//
//  AspectFitAutoLayoutImageView.swift
//
//  Created by Tanguy Gourvez on 28/06/2016.
//  Copyright © 2016 10sApps. All rights reserved.
//

import UIKit

class AspectFitAutoLayoutImageView: UIImageView {

    var aspectFitRatioConstraint: NSLayoutConstraint?

    override var image: UIImage? {
        didSet {
            updateImageConstraintsIfNeeded()
        }
    }


    override func awakeFromNib() {
        updateImageConstraintsIfNeeded()
    }

    // MARK: - Constraints

    func updateImageConstraintsIfNeeded() {
        if self.contentMode == .ScaleAspectFit {
            setNeedsUpdateConstraints()
            updateFocusIfNeeded()
        }
    }

    override func updateConstraints() {
        if let aspectFitRatioConstraint = aspectFitRatioConstraint {
            removeConstraint(aspectFitRatioConstraint)
        }

        if let image = image {
            let aspectRatio = image.size.height / image.size.width
            if !isnan(aspectRatio) {
                aspectFitRatioConstraint = NSLayoutConstraint(item: self, attribute: .Height, relatedBy: .Equal, toItem: self, attribute: .Width, multiplier: aspectRatio, constant: 0)
                aspectFitRatioConstraint?.priority = UILayoutPriorityRequired
                addConstraint(aspectFitRatioConstraint!)

                setContentCompressionResistancePriority(UILayoutPriorityDefaultLow, forAxis: .Horizontal)
                setContentCompressionResistancePriority(UILayoutPriorityDefaultLow, forAxis: .Vertical)
            }
        }
        super.updateConstraints()
    }


}