//
//  YPBottomPager.swift
//  YPImagePicker
//
//  Created by Sacha Durand Saint Omer on 27/10/16.
//  Copyright © 2016 Yummypets. All rights reserved.
//

import UIKit
import Stevia

protocol YPBottomPagerDelegate: class {
    func pagerScrollViewDidScroll(_ scrollView: UIScrollView)
    func pagerDidSelectController(_ vc: UIViewController)
}

public class YPBottomPager: UIViewController, UIScrollViewDelegate {
    
    weak var delegate: YPBottomPagerDelegate?
    var controllers = [UIViewController]() { didSet { reload() } }
    
    var v = YPBottomPagerView()
    
    var currentPage = 0
    
    var currentController: UIViewController {
        return controllers[currentPage]
    }
    
    override public func loadView() {
        self.automaticallyAdjustsScrollViewInsets = false
        v.scrollView.delegate = self
        view = v
    }
    
    public func scrollViewDidScroll(_ scrollView: UIScrollView) {
        delegate?.pagerScrollViewDidScroll(scrollView)
    }

    public func scrollViewWillEndDragging(_ scrollView: UIScrollView,
                                          withVelocity velocity: CGPoint,
                                          targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        if !v.header.menuItems.isEmpty {
            let menuIndex = (targetContentOffset.pointee.x + v.frame.size.width) / v.frame.size.width
            let selectedIndex = Int(round(menuIndex)) - 1
            if selectedIndex != currentPage {
                selectPage(selectedIndex)
            }
        }
    }
    
    func reload() {
        let viewWidth: CGFloat = UIScreen.main.bounds.width
        for (index, c) in controllers.enumerated() {
            addChildViewController(c)
            let x: CGFloat = CGFloat(index) * viewWidth
            v.scrollView.sv(c.view)
            c.view.left(x)
            c.view.top(0)
            c.view.width(viewWidth)
            equal(heights: c.view, v.scrollView)
        }
        
        let scrollableWidth: CGFloat = CGFloat(controllers.count) * CGFloat(viewWidth)
        v.scrollView.contentSize = CGSize(width: scrollableWidth, height: 0)
        
        // Build headers
        for (index, c) in controllers.enumerated() {
            let menuItem = YPMenuItem()
            menuItem.text.text = c.title?.capitalized
            menuItem.button.tag = index
            menuItem.button.addTarget(self,
                                      action: #selector(tabTapped(_:)),
                                      for: .touchUpInside)
            v.header.menuItems.append(menuItem)
        }
        
        let currentMenuItem = v.header.menuItems[0]
        currentMenuItem.select()
        v.header.refreshMenuItems()
    }
    
    @objc
    func tabTapped(_ b: UIButton) {
        showPage(b.tag)
    }
    
    func showPage(_ page: Int, animated: Bool = true) {
        let x = CGFloat(page) * UIScreen.main.bounds.width
        v.scrollView.setContentOffset(CGPoint(x: x, y: 0), animated: animated)
        selectPage(page)
    }

    func selectPage(_ page: Int) {
        if page != currentPage {
            currentPage = page
            //select menut item and deselect others
            for mi in v.header.menuItems {
                mi.unselect()
            }
            let currentMenuItem = v.header.menuItems[page]
            currentMenuItem.select()
            delegate?.pagerDidSelectController(controllers[page])
        }
    }
    
    func startOnPage(_ page: Int) {
        currentPage = page
        let x = CGFloat(page) * UIScreen.main.bounds.width
        v.scrollView.setContentOffset(CGPoint(x: x, y: 0), animated: false)
        //select menut item and deselect others
        for mi in v.header.menuItems {
            mi.unselect()
        }
        let currentMenuItem = v.header.menuItems[page]
        currentMenuItem.select()
    }
}
