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package com.oracle.truffle.api.test.source;

import java.lang.reflect.Method;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.util.Random;

import org.junit.Assert;
import org.junit.Test;

import com.oracle.truffle.api.test.ReflectionUtils;

public class ContentDigestTest {
    @Test
    public void emptySHA256() throws Exception {
        assertDigest(new byte[0], "Empty SHA-256 digest");
    }

    @Test
    public void hiSHA256() throws Exception {
        assertDigest("Hi".getBytes("UTF-8"), "Empty SHA-256 digest");
    }

    @Test
    public void helloWorldSHA256() throws Exception {
        assertDigest("Hello World!".getBytes("UTF-8"), "Empty SHA-256 digest");
    }

    @Test
    public void minusSHA256() throws Exception {
        assertDigest(new byte[]{-75, 119}, "SHA-256 digest for negative byte");
    }

    @Test
    public void computeSHA256s() throws Exception {
        for (int i = 0; i < 100; i++) {
            long seed = System.currentTimeMillis();
            final String msg = "Digest for seed " + seed + " is the same";

            Random random = new Random(seed);

            int len = random.nextInt(2048);
            byte[] arr = new byte[len];
            random.nextBytes(arr);

            assertDigest(arr, msg);
        }
    }

    private static void assertDigest(byte[] arr, final String msg) throws Exception {
        byte[] result = MessageDigest.getInstance("SHA-256").digest(arr);
        String expecting = new BigInteger(1, result).toString(16);
        // Add leading `0`s if missing to allign to standard 64 digit SHA-256 format.
        while (expecting.length() < 64) {
            expecting = '0' + expecting;
        }

        Method m = Class.forName("com.oracle.truffle.api.source.Source").getDeclaredMethod("digest", byte[].class, int.class, int.class);
        ReflectionUtils.setAccessible(m, true);
        String own = (String) m.invoke(null, arr, 0, arr.length);

        Assert.assertEquals(msg, expecting, own);
    }

}