//
//  CollectionHFlowLayout.swift
//  dinoGo
//
//  Created by osell on 2023/1/17.
//  Copyright © 2023 dino. All rights reserved.
//

import UIKit

class CollectionHFlowLayout: UICollectionViewLayout {
    
    var rows: Int = 5
    var colums: Int = 2
    var itemSize: CGSize = .zero
    var hSpacing: CGFloat = 10
    var vSpacing: CGFloat = 10
    var sectionInset: UIEdgeInsets = .zero
    
    var attributesArr: [UICollectionViewLayoutAttributes] = []
    
    var contentWidth: CGFloat = 0
    var page = 0
    // MARK: - Lifecycle
    private var pageWidth: CGFloat {
        let width = collectionView?.bounds.width ?? 0
        return width > 1 ? width : UIScreen.main.bounds.width
    }

    override func prepare() {
        super.prepare()
        attributesArr = []
        contentWidth = 0
        page = 0
        let pageTotal = rows * colums
        guard let itemCount = collectionView?.numberOfItems(inSection: 0) else { return }
        let pageWidth = self.pageWidth
        
        for index in 0..<itemCount {
            
            let indexPath = IndexPath(item: index, section: 0)
            let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
            
            page = index / pageTotal
            
            var x = ((itemSize.width + hSpacing) * CGFloat((index % pageTotal % colums)) + sectionInset.left)
            x = x + CGFloat(page) * pageWidth
            let y = (itemSize.height + vSpacing) * CGFloat((index % pageTotal / colums)) + sectionInset.top
            attributes.frame = CGRect(origin: CGPoint(x: x, y: y), size: itemSize)
            attributesArr.append(attributes)
        }
        
    }

    override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        abs((collectionView?.bounds.width ?? 0) - newBounds.width) > 0.5
    }
    
    
    
    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        attributesArr[indexPath.item]
    }
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        attributesArr.compactMap {
            if rect.intersects($0.frame) {
                return $0
            }
            return nil
        }
    }
    

    override var collectionViewContentSize: CGSize {
        var height = itemSize.height * CGFloat(rows)
        height = height + CGFloat(rows - 1) * vSpacing + sectionInset.top + sectionInset.bottom
        return CGSize(width: CGFloat(page + 1) * pageWidth, height: height)
    }
}