// Copyright 2017 The Abseil 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
//
//      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.

#include "absl/random/internal/salted_seed_seq.h"

#include <iterator>
#include <random>
#include <utility>
#include <vector>

#include "gmock/gmock.h"
#include "gtest/gtest.h"

using absl::random_internal::GetSaltMaterial;
using absl::random_internal::MakeSaltedSeedSeq;
using absl::random_internal::SaltedSeedSeq;
using testing::Eq;
using testing::Pointwise;

namespace {

template <typename Sseq>
void ConformsToInterface() {
  // Check that the SeedSequence can be default-constructed.
  { Sseq default_constructed_seq; }
  // Check that the SeedSequence can be constructed with two iterators.
  {
    uint32_t init_array[] = {1, 3, 5, 7, 9};
    Sseq iterator_constructed_seq(std::begin(init_array), std::end(init_array));
  }
  // Check that the SeedSequence can be std::initializer_list-constructed.
  { Sseq list_constructed_seq = {1, 3, 5, 7, 9, 11, 13}; }
  // Check that param() and size() return state provided to constructor.
  {
    uint32_t init_array[] = {1, 2, 3, 4, 5};
    Sseq seq(std::begin(init_array), std::end(init_array));
    EXPECT_EQ(seq.size(), ABSL_ARRAYSIZE(init_array));

    std::vector<uint32_t> state_vector;
    seq.param(std::back_inserter(state_vector));

    EXPECT_EQ(state_vector.size(), ABSL_ARRAYSIZE(init_array));
    for (int i = 0; i < state_vector.size(); i++) {
      EXPECT_EQ(state_vector[i], i + 1);
    }
  }
  // Check for presence of generate() method.
  {
    Sseq seq;
    uint32_t seeds[5];

    seq.generate(std::begin(seeds), std::end(seeds));
  }
}

TEST(SaltedSeedSeq, CheckInterfaces) {
  // Control case
  ConformsToInterface<std::seed_seq>();

  // Abseil classes
  ConformsToInterface<SaltedSeedSeq<std::seed_seq>>();
}

TEST(SaltedSeedSeq, CheckConstructingFromOtherSequence) {
  std::vector<uint32_t> seed_values(10, 1);
  std::seed_seq seq(seed_values.begin(), seed_values.end());
  auto salted_seq = MakeSaltedSeedSeq(std::move(seq));

  EXPECT_EQ(seq.size(), salted_seq.size());

  std::vector<uint32_t> param_result;
  seq.param(std::back_inserter(param_result));

  EXPECT_EQ(seed_values, param_result);
}

TEST(SaltedSeedSeq, SaltedSaltedSeedSeqIsNotDoubleSalted) {
  uint32_t init[] = {1, 3, 5, 7, 9};

  std::seed_seq seq(std::begin(init), std::end(init));

  // The first salting.
  SaltedSeedSeq<std::seed_seq> salted_seq = MakeSaltedSeedSeq(std::move(seq));
  uint32_t a[16];
  salted_seq.generate(std::begin(a), std::end(a));

  // The second salting.
  SaltedSeedSeq<std::seed_seq> salted_salted_seq =
      MakeSaltedSeedSeq(std::move(salted_seq));
  uint32_t b[16];
  salted_salted_seq.generate(std::begin(b), std::end(b));

  // ... both should be equal.
  EXPECT_THAT(b, Pointwise(Eq(), a)) << "a[0] " << a[0];
}

TEST(SaltedSeedSeq, SeedMaterialIsSalted) {
  const size_t kNumBlocks = 16;

  uint32_t seed_material[kNumBlocks];
  std::random_device urandom{"/dev/urandom"};
  for (uint32_t& seed : seed_material) {
    seed = urandom();
  }

  std::seed_seq seq(std::begin(seed_material), std::end(seed_material));
  SaltedSeedSeq<std::seed_seq> salted_seq(std::begin(seed_material),
                                          std::end(seed_material));

  bool salt_is_available = GetSaltMaterial().has_value();

  // If salt is available generated sequence should be different.
  if (salt_is_available) {
    uint32_t outputs[kNumBlocks];
    uint32_t salted_outputs[kNumBlocks];

    seq.generate(std::begin(outputs), std::end(outputs));
    salted_seq.generate(std::begin(salted_outputs), std::end(salted_outputs));

    EXPECT_THAT(outputs, Pointwise(testing::Ne(), salted_outputs));
  }
}

TEST(SaltedSeedSeq, GenerateAcceptsDifferentTypes) {
  const size_t kNumBlocks = 4;

  SaltedSeedSeq<std::seed_seq> seq({1, 2, 3});

  uint32_t expected[kNumBlocks];
  seq.generate(std::begin(expected), std::end(expected));

  // 32-bit outputs
  {
    unsigned long seed_material[kNumBlocks];  // NOLINT(runtime/int)
    seq.generate(std::begin(seed_material), std::end(seed_material));
    EXPECT_THAT(seed_material, Pointwise(Eq(), expected));
  }
  {
    unsigned int seed_material[kNumBlocks];  // NOLINT(runtime/int)
    seq.generate(std::begin(seed_material), std::end(seed_material));
    EXPECT_THAT(seed_material, Pointwise(Eq(), expected));
  }

  // 64-bit outputs.
  {
    uint64_t seed_material[kNumBlocks];
    seq.generate(std::begin(seed_material), std::end(seed_material));
    EXPECT_THAT(seed_material, Pointwise(Eq(), expected));
  }
  {
    int64_t seed_material[kNumBlocks];
    seq.generate(std::begin(seed_material), std::end(seed_material));
    EXPECT_THAT(seed_material, Pointwise(Eq(), expected));
  }
}

}  // namespace