/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
/**
 * @author Elena Semukhina
 */

package org.apache.harmony.tests.java.math;

import junit.framework.TestCase;
import java.math.BigInteger;

/**
 * Class:   java.math.BigInteger
 * Methods: modPow, modInverse, and gcd 
 */
public class BigIntegerModPowTest extends TestCase {
	/**
	 * modPow: non-positive modulus
	 */
	public void testModPowException() {
		byte aBytes[] = {1, 2, 3, 4, 5, 6, 7};
		byte eBytes[] = {1, 2, 3, 4, 5};
		byte mBytes[] = {1, 2, 3};
		int aSign = 1;
		int eSign = 1;		
		int mSign = -1;		
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger exp = new BigInteger(eSign, eBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		try {
			aNumber.modPow(exp, modulus);
			fail("ArithmeticException has not been caught");
		} catch (ArithmeticException e) {
		}

        try {
            BigInteger.ZERO.modPow(new BigInteger("-1"), new BigInteger("10"));
            fail("ArithmeticException has not been caught");
        } catch (ArithmeticException e) {
            // expected
        }
	}

	/**
	 * modPow: positive exponent
	 */
	public void testModPowPosExp() {
		byte aBytes[] = {-127, 100, 56, 7, 98, -1, 39, -128, 127, 75, 48, -7};
		byte eBytes[] = {27, -15, 65, 39};
		byte mBytes[] = {-128, 2, 3, 4, 5};
		int aSign = 1;
		int eSign = 1;		
		int mSign = 1;		
		byte rBytes[] = {113, 100, -84, -28, -85};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger exp = 	 new BigInteger(eSign, eBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		BigInteger result = aNumber.modPow(exp, modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}
	
	/**
	 * modPow: negative exponent
	 */
	public void testModPowNegExp() {
		byte aBytes[] = {-127, 100, 56, 7, 98, -1, 39, -128, 127, 75, 48, -7};
		byte eBytes[] = {27, -15, 65, 39};
		byte mBytes[] = {-128, 2, 3, 4, 5};
		int aSign = 1;
		int eSign = -1;		
		int mSign = 1;		
		byte rBytes[] = {12, 118, 46, 86, 92};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger exp = 	 new BigInteger(eSign, eBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		BigInteger result = aNumber.modPow(exp, modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

    public void testModPowZeroExp() {
        BigInteger exp = new BigInteger("0");
        BigInteger[] base = new BigInteger[] {new BigInteger("-1"), new BigInteger("0"), new BigInteger("1")};
        BigInteger[] mod = new BigInteger[] {new BigInteger("2"), new BigInteger("10"), new BigInteger("2147483648")};

        for (int i = 0; i < base.length; ++i) {
            for (int j = 0; j < mod.length; ++j) {
                assertEquals(base[i] + " modePow(" + exp + ", " + mod[j]
                        + ") should be " + BigInteger.ONE, BigInteger.ONE,
                        base[i].modPow(exp, mod[j]));
            }
        }

        mod = new BigInteger[] {new BigInteger("1")};
        for (int i = 0; i < base.length; ++i) {
            for (int j = 0; j < mod.length; ++j) {
                assertEquals(base[i] + " modePow(" + exp + ", " + mod[j]
                        + ") should be " + BigInteger.ZERO, BigInteger.ZERO,
                        base[i].modPow(exp, mod[j]));
            }
        }
    }

	/**
	 * modInverse: non-positive modulus
	 */
	public void testmodInverseException() {
		byte aBytes[] = {1, 2, 3, 4, 5, 6, 7};
		byte mBytes[] = {1, 2, 3};
		int aSign = 1;
		int mSign = -1;		
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		try {
			aNumber.modInverse(modulus);
			fail("ArithmeticException has not been caught");
		} catch (ArithmeticException e) {
		}
	}
	
	/**
	 * modInverse: non-invertible number
	 */
	public void testmodInverseNonInvertible() {
		byte aBytes[] = {-15, 24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		byte mBytes[] = {-12, 1, 0, 0, 0, 23, 44, 55, 66};
		int aSign = 1;
		int mSign = 1;		
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		try {
			aNumber.modInverse(modulus);
			fail("ArithmeticException has not been caught");
		} catch (ArithmeticException e) {
		}
	}

	/**
	 * modInverse: positive number
	 */
	public void testmodInversePos1() {
		byte aBytes[] = {24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		byte mBytes[] = {122, 45, 36, 100, 122, 45};
		int aSign = 1;
		int mSign = 1;		
		byte rBytes[] = {47, 3, 96, 62, 87, 19};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		BigInteger result = aNumber.modInverse(modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * modInverse: positive number (another case: a < 0)
	 */
	public void testmodInversePos2() {
		byte aBytes[] = {15, 24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		byte mBytes[] = {2, 122, 45, 36, 100};
		int aSign = 1;
		int mSign = 1;		
		byte rBytes[] = {1, -93, 40, 127, 73};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		BigInteger result = aNumber.modInverse(modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * modInverse: negative number
	 */
	public void testmodInverseNeg1() {
		byte aBytes[] = {15, 24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		byte mBytes[] = {2, 122, 45, 36, 100};
		int aSign = -1;
		int mSign = 1;		
		byte rBytes[] = {0, -41, 4, -91, 27};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger modulus = new BigInteger(mSign, mBytes);
		BigInteger result = aNumber.modInverse(modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * modInverse: negative number (another case: x < 0)
	 */
	public void testmodInverseNeg2() {
		byte aBytes[] = {-15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		byte mBytes[] = {122, 2, 4, 122, 2, 4};
		byte rBytes[] = {85, 47, 127, 4, -128, 45};
		BigInteger aNumber = new BigInteger(aBytes);
		BigInteger modulus = new BigInteger(mBytes);
		BigInteger result = aNumber.modInverse(modulus);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}
	
	/**
	 * gcd: the second number is zero
	 */
	public void testGcdSecondZero() {
		byte aBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		byte bBytes[] = {0};
		int aSign = 1;
		int bSign = 1;
		byte rBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger bNumber = new BigInteger(bSign, bBytes);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * gcd: the first number is zero
	 */
	public void testGcdFirstZero() {
		byte aBytes[] = {0};
		byte bBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		int aSign = 1;
		int bSign = 1;
		byte rBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger bNumber = new BigInteger(bSign, bBytes);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}
	
	/**
	 * gcd: the first number is ZERO
	 */
	public void testGcdFirstZERO() {
		byte bBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		int bSign = 1;
		byte rBytes[] = {15, 24, 123, 57, -15, 24, 123, 57, -15, 24, 123, 57};
		BigInteger aNumber = BigInteger.ZERO;
		BigInteger bNumber = new BigInteger(bSign, bBytes);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * gcd: both numbers are zeros
	 */
	public void testGcdBothZeros() {
		byte rBytes[] = {0};
		BigInteger aNumber = new BigInteger("0");
		BigInteger bNumber = BigInteger.valueOf(0L);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 0, result.signum());
	}

	/**
	 * gcd: the first number is longer
	 */
	public void testGcdFirstLonger() {
		byte aBytes[] = {-15, 24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		byte bBytes[] = {-12, 1, 0, 0, 0, 23, 44, 55, 66};
		int aSign = 1;
		int bSign = 1;
		byte rBytes[] = {7};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger bNumber = new BigInteger(bSign, bBytes);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}

	/**
	 * gcd: the second number is longer
	 */
	public void testGcdSecondLonger() {
		byte aBytes[] = {-12, 1, 0, 0, 0, 23, 44, 55, 66};
		byte bBytes[] = {-15, 24, 123, 56, -11, -112, -34, -98, 8, 10, 12, 14, 25, 125, -15, 28, -127};
		int aSign = 1;
		int bSign = 1;
		byte rBytes[] = {7};
		BigInteger aNumber = new BigInteger(aSign, aBytes);
		BigInteger bNumber = new BigInteger(bSign, bBytes);
		BigInteger result = aNumber.gcd(bNumber);
		byte resBytes[] = new byte[rBytes.length];
		resBytes = result.toByteArray();
		for(int i = 0; i < resBytes.length; i++) {
			assertTrue(resBytes[i] == rBytes[i]);
		}
		assertEquals("incorrect sign", 1, result.signum());
	}
}