import Foundation
import UIKit

class GridLayout: UICollectionViewFlowLayout {

    private var numberOfColumns: Int = 3
    private var height: CGFloat = 0
    private var width: CGFloat = 0

    init(numberOfColumns: Int) {
        super.init()
        minimumLineSpacing = 1
        minimumInteritemSpacing = 1

        self.numberOfColumns = numberOfColumns
    }

    init(numberOfColumns: Int, height: CGFloat, width: CGFloat, lineSpacing: CGFloat, interItemSpacing: CGFloat) {
        super.init()

        minimumLineSpacing = lineSpacing
        minimumInteritemSpacing = interItemSpacing

        self.numberOfColumns = numberOfColumns
        self.height = height
        self.width = width
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var itemSize: CGSize {
        get {
            if let collectionView = collectionView {
                if width == 0 {
                    width = (collectionView.frame.width/CGFloat(self.numberOfColumns)) - self.minimumInteritemSpacing
                }

                if height == 0 {
                    height = (collectionView.frame.width/CGFloat(self.numberOfColumns)) - self.minimumInteritemSpacing
                }

                return CGSize(width: width, height: height)
            }

            // Default fallback
            return CGSize(width: 100, height: 100)
        }
        set {
            super.itemSize = newValue
        }
    }

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        if let collectionView = collectionView {
            return collectionView.contentOffset
        }
        return CGPoint.zero
    }

}