Tusker/Tusker/Screens/Large Image/LargeImageViewController.swift

//
//  LargeImageViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 8/31/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit

class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeImageAnimatableViewController {
    
    typealias ContentView = UIView & LargeImageContentView

    weak var animationSourceView: UIImageView?
    var largeImageController: LargeImageViewController? { self }
    var animationImage: UIImage? { contentView.animationImage }
    var animationGifData: Data? { contentView.animationGifData }
    var dismissInteractionController: LargeImageInteractionController?
    
    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var topControlsView: UIView!
    @IBOutlet weak var topControlsHeightConstraint: NSLayoutConstraint!
    @IBOutlet weak var shareButton: UIButton!
    @IBOutlet weak var shareButtonTopConstraint: NSLayoutConstraint!
    @IBOutlet weak var shareButtonLeadingConstraint: NSLayoutConstraint!
    @IBOutlet weak var closeButton: UIButton!
    @IBOutlet weak var closeButtonTopConstraint: NSLayoutConstraint!
    @IBOutlet weak var closeButtonTrailingConstraint: NSLayoutConstraint!
    
    @IBOutlet weak var bottomControlsView: UIView!
    @IBOutlet weak var descriptionLabel: UILabel!
    
    var contentView: ContentView {
        didSet {
            oldValue.removeFromSuperview()
            setupContentView()
        }
    }
    var contentViewLeadingConstraint: NSLayoutConstraint!
    var contentViewTopConstraint: NSLayoutConstraint!

    var imageDescription: String?
    
    var initialControlsVisible = true
    private(set) var controlsVisible = true {
        didSet {
            setNeedsUpdateOfHomeIndicatorAutoHidden()
        }
    }
    var shrinkGestureEnabled = true
    
    var prevZoomScale: CGFloat?
    
    override var prefersStatusBarHidden: Bool {
        return true
    }
    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return .none
    }
    
    override var prefersHomeIndicatorAutoHidden: Bool {
        return !controlsVisible
    }
    
    init(contentView: ContentView, description: String?, sourceView: UIImageView?) {
        self.imageDescription = description
        self.animationSourceView = sourceView
        
        self.contentView = contentView

        super.init(nibName: "LargeImageViewController", bundle: nil)
        
        modalPresentationStyle = .fullScreen
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        setupContentView()

        setControlsVisible(initialControlsVisible, animated: false)
        shareButton.isEnabled = !contentView.activityItemsForSharing.isEmpty

        scrollView.delegate = self

        if let imageDescription = imageDescription,
           !imageDescription.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
            descriptionLabel.text = imageDescription.trimmingCharacters(in: .whitespacesAndNewlines)
        } else {
            bottomControlsView.isHidden = true
        }
        
        if shrinkGestureEnabled {
            dismissInteractionController = LargeImageInteractionController(viewController: self)
        }
        
        view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(scrollViewPressed(_:))))
        let doubleTap = UITapGestureRecognizer(target: self, action: #selector(scrollViewDoubleTapped(_:)))
        doubleTap.numberOfTapsRequired = 2
        view.addGestureRecognizer(doubleTap)
    }
    
    private func setupContentView() {
        contentView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(contentView)
        contentViewLeadingConstraint = contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor)
        contentViewTopConstraint = contentView.topAnchor.constraint(equalTo: scrollView.topAnchor)
        NSLayoutConstraint.activate([
            contentViewLeadingConstraint,
            contentViewTopConstraint,
        ])
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        // todo: does this need to be in viewDidLayoutSubviews?
        // limit the image height to the safe area height, so the image doesn't overlap the top controls
        // while zoomed all the way out
        let maxHeight = view.bounds.height - view.safeAreaInsets.top - view.safeAreaInsets.bottom
        let heightScale = maxHeight / contentView.intrinsicContentSize.height
        let widthScale = view.bounds.width / contentView.intrinsicContentSize.width
        let minScale = min(widthScale, heightScale)
        scrollView.minimumZoomScale = minScale
        scrollView.zoomScale = minScale
        scrollView.maximumZoomScale = minScale >= 1 ? minScale + 2 : 2

        centerImage()
        
        // todo: does this need to be in viewDidLayoutSubviews?
        if view.safeAreaInsets.top == 44 {
            // running on iPhone X style notched device
            let notchWidth: CGFloat = 209
            let earWidth = (view.bounds.width - notchWidth) / 2
            let offset = (earWidth - shareButton.bounds.width) / 2
            shareButtonLeadingConstraint.constant = offset
            closeButtonTrailingConstraint.constant = offset
        }
    }

    func setControlsVisible(_ controlsVisible: Bool, animated: Bool) {
        self.controlsVisible = controlsVisible
        if animated {
            UIView.animate(withDuration: 0.2) {
                self.updateControlsView()
            }
        } else {
            updateControlsView()
        }
    }
    
    func updateControlsView() {
        let topOffset = self.controlsVisible ? 0 : -self.topControlsView.bounds.height
        self.topControlsView.transform = CGAffineTransform(translationX: 0, y: topOffset)
        if self.imageDescription != nil {
            let bottomOffset = self.controlsVisible ? 0 : self.bottomControlsView.bounds.height + self.view.safeAreaInsets.bottom
            self.bottomControlsView.transform = CGAffineTransform(translationX: 0, y: bottomOffset)
        }
    }
    
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return contentView
    }
    
    func scrollViewDidZoom(_ scrollView: UIScrollView) {
        centerImage()
        
        let prevZoomScale = self.prevZoomScale ?? scrollView.minimumZoomScale
        if scrollView.zoomScale <= scrollView.minimumZoomScale {
            setControlsVisible(true, animated: true)
        } else if scrollView.zoomScale > prevZoomScale {
            setControlsVisible(false, animated: true)
        }
        self.prevZoomScale = scrollView.zoomScale
    }
    
    func centerImage() {
        let yOffset = max(0, (view.bounds.size.height - contentView.frame.height) / 2)
        contentViewTopConstraint.constant = yOffset

        let xOffset = max(0, (view.bounds.size.width - contentView.frame.width) / 2)
        contentViewLeadingConstraint.constant = xOffset
    }
    
    func zoomRectFor(scale: CGFloat, center: CGPoint) -> CGRect {
        var zoomRect = CGRect.zero
        zoomRect.size.width = contentView.frame.width / scale
        zoomRect.size.height = contentView.frame.height / scale
        let newCenter = scrollView.convert(center, to: contentView)
        zoomRect.origin.x = newCenter.x - (zoomRect.width / 2)
        zoomRect.origin.y = newCenter.y - (zoomRect.height / 2)
        return zoomRect
    }
    
    // MARK: Interaction
    
    func animateZoomOut() {
        UIView.animate(withDuration: 0.3, animations: {
            self.scrollView.zoomScale = self.scrollView.minimumZoomScale
            self.view.layoutIfNeeded()
        })
    }
    
    @objc func scrollViewPressed(_ sender: UITapGestureRecognizer) {
        if scrollView.zoomScale > scrollView.minimumZoomScale {
            animateZoomOut()
        } else {
            setControlsVisible(!controlsVisible, animated: true)
        }
    }
    
    @objc func scrollViewDoubleTapped(_ recognizer: UITapGestureRecognizer) {
        if scrollView.zoomScale <= scrollView.minimumZoomScale {
            let point = recognizer.location(in: recognizer.view)
            let scale: CGFloat
            if scrollView.minimumZoomScale < 1 {
                if 1 - scrollView.zoomScale <= 0.5 {
                    scale = scrollView.zoomScale + 1
                } else {
                    scale = 1
                }
            } else {
                scale = scrollView.maximumZoomScale
            }
            let rect = zoomRectFor(scale: scale, center: point)
            UIView.animate(withDuration: 0.3) {
                self.scrollView.zoom(to: rect, animated: false)
                self.view.layoutIfNeeded()
            }
        } else {
            animateZoomOut()
        }
    }
    
    @IBAction func closeButtonPressed(_ sender: Any) {
        dismiss(animated: true)
    }
    
    @IBAction func sharePressed(_ sender: Any) {
        let activityVC = UIActivityViewController(activityItems: contentView.activityItemsForSharing, applicationActivities: nil)
        activityVC.popoverPresentationController?.sourceView = shareButton
        present(activityVC, animated: true)
    }
    
}