottomAnchor, constant: 30),
            formContainer.centerYAnchor.constraint(equalTo: contentContainer.centerYAnchor, constant: -20),
            formContainer.leadingAnchor.constraint(equalTo: contentContainer.leadingAnchor),
            formContainer.trailingAnchor.constraint(equalTo: contentContainer.trailingAnchor),

            activityIndicator.centerXAnchor.constraint(equalTo: statusImageView.centerXAnchor),
            activityIndicator.centerYAnchor.constraint(equalTo: statusImageView.centerYAnchor),

            titleLabel.topAnchor.constraint(equalTo: formContainer.topAnchor),
            titleLabel.leadingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.leadingAnchor),
            titleLabel.trailingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.trailingAnchor),

            messageLabel.topAnchor.constraint(equalToSystemSpacingBelow: titleLabel.bottomAnchor, multiplier: 1),
            messageLabel.leadingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.leadingAnchor),
            messageLabel.trailingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.trailingAnchor),

            accountInputGroup.topAnchor.constraint(equalToSystemSpacingBelow: messageLabel.bottomAnchor, multiplier: 1),
            accountInputGroup.leadingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.leadingAnchor),
            accountInputGroup.trailingAnchor.constraint(equalTo: formContainer.layoutMarginsGuide.trailingAnchor),
            accountInputGroup.bottomAnchor.constraint(equalTo: formContainer.bottomAnchor),
        ])
    }

    private func addKeyboardHandlers() {
        let notificationCenter = NotificationCenter.default

        notificationCenter.addObserver(self,
                                       selector: #selector(keyboardWillShow(_:)),
                                       name: UIWindow.keyboardWillShowNotification,
                                       object: nil)
        notificationCenter.addObserver(self,
                                       selector: #selector(keyboardWillChangeFrame(_:)),
                                       name: UIWindow.keyboardWillChangeFrameNotification,
                                       object: nil)
        notificationCenter.addObserver(self,
                                       selector: #selector(keyboardWillHide(_:)),
                                       name: UIWindow.keyboardWillHideNotification,
                                       object: nil)
    }


    // MARK: - Keyboard notifications

    @objc private func keyboardWillShow(_ notification: Notification) {
        guard let keyboardFrameValue = notification.userInfo?[UIWindow.keyboardFrameEndUserInfoKey] as? NSValue else { return }

        makeLoginFormVisible(keyboardFrame: keyboardFrameValue.cgRectValue)
    }

    @objc private func keyboardWillChangeFrame(_ notification: Notification) {
        guard let keyboardFrameValue = notification.userInfo?[UIWindow.keyboardFrameEndUserInfoKey] as? NSValue else { return }

        makeLoginFormVisible(keyboardFrame: keyboardFrameValue.cgRectValue)
    }

    @objc private func keyboardWillHide(_ notification: Notification) {
        contentContainerBottomConstraint?.constant = 0
        layoutIfNeeded()
        updateStatusImageVisibility(animated: false)
    }

    private func makeLoginFormVisible(keyboardFrame: CGRect) {
        let viewFrame = convert(bounds, to: nil)
        let intersection = viewFrame.intersection(keyboardFrame)

        contentContainerBottomConstraint?.constant = intersection.height

        layoutIfNeeded()
        updateStatusImageVisibility(animated: false)
    }
}