//
//  GKNavigationInteractiveTransition.swift
//  GKNavigationBarSwift
//
//  Created by QuintGao on 2020/11/27.
//  Copyright © 2020 QuintGao. All rights reserved.
//

import UIKit

class GKNavigationInteractiveTransition: NSObject {
    var isGesturePush: Bool = false
    var pushTransition: UIPercentDrivenInteractiveTransition?
    var popTransition: UIPercentDrivenInteractiveTransition?
    weak var navigationController: UINavigationController!
    weak var visibleVC: UIViewController?
    var systemTarget: Any?
    var systemAction: Selector?
    
    // MARK: - 滑动手势处理
    @objc public func panGestureAction(_ gesture: UIPanGestureRecognizer) {
        // 进度
        guard let width = gesture.view?.bounds.size.width else { return }
        if width == 0 { return }
        
        var progress = gesture.translation(in: gesture.view).x / width
        let velocity = gesture.velocity(in: gesture.view)
        
        // 在手势开始的时候判断是push操作还是pop操作
        if gesture.state == .began {
            self.isGesturePush = velocity.x < 0 ? true : false
            self.visibleVC = self.navigationController.visibleViewController
        }
        
        // push时progress < 0 需要做处理
        if self.isGesturePush {
            progress = -progress
        }
        
        progress = min(1.0, max(0.0, progress))
        
        if gesture.state == .began {
            if self.isGesturePush { // push
                if self.navigationController.gk_openScrollLeftPush {
                    if let visibleVC = self.visibleVC {
                        if visibleVC.gk_pushDelegate != nil {
                            self.pushTransition = UIPercentDrivenInteractiveTransition()
                            visibleVC.gk_pushDelegate?.pushToNextViewController?()
                        }
                    }
                }
                pushScrollBegan()
            }else { // pop
                if self.navigationController.gk_transitionScale {
                    self.popTransition = UIPercentDrivenInteractiveTransition()
                    self.navigationController.popViewController(animated: true)
                }else {
                    if let visibleVC = self.visibleVC {
                        if visibleVC.gk_systemGestureHandleDisabled {
                            var shouldPop = visibleVC.navigationShouldPop()
                            let selector = NSSelectorFromString("navigationShouldPopOnGesture")
                            
                            if visibleVC.responds(to: selector) {
                                if visibleVC.perform(selector) != nil {
                                    shouldPop = true
                                }else {
                                    shouldPop = false
                                }
                            }
            
                            if shouldPop {
                                self.popTransition = UIPercentDrivenInteractiveTransition()
                                self.navigationController.popViewController(animated: true)
                            }
                        }
                    }
                }
                popScrollBegan()
            }
        }else if gesture.state == .changed {
            if self.isGesturePush {
                if self.pushTransition != nil {
                    self.pushTransition?.update(progress)
                }
                pushScrollUpdate(progress: progress)
            }else {
                if self.popTransition != nil {
                    self.popTransition?.update(progress)
                }
                popScrollUpdate(progress: progress)
            }
        }else if gesture.state == .ended || gesture.state == .cancelled {
            if self.isGesturePush {
                var pushFinished: Bool = progress > 0.5
                if self.pushTransition != nil {
                    if GKConfigure.isVelocityInsensitivity(velocity.x) && velocity.x < 0 {
                        pushFinished = true
                        self.pushTransition?.finish()
                    }else {
                        if progress > GKConfigure.gk_pushTransitionCriticalValue {
                            pushFinished = true
                            self.pushTransition?.finish()
                        }else {
                            pushFinished = false
                            self.pushTransition?.cancel()
                        }
                    }
                }
                pushScrollEnded(finished: pushFinished)
            }else {
                var popFinished: Bool = progress > 0.5
                if self.popTransition != nil {
                    if GKConfigure.isVelocityInsensitivity(velocity.x) && velocity.x > 0 {
                        popFinished = true
                        self.popTransition?.finish()
                    }else {
                        if progress > GKConfigure.gk_popTransitionCriticalValue {
                            popFinished = true
                            self.popTransition?.finish()
                        }else {
                            popFinished = false
                            self.popTransition?.cancel()
                        }
                    }
                }
                popScrollEnded(finished: popFinished)
            }
            self.pushTransition = nil
            self.popTransition  = nil
            self.visibleVC      = nil
            self.isGesturePush  = false
        }
    }
    
    func pushScrollBegan() {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_pushDelegate?.viewControllerPushScrollBegan?()
        }
    }
    
    func pushScrollUpdate(progress: CGFloat) {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_pushDelegate?.viewControllerPushScrollUpdate?(progress: progress)
        }
    }
    
    func pushScrollEnded(finished: Bool) {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_pushDelegate?.viewControllerPushScrollEnded?(finished: finished)
        }
    }
    
    func popScrollBegan() {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_popDelegate?.viewControllerPopScrollBegan?()
        }
    }
    
    func popScrollUpdate(progress: CGFloat) {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_popDelegate?.viewControllerPopScrollUpdate?(progress: progress)
        }
    }
    
    func popScrollEnded(finished: Bool) {
        if let visibleVC = self.visibleVC {
            visibleVC.gk_popDelegate?.viewControllerPopScrollEnded?(finished: finished)
        }
    }
}

extension GKNavigationInteractiveTransition: UINavigationControllerDelegate {
    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationController.Operation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        if fromVC.gk_pushTransition != nil && operation == .push {
            return fromVC.gk_pushTransition
        }
        if fromVC.gk_popTransition != nil && operation == .pop {
            return fromVC.gk_popTransition
        }
        let isScale = self.navigationController.gk_transitionScale
        if (isScale || self.pushTransition != nil) && operation == .push {
            return GKPushAnimatedTransition(scale: isScale)
        }
        if (isScale || self.popTransition != nil) && operation == .pop {
            return GKPopAnimatedTransition(scale: isScale)
        }
        return nil
    }
    
    func navigationController(_ navigationController: UINavigationController, interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        if self.pushTransition != nil && animationController.isKind(of: GKPushAnimatedTransition.self) {
            return self.pushTransition
        }
        if self.popTransition != nil && animationController.isKind(of: GKPopAnimatedTransition.self) {
            return self.popTransition
        }
        return nil
    }
}

extension GKNavigationInteractiveTransition: UIGestureRecognizerDelegate {
    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        // 不是UIPanGestureRecognizer，不作处理
        if gestureRecognizer.isKind(of: UIPanGestureRecognizer.self) == false {
            return true
        }
        
        // 转为UIPanGestureRecognizer
        let panGesture = gestureRecognizer as! UIPanGestureRecognizer
        
        // 如果没有visibleViewController，不作处理
        guard let visibleVC = self.navigationController.visibleViewController else {
            return true
        }
        
        // 当前VC禁止滑动返回
        if visibleVC.gk_interactivePopDisabled {
            return false
        }
        
        // 根据transition判断是左滑还是右滑
        let transition = panGesture.translation(in: gestureRecognizer.view)
        
        // 如果开启缩放，则移除系统处理
        if self.navigationController.gk_transitionScale {
            gestureRecognizer.removeTarget(self.systemTarget, action: self.systemAction)
        }
        
        if transition.x < 0 { // 左滑
            // 开启了左滑push并设置了代理
            if self.navigationController.gk_openScrollLeftPush && visibleVC.gk_pushDelegate != nil {
                gestureRecognizer.removeTarget(self.systemTarget, action: self.systemAction)
            }else {
                return false
            }
        }else if (transition.x > 0) { // 右滑
            if !visibleVC.gk_systemGestureHandleDisabled {
                var shouldPop = visibleVC.navigationShouldPop()
                let selector = NSSelectorFromString("navigationShouldPopOnGesture")
                if visibleVC.responds(to: selector) {
                    if visibleVC.perform(selector) != nil {
                        shouldPop = true
                    }else {
                        shouldPop = false
                    }
                }
                if shouldPop == false { return false }
            }
            
            // 解决根控制器右滑时出现的卡死情况
            if self.navigationController.viewControllers.count <= 1 { return false }
            
            // 忽略超出手势区域
            let beginningLocation = gestureRecognizer.location(in: gestureRecognizer.view)
            let maxAllowDistance = visibleVC.gk_maxPopDistance
            
            if maxAllowDistance > 0 && beginningLocation.x > maxAllowDistance { return false }
        }else {
            if visibleVC.gk_fullScreenPopDisabled {
                // 修复边缘侧滑返回失效的bug
                if self.navigationController.viewControllers.count <= 1 {
                    return false
                }
            }else {
                // 修复全屏返回手势上下滑动时可能导致的卡死情况
                return false
            }
        }
        
        // 忽略导航控制器正在做转场动画
        if self.navigationController.value(forKey: "_isTransitioning") as? Bool == true { return false }
        
        return true
    }
    
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        // 获取当前显示的VC
        guard let visibleVC = navigationController.visibleViewController else { return false }
        
        let selector = NSSelectorFromString("popGestureRecognizer:shouldRecognizeSimultaneouslyWith:")
        if visibleVC.responds(to: selector) {
            if visibleVC.perform(selector, with: gestureRecognizer, with: otherGestureRecognizer) != nil {
                return true
            }else {
                return false
            }
        }
        
        return false
    }
}