//
//  BilibiliCollectionViewLayout.swift
//  SwiftBilibili
//
//  Created by 罗文 on 2021/7/18.
//  Copyright © 2021年 罗文. All rights reserved.
//  处理cell间距为0仍有间隙的问题

import UIKit

final class BilibiliCollectionViewLayout: UICollectionViewFlowLayout {
    
    var maxInteritemSpacing: CGFloat = 0
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        
        guard let superAttributes = super.layoutAttributesForElements(in: rect) else { return nil }
        
        let attributes = NSArray(array: superAttributes, copyItems: true) as! [UICollectionViewLayoutAttributes]
        
        if attributes.count < 2 { return attributes }
        
        for i in 1..<attributes.count {
            let currentLayoutAttributes = attributes[i]
            let prevLayoutAttributes = attributes[i-1]
            let origin = prevLayoutAttributes.frame.maxX
            if origin + maxInteritemSpacing + currentLayoutAttributes.frame.size.width <= self.collectionViewContentSize.width {
                
                var frame = currentLayoutAttributes.frame
                frame.origin.x = origin + maxInteritemSpacing
                currentLayoutAttributes.frame = frame
            }
        }
        return attributes
    }
}