import UIKit
import ImageIO

/// 图片降采样 + JPEG 压缩(头像/反馈截图上传前)。用 ImageIO 流式缩略,避免大图整张解进内存。
enum ImageDownsampler {
    static func jpeg(_ data: Data, maxDimension: CGFloat = 1024, quality: CGFloat = 0.8) -> Data? {
        let srcOpts: [CFString: Any] = [kCGImageSourceShouldCache: false]
        guard let src = CGImageSourceCreateWithData(data as CFData, srcOpts as CFDictionary) else {
            return UIImage(data: data)?.jpegData(compressionQuality: quality)
        }
        let thumbOpts: [CFString: Any] = [
            kCGImageSourceCreateThumbnailFromImageAlways: true,
            kCGImageSourceCreateThumbnailWithTransform: true,   // 按 EXIF 自动旋转
            kCGImageSourceThumbnailMaxPixelSize: maxDimension,
        ]
        guard let cg = CGImageSourceCreateThumbnailAtIndex(src, 0, thumbOpts as CFDictionary) else {
            return UIImage(data: data)?.jpegData(compressionQuality: quality)
        }
        return UIImage(cgImage: cg).jpegData(compressionQuality: quality)
    }
}