/**
 * Copyright 2017-2024, XGBoost contributors
 */
#include "../../../src/common/compressed_iterator.h"
#include "gtest/gtest.h"
#include <algorithm>

namespace xgboost::common {
TEST(CompressedIterator, Size) {
  bst_idx_t n = 2048;
  {
    bst_idx_t n_symbols = 256;
    auto n_bytes = CompressedBufferWriter::CalculateBufferSize(n, n_symbols);
    ASSERT_EQ(n_bytes, 2052);
  }
  {
    bst_idx_t n_symbols = 64;
    auto n_bytes = CompressedBufferWriter::CalculateBufferSize(n, n_symbols);
    ASSERT_EQ(n_bytes, 1540);
  }
}

TEST(CompressedIterator, Test) {
  ASSERT_TRUE(detail::SymbolBits(256) == 8);
  ASSERT_TRUE(detail::SymbolBits(150) == 8);
  std::vector<int> test_cases = {1, 3, 426, 21, 64, 256, 100000, INT32_MAX};
  int num_elements = 1000;
  int repetitions = 1000;
  srand(9);

  for (auto alphabet_size : test_cases) {
    for (int i = 0; i < repetitions; i++) {
      std::vector<int> input(num_elements);
      std::generate(input.begin(), input.end(),
        [=]() { return rand() % alphabet_size; });
      CompressedBufferWriter cbw(alphabet_size);

      // Test write entire array
      std::vector<unsigned char> buffer(
        CompressedBufferWriter::CalculateBufferSize(input.size(),
          alphabet_size));

      cbw.Write(buffer.data(), input.begin(), input.end());

      CompressedIterator<int> ci(buffer.data(), alphabet_size);
      std::vector<int> output(input.size());
      for (size_t i = 0; i < input.size(); i++) {
        output[i] = ci[i];
      }

      ASSERT_TRUE(input == output);

      // Test write Symbol
      std::vector<unsigned char> buffer2(
        CompressedBufferWriter::CalculateBufferSize(input.size(),
          alphabet_size));
      for (size_t i = 0; i < input.size(); i++) {
        cbw.WriteSymbol(buffer2.data(), input[i], i);
      }
      CompressedIterator<int> ci2(buffer.data(), alphabet_size);
      std::vector<int> output2(input.size());
      for (size_t i = 0; i < input.size(); i++) {
        output2[i] = ci2[i];
      }
      ASSERT_TRUE(input == output2);
    }
  }
}
}  // namespace xgboost::common
