//  GalleryViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 6/13/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class GalleryViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {

    var dismissInteractionController: LargeImageInteractionController?
    
    let attachments: [Attachment]
    let sourcesInfo: [(CGRect, CGFloat)]
    let startIndex: Int
    
    let pages: [AttachmentViewController]
    
    var currentIndex: Int {
        guard let vc = viewControllers?.first as? AttachmentViewController,
            let index = pages.firstIndex(of: vc) else {
                fatalError()
        }
        return index
    }
    
    override var prefersStatusBarHidden: Bool {
        return true
    }
    override var childForHomeIndicatorAutoHidden: UIViewController? {
        return
            viewControllers?.first
    }
    
    init(attachments: [Attachment], sourcesInfo: [(CGRect, CGFloat)], startIndex: Int) {
        self.attachments = attachments
        self.sourcesInfo = sourcesInfo
        self.startIndex = startIndex
        
        self.pages = attachments.map(AttachmentViewController.init)
        
        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal)
        
        setViewControllers([pages[startIndex]], direction: .forward, animated: false)
        
        modalPresentationStyle = .fullScreen
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        self.dataSource = self
        self.delegate = self
        
        dismissInteractionController = LargeImageInteractionController(viewController: self)
    }

    
    // MARK: - Page View Controller Data Source
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let attachment = viewController as? AttachmentViewController,
            let index = pages.firstIndex(of: attachment),
            index > 0 else {
            return nil
        }
        return pages[index - 1]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let attachment = viewController as? AttachmentViewController,
            let index = pages.firstIndex(of: attachment),
            index < pages.count - 1 else {
                return nil
        }
        return pages[index + 1]
    }
    
    // MARK: - Page View Controller Delegate
    func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
        let pending = pendingViewControllers.first as! AttachmentViewController
        let current = viewControllers!.first as! AttachmentViewController
        pending.controlsVisible = current.controlsVisible
    }

}