//
//  SegmentedPageViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 9/13/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit

class SegmentedPageViewController: UIPageViewController, UIPageViewControllerDelegate {

    let titles: [String]
    let pageControllers: [UIViewController]
    
    private(set) var currentIndex: Int!
    
    var segmentedControl: UISegmentedControl!

    init(titles: [String], pageControllers: [UIViewController]) {
        self.titles = titles
        self.pageControllers = pageControllers
        
        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)

        self.delegate = self
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .systemBackground
        
        segmentedControl = UISegmentedControl(items: titles)
        segmentedControl.addTarget(self, action: #selector(segmentedControlChanged), for: .valueChanged)
        navigationItem.titleView = segmentedControl
        
        segmentedControl.selectedSegmentIndex = 0
        selectPage(at: 0, animated: false)
        
        addKeyCommand(MenuController.prevSubTabCommand)
        addKeyCommand(MenuController.nextSubTabCommand)
        
        // disable the transparent nav bar because it gets messy with multiple pages at different scroll positions
        if let nav = navigationController {
            let appearance = UINavigationBarAppearance()
            appearance.configureWithDefaultBackground()
            nav.navigationBar.scrollEdgeAppearance = appearance
        }
    }
    
    func selectPage(at index: Int, animated: Bool) {
        let direction: UIPageViewController.NavigationDirection = currentIndex == nil ? .forward  : index - currentIndex > 0 ? .forward : .reverse
        setViewControllers([pageControllers[index]], direction: direction, animated: animated)
        navigationItem.title = pageControllers[index].title
        currentIndex = index
        segmentedControl.selectedSegmentIndex = index
    }
    
    @objc func segmentedControlChanged() {
        selectPage(at: segmentedControl.selectedSegmentIndex, animated: true)
        UIImpactFeedbackGenerator(style: .light).impactOccurred()
    }

    // MARK: - Page View Controller Delegate
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        currentIndex = pageControllers.firstIndex(of: viewControllers!.first!)!
        segmentedControl.selectedSegmentIndex = currentIndex
        navigationItem.title = viewControllers!.first!.title
    }

}

extension SegmentedPageViewController: TabBarScrollableViewController {
    func tabBarScrollToTop() {
        if let scrollableVC = pageControllers[currentIndex] as? TabBarScrollableViewController {
            scrollableVC.tabBarScrollToTop()
        }
    }
}

extension SegmentedPageViewController: TabbedPageViewController {
    func selectNextPage() {
        guard currentIndex < pageControllers.count - 1 else { return }
        selectPage(at: currentIndex + 1, animated: true)
    }
    
    func selectPrevPage() {
        guard currentIndex > 0 else { return }
        selectPage(at: currentIndex - 1, animated: true)
    }
}

extension SegmentedPageViewController: BackgroundableViewController {
    func sceneDidEnterBackground() {
        if let current = pageControllers[currentIndex] as? BackgroundableViewController {
            current.sceneDidEnterBackground()
        }
    }
}