/*
    * Copyright (C) 2011 The Guava Authors
    *
    * Licensed 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.
   */
  
  package com.google.common.math;
  
  import static com.google.common.math.MathTesting.ALL_INTEGER_CANDIDATES;
  import static com.google.common.math.MathTesting.ALL_ROUNDING_MODES;
  import static com.google.common.math.MathTesting.ALL_SAFE_ROUNDING_MODES;
  import static com.google.common.math.MathTesting.EXPONENTS;
  import static com.google.common.math.MathTesting.NEGATIVE_INTEGER_CANDIDATES;
  import static com.google.common.math.MathTesting.NONZERO_INTEGER_CANDIDATES;
  import static com.google.common.math.MathTesting.POSITIVE_INTEGER_CANDIDATES;
  import static com.google.common.math.TestPlatform.intsCanGoOutOfRange;
  import static java.math.BigInteger.valueOf;
  import static java.math.RoundingMode.FLOOR;
  import static java.math.RoundingMode.UNNECESSARY;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  import com.google.common.testing.NullPointerTester;
  
  import junit.framework.TestCase;
  
  import java.math.BigDecimal;
  import java.math.BigInteger;
  import java.math.RoundingMode;
  
  /**
   * Tests for {@link IntMath}.
   *
   * @author Louis Wasserman
   */
  @GwtCompatible(emulated = true)
  public class IntMathTest extends TestCase {
    @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
    public void testConstantMaxPowerOfSqrt2Unsigned() {
      assertEquals(
          BigIntegerMath.sqrt(BigInteger.ZERO.setBit(2 * Integer.SIZE - 1), FLOOR).intValue(),
          IntMath.MAX_POWER_OF_SQRT2_UNSIGNED);
    }
  
    @GwtIncompatible("pow()")
    public void testConstantsPowersOf10() {
      for (int i = 0; i < IntMath.powersOf10.length - 1; i++) {
        assertEquals(IntMath.pow(10, i), IntMath.powersOf10[i]);
      }
    }
  
    @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
    public void testMaxLog10ForLeadingZeros() {
      for (int i = 0; i < Integer.SIZE; i++) {
        assertEquals(
            BigIntegerMath.log10(BigInteger.ONE.shiftLeft(Integer.SIZE - i), FLOOR),
            IntMath.maxLog10ForLeadingZeros[i]);
      }
    }
  
    @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
    public void testConstantsHalfPowersOf10() {
      for (int i = 0; i < IntMath.halfPowersOf10.length; i++) {
        assert IntMath.halfPowersOf10[i]
            == Math.min(Integer.MAX_VALUE,
                BigIntegerMath.sqrt(BigInteger.TEN.pow(2 * i + 1), FLOOR).longValue());
      }
    }
  
    @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
    public void testConstantsBiggestBinomials() {
      for (int k = 0; k < IntMath.biggestBinomials.length; k++) {
        assertTrue(fitsInInt(BigIntegerMath.binomial(IntMath.biggestBinomials[k], k)));
        assertTrue(IntMath.biggestBinomials[k] == Integer.MAX_VALUE
            || !fitsInInt(BigIntegerMath.binomial(IntMath.biggestBinomials[k] + 1, k)));
        // In the first case, any int is valid; in the second, we want to test that the next-bigger
        // int overflows.
      }
      assertFalse(
          fitsInInt(BigIntegerMath.binomial(
              2 * IntMath.biggestBinomials.length, IntMath.biggestBinomials.length)));
    }
  
    @GwtIncompatible("sqrt")
    public void testPowersSqrtMaxInt() {
      assertEquals(IntMath.sqrt(Integer.MAX_VALUE, FLOOR), IntMath.FLOOR_SQRT_MAX_INT);
    }
  
    public void testLessThanBranchFree() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       for (int y : ALL_INTEGER_CANDIDATES) {
         if (LongMath.fitsInInt((long) x - y)) {
           int expected = (x < y) ? 1 : 0;
           int actual = IntMath.lessThanBranchFree(x, y);
           assertEquals(expected, actual);
         }
       }
     }
   }
 
   @GwtIncompatible("java.math.BigInteger")
   public void testIsPowerOfTwo() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       // Checks for a single bit set.
       BigInteger bigX = BigInteger.valueOf(x);
       boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
       assertEquals(expected, IntMath.isPowerOfTwo(x));
     }
   }
 
   public void testLog2ZeroAlwaysThrows() {
     for (RoundingMode mode : ALL_ROUNDING_MODES) {
       try {
         IntMath.log2(0, mode);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   public void testLog2NegativeAlwaysThrows() {
     for (int x : NEGATIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         try {
           IntMath.log2(x, mode);
           fail("Expected IllegalArgumentException");
         } catch (IllegalArgumentException expected) {}
       }
     }
   }
 
   // Relies on the correctness of BigIntegrerMath.log2 for all modes except UNNECESSARY.
   public void testLog2MatchesBigInteger() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
         assertEquals(BigIntegerMath.log2(valueOf(x), mode), IntMath.log2(x, mode));
       }
     }
   }
 
   // Relies on the correctness of isPowerOfTwo(int).
   public void testLog2Exact() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       // We only expect an exception if x was not a power of 2.
       boolean isPowerOf2 = IntMath.isPowerOfTwo(x);
       try {
         assertEquals(x, 1 << IntMath.log2(x, UNNECESSARY));
         assertTrue(isPowerOf2);
       } catch (ArithmeticException e) {
         assertFalse(isPowerOf2);
       }
     }
   }
 
   @GwtIncompatible("log10")
   public void testLog10ZeroAlwaysThrows() {
     for (RoundingMode mode : ALL_ROUNDING_MODES) {
       try {
         IntMath.log10(0, mode);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   @GwtIncompatible("log10")
   public void testLog10NegativeAlwaysThrows() {
     for (int x : NEGATIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         try {
           IntMath.log10(x, mode);
           fail("Expected IllegalArgumentException");
         } catch (IllegalArgumentException expected) {}
       }
     }
   }
 
   // Relies on the correctness of BigIntegerMath.log10 for all modes except UNNECESSARY.
   @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
   public void testLog10MatchesBigInteger() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
         // The BigInteger implementation is tested separately, use it as the reference.
         assertEquals(BigIntegerMath.log10(valueOf(x), mode), IntMath.log10(x, mode));
       }
     }
   }
 
   // Relies on the correctness of log10(int, FLOOR) and of pow(int, int).
   @GwtIncompatible("pow()")
   public void testLog10Exact() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       int floor = IntMath.log10(x, FLOOR);
       boolean expectSuccess = IntMath.pow(10, floor) == x;
       try {
         assertEquals(floor, IntMath.log10(x, UNNECESSARY));
         assertTrue(expectSuccess);
       } catch (ArithmeticException e) {
         assertFalse(expectSuccess);
       }
     }
   }
 
   @GwtIncompatible("log10")
   public void testLog10TrivialOnPowerOfTen() {
     int x = 1000000;
     for (RoundingMode mode : ALL_ROUNDING_MODES) {
       assertEquals(6, IntMath.log10(x, mode));
     }
   }
 
   // Simple test to cover sqrt(0) for all types and all modes.
   @GwtIncompatible("sqrt")
   public void testSqrtZeroAlwaysZero() {
     for (RoundingMode mode : ALL_ROUNDING_MODES) {
       assertEquals(0, IntMath.sqrt(0, mode));
     }
   }
 
   @GwtIncompatible("sqrt")
   public void testSqrtNegativeAlwaysThrows() {
     for (int x : NEGATIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : RoundingMode.values()) {
         try {
           IntMath.sqrt(x, mode);
           fail("Expected IllegalArgumentException");
         } catch (IllegalArgumentException expected) {}
       }
     }
   }
 
   /* Relies on the correctness of BigIntegerMath.sqrt for all modes except UNNECESSARY. */
   @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
   public void testSqrtMatchesBigInteger() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
         // The BigInteger implementation is tested separately, use it as the reference.
         // Promote the int value (rather than using intValue() on the expected value) to avoid
         // any risk of truncation which could lead to a false positive.
         assertEquals(BigIntegerMath.sqrt(valueOf(x), mode), valueOf(IntMath.sqrt(x, mode)));
       }
     }
   }
 
   /* Relies on the correctness of sqrt(int, FLOOR). */
   @GwtIncompatible("sqrt")
   public void testSqrtExactMatchesFloorOrThrows() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       int floor = IntMath.sqrt(x, FLOOR);
       // We only expect an exception if x was not a perfect square.
       boolean isPerfectSquare = (floor * floor == x);
       try {
         assertEquals(floor, IntMath.sqrt(x, UNNECESSARY));
         assertTrue(isPerfectSquare);
       } catch (ArithmeticException e) {
         assertFalse(isPerfectSquare);
       }
     }
   }
 
   @GwtIncompatible("2147483646^2 expected=4")
   public void testPow() {
     for (int i : ALL_INTEGER_CANDIDATES) {
       for (int pow : EXPONENTS) {
         assertEquals(i + "^" + pow, BigInteger.valueOf(i).pow(pow).intValue(), IntMath.pow(i, pow));
       }
     }
   }
 
   public void testDivNonZero() {
     for (int p : NONZERO_INTEGER_CANDIDATES) {
       for (int q : NONZERO_INTEGER_CANDIDATES) {
         for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
           // Skip some tests that fail due to GWT's non-compliant int implementation.
           // TODO(cpovirk): does this test fail for only some rounding modes or for all?
           if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
             continue;
           }
           int expected =
               new BigDecimal(valueOf(p)).divide(new BigDecimal(valueOf(q)), 0, mode).intValue();
           assertEquals(p + "/" + q, force32(expected), IntMath.divide(p, q, mode));
         }
       }
     }
   }
 
   public void testDivNonZeroExact() {
     for (int p : NONZERO_INTEGER_CANDIDATES) {
       for (int q : NONZERO_INTEGER_CANDIDATES) {
         // Skip some tests that fail due to GWT's non-compliant int implementation.
         if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
           continue;
         }
         boolean dividesEvenly = (p % q) == 0;
         try {
           assertEquals(p + "/" + q, p, IntMath.divide(p, q, UNNECESSARY) * q);
           assertTrue(p + "/" + q + " not expected to divide evenly", dividesEvenly);
         } catch (ArithmeticException e) {
           assertFalse(p + "/" + q + " expected to divide evenly", dividesEvenly);
         }
       }
     }
   }
 
   public void testZeroDivIsAlwaysZero() {
     for (int q : NONZERO_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         assertEquals(0, IntMath.divide(0, q, mode));
       }
     }
   }
 
   public void testDivByZeroAlwaysFails() {
     for (int p : ALL_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         try {
           IntMath.divide(p, 0, mode);
           fail("Expected ArithmeticException");
         } catch (ArithmeticException expected) {}
       }
     }
   }
 
   public void testMod() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       for (int m : POSITIVE_INTEGER_CANDIDATES) {
         assertEquals(valueOf(x).mod(valueOf(m)).intValue(), IntMath.mod(x, m));
       }
     }
   }
 
   public void testModNegativeModulusFails() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (int m : NEGATIVE_INTEGER_CANDIDATES) {
         try {
           IntMath.mod(x, m);
           fail("Expected ArithmeticException");
         } catch (ArithmeticException expected) {}
       }
     }
   }
 
   public void testModZeroModulusFails() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       try {
         IntMath.mod(x, 0);
         fail("Expected ArithmeticException");
       } catch (ArithmeticException expected) {}
     }
   }
 
   public void testGCD() {
     for (int a : POSITIVE_INTEGER_CANDIDATES) {
       for (int b : POSITIVE_INTEGER_CANDIDATES) {
         assertEquals(valueOf(a).gcd(valueOf(b)), valueOf(IntMath.gcd(a, b)));
       }
     }
   }
 
   public void testGCDZero() {
     for (int a : POSITIVE_INTEGER_CANDIDATES) {
       assertEquals(a, IntMath.gcd(a, 0));
       assertEquals(a, IntMath.gcd(0, a));
     }
     assertEquals(0, IntMath.gcd(0, 0));
   }
 
   public void testGCDNegativePositiveThrows() {
     for (int a : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.gcd(a, 3);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
       try {
         IntMath.gcd(3, a);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   public void testGCDNegativeZeroThrows() {
     for (int a : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.gcd(a, 0);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
       try {
         IntMath.gcd(0, a);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   public void testCheckedAdd() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).add(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a + b, IntMath.checkedAdd(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }
 
   public void testCheckedSubtract() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).subtract(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a - b, IntMath.checkedSubtract(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }
 
   public void testCheckedMultiply() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).multiply(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a * b, IntMath.checkedMultiply(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }
 
   public void testCheckedPow() {
     for (int b : ALL_INTEGER_CANDIDATES) {
       for (int k : EXPONENTS) {
         BigInteger expectedResult = valueOf(b).pow(k);
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(b + "^" + k, force32(expectedResult.intValue()), IntMath.checkedPow(b, k));
           assertTrue(b + "^" + k + " should have succeeded", expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(b + "^" + k + " should have failed", expectedSuccess);
         }
       }
     }
   }
 
   // Depends on the correctness of BigIntegerMath.factorial.
   public void testFactorial() {
     for (int n = 0; n <= 50; n++) {
       BigInteger expectedBig = BigIntegerMath.factorial(n);
       int expectedInt = fitsInInt(expectedBig) ? expectedBig.intValue() : Integer.MAX_VALUE;
       assertEquals(expectedInt, IntMath.factorial(n));
     }
   }
 
   public void testFactorialNegative() {
     for (int n : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.factorial(n);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   // Depends on the correctness of BigIntegerMath.binomial.
   @GwtIncompatible("BigIntegerMath") // TODO(cpovirk): GWT-enable BigIntegerMath
   public void testBinomial() {
     for (int n = 0; n <= 50; n++) {
       for (int k = 0; k <= n; k++) {
         BigInteger expectedBig = BigIntegerMath.binomial(n, k);
         int expectedInt = fitsInInt(expectedBig) ? expectedBig.intValue() : Integer.MAX_VALUE;
         assertEquals(expectedInt, IntMath.binomial(n, k));
       }
     }
   }
 
   @GwtIncompatible("binomial")
   public void testBinomialOutside() {
     for (int n = 0; n <= 50; n++) {
       try {
         IntMath.binomial(n, -1);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
       try {
         IntMath.binomial(n, n + 1);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   @GwtIncompatible("binomial")
   public void testBinomialNegative() {
     for (int n : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.binomial(n, 0);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }
 
   @GwtIncompatible("java.math.BigInteger")
   public void testMean() {
     // Odd-sized ranges have an obvious mean
     assertMean(2, 1, 3);
 
     assertMean(-2, -3, -1);
     assertMean(0, -1, 1);
     assertMean(1, -1, 3);
     assertMean((1 << 30) - 1, -1, Integer.MAX_VALUE);
 
     // Even-sized ranges should prefer the lower mean
     assertMean(2, 1, 4);
     assertMean(-3, -4, -1);
     assertMean(0, -1, 2);
     assertMean(0, Integer.MIN_VALUE + 2, Integer.MAX_VALUE);
     assertMean(0, 0, 1);
     assertMean(-1, -1, 0);
     assertMean(-1, Integer.MIN_VALUE, Integer.MAX_VALUE);
 
     // x == y == mean
     assertMean(1, 1, 1);
     assertMean(0, 0, 0);
     assertMean(-1, -1, -1);
     assertMean(Integer.MIN_VALUE, Integer.MIN_VALUE, Integer.MIN_VALUE);
     assertMean(Integer.MAX_VALUE, Integer.MAX_VALUE, Integer.MAX_VALUE);
 
     // Exhaustive checks
     for (int x : ALL_INTEGER_CANDIDATES) {
       for (int y : ALL_INTEGER_CANDIDATES) {
         assertMean(x, y);
       }
     }
   }
 
   /**
    * Helper method that asserts the arithmetic mean of x and y is equal
    * to the expectedMean.
    */
   private static void assertMean(int expectedMean, int x, int y) {
     assertEquals("The expectedMean should be the same as computeMeanSafely",
         expectedMean, computeMeanSafely(x, y));
     assertMean(x, y);
   }
 
   /**
    * Helper method that asserts the arithmetic mean of x and y is equal
    * to the result of computeMeanSafely.
    */
   private static void assertMean(int x, int y) {
     int expectedMean = computeMeanSafely(x, y);
     assertEquals(expectedMean, IntMath.mean(x, y));
     assertEquals("The mean of x and y should equal the mean of y and x",
         expectedMean, IntMath.mean(y, x));
   }
 
   /**
    * Computes the mean in a way that is obvious and resilient to
    * overflow by using BigInteger arithmetic.
    */
   private static int computeMeanSafely(int x, int y) {
     BigInteger bigX = BigInteger.valueOf(x);
     BigInteger bigY = BigInteger.valueOf(y);
     BigDecimal bigMean = new BigDecimal(bigX.add(bigY))
         .divide(BigDecimal.valueOf(2), BigDecimal.ROUND_FLOOR);
     // parseInt blows up on overflow as opposed to intValue() which does not.
     return Integer.parseInt(bigMean.toString());
   }
 
   private static boolean fitsInInt(BigInteger big) {
     return big.bitLength() <= 31;
   }
 
   @GwtIncompatible("NullPointerTester")
   public void testNullPointers() {
     NullPointerTester tester = new NullPointerTester();
     tester.setDefault(int.class, 1);
     tester.testAllPublicStaticMethods(IntMath.class);
   }
 
   private static int force32(int value) {
     // GWT doesn't consistently overflow values to make them 32-bit, so we need to force it.
     return value & 0xffffffff;
   }
 }