//
//  JYPageController.swift
//  JYPageController
//
//  Created by wang tao on 2022/7/14.
//

import UIKit


@objc public protocol JYPageControllerDataSource {
    
    ///segmentview frame
    func pageController(_ pageController: JYPageController, frameForSegmentedView segmentedView: JYSegmentedView) -> CGRect
    
    ///子页面下滚动区域frame
    func pageController(_ pageController: JYPageController, frameForContainerView container: UIScrollView) -> CGRect
    
    ///第index位置上item的title
    func pageController(_ pageController: JYPageController, titleAt index: Int) -> String
    
    ///第index位置上自定义item
    @objc optional func pageController(_ pageController: JYPageController, customViewAt index: Int) -> UIView?
    
    ///第index位置上item右上角的badgeView(eg. 标签/小红点，必须设置frame.size)
    @objc optional func pageController(_ pageController: JYPageController, badgeViewAt index: Int) -> UIView?
    
    ///子页面数量
    func numberOfChildControllers() -> Int
    
    ///返回第index位置上的UIViewController
    func childController(atIndex index: Int) -> JYPageChildContollerProtocol
}

@objc public protocol JYPageControllerDelegate {
    
    ///第一次加载childController调用
    @objc optional func pageController(_ pageController: JYPageController, didLoadChildController: UIViewController, index: Int)
    
    ///scrollView停止滚动，childController完全显示调用
    @objc optional func pageController(_ pageController: JYPageController, didEnterControllerAt index: Int)
    
    @objc optional func pageController(_ pageController: JYPageController, mainDidScroll offsetY: CGFloat)
}


open class JYPageController: UIViewController {
    
    ///config
    public var config: JYPageConfig = JYPageConfig.init()
    
    ///headerView
    public var headerView: UIView? {
        didSet {
            if let header = headerView {
                headerHeight = header.frame.size.height - self.config.hoverOffset
                mainScrollView.tableHeaderView = header
            }
        }
    }
    
    ///scrollView
    public var scrollView: UIScrollView? {
        get {
            if headerView != nil {
                return mainScrollView
            }else {
                return nil
            }
        }
    }
    
    ///header view height
    private var headerHeight: CGFloat = 0
    
    ///当前选中的index
    public var selectedIndex: Int = 0
    
    ///delegate
    weak public var delegate: JYPageControllerDelegate?
    
    ///dataSource
    weak public var dataSource: JYPageControllerDataSource?
    
    ///childViewController cache
    private var childControllerCache: NSCache = NSCache<NSString, UIViewController>()
    
    ///缓存当前scrollView上展示的vc，用于处理子vc的生命周期逻辑
    private var displayControllerCache = Dictionary<NSString, UIViewController>()
    
    ///childController scrollView cache
    private var childScrollViewCache: Dictionary = Dictionary<NSString, UIScrollView?>()
    
    ///menuview frame
    private var menuViewFrame: CGRect = .zero
    
    ///滚动区域container(scrollView)的frame
    private var childControllerViewFrame: CGRect = .zero
    
    ///标记scorllView滚动是否由拖拽触发
    private var scrollByDragging = false
    
    ///当前的偏移量，用来判断向左还是向右滑动
    private var currentOffsetX: CGFloat = 0
    
    ///有headerView的场景，记录menuView是都在顶部悬停
    private var scrollToTop: Bool = false
    
    ///竖直方向滚动的scrollView，contentOffsetY
    private var verScrollViewContentOffsetY: CGFloat = 0
    
    deinit {
        childScrollViewCache.forEach { (key: NSString, value: UIScrollView?) in
            value?.removeObserver(self, forKeyPath: "contentOffset")
        }
    }
    
    

    public override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nil, bundle: nil)
        
        delegate = self
        dataSource = self
        /**
         子类重写init方法，设置pageConfig,menuConfig的属性
         eg.
         config.showIndicatorLineView = false
         config.selectedTitleColor = .red
         config.normalTitleColor = .red
         config.selectedTitleFont = .systemFont(ofSize: 18, weight: .medium)
         config.normalTitleFont = .systemFont(ofSize: 18, weight: .medium)
         config.menuItemMargin = 10
         */
    }
    
    required public init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    open override func viewDidLoad() {
        super.viewDidLoad()
        pageViewSetup()
        segmentedView.select(selectedIndex)
    }
    
    open override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        mainScrollView.isScrollEnabled = headerView != nil
    }
    
    
    //MARK: - Public
    ///刷新方法，动态改变数据源的时候调用，其他场景不需要主动调用
    public func reload() {
        for i in 0 ..< childControllersCount {
            let cacheKey = String(i) as NSString
            if let childController = childControllerCache.object(forKey: cacheKey) {
                childController.view.removeFromSuperview()
                childController.willMove(toParent: nil)
                childController.removeFromParent()
            }
        }
        mainScrollView.removeFromSuperview()
        
        childControllersCount = dataSource?.numberOfChildControllers() ?? 0
        childControllerCache.removeAllObjects()
        displayControllerCache.removeAll()
        
        selectedIndex = 0
        segmentedView.reload()
        segmentedView.select(selectedIndex)
        
        pageViewSetup()
        pageContentScrollView.setContentOffset(CGPoint(x: CGFloat(selectedIndex) * childControllerViewFrame.width, y: 0), animated: false)
    }
    
    ///获取menuview中scrollview的contentsize
    public func contentSizeForMenuView() -> CGSize {
        return segmentedView.contentSize()
    }
    
    ///更新menuview的frame
    public func updateMenuViewFrame(frame: CGRect) {
        menuViewFrame = frame
        segmentedView.updateFrame(frame: frame)
    }
    
    ///添加指定index的menuItem的badgeView
    public func insertMenuItemBadgeView(_ badgeView: UIView, atIndex index: Int) {
        segmentedView.addSegmentedItemBadgeView(badgeView, atIndex: index)
    }
    
    ///移除指定index的menuItem的badgeView
    public func removeMenuItemBadgeView(atIndex index: Int) {
        segmentedView.removeSegmentedItemBadgeView(atIndex: index)
    }
    
    //MARK: - Private
    private func pageViewSetup() {
        guard let source = dataSource else {
            return
        }
        
        pageContentScrollView.bounces = config.pageScrollBounces
        menuViewFrame = source.pageController(self, frameForSegmentedView: segmentedView)
        childControllerViewFrame = source.pageController(self, frameForContainerView: pageContentScrollView)
        
        let mainScrollViewY : CGFloat = 0
//        if let navBar = navigationController?.navigationBar {
//            mainScrollViewY = navBar.frame.height + UIApplication.shared.statusBarFrame.size.height
//        }
        
        segmentedView.frame = menuViewFrame
        pageContentScrollView.frame = childControllerViewFrame
        mainScrollView.frame = CGRect(x: childControllerViewFrame.origin.x, y: mainScrollViewY, width: childControllerViewFrame.width, height: childControllerViewFrame.origin.y + childControllerViewFrame.height + self.config.hoverOffset)
//        mainScrollView.frame = mainControllerViewFrame
        
        let contentSize = CGSize(width: CGFloat(childControllersCount)*childControllerViewFrame.width, height: childControllerViewFrame.height)
        pageContentScrollView.contentSize = contentSize
        
        if config.segmentedViewShowInNavigationBar {
            view.addSubview(pageContentScrollView)
            navigationItem.titleView = segmentedView
        }else {
            view.addSubview(mainScrollView)
        }
    }
    
    
    ///添加指定index的controller
    private func addChildController(index: Int) {
        
        var childController = UIViewController()
        let cacheKey = String(index) as NSString
        if let controlller = childControllerCache.object(forKey: cacheKey) {
            childController = controlller
        }else {
            if let controlller = dataSource?.childController(atIndex: index) {
                if let childScrollView = controlller.fetchChildControllerScrollView?(),childScrollView.isKind(of: UIScrollView.classForCoder()) {
                    childScrollView.addObserver(self, forKeyPath: "contentOffset", options: [.old,.new], context: nil)
                    childScrollViewCache[cacheKey] = childScrollView
                }
                childControllerCache.setObject(controlller, forKey: cacheKey)
                delegate?.pageController?(self, didLoadChildController: controlller, index: index)
                childController = controlller
            }
        }
        
        if displayControllerCache[cacheKey] == nil {
            addChild(childController)
        }
        
        childController.view.frame = CGRect(x: CGFloat(index)*childControllerViewFrame.size.width, y: 0, width: childControllerViewFrame.size.width, height: childControllerViewFrame.size.height)
        childController.didMove(toParent: self)
        pageContentScrollView.addSubview(childController.view)
        displayControllerCache[cacheKey] = childController
    }
    
    private func loadChildControllerIfNeeded() {
        
        let offsetX = pageContentScrollView.contentOffset.x
        if offsetX < 0 || offsetX > pageContentScrollView.contentSize.width {
            return
        }
        guard offsetX.truncatingRemainder(dividingBy: childControllerViewFrame.size.width) == 0 else {
            var targetIndex = 0
            if offsetX > currentOffsetX {
                targetIndex = Int(offsetX/childControllerViewFrame.size.width) + 1
            }else {
                targetIndex = Int(offsetX/childControllerViewFrame.size.width)
            }
            let cacheKey = String(targetIndex) as NSString
            let controller = displayControllerCache[cacheKey]
            if targetIndex < childControllersCount, controller == nil {
                addChildController(index: targetIndex)
            }
            return
        }
    }
    
    private func removeChildControllerIfNeeded() {
        for i in 0 ..< childControllersCount {
            let cacheKey = String(i) as NSString
            if let childController = displayControllerCache[cacheKey], childControllerIsInScreen(childController) == false {
                childController.view.removeFromSuperview()
                childController.willMove(toParent: nil)
                childController.removeFromParent()
                displayControllerCache.removeValue(forKey: cacheKey)
            }
        }
    }
    
    private func childControllerIsInScreen(_ childController: UIViewController) -> Bool {
        let offsetX = pageContentScrollView.contentOffset.x
        let screenWidth = pageContentScrollView.frame.width
        let childViewMaxX = childController.view.frame.maxX
        let childViewMinX = childController.view.frame.minX

        if childViewMaxX > offsetX, childViewMinX - offsetX < screenWidth {
            return true
        }else{
            return false
        }
    }
    
    open override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "contentOffset", headerHeight > 0 {
            let cacheKey = String(selectedIndex) as NSString
            
            //1.处理mainScrollView和currentChildListScrollView的滚动冲突，向上滚动且segmentedView没有到悬浮位置之前，禁止currentChildListScrollView滚动
            if let newContentOffset = change?[NSKeyValueChangeKey.newKey] as? CGPoint, newContentOffset.y > 0, mainScrollView.contentOffset.y < headerHeight {
                let currentChildListScrollView = childScrollViewCache[cacheKey]
                currentChildListScrollView??.contentOffset = .zero
            }
            
            //2.下拉刷新位置在mainScrollView顶部，控制子页面的scrollview不能向下弹性滚动
            if config.headerRefreshLocation == .headerViewTop, let newContentOffset = change?[NSKeyValueChangeKey.newKey] as? CGPoint, newContentOffset.y < 0 {
                let currentChildListScrollView = childScrollViewCache[cacheKey]
                currentChildListScrollView??.contentOffset = .zero
            }
            
            //3.下拉刷新位置在子控制器scrollView顶部
            if config.headerRefreshLocation == .childControllerViewTop {
                //3.1处理segmentedView从悬浮状态下拉一直到headerView完全展示，整个过程中子页面的scrollview禁止下拉刷新
                if mainScrollView.contentOffset.y > 0, mainScrollView.contentOffset.y < headerHeight, let newContentOffset = change?[NSKeyValueChangeKey.newKey] as? CGPoint, newContentOffset.y < 0 {
                    let currentChildListScrollView = childScrollViewCache[cacheKey]
                    currentChildListScrollView??.contentOffset = .zero
                }
            }
        }
    }
    
    //MARK: - Lazy
    private lazy var childControllersCount: Int = {
        return dataSource?.numberOfChildControllers() ?? 0
    }()
    
    private(set) lazy var segmentedView: JYSegmentedView = {
        let segment = JYSegmentedView.init(pageConfig: config)
        segment.dataSource = self
        segment.delegate = self
        return segment
    }()
    
    private lazy var pageContentScrollView : UIScrollView = {
        let scrollView = UIScrollView()
//        scrollView.backgroundColor = .white
        scrollView.showsHorizontalScrollIndicator = false
        scrollView.delegate = self
        scrollView.isPagingEnabled = true
        if #available(iOS 11.0, *) {
            scrollView.contentInsetAdjustmentBehavior = .never
        }
        return scrollView
    }()
    
    private lazy var mainScrollView : JYScrollView = {
        let scrollView = JYScrollView(frame: .zero, style: .plain)
        scrollView.register(UITableViewCell.self, forCellReuseIdentifier: "UITableViewCell")
        scrollView.backgroundColor = .clear
        scrollView.showsVerticalScrollIndicator = false
        scrollView.isScrollEnabled = false
        scrollView.separatorStyle = .none
        scrollView.delegate = self
        scrollView.dataSource = self
        if #available(iOS 11.0, *) {
            scrollView.contentInsetAdjustmentBehavior = .never
        }
        if #available(iOS 15.0, *) {
            scrollView.sectionHeaderTopPadding = 0
        }
        return scrollView
    }()
}

//MARK: - UIScrollViewDelegate
extension JYPageController:UIScrollViewDelegate {
    
    public func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        if scrollView == pageContentScrollView {
            currentOffsetX = scrollView.contentOffset.x
            scrollByDragging = true
        }
    }
    
    public func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        if scrollView == pageContentScrollView {
            selectedIndex = Int(scrollView.contentOffset.x/scrollView.frame.width)
            segmentedView.segmentedViewScrollEnd(byScrollEndDecelerating: scrollView)
            delegate?.pageController?(self, didEnterControllerAt: selectedIndex)
        }
    }
    
    public func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if scrollView == pageContentScrollView {
            removeChildControllerIfNeeded()
            if scrollByDragging {
                loadChildControllerIfNeeded()
                segmentedView.segmentedViewScroll(by:scrollView)
                currentOffsetX = scrollView.contentOffset.x
            }
        }
        
        if scrollView == mainScrollView, headerView != nil,headerView?.frame.height ?? 0 > 0 {
            
            let cacheKey = String(selectedIndex) as NSString
            let currentChildListScrollView = childScrollViewCache[cacheKey]
            
            //1.segmentedView悬浮的时候禁止mainScrollView滚动
            if currentChildListScrollView??.contentOffset.y ?? 0 > 0 || scrollView.contentOffset.y >= headerHeight {
                mainScrollView.contentOffset = CGPoint(x: 0, y: headerHeight)
            }
            
            //2.下拉刷新位置在子页面顶部时候，mainScrollView滑动到顶部之后禁止向下拉
            if config.headerRefreshLocation == .childControllerViewTop, mainScrollView.contentOffset.y < 0 {
                mainScrollView.contentOffset = .zero
            }

            //3.子页面左右滚动的时候禁止mainScrollView上下滚动
            if pageContentScrollView.contentOffset.x.truncatingRemainder(dividingBy: childControllerViewFrame.size.width) > 0, mainScrollView.contentOffset.y != verScrollViewContentOffsetY {
                mainScrollView.setContentOffset(CGPoint(x: 0, y: verScrollViewContentOffsetY), animated: false)
            }
            
            verScrollViewContentOffsetY = mainScrollView.contentOffset.y
            
            self.delegate?.pageController?(self, mainDidScroll: verScrollViewContentOffsetY)
        }
    }
}



//MARK: - JYPageControllerDelegate, JYPageControllerDataSource
extension JYPageController: JYPageControllerDelegate, JYPageControllerDataSource {
    
    open func pageController(_ pageView: JYPageController, frameForSegmentedView segmentedView: JYSegmentedView) -> CGRect {
        return .zero
    }

    open func pageController(_ pageView: JYPageController, frameForContainerView container: UIScrollView) -> CGRect {
        return .zero
    }

    open func pageController(_ pageView: JYPageController, titleAt index: Int) -> String {
        return ""
    }
    
    open func pageController(_ pageController: JYPageController, customViewAt index: Int) -> UIView? {
        return nil
    }
    
    open func pageController(_ pageView: JYPageController, badgeViewAt index: Int) -> UIView? {
        return nil
    }

    open func numberOfChildControllers() -> Int {
        return 0
    }

    open func childController(atIndex index: Int) -> JYPageChildContollerProtocol {
        return JYPlaceHolderController()
    }
    
    open func pageController(_ pageController: JYPageController, didLoadChildController: UIViewController, index: Int) {
    }
    
    open func pageController(_ pageController: JYPageController, didEnterControllerAt index: Int) {
    }
}


//MARK: - JYSegmentedViewDelegate,JYSegmentedViewDatasource
extension JYPageController: JYSegmentedViewDelegate, JYSegmentedViewDataSource {
    public func numberOfSegmentedViewItems() -> Int {
        return childControllersCount
    }
    
    public func segmentedView(_ segmentedView: JYSegmentedView, titleAt index: Int) -> String {
        guard let source = dataSource else {
            return ""
        }
        return source.pageController(self, titleAt: index)
    }
    
    public func segmentedView(_ segmentedView: JYSegmentedView, customViewAt index: Int) -> UIView? {
        guard let source = dataSource else {
            return nil
        }
        return source.pageController?(self, customViewAt: index)
    }
    
    public func segmentedView(_ segmentedView: JYSegmentedView, badgeViewAt index: Int) -> UIView? {
        guard let source = dataSource else {
            return nil
        }
        return source.pageController?(self, badgeViewAt: index)
    }
    
    public func segmentedView(_ segmentedView: JYSegmentedView, didSelectItemAt index: Int) {
        scrollByDragging = false
        let cacheKey = String(index) as NSString
        let controller = displayControllerCache[cacheKey]
        if index < childControllersCount {
            if controller == nil {
                addChildController(index: index)
            }
            selectedIndex = index
            let contentOffsetX = CGFloat(index)*childControllerViewFrame.size.width
            pageContentScrollView.setContentOffset(CGPoint(x: contentOffsetX, y: 0), animated: config.scrollViewAnimationWhenSegmentItemSelected)
            delegate?.pageController?(self, didEnterControllerAt: index)
        }
    }
}

//MARK: - UITableViewDelegate,UITableViewDatasource
extension JYPageController: UITableViewDelegate, UITableViewDataSource {
    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }
    
//    public func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
//        return menuViewFrame.height
//    }
    
    public func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
//        return pageContentScrollView.frame.height
//        return self.view.frame.size.height
        return mainScrollView.frame.height - self.config.hoverOffset
    }
    
//    public func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
//        let headerContentView = UIView(frame: CGRect(x: 0, y: 0, width: menuViewFrame.size.width, height: menuViewFrame.size.height))
//        headerContentView.backgroundColor = .white
//        headerContentView.addSubview(segmentedView)
//        return headerContentView
//    }
    
    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "UITableViewCell", for: indexPath)
        cell.backgroundColor = .clear
        cell.selectionStyle = .none
//        pageContentScrollView.frame = CGRect(x: 0, y: 0, width: childControllerViewFrame.width, height: childControllerViewFrame.height)
        cell.contentView.addSubview(pageContentScrollView)
        cell.contentView.addSubview(segmentedView)
        return cell
    }
}