package net.jpountz.util;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * @author Tuukka Lehtonen
 */
public final class ChecksumUtil {

    private static byte[] computeSum(InputStream in) throws IOException {
        if (in == null)
            throw new IllegalArgumentException("Input cannot be null!");

        MessageDigest md;
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new Error("MD5 digest must be supported by JVM");
        }
        byte[] data = new byte[64 * 1024];

        while (true) {
            int read = in.read(data);
            if (read == -1) {
                return md.digest();
            }
            md.update(data, 0, read);
        }
    }

    public static byte[] computeSum(Path p) throws IOException {
        try (InputStream in = Files.newInputStream(p)) {
            return computeSum(in);
        }
    }

    public static byte[] computeSum(URL url) throws IOException {
        try (InputStream in = url.openStream()) {
            return computeSum(in);
        }
    }

}