paiai_ios/PaiAi/PaiaiUIKit/Reusable/UIKit/NavigationBar/NavigationBar.swift

//
//  NavigationBar.swift
//  PaiaiUIKit
//
//  Created by ffib on 2019/1/15.
//  Copyright © 2019 yb. All rights reserved.
//

import UIKit

public protocol NavigationBarInOut: class {
    var navigationView: UIView { get }
    func navigationBarFadeIn()
    func navigationBarFadeOut()
}

extension NavigationBarInOut where Self: UIViewController {
    func navigationBarFadeIn() {
        let animation = UIViewPropertyAnimator(duration: 0.5, curve: .easeOut, animations: nil)
        animation.addAnimations {
            self.navigationView.alpha = 0
        }
        
        animation.addAnimations {
            self.navigationView.frame = CGRect(x: self.navigationView.frame.origin.x + self.calculateOffsetsX(),
                                               y: self.navigationView.frame.origin.y,
                                               width: self.navigationView.frame.width,
                                               height: self.navigationView.frame.height)
        }
        animation.startAnimation()
    }
    
    func navigationBarFadeOut() {
        let animation = UIViewPropertyAnimator(duration: 0.5, curve: .easeOut, animations: nil)
        animation.addAnimations {
            self.navigationView.alpha = 1
        }
        
        animation.addAnimations {
            self.navigationView.frame = CGRect(x: self.navigationView.frame.origin.x - self.calculateOffsetsX(),
                                               y: self.navigationView.frame.origin.y,
                                               width: self.navigationView.frame.width,
                                               height: self.navigationView.frame.height)
        }
        animation.startAnimation()
    }
    
    private func calculateOffsetsX() -> CGFloat {
        guard let barButtonItems = navigationItem.rightBarButtonItems else { return 0 }
        
        return barButtonItems.reduce(0) { (res, item) -> CGFloat in
            if let view = item.customView {
                return res + view.bounds.width
            } else {
                return res
            }
        }
    }
}