PJPageControl.swift

import Foundation

protocol PJPageControlUsable {
    
    var indicatorType: PJPageControl.Indicator { get }
    
}

protocol PJPageControlDelegate: class {
    
    func alertIndicatorPressed(pageControl: PJPageControl)
    
}

final class PJPageControl: NSObject {
    
    enum Indicator {
        case dot
        case alert
        
        func indicator() -> UIView {
            switch self {
            case .dot:
                let image = UIImage(named: "paging-dot-active")!
                let imageView = UIImageView(image: image)
                
                return imageView
            case .alert:
                let button = UIButton(type: .custom)
                let image = UIImage(named: "alert-bell")!
                button.setImage(image, for: .normal)
                
                return button
            }
        }

    }
    
    var indicators: [Indicator] {
        didSet {
            self.configure(with: indicators)
        }
    }
    
    var totalNumberOfPages: Int {
        return self.indicators.count
    }
    
    var currentPage: Int {
        didSet {
            self.makePageActive(page: currentPage)
        }
    }
    
    var pageIndicatorColor = UIColor(red: 81 / 255, green: 81 / 255, blue: 81 / 255, alpha: 1.0)
    var currentPageIndicatorColor = UIColor(red: 219 / 255, green: 219 / 255, blue: 219 / 255, alpha: 1.0)
    
    weak var delegate: PJPageControlDelegate?
    
    let stackView: UIStackView
    
    override init() {
        let sv = UIStackView()
        sv.spacing = 9
        sv.distribution = .fill
        sv.alignment = .center
        sv.translatesAutoresizingMaskIntoConstraints = false
        
        self.currentPage = 0
        self.stackView = sv
        self.indicators = []
        
        super.init()
    }
    
    private func makePageActive(page: Int) {
        guard !self.stackView.arrangedSubviews.isEmpty else { return }
        
        self.stackView.arrangedSubviews.forEach({ view in
            if let view = view as? ColorTemplateable {
                view.renderImage(with: self.pageIndicatorColor)
            }
            
            view.transform = .identity
        })
        
        let view = self.stackView.arrangedSubviews[page]
        if case PJPageControl.Indicator.dot = self.indicators[page] {
            view.transform = CGAffineTransform(scaleX: 1.13, y: 1.13)
        }
        
        if let view = view as? ColorTemplateable {
            view.renderImage(with: self.currentPageIndicatorColor)
        }
    }
    
    private func resetStackView() {
        for subview in self.stackView.arrangedSubviews {
            self.stackView.removeArrangedSubview(subview)
            subview.removeFromSuperview()
        }
    }
    
    private func configure(with indicators: [Indicator]) {
        resetStackView()
        let imageViews = indicators.map({ return $0.indicator() })
        imageViews.forEach({ view in
            if let view = view as? ColorTemplateable {
                view.renderImage(with: self.pageIndicatorColor)
            }
            
            if let view = view as? UIButton {
                view.addTarget(self, action: #selector(PJPageControl.alertButtonPressed(sender:)), for: .touchUpInside)
            }
            
            self.stackView.addArrangedSubview(view)
        })
    }
    
    @objc private func alertButtonPressed(sender: UIButton) {
        self.delegate?.alertIndicatorPressed(pageControl: self)
    }
    
}

protocol ColorTemplateable {
    func renderImage(with color: UIColor)
}

extension UIImageView: ColorTemplateable {
    
    func renderImage(with color: UIColor) {
        let image = self.image?.withRenderingMode(.alwaysTemplate)
        self.tintColor = color
        self.image = image
    }
    
}

extension UIButton: ColorTemplateable {
    
    func renderImage(with color: UIColor) {
        let image = self.image(for: .normal)?.withRenderingMode(.alwaysTemplate)
        self.tintColor = color
        self.setImage(image, for: .normal)
    }
}