//
//  CustomNavigationBar.swift
//  MullvadVPN
//
//  Created by pronebird on 22/05/2019.
//  Copyright © 2019 Mullvad VPN AB. All rights reserved.
//

import UIKit

class CustomNavigationBar: UINavigationBar {
    private static let titleTextAttributes: [NSAttributedString.Key: Any] = [
        .foregroundColor: UIColor.NavigationBar.titleColor
    ]

    private static let backButtonTitlePositionOffset = UIOffset(horizontal: 4, vertical: 0)
    private static let backButtonTitleTextAttributes: [NSAttributedString.Key: Any] = [
        .foregroundColor: UIColor.NavigationBar.backButtonTitleColor
    ]

    private static let setupAppearanceForIOS12Once: Void = {
        if #available(iOS 13, *) {
            // no-op
        } else {
            let buttonAppearance = UIBarButtonItem.appearance(whenContainedInInstancesOf: [CustomNavigationBar.self])
            buttonAppearance.setBackButtonTitlePositionAdjustment(CustomNavigationBar.backButtonTitlePositionOffset, for: .default)
            buttonAppearance.setTitleTextAttributes(CustomNavigationBar.titleTextAttributes, for: .normal)
        }
    }()

    private let customBackIndicatorImage = UIImage(named: "IconBack")?
        .backport_withTintColor(UIColor.NavigationBar.backButtonIndicatorColor, renderingMode: .alwaysOriginal)
    private let customBackIndicatorTransitionMask = UIImage(named: "IconBackTransitionMask")

    // Returns the distance from the title label to the bottom of navigation bar
    var titleLabelBottomInset: CGFloat {
        // Go two levels deep only
        let subviewsToExamine = subviews.flatMap { (view) -> [UIView] in
            return [view] + view.subviews
        }

        let titleLabel = subviewsToExamine.first { (view) -> Bool in
            return view is UILabel
        }

        if let titleLabel = titleLabel {
            let titleFrame = titleLabel.convert(titleLabel.bounds, to: self)
            return max(bounds.maxY - titleFrame.maxY, 0)
        } else {
            return 0
        }
    }

    override init(frame: CGRect) {
        Self.setupAppearanceForIOS12Once

        super.init(frame: frame)

        var margins = layoutMargins
        margins.left = UIMetrics.contentLayoutMargins.left
        margins.right = UIMetrics.contentLayoutMargins.right
        layoutMargins = margins

        setupNavigationBarAppearance()
    }

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

    private func setupNavigationBarAppearance() {
        tintColor = UIColor.NavigationBar.titleColor
        backgroundColor = UIColor.NavigationBar.backgroundColor
        isTranslucent = false

        if #available(iOS 13, *) {
            standardAppearance = makeNavigationBarAppearance()
            scrollEdgeAppearance = makeNavigationBarAppearance()
        } else {
            backIndicatorImage = customBackIndicatorImage
            backIndicatorTransitionMaskImage = customBackIndicatorTransitionMask
            barTintColor = UIColor.NavigationBar.backgroundColor

            titleTextAttributes = Self.titleTextAttributes
            largeTitleTextAttributes = Self.titleTextAttributes
            shadowImage = UIImage()
        }
    }

    @available(iOS 13, *)
    private func makeNavigationBarAppearance() -> UINavigationBarAppearance {
        let navigationBarAppearance = UINavigationBarAppearance()
        navigationBarAppearance.configureWithTransparentBackground()
        navigationBarAppearance.titleTextAttributes = Self.titleTextAttributes
        navigationBarAppearance.largeTitleTextAttributes = Self.titleTextAttributes

        let plainBarButtonAppearance = UIBarButtonItemAppearance(style: .plain)
        plainBarButtonAppearance.normal.titleTextAttributes = Self.titleTextAttributes

        let doneBarButtonAppearance = UIBarButtonItemAppearance(style: .done)
        doneBarButtonAppearance.normal.titleTextAttributes = Self.titleTextAttributes

        let backButtonAppearance = UIBarButtonItemAppearance(style: .plain)
        backButtonAppearance.normal.titlePositionAdjustment = Self.backButtonTitlePositionOffset
        backButtonAppearance.normal.titleTextAttributes = Self.backButtonTitleTextAttributes

        navigationBarAppearance.buttonAppearance = plainBarButtonAppearance
        navigationBarAppearance.doneButtonAppearance = doneBarButtonAppearance
        navigationBarAppearance.backButtonAppearance = backButtonAppearance

        if #available(iOS 14, *) {
            navigationBarAppearance.setBackIndicatorImage(customBackIndicatorImage, transitionMaskImage: customBackIndicatorTransitionMask)
        } else {
            // Bug: on iOS 13 setBackIndicatorImage accepts parameters in backward order
            // https://stackoverflow.com/a/58171229/351305
            navigationBarAppearance.setBackIndicatorImage(customBackIndicatorTransitionMask, transitionMaskImage: customBackIndicatorImage)
        }

        return navigationBarAppearance
    }

}