//
//  UICollectionViewLeftAlignedLayout.swift
//  MVMCoreUI
//
//  Created by Dhamodaram Nandi on 05/06/20.
//  Copyright © 2020 Verizon Wireless. All rights reserved.
//

import Foundation

class UICollectionViewLeftAlignedLayout: UICollectionViewFlowLayout {
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let attributes = super.layoutAttributesForElements(in: rect) else {
            return nil
        }
        var rows = [Row]()
        var currentRowY: CGFloat = -1
        for attribute in attributes {
            if currentRowY != attribute.frame.origin.y {
                currentRowY = attribute.frame.origin.y
                rows.append(Row(spacing: 10))
            }
            rows.last?.add(attribute: attribute)
        }
        rows.forEach { $0.tagLayout(collectionViewWidth: collectionView?.frame.width ?? 0) }
        return rows.flatMap { $0.attributes }
    }
}

class Row {
    
    var attributes = [UICollectionViewLayoutAttributes]()
    var spacing: CGFloat = 0
    
    init(spacing: CGFloat) {
        self.spacing = spacing
    }
    
    func add(attribute: UICollectionViewLayoutAttributes) {
        attributes.append(attribute)
    }
    
    func tagLayout(collectionViewWidth: CGFloat) {
        let padding = 8
        var offset = padding
        for attribute in attributes {
            attribute.frame.origin.x = CGFloat(offset)
            offset += Int(attribute.frame.width + spacing)
        }
    }
}