JPEGConverter.swift

import Foundation
import MobileCoreServices
import CoreImage

public struct JPEGConverter {
    let data: Data
    let dataUTI: String

    public init(data: Data, with dataUTI: String) {
        self.data = data
        self.dataUTI = dataUTI
    }

    public func convertJPEG() -> Data? {

        if UTTypeConformsTo(dataUTI as CFString, kUTTypeJPEG) {
            return data
        } else if dataUTI.range(of: ".heic") != nil || dataUTI.range(of: ".heif") != nil {
            guard let ciImage = CIImage(data: data) else {
                fatalError("Can't convert despite HEIF.")
            }

            return CIContext().jpegRepresentation(
                of: ciImage,
                colorSpace: CGColorSpaceCreateDeviceRGB()
            )!
        } else {
            return nil
        }
    }

    public func callAsFunction() -> Data? {
        convertJPEG()
    }
}