// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <algorithm>
#include <climits>

#include "src/base/utils/random-number-generator.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace v8 {
namespace base {

class RandomNumberGeneratorTest : public ::testing::TestWithParam<int> {};

static const int kMaxRuns = 12345;

static void CheckSample(std::vector<uint64_t> sample, uint64_t max,
                        size_t size) {
  EXPECT_EQ(sample.size(), size);

  // Check if values are unique.
  std::sort(sample.begin(), sample.end());
  EXPECT_EQ(std::adjacent_find(sample.begin(), sample.end()), sample.end());

  for (uint64_t x : sample) {
    EXPECT_LT(x, max);
  }
}

static void CheckSlowSample(const std::vector<uint64_t>& sample, uint64_t max,
                            size_t size,
                            const std::unordered_set<uint64_t>& excluded) {
  CheckSample(sample, max, size);

  for (uint64_t i : sample) {
    EXPECT_FALSE(excluded.count(i));
  }
}

static void TestNextSample(RandomNumberGenerator* rng, uint64_t max,
                           size_t size, bool slow = false) {
  std::vector<uint64_t> sample =
      slow ? rng->NextSampleSlow(max, size) : rng->NextSample(max, size);

  CheckSample(sample, max, size);
}

TEST_P(RandomNumberGeneratorTest, NextIntWithMaxValue) {
  RandomNumberGenerator rng(GetParam());
  for (int max = 1; max <= kMaxRuns; ++max) {
    int n = rng.NextInt(max);
    EXPECT_LE(0, n);
    EXPECT_LT(n, max);
  }
}


TEST_P(RandomNumberGeneratorTest, NextBooleanReturnsFalseOrTrue) {
  RandomNumberGenerator rng(GetParam());
  for (int k = 0; k < kMaxRuns; ++k) {
    bool b = rng.NextBool();
    EXPECT_TRUE(b == false || b == true);
  }
}


TEST_P(RandomNumberGeneratorTest, NextDoubleReturnsValueBetween0And1) {
  RandomNumberGenerator rng(GetParam());
  for (int k = 0; k < kMaxRuns; ++k) {
    double d = rng.NextDouble();
    EXPECT_LE(0.0, d);
    EXPECT_LT(d, 1.0);
  }
}

#if GTEST_HAS_DEATH_TEST
TEST(RandomNumberGenerator, NextSampleInvalidParam) {
  RandomNumberGenerator rng(123);
  std::vector<uint64_t> sample;
  EXPECT_DEATH(sample = rng.NextSample(10, 11), ".*Check failed: n <= max.*");
}

TEST(RandomNumberGenerator, NextSampleSlowInvalidParam1) {
  RandomNumberGenerator rng(123);
  std::vector<uint64_t> sample;
  EXPECT_DEATH(sample = rng.NextSampleSlow(10, 11),
               ".*Check failed: max - excluded.size*");
}

TEST(RandomNumberGenerator, NextSampleSlowInvalidParam2) {
  RandomNumberGenerator rng(123);
  std::vector<uint64_t> sample;
  EXPECT_DEATH(sample = rng.NextSampleSlow(5, 3, {0, 2, 3}),
               ".*Check failed: max - excluded.size*");
}
#endif

TEST_P(RandomNumberGeneratorTest, NextSample0) {
  size_t m = 1;
  RandomNumberGenerator rng(GetParam());

  TestNextSample(&rng, m, 0);
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlow0) {
  size_t m = 1;
  RandomNumberGenerator rng(GetParam());

  TestNextSample(&rng, m, 0, true);
}

TEST_P(RandomNumberGeneratorTest, NextSample1) {
  size_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, 1);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlow1) {
  size_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, 1, true);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleMax) {
  size_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, m);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowMax) {
  size_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, m, true);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleHalf) {
  size_t n = 5;
  uint64_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowHalf) {
  size_t n = 5;
  uint64_t m = 10;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n, true);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleMoreThanHalf) {
  size_t n = 90;
  uint64_t m = 100;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowMoreThanHalf) {
  size_t n = 90;
  uint64_t m = 100;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n, true);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleLessThanHalf) {
  size_t n = 10;
  uint64_t m = 100;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowLessThanHalf) {
  size_t n = 10;
  uint64_t m = 100;
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    TestNextSample(&rng, m, n, true);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowExcluded) {
  size_t n = 2;
  uint64_t m = 10;
  std::unordered_set<uint64_t> excluded = {2, 4, 5, 9};
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    std::vector<uint64_t> sample = rng.NextSampleSlow(m, n, excluded);

    CheckSlowSample(sample, m, n, excluded);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowExcludedMax1) {
  size_t n = 1;
  uint64_t m = 5;
  std::unordered_set<uint64_t> excluded = {0, 2, 3, 4};
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    std::vector<uint64_t> sample = rng.NextSampleSlow(m, n, excluded);

    CheckSlowSample(sample, m, n, excluded);
  }
}

TEST_P(RandomNumberGeneratorTest, NextSampleSlowExcludedMax2) {
  size_t n = 7;
  uint64_t m = 10;
  std::unordered_set<uint64_t> excluded = {0, 4, 8};
  RandomNumberGenerator rng(GetParam());

  for (int k = 0; k < kMaxRuns; ++k) {
    std::vector<uint64_t> sample = rng.NextSampleSlow(m, n, excluded);

    CheckSlowSample(sample, m, n, excluded);
  }
}

INSTANTIATE_TEST_SUITE_P(RandomSeeds, RandomNumberGeneratorTest,
                         ::testing::Values(INT_MIN, -1, 0, 1, 42, 100,
                                           1234567890, 987654321, INT_MAX));

}  // namespace base
}  // namespace v8