//
//  SPZoomCollectionViewLayout.swift
//  Thimra
//
//  Created by Overseas on 2025/4/22.
//

import UIKit

class SPZoomCollectionViewLayout: UICollectionViewFlowLayout {

    let minimumScale: CGFloat = 0.08 // 调整缩放大小
    
    private(set) var currentIndexPath: IndexPath = IndexPath(row: 0, section: 0)

    
    private var cellWidth: CGFloat {
        return itemSize.width + minimumLineSpacing
    }
    
    override func prepare() {
        super.prepare()
        scrollDirection = .horizontal
        self.collectionView?.decelerationRate = .fast
        let screenWidth = UIScreen.main.bounds.size.width
        let insetLeft = (screenWidth - self.itemSize.width) / 2
        collectionView?.contentInset = UIEdgeInsets(top: 0, left: insetLeft, bottom: 0, right: insetLeft)
    }
    
    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        guard let collectionView = collectionView else { return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity) }
        
        let proposedRect = CGRect(x: proposedContentOffset.x, y: 0, width: collectionView.bounds.width, height: collectionView.bounds.height)
        
        guard let layoutAttributes = layoutAttributesForElements(in: proposedRect) else {
            return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
        }
        
        let horizontalCenterX = proposedContentOffset.x + collectionView.bounds.width / 2
        var offsetAdjustment = CGFloat.greatestFiniteMagnitude
//        ydLog(message: "offsetAdjustment = \(offsetAdjustment)")
//        ydLog(message: "horizontalCenterX = \(horizontalCenterX)")
        
        var currentIndexPath: IndexPath = IndexPath(row: 0, section: 0)
        for attributes in layoutAttributes {
            let itemHorizontalCenterX = attributes.center.x
            let distance = itemHorizontalCenterX - horizontalCenterX
//            ydLog(message: "distance = \(distance)")
            //离中心距离最近的
            if abs(distance) < abs(offsetAdjustment) {
                offsetAdjustment = distance
                currentIndexPath = attributes.indexPath
            }
        }
        self.currentIndexPath = currentIndexPath
        
        let point = CGPoint(x: proposedContentOffset.x + offsetAdjustment, y: proposedContentOffset.y)
//        ydLog(message: "proposedContentOffset = \(proposedContentOffset)")
//        ydLog(message: "offsetAdjustment = \(offsetAdjustment)")
//        ydLog(message: "point = \(point)")
//        ydLog(message: "currentIndex = \(currentIndex)")
        
        return point
    }
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let collectionView = collectionView else { return nil }
        
        let visibleRect = CGRect(origin: collectionView.contentOffset, size: collectionView.bounds.size)
        let attributes = super.layoutAttributesForElements(in: rect)?.compactMap { $0.copy() as? UICollectionViewLayoutAttributes }
        
        for attribute in attributes ?? [] {
            let distance = visibleRect.midX - attribute.center.x
            let normalizedDistance = distance / (collectionView.bounds.width * 0.5)
            let zoom = 1 - abs(normalizedDistance) * minimumScale
            
            //缩放
            let scaleTransform = CGAffineTransform(scaleX: zoom, y: zoom)
            
            
            //旋转
            let rotationAngle = kSPAngleToRadians(angle: -normalizedDistance * 4)
            let rotationTransform = CGAffineTransform(rotationAngle: rotationAngle)
            
            // 组合旋转和缩放变换
            let combinedTransform = rotationTransform.concatenating(scaleTransform)
            // 应用变换
            attribute.transform = combinedTransform
            
            var alpha = 1.8 - abs(normalizedDistance)
            if alpha < 0 {
                alpha = 0
            } else if alpha > 1 {
                alpha = 1
            }
            attribute.alpha = alpha
        }
        
        return attributes
    }
    
    override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }
    
    
}