ButtonBarPagerTabStripViewController.swift

//  ButtonBarPagerTabStripViewController.swift
//  XLPagerTabStrip ( https://github.com/xmartlabs/XLPagerTabStrip )
//
//  Copyright (c) 2017 Xmartlabs ( http://xmartlabs.com )
//
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

import Foundation

public enum ButtonBarItemSpec<CellType: UICollectionViewCell> {

    case nibFile(nibName: String, bundle: Bundle?, width:((IndicatorInfo)-> CGFloat))
    case cellClass(width:((IndicatorInfo)-> CGFloat))

    public var weight: ((IndicatorInfo) -> CGFloat) {
        switch self {
        case .cellClass(let widthCallback):
            return widthCallback
        case .nibFile(_, _, let widthCallback):
            return widthCallback
        }
    }
}

public struct ButtonBarPagerTabStripSettings {

    public struct Style {
        public var buttonBarBackgroundColor: UIColor?
        public var buttonBarMinimumInteritemSpacing: CGFloat?
        public var buttonBarMinimumLineSpacing: CGFloat?
        public var buttonBarLeftContentInset: CGFloat?
        public var buttonBarRightContentInset: CGFloat?

        public var selectedBarBackgroundColor = UIColor.black
        public var selectedBarHeight: CGFloat = 5
        public var selectedBarVerticalAlignment: SelectedBarVerticalAlignment = .bottom

        public var buttonBarItemBackgroundColor: UIColor?
        public var buttonBarItemFont = UIFont.systemFont(ofSize: 18)
        public var buttonBarItemLeftRightMargin: CGFloat = 8
        public var buttonBarItemTitleColor: UIColor?
        @available(*, deprecated: 7.0.0) public var buttonBarItemsShouldFillAvailiableWidth: Bool {
            set {
                buttonBarItemsShouldFillAvailableWidth = newValue
            }
            get {
                return buttonBarItemsShouldFillAvailableWidth
            }
        }
        public var buttonBarItemsShouldFillAvailableWidth = true
        // only used if button bar is created programaticaly and not using storyboards or nib files
        public var buttonBarHeight: CGFloat?
    }

    public var style = Style()
}

open class ButtonBarPagerTabStripViewController: PagerTabStripViewController, PagerTabStripDataSource, PagerTabStripIsProgressiveDelegate, UICollectionViewDelegate, UICollectionViewDataSource {

    public var settings = ButtonBarPagerTabStripSettings()

    public var buttonBarItemSpec: ButtonBarItemSpec<ButtonBarViewCell>!

    public var changeCurrentIndex: ((_ oldCell: ButtonBarViewCell?, _ newCell: ButtonBarViewCell?, _ animated: Bool) -> Void)?
    public var changeCurrentIndexProgressive: ((_ oldCell: ButtonBarViewCell?, _ newCell: ButtonBarViewCell?, _ progressPercentage: CGFloat, _ changeCurrentIndex: Bool, _ animated: Bool) -> Void)?

    @IBOutlet public weak var buttonBarView: ButtonBarView!

    lazy private var cachedCellWidths: [CGFloat]? = { [unowned self] in
        return self.calculateWidths()
    }()

    override public init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        delegate = self
        datasource = self
    }

    required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        delegate = self
        datasource = self
    }

    open override func viewDidLoad() {
        super.viewDidLoad()
        
        var bundle = Bundle(for: ButtonBarViewCell.self)
        if let resourcePath = bundle.path(forResource: "XLPagerTabStrip", ofType: "bundle") {
            if let resourcesBundle = Bundle(path: resourcePath) {
                bundle = resourcesBundle
            }
        }
        
        buttonBarItemSpec = .nibFile(nibName: "ButtonCell", bundle: bundle, width: { [weak self] (childItemInfo) -> CGFloat in
                let label = UILabel()
                label.translatesAutoresizingMaskIntoConstraints = false
                label.font = self?.settings.style.buttonBarItemFont
                label.text = childItemInfo.title
                let labelSize = label.intrinsicContentSize
                return labelSize.width + (self?.settings.style.buttonBarItemLeftRightMargin ?? 8) * 2
        })

        let buttonBarViewAux = buttonBarView ?? {
                let flowLayout = UICollectionViewFlowLayout()
                flowLayout.scrollDirection = .horizontal
                let buttonBarHeight = settings.style.buttonBarHeight ?? 44
                let buttonBar = ButtonBarView(frame: CGRect(x: 0, y: 0, width: view.frame.size.width, height: buttonBarHeight), collectionViewLayout: flowLayout)
                buttonBar.backgroundColor = .orange
                buttonBar.selectedBar.backgroundColor = .black
                buttonBar.autoresizingMask = .flexibleWidth
                var newContainerViewFrame = containerView.frame
                newContainerViewFrame.origin.y = buttonBarHeight
                newContainerViewFrame.size.height = containerView.frame.size.height - (buttonBarHeight - containerView.frame.origin.y)
                containerView.frame = newContainerViewFrame
                return buttonBar
            }()
        buttonBarView = buttonBarViewAux

        if buttonBarView.superview == nil {
            view.addSubview(buttonBarView)
        }
        if buttonBarView.delegate == nil {
            buttonBarView.delegate = self
        }
        if buttonBarView.dataSource == nil {
            buttonBarView.dataSource = self
        }
        buttonBarView.scrollsToTop = false
        let flowLayout = buttonBarView.collectionViewLayout as! UICollectionViewFlowLayout // swiftlint:disable:this force_cast
        flowLayout.scrollDirection = .horizontal
        flowLayout.minimumInteritemSpacing = settings.style.buttonBarMinimumInteritemSpacing ?? flowLayout.minimumInteritemSpacing
        flowLayout.minimumLineSpacing = settings.style.buttonBarMinimumLineSpacing ?? flowLayout.minimumLineSpacing
        let sectionInset = flowLayout.sectionInset
        flowLayout.sectionInset = UIEdgeInsets(top: sectionInset.top, left: settings.style.buttonBarLeftContentInset ?? sectionInset.left, bottom: sectionInset.bottom, right: settings.style.buttonBarRightContentInset ?? sectionInset.right)

        buttonBarView.showsHorizontalScrollIndicator = false
        buttonBarView.backgroundColor = settings.style.buttonBarBackgroundColor ?? buttonBarView.backgroundColor
        buttonBarView.selectedBar.backgroundColor = settings.style.selectedBarBackgroundColor

        buttonBarView.selectedBarHeight = settings.style.selectedBarHeight
        buttonBarView.selectedBarVerticalAlignment = settings.style.selectedBarVerticalAlignment

        // register button bar item cell
        switch buttonBarItemSpec! {
        case .nibFile(let nibName, let bundle, _):
            buttonBarView.register(UINib(nibName: nibName, bundle: bundle), forCellWithReuseIdentifier:"Cell")
        case .cellClass:
            buttonBarView.register(ButtonBarViewCell.self, forCellWithReuseIdentifier:"Cell")
        }
        //-
    }

    open override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        buttonBarView.layoutIfNeeded()
    }

    open override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        guard isViewAppearing || isViewRotating else { return }

        // Force the UICollectionViewFlowLayout to get laid out again with the new size if
        // a) The view is appearing.  This ensures that
        //    collectionView:layout:sizeForItemAtIndexPath: is called for a second time
        //    when the view is shown and when the view *frame(s)* are actually set
        //    (we need the view frame's to have been set to work out the size's and on the
        //    first call to collectionView:layout:sizeForItemAtIndexPath: the view frame(s)
        //    aren't set correctly)
        // b) The view is rotating.  This ensures that
        //    collectionView:layout:sizeForItemAtIndexPath: is called again and can use the views
        //    *new* frame so that the buttonBarView cell's actually get resized correctly
        cachedCellWidths = calculateWidths()
        buttonBarView.collectionViewLayout.invalidateLayout()
        // When the view first appears or is rotated we also need to ensure that the barButtonView's
        // selectedBar is resized and its contentOffset/scroll is set correctly (the selected
        // tab/cell may end up either skewed or off screen after a rotation otherwise)
        buttonBarView.moveTo(index: currentIndex, animated: false, swipeDirection: .none, pagerScroll: .scrollOnlyIfOutOfScreen)
        buttonBarView.selectItem(at: IndexPath(item: currentIndex, section: 0), animated: false, scrollPosition: [])
    }

    // MARK: - Public Methods

    open override func reloadPagerTabStripView() {
        super.reloadPagerTabStripView()
        guard isViewLoaded else { return }
        buttonBarView.reloadData()
        cachedCellWidths = calculateWidths()
        buttonBarView.moveTo(index: currentIndex, animated: false, swipeDirection: .none, pagerScroll: .yes)
    }

    open func calculateStretchedCellWidths(_ minimumCellWidths: [CGFloat], suggestedStretchedCellWidth: CGFloat, previousNumberOfLargeCells: Int) -> CGFloat {
        var numberOfLargeCells = 0
        var totalWidthOfLargeCells: CGFloat = 0

        for minimumCellWidthValue in minimumCellWidths where minimumCellWidthValue > suggestedStretchedCellWidth {
            totalWidthOfLargeCells += minimumCellWidthValue
            numberOfLargeCells += 1
        }

        guard numberOfLargeCells > previousNumberOfLargeCells else { return suggestedStretchedCellWidth }

        let flowLayout = buttonBarView.collectionViewLayout as! UICollectionViewFlowLayout // swiftlint:disable:this force_cast
        let collectionViewAvailiableWidth = buttonBarView.frame.size.width - flowLayout.sectionInset.left - flowLayout.sectionInset.right
        let numberOfCells = minimumCellWidths.count
        let cellSpacingTotal = CGFloat(numberOfCells - 1) * flowLayout.minimumLineSpacing

        let numberOfSmallCells = numberOfCells - numberOfLargeCells
        let newSuggestedStretchedCellWidth = (collectionViewAvailiableWidth - totalWidthOfLargeCells - cellSpacingTotal) / CGFloat(numberOfSmallCells)

        return calculateStretchedCellWidths(minimumCellWidths, suggestedStretchedCellWidth: newSuggestedStretchedCellWidth, previousNumberOfLargeCells: numberOfLargeCells)
    }

    open func updateIndicator(for viewController: PagerTabStripViewController, fromIndex: Int, toIndex: Int) {
        guard shouldUpdateButtonBarView else { return }
        buttonBarView.moveTo(index: toIndex, animated: false, swipeDirection: toIndex < fromIndex ? .right : .left, pagerScroll: .yes)

        if let changeCurrentIndex = changeCurrentIndex {
            let oldIndexPath = IndexPath(item: currentIndex != fromIndex ? fromIndex : toIndex, section: 0)
            let newIndexPath = IndexPath(item: currentIndex, section: 0)

            let cells = cellForItems(at: [oldIndexPath, newIndexPath], reloadIfNotVisible: collectionViewDidLoad)
            changeCurrentIndex(cells.first!, cells.last!, true)
        }
    }

    open func updateIndicator(for viewController: PagerTabStripViewController, fromIndex: Int, toIndex: Int, withProgressPercentage progressPercentage: CGFloat, indexWasChanged: Bool) {
        guard shouldUpdateButtonBarView else { return }
        buttonBarView.move(fromIndex: fromIndex, toIndex: toIndex, progressPercentage: progressPercentage, pagerScroll: .yes)
        if let changeCurrentIndexProgressive = changeCurrentIndexProgressive {
            let oldIndexPath = IndexPath(item: currentIndex != fromIndex ? fromIndex : toIndex, section: 0)
            let newIndexPath = IndexPath(item: currentIndex, section: 0)

            let cells = cellForItems(at: [oldIndexPath, newIndexPath], reloadIfNotVisible: collectionViewDidLoad)
            changeCurrentIndexProgressive(cells.first!, cells.last!, progressPercentage, indexWasChanged, true)
        }
    }

    private func cellForItems(at indexPaths: [IndexPath], reloadIfNotVisible reload: Bool = true) -> [ButtonBarViewCell?] {
        let cells = indexPaths.map { buttonBarView.cellForItem(at: $0) as? ButtonBarViewCell }

        if reload {
            let indexPathsToReload = cells.enumerated()
                .compactMap { (arg) -> IndexPath? in
                    let (index, cell) = arg
                    return cell == nil ? indexPaths[index] : nil
                }
                .compactMap { (indexPath: IndexPath) -> IndexPath? in
                    return (indexPath.item >= 0 && indexPath.item < buttonBarView.numberOfItems(inSection: indexPath.section)) ? indexPath : nil
                }

            if !indexPathsToReload.isEmpty {
                buttonBarView.reloadItems(at: indexPathsToReload)
            }
        }

        return cells
    }

    // MARK: - UICollectionViewDelegateFlowLayut

    @objc open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: IndexPath) -> CGSize {
        guard let cellWidthValue = cachedCellWidths?[indexPath.row] else {
            fatalError("cachedCellWidths for \(indexPath.row) must not be nil")
        }
        return CGSize(width: cellWidthValue, height: collectionView.frame.size.height)
    }

    open func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard indexPath.item != currentIndex else { return }

        buttonBarView.moveTo(index: indexPath.item, animated: true, swipeDirection: .none, pagerScroll: .yes)
        shouldUpdateButtonBarView = false

        let oldIndexPath = IndexPath(item: currentIndex, section: 0)
        let newIndexPath = IndexPath(item: indexPath.item, section: 0)

        let cells = cellForItems(at: [oldIndexPath, newIndexPath], reloadIfNotVisible: collectionViewDidLoad)

        if pagerBehaviour.isProgressiveIndicator {
            if let changeCurrentIndexProgressive = changeCurrentIndexProgressive {
                changeCurrentIndexProgressive(cells.first!, cells.last!, 1, true, true)
            }
        } else {
            if let changeCurrentIndex = changeCurrentIndex {
                changeCurrentIndex(cells.first!, cells.last!, true)
            }
        }
        moveToViewController(at: indexPath.item)
    }

    // MARK: - UICollectionViewDataSource

    open func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return viewControllers.count
    }

    open func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as? ButtonBarViewCell else {
            fatalError("UICollectionViewCell should be or extend from ButtonBarViewCell")
        }

        collectionViewDidLoad = true

        let childController = viewControllers[indexPath.item] as! IndicatorInfoProvider // swiftlint:disable:this force_cast
        let indicatorInfo = childController.indicatorInfo(for: self)

        cell.label.text = indicatorInfo.title
        cell.label.font = settings.style.buttonBarItemFont
        cell.label.textColor = settings.style.buttonBarItemTitleColor ?? cell.label.textColor
        cell.contentView.backgroundColor = settings.style.buttonBarItemBackgroundColor ?? cell.contentView.backgroundColor
        cell.backgroundColor = settings.style.buttonBarItemBackgroundColor ?? cell.backgroundColor
        if let image = indicatorInfo.image {
            cell.imageView.image = image
        }
        if let highlightedImage = indicatorInfo.highlightedImage {
            cell.imageView.highlightedImage = highlightedImage
        }

        configureCell(cell, indicatorInfo: indicatorInfo)

        if pagerBehaviour.isProgressiveIndicator {
            if let changeCurrentIndexProgressive = changeCurrentIndexProgressive {
                changeCurrentIndexProgressive(currentIndex == indexPath.item ? nil : cell, currentIndex == indexPath.item ? cell : nil, 1, true, false)
            }
        } else {
            if let changeCurrentIndex = changeCurrentIndex {
                changeCurrentIndex(currentIndex == indexPath.item ? nil : cell, currentIndex == indexPath.item ? cell : nil, false)
            }
        }
        cell.isAccessibilityElement = true
        cell.accessibilityLabel = indicatorInfo.accessibilityLabel ?? cell.label.text
        cell.accessibilityTraits.insert([.button, .header])
        return cell
    }

    // MARK: - UIScrollViewDelegate

    open override func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
        super.scrollViewDidEndScrollingAnimation(scrollView)

        guard scrollView == containerView else { return }
        shouldUpdateButtonBarView = true
    }

    open func configureCell(_ cell: ButtonBarViewCell, indicatorInfo: IndicatorInfo) {
    }

    private func calculateWidths() -> [CGFloat] {
        let flowLayout = buttonBarView.collectionViewLayout as! UICollectionViewFlowLayout // swiftlint:disable:this force_cast
        let numberOfCells = viewControllers.count

        var minimumCellWidths = [CGFloat]()
        var collectionViewContentWidth: CGFloat = 0

        for viewController in viewControllers {
            let childController = viewController as! IndicatorInfoProvider // swiftlint:disable:this force_cast
            let indicatorInfo = childController.indicatorInfo(for: self)
            switch buttonBarItemSpec! {
            case .cellClass(let widthCallback):
                let width = widthCallback(indicatorInfo)
                minimumCellWidths.append(width)
                collectionViewContentWidth += width
            case .nibFile(_, _, let widthCallback):
                let width = widthCallback(indicatorInfo)
                minimumCellWidths.append(width)
                collectionViewContentWidth += width
            }
        }

        let cellSpacingTotal = CGFloat(numberOfCells - 1) * flowLayout.minimumLineSpacing
        collectionViewContentWidth += cellSpacingTotal

        let collectionViewAvailableVisibleWidth = buttonBarView.frame.size.width - flowLayout.sectionInset.left - flowLayout.sectionInset.right

        if !settings.style.buttonBarItemsShouldFillAvailableWidth || collectionViewAvailableVisibleWidth < collectionViewContentWidth {
            return minimumCellWidths
        } else {
            let stretchedCellWidthIfAllEqual = (collectionViewAvailableVisibleWidth - cellSpacingTotal) / CGFloat(numberOfCells)
            let generalMinimumCellWidth = calculateStretchedCellWidths(minimumCellWidths, suggestedStretchedCellWidth: stretchedCellWidthIfAllEqual, previousNumberOfLargeCells: 0)
            var stretchedCellWidths = [CGFloat]()

            for minimumCellWidthValue in minimumCellWidths {
                let cellWidth = (minimumCellWidthValue > generalMinimumCellWidth) ? minimumCellWidthValue : generalMinimumCellWidth
                stretchedCellWidths.append(cellWidth)
            }

            return stretchedCellWidths
        }
    }

    private var shouldUpdateButtonBarView = true
    private var collectionViewDidLoad = false

}