pagination.playground

import PlaygroundSupport
import UIKit

extension NSLayoutConstraint {
    class func equalConstraint(item: UIView, attribute: NSLayoutAttribute, toItem: UIView) -> NSLayoutConstraint{
        return NSLayoutConstraint(item: item,
                                  attribute: attribute,
                                  relatedBy: .equal,
                                  toItem: toItem,
                                  attribute: attribute,
                                  multiplier: 1.0,
                                  constant: 0.0)
        
    }
    
    class func constraints(from attributes: [NSLayoutAttribute], item: UIView, toItem:UIView) -> [NSLayoutConstraint] {
        return attributes.map(){
            equalConstraint(item: item,
                            attribute: $0,
                            toItem: toItem)
        }
    }
    
    class func rectCostraints(item: UIView, toItem: UIView) -> [NSLayoutConstraint] {
        return constraints(from: [.top, .bottom, .trailing, .leading],
                           item: item,
                           toItem: toItem)
    }
}

class CircleView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    
    func commonInit() {
        layer.masksToBounds = true

    }
    
    override func layoutSubviews() {
        layer.cornerRadius = layer.bounds.width/2
    }
}
let frame = CGRect(x:0, y:0, width: 300, height:300)
let view = UIView(frame: frame)
view.backgroundColor = UIColor.white

let stack = UIStackView(frame: frame)
stack.axis = .horizontal
stack.alignment = .fill
stack.distribution = .fillEqually
stack.spacing = 8.0

stack.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stack)
view.addConstraints(
    NSLayoutConstraint.constraints(from: [.trailing, .leading, .centerY],
                                   item: stack,
                                   toItem: view))

for index in 1...5 {
    if index % 2 == 0 {
        print("-", terminator:" ")
        let containerView = UIView(frame: CGRect(x:0, y:0, width: 40, height:20))
        let line = UIView(frame: CGRect(x:0, y:0, width: 40, height:2))
        line.backgroundColor = UIColor.gray
        containerView.addSubview(line)
        line.translatesAutoresizingMaskIntoConstraints = false
        containerView.addConstraints(
            NSLayoutConstraint.constraints(from: [.trailing, .leading, .centerY],
                                           item: line,
                                           toItem: containerView))
        line.addConstraint(NSLayoutConstraint(item: line,
                                              attribute: .height,
                                              relatedBy: .equal,
                                              toItem: nil ,
                                              attribute: .notAnAttribute,
                                              multiplier: 1.0,
                                              constant: 2.0))
        
        stack.addArrangedSubview(containerView)
    } else {
        print(String(index/2 + 1), terminator:" ")
        let containerView = CircleView(frame: CGRect(x:0, y:0, width: 20, height:20))
        containerView.backgroundColor = index == 1 ? UIColor.blue : UIColor.gray
        let label = UILabel()
        label.text = String(index/2 + 1)
        label.textAlignment = .center
        label.textColor = UIColor.white
        label.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(label)
        containerView.addConstraints(
            NSLayoutConstraint.rectCostraints(item: label, toItem: containerView).map(){ consraint in
                switch consraint.firstAttribute {
                case .leading, .top:
                    consraint.constant = 2.0
                default:
                    consraint.constant = -2.0
                }
                return consraint
            }
        )
        containerView.addConstraint(NSLayoutConstraint(item: containerView, attribute: .width,
                                                       relatedBy: .equal,
                                                       toItem: containerView,
                                                       attribute: .height,
                                                       multiplier: 1.0,
                                                       constant: 0.0))
        
        stack.addArrangedSubview(containerView)
    }
}


PlaygroundPage.current.liveView = view