/*
    * 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
    *
    *      https://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.
   */
  
  /*
   * This is not the original file distributed by the Apache Software Foundation
   * It has been modified by the Hipparchus project
   */
  package org.hipparchus.random;
  
  import org.hipparchus.UnitTestUtils;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.util.FastMath;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  
  import static org.junit.jupiter.api.Assertions.assertArrayEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.junit.jupiter.api.Assertions.fail;
  
  /**
   * Base class for RandomGenerator tests.
   * <p>
   * Tests RandomGenerator methods directly and also executes RandomDataTest
   * test cases against a RandomDataImpl created using the provided generator.
   * <p>
   * RandomGenerator test classes should extend this class, implementing
   * makeGenerator() to provide a concrete generator to test. The generator
   * returned by makeGenerator should be seeded with a fixed seed.
   */
  public abstract class RandomGeneratorAbstractTest extends RandomDataGeneratorTest {
  
      /** RandomGenerator under test */
      protected RandomGenerator generator;
  
      /**
       * Override this method in subclasses to provide a concrete generator to test.
       * Return a generator seeded with a fixed seed.
       */
      protected abstract RandomGenerator makeGenerator();
  
      /**
       * Initialize generator and randomData instance in superclass.
       */
      public RandomGeneratorAbstractTest() {
          generator = makeGenerator();
          randomData = RandomDataGenerator.of(generator);
      }
  
      /**
       * Set a fixed seed for the tests
       */
      @BeforeEach
      public void setUp() {
          generator = makeGenerator();
      }
  
      /**
       * Tests uniformity of nextInt(int) distribution by generating 1000
       * samples for each of 10 test values and for each sample performing
       * a chi-square test of homogeneity of the observed distribution with
       * the expected uniform distribution.  Tests are performed at the .01
       * level and an average failure rate higher than 2% (i.e. more than 20
       * null hypothesis rejections) causes the test case to fail.
       *
       * All random values are generated using the generator instance used by
       * other tests and the generator is not reseeded, so this is a fixed seed
       * test.
       */
      @Test
      public void testNextIntDirect() {
          // Set up test values - end of the array filled randomly
          int[] testValues = new int[] {4, 10, 12, 32, 100, 10000, 0, 0, 0, 0};
          for (int i = 6; i < 10; i++) {
              final int val = generator.nextInt();
              testValues[i] = val < 0 ? -val : val + 1;
          }
  
          final int numTests = 1000;
          for (int i = 0; i < testValues.length; i++) {
              final int n = testValues[i];
              // Set up bins
              int[] binUpperBounds;
             if (n < 32) {
                 binUpperBounds = new int[n];
                 for (int k = 0; k < n; k++) {
                     binUpperBounds[k] = k;
                 }
             } else {
                 binUpperBounds = new int[10];
                 final int step = n / 10;
                 for (int k = 0; k < 9; k++) {
                     binUpperBounds[k] = (k + 1) * step;
                 }
                 binUpperBounds[9] = n - 1;
             }
             // Run the tests
             int numFailures = 0;
             final int binCount = binUpperBounds.length;
             final long[] observed = new long[binCount];
             final double[] expected = new double[binCount];
             expected[0] = binUpperBounds[0] == 0 ? (double) smallSampleSize / (double) n :
                 (double) ((binUpperBounds[0] + 1) * smallSampleSize) / (double) n;
             for (int k = 1; k < binCount; k++) {
                 expected[k] = (double) smallSampleSize *
                 (double) (binUpperBounds[k] - binUpperBounds[k - 1]) / n;
             }
             for (int j = 0; j < numTests; j++) {
                 Arrays.fill(observed, 0);
                 for (int k = 0; k < smallSampleSize; k++) {
                     final int value = generator.nextInt(n);
                     assertTrue((value >= 0) && (value < n),"nextInt range");
                     for (int l = 0; l < binCount; l++) {
                         if (binUpperBounds[l] >= value) {
                             observed[l]++;
                             break;
                         }
                     }
                 }
                 if (UnitTestUtils.chiSquareTest(expected, observed) < 0.01) {
                     numFailures++;
                 }
             }
             if ((double) numFailures / (double) numTests > 0.02) {
                 fail("Too many failures for n = " + n +
                      " " + numFailures + " out of " + numTests + " tests failed.");
             }
         }
     }
 
     @Test
     public void testNextLongDirect() {
         long q1 = Long.MAX_VALUE/4;
         long q2 = 2 *  q1;
         long q3 = 3 * q1;
 
         long[] observed = new long[4];
         long val = 0;
         for (int i = 0; i < smallSampleSize; i++) {
             val = generator.nextLong();
             val = val < 0 ? -val : val;
             if (val < q1) {
                observed[0] = ++observed[0];
             } else if (val < q2) {
                observed[1] = ++observed[1];
             } else if (val < q3) {
                observed[2] = ++observed[2];
             } else {
                observed[3] = ++observed[3];
             }
         }
 
         /* Use ChiSquare dist with df = 4-1 = 3, alpha = .001
          * Change to 11.34 for alpha = .01
          */
         assertTrue(UnitTestUtils.chiSquare(expected,observed) < 16.27,
                    "chi-square test -- will fail about 1 in 1000 times");
     }
 
     @Test
     public void testNextBooleanDirect() {
         long halfSampleSize = smallSampleSize / 2;
         double[] expected = {halfSampleSize, halfSampleSize};
         long[] observed = new long[2];
         for (int i=0; i<smallSampleSize; i++) {
             if (generator.nextBoolean()) {
                 observed[0]++;
             } else {
                 observed[1]++;
             }
         }
         /* Use ChiSquare dist with df = 2-1 = 1, alpha = .001
          * Change to 6.635 for alpha = .01
          */
         assertTrue(UnitTestUtils.chiSquare(expected,observed) < 10.828,
                    "chi-square test -- will fail about 1 in 1000 times");
     }
 
     @Test
     public void testNextFloatDirect() {
         long[] observed = new long[4];
         for (int i=0; i<smallSampleSize; i++) {
             float val = generator.nextFloat();
             if (val < 0.25) {
                 observed[0] = ++observed[0];
             } else if (val < 0.5) {
                 observed[1] = ++observed[1];
             } else if (val < 0.75) {
                 observed[2] = ++observed[2];
             } else {
                 observed[3] = ++observed[3];
             }
         }
 
         /* Use ChiSquare dist with df = 4-1 = 3, alpha = .001
          * Change to 11.34 for alpha = .01
          */
         assertTrue(UnitTestUtils.chiSquare(expected,observed) < 16.27,
                    "chi-square test -- will fail about 1 in 1000 times");
     }
 
     @Test
     public void testNextDouble() {
         final double[] sample = new double[10000];
         final double[] expected = new double[100];
         final long[] observed = new long[100];
         Arrays.fill(expected, 100d);
         for (int i = 0; i < sample.length; i++) {
             sample[i] = generator.nextDouble();
             int j = 0;
             while (sample[i] < j / 100) {
                 j++;
             }
             observed[j] = observed[j]++;
         }
         UnitTestUtils.customAssertChiSquareAccept(expected, observed, 0.01);
     }
 
 
     @Test
     public void testNextIntPrecondition1() {
         assertThrows(MathIllegalArgumentException.class, () -> {
             generator.nextInt(-1);
         });
     }
 
     @Test
     public void testNextIntPrecondition2() {
         assertThrows(MathIllegalArgumentException.class, () -> {
             generator.nextInt(0);
         });
     }
 
     @Test
     public void testNextInt2() {
         int walk = 0;
         final int N = 10000;
         for (int k = 0; k < N; ++k) {
            if (generator.nextInt() >= 0) {
                ++walk;
            } else {
                --walk;
            }
         }
         assertTrue(FastMath.abs(walk) < FastMath.sqrt(N) * 2.576,
                    "Walked too far astray: " + walk + "\nNote: This " +
                    "test will fail randomly about 1 in 100 times.");
     }
 
     @Test
     public void testNextLong2() {
         int walk = 0;
         final int N = 1000;
         for (int k = 0; k < N; ++k) {
            if (generator.nextLong() >= 0) {
                ++walk;
            } else {
                --walk;
            }
         }
         assertTrue(FastMath.abs(walk) < FastMath.sqrt(N) * 2.576,
                    "Walked too far astray: " + walk + "\nNote: This " +
                    "test will fail randomly about 1 in 100 times.");
     }
 
     @Test
     public void testNextBoolean2() {
         int walk = 0;
         final int N = 10000;
         for (int k = 0; k < N; ++k) {
            if (generator.nextBoolean()) {
                ++walk;
            } else {
                --walk;
            }
         }
         assertTrue(FastMath.abs(walk) < FastMath.sqrt(N) * 2.576,
                    "Walked too far astray: " + walk + "\nNote: This " +
                    "test will fail randomly about 1 in 100 times.");
     }
 
     @Test
     public void testNextBytes() {
         long[] count = new long[256];
         byte[] bytes = new byte[10];
         double[] expected = new double[256];
         final int sampleSize = 100000;
 
         for (int i = 0; i < 256; i++) {
             expected[i] = (double) sampleSize / 265f;
         }
 
         for (int k = 0; k < sampleSize; ++k) {
            generator.nextBytes(bytes);
            for (byte b : bytes) {
                ++count[b + 128];
            }
         }
 
         UnitTestUtils.customAssertChiSquareAccept(expected, count, 0.001);
     }
 
     // MATH-1300
     @Test
     public void testNextBytesChunks() {
         final int[] chunkSizes = { 4, 8, 12, 16 };
         final int[] chunks = { 1, 2, 3, 4, 5 };
         for (int chunkSize : chunkSizes) {
             for (int numChunks : chunks) {
                 checkNextBytesChunks(chunkSize, numChunks);
             }
         }
     }
 
     @Test
     public void testSeeding() {
         // makeGenerator initializes with fixed seed
         RandomGenerator gen = makeGenerator();
         RandomGenerator gen1 = makeGenerator();
         checkSameSequence(gen, gen1);
         // reseed, but recreate the second one
         // verifies MATH-723
         gen.setSeed(100);
         gen1 = makeGenerator();
         gen1.setSeed(100);
         checkSameSequence(gen, gen1);
     }
 
     private void checkSameSequence(RandomGenerator gen1, RandomGenerator gen2) {
         final int len = 11;  // Needs to be an odd number to check MATH-723
         final double[][] values = new double[2][len];
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextDouble();
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextDouble();
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextFloat();
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextFloat();
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextInt();
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextInt();
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextLong();
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextLong();
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextInt(len);
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextInt(len);
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextBoolean() ? 1 : 0;
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextBoolean() ? 1 : 0;
         }
         assertTrue(Arrays.equals(values[0], values[1]));
         for (int i = 0; i < len; i++) {
             values[0][i] = gen1.nextGaussian();
         }
         for (int i = 0; i < len; i++) {
             values[1][i] = gen2.nextGaussian();
         }
         assertTrue(Arrays.equals(values[0], values[1]));
     }
 
     // MATH-1300
     private void checkNextBytesChunks(int chunkSize,
                                       int numChunks) {
         final RandomGenerator rg = makeGenerator();
         final long seed = 1234567L;
 
         final byte[] b1 = new byte[chunkSize * numChunks];
         final byte[] b2 = new byte[chunkSize];
 
         // Generate the chunks in a single call.
         rg.setSeed(seed);
         rg.nextBytes(b1);
 
         // Reset.
         rg.setSeed(seed);
         // Generate the chunks in consecutive calls.
         for (int i = 0; i < numChunks; i++) {
             rg.nextBytes(b2);
         }
 
         // Store last 128 bytes chunk of b1 into b3.
         final byte[] b3 = new byte[chunkSize];
         System.arraycopy(b1, b1.length - b3.length, b3, 0, b3.length);
 
         // Sequence of calls must be the same.
         assertArrayEquals(b2, b3, "chunkSize=" + chunkSize + " numChunks=" + numChunks);
     }
 
     @Override
     @Test
     public void testNextZipf() {
         // Skip this test for the individual generators
     }
 }