//
//  ThreeLayerCollectionViewController.swift
//  MVMCoreUI
//
//  Created by Scott Pfeil on 4/6/20.
//  Copyright © 2020 Verizon Wireless. All rights reserved.
//

import Foundation

@objc open class ThreeLayerCollectionViewController: ScrollingViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
    public var collectionView: UICollectionView?
    
    // The three main views
    private var topView: UIView?
    private var bottomView: UIView?
    private var headerView: ContainerCollectionReusableView?
    private var footerView: ContainerCollectionReusableView?
    var useMargins: Bool = true
    private let headerID = "header"
    private let footerID = "footer"
    
    //MARK: - MFViewController
    open override func updateViews() {
        super.updateViews()
        let width = view.bounds.width
        if let topView = topView as? MVMCoreViewProtocol {
            topView.updateView(width)
           // showHeader(width)
        }
        if let bottomView = bottomView as? MVMCoreViewProtocol {
            bottomView.updateView(width)
            //showFooter(width)
        }
        self.collectionView?.collectionViewLayout.invalidateLayout()
    }
    
    open override func handleNewData() {
        super.handleNewData()
        createViewForTableHeader()
        createViewForTableFooter()
        collectionView?.reloadData()
    }
    
    override open func viewDidLoad() {
        let collection = createCollectionView()
        collectionView = collection
        view.addSubview(collection)
        NSLayoutConstraint.constraintPinSubview(toSuperview: collection)
        scrollView = collectionView
        
        registerCells()
        
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }
    
    //MARK: - Spacing
    // If both are subclassed to return a value, then the buttons will not be pinned towards the bottom because neither spacing would try to fill the screen.
    /// Space between the top view and the table sections, nil to fill. 0 default
    open func spaceBelowTopView() -> CGFloat? {
        return 0
    }
    
    /// Space between the bottom view and the table sections, nil to fill. nil default
    open func spaceAboveBottomView() -> CGFloat? {
        return nil
    }
    
    /// can override to return a minimum fill space.
    open func minimumFillSpace() -> CGFloat {
        return 0
    }
    
    open override func updateViewConstraints() {
        super.updateViewConstraints()

        guard let tableView = collectionView else { return }

        let minimumSpace: CGFloat = minimumFillSpace()
        var currentSpace: CGFloat = 0
        var totalMinimumSpace: CGFloat = 0

        var fillTop = false
        if spaceBelowTopView() == nil, headerView != nil {
            fillTop = true
            currentSpace += headerView?.bottomConstraint?.constant ?? 0
            totalMinimumSpace += minimumSpace
        }

        var fillBottom = false
        if spaceAboveBottomView() == nil, footerView != nil {
            fillBottom = true
            currentSpace += footerView?.topConstraint?.constant ?? 0
            totalMinimumSpace += minimumSpace
        }

        guard fillTop || fillBottom else { return }

        let newSpace = MVMCoreUIUtility.getVariableConstraintHeight(currentSpace, in: tableView, minimumHeight: totalMinimumSpace)

        // If the bottom view is outside of the scroll, then only the top view constraint is being used, so we have to double it to account for the bottom constraint not being there when we compare to the new value.
        var currentSpaceForCompare: CGFloat = currentSpace
        if fillTop {
            currentSpaceForCompare = currentSpace * 2;
        }

        if !MVMCoreGetterUtility.cgfequalwiththreshold(newSpace, currentSpaceForCompare, 0.1) {
            if fillTop && fillBottom {
                // space both
                let half = newSpace / 2
                headerView?.bottomConstraint?.constant = half
                footerView?.topConstraint?.constant = half
                collectionView?.invalidateIntrinsicContentSize()
            } else if fillTop {
                // Only top is spaced (half the size if the bottom view is out of the scroll because it needs to be sized as if there are two spacers but there is only one.
                headerView?.bottomConstraint?.constant = newSpace
                collectionView?.invalidateIntrinsicContentSize()
            } else if fillBottom {
                // Only bottom is spaced.
                print("newSpace \(newSpace)")
                footerView?.topConstraint?.constant = newSpace
                collectionView?.invalidateIntrinsicContentSize()
            }
        }
    }
    
    //MARK: - Header Footer
    /// Gets the top view and adds it to a spacing view, headerView, and then calls showHeader.
    open func createViewForTableHeader() {
        guard let topView = viewForTop() else {
            self.topView = nil
            self.headerView = nil
            return
        }
        self.topView = topView
    }

    /// Gets the bottom view and adds it to a spacing view, footerView, and then calls showFooter.
    open func createViewForTableFooter() {
        guard let bottomView = viewForBottom() else {
            self.bottomView = nil
            self.footerView = nil
            return
        }
        self.bottomView = bottomView
    }
    
//    /// Takes the current headerView and adds it to the tableHeaderView
//    func showHeader(_ sizingWidth: CGFloat?) {
//        headerView?.removeFromSuperview()
//        tableView?.tableHeaderView = nil
//        guard let headerView = headerView else {
//            return
//        }
//
//        // This extra view is needed because of the wonkiness of apple's table header. Things breaks if using autolayout.
//        headerView.setNeedsLayout()
//        headerView.layoutIfNeeded()
//        MVMCoreUIUtility.sizeView(toFit: headerView)
//        let tableHeaderView = UIView(frame: CGRect(x: 0, y: 0, width: MVMCoreUIUtility.getWidth(), height: headerView.frame.height))
//        tableHeaderView.addSubview(headerView)
//        NSLayoutConstraint.constraintPinSubview(toSuperview: headerView)
//        tableView?.tableHeaderView = tableHeaderView
//    }
//
//    /// Takes the current footerView and adds it to the tableFooterView
//    func showFooter(_ sizingWidth: CGFloat?) {
//        footerView?.removeFromSuperview()
//        safeAreaView?.removeFromSuperview()
//        guard let footerView = footerView, let tableView = tableView else {
//            return
//        }
//
//        if bottomViewOutsideOfScrollArea {
//            // put bottom view outside of scrolling area.
//            bottomConstraint?.isActive = false
//            view.addSubview(footerView)
//            footerView.topAnchor.constraint(equalTo: tableView.bottomAnchor).isActive = true
//            footerView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
//            view.rightAnchor.constraint(equalTo: footerView.rightAnchor).isActive = true
//            view.safeAreaLayoutGuide.bottomAnchor.constraint(equalTo: footerView.bottomAnchor).isActive = true
//            safeAreaView = MVMCoreUICommonViewsUtility.getAndSetupSafeAreaView(on: view)
//            safeAreaView?.backgroundColor = bottomView?.backgroundColor
//        } else {
//            bottomConstraint?.isActive = true
//            var y: CGFloat?
//            if let tableFooterView = tableView.tableFooterView {
//                // if footer already exists, use the same y location to avoid strange moving animation
//                y = tableFooterView.frame.minY
//            }
//
//            // This extra view is needed because of the wonkiness of apple's table footer. Things breaks if using autolayout.
//            MVMCoreUIUtility.sizeView(toFit: footerView)
//            let tableFooterView = UIView(frame: CGRect(x: 0, y: y ?? 0, width: MVMCoreUIUtility.getWidth(), height: footerView.frame.height))
//            tableFooterView.addSubview(footerView)
//            NSLayoutConstraint.constraintPinSubview(toSuperview: footerView)
//            tableView.tableFooterView = tableFooterView
//        }
//    }
    
    //MARK: - Functions to subclass
    /// Subclass for a top view.
    open func viewForTop() -> UIView? {
        return nil
    }
        
    /// Subclass for a bottom view.
    open func viewForBottom() -> UIView? {
        return nil
    }
    
    open func createCollectionViewLayout() -> UICollectionViewLayout {
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .vertical
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        layout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
        return layout
    }
    
    open func createCollectionView() -> UICollectionView {
        let collection = UICollectionView(frame: .zero, collectionViewLayout: createCollectionViewLayout())
        collection.translatesAutoresizingMaskIntoConstraints = false
        collection.dataSource = self
        collection.delegate = self
        collection.showsHorizontalScrollIndicator = false
        collection.backgroundColor = .white
        collection.isAccessibilityElement = false
        collection.contentInsetAdjustmentBehavior = .always
        return collection
    }
    
    deinit {
        collectionView?.delegate = nil
        collectionView?.dataSource = nil
    }
    
    //MARK: - Collection
    
    open func registerCells() {
        collectionView?.register(ContainerCollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: headerID)
        collectionView?.register(ContainerCollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter, withReuseIdentifier: footerID)
    }
    
    open func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 0
    }
    
    open func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    open func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionItem", for: indexPath) as! MoleculeCollectionViewCell
        let labelModel = LabelModel(text: "hello")
        let model = MoleculeCollectionItemModel(with: labelModel)
        cell.set(with: model, delegateObjectIVar, nil)
        return cell
    }
    
    open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        guard let view = headerView ?? topView,
            section == 0 else { return .zero }

        // Use this view to calculate the optimal size based on the collection view's width
        return view.systemLayoutSizeFitting(CGSize(width: collectionView.frame.width, height: UIView.layoutFittingExpandedSize.height),
                                 withHorizontalFittingPriority: .required, // Width is fixed
                                       verticalFittingPriority: .fittingSizeLevel) // Height can be as large as needed
    }
    
    open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        guard let view = footerView ?? bottomView,
            section == numberOfSections(in: collectionView) - 1 else { return .zero }

        // Use this view to calculate the optimal size based on the collection view's width
        let size = view.systemLayoutSizeFitting(CGSize(width: collectionView.frame.width, height: UIView.layoutFittingExpandedSize.height),
        withHorizontalFittingPriority: .required, // Width is fixed
              verticalFittingPriority: .fittingSizeLevel) // Height can be as large as needed
        print("SIZEEE \(size.height) \(String(describing: footerView?.topConstraint?.constant))")
        return size
    }
    
    open func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        if (kind == UICollectionView.elementKindSectionFooter) {
           let footerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: footerID, for: indexPath) as! ContainerCollectionReusableView
            footerView.addAndContain(view: bottomView!)
            footerView.topConstraint?.constant = spaceAboveBottomView() ?? 0
            self.footerView = footerView
            return footerView
        } else if (kind == UICollectionView.elementKindSectionHeader) {
            let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerID, for: indexPath) as! ContainerCollectionReusableView
            headerView.addAndContain(view: topView!)
            headerView.bottomConstraint?.constant = spaceBelowTopView() ?? 0
            self.headerView = headerView
            return headerView
        }
        fatalError()
    }
}