// Copyright Epic Games, Inc. All Rights Reserved.

#include <zentelemetry/hyperloglog.h>

namespace zen {
void
hyperloglog_forcelink()
{
}
}  // namespace zen

#if ZEN_WITH_TESTS

#	include <zencore/testing.h>

#	include <fmt/format.h>

#	include <set>
#	include <string>

namespace zen::tests {

TEST_SUITE_BEGIN("telemetry.hyperloglog");

TEST_CASE("hyperloglog.empty")
{
	metrics::HyperLogLog<> Hll;
	CHECK_EQ(Hll.Count(), 0);
}

TEST_CASE("hyperloglog.single_element")
{
	metrics::HyperLogLog<> Hll;
	Hll.Add("hello");
	CHECK(Hll.Count() >= 1);
	CHECK(Hll.Count() <= 2);
}

TEST_CASE("hyperloglog.duplicates")
{
	metrics::HyperLogLog<> Hll;
	for (int i = 0; i < 1000; ++i)
	{
		Hll.Add("same_value");
	}
	CHECK_EQ(Hll.Count(), 1);
}

TEST_CASE("hyperloglog.estimate_accuracy")
{
	// With precision 14, expected error is ~0.81%
	// Use a generous margin (5%) for the test to be reliable
	constexpr uint64_t N = 100000;

	metrics::HyperLogLog<14> Hll;
	for (uint64_t i = 0; i < N; ++i)
	{
		std::string Value = fmt::format("item_{}", i);
		Hll.Add(Value);
	}

	uint64_t Estimate = Hll.Count();
	double	 Error	  = std::abs(static_cast<double>(Estimate) - static_cast<double>(N)) / static_cast<double>(N);

	CHECK(Error < 0.05);
}

TEST_CASE("hyperloglog.small_cardinality")
{
	metrics::HyperLogLog<> Hll;
	for (int i = 0; i < 10; ++i)
	{
		std::string Value = fmt::format("key_{}", i);
		Hll.Add(Value);
	}

	uint64_t Estimate = Hll.Count();
	CHECK(Estimate >= 8);
	CHECK(Estimate <= 12);
}

TEST_CASE("hyperloglog.clear")
{
	metrics::HyperLogLog<> Hll;
	for (int i = 0; i < 100; ++i)
	{
		std::string Value = fmt::format("v_{}", i);
		Hll.Add(Value);
	}
	CHECK(Hll.Count() > 0);

	Hll.Clear();
	CHECK_EQ(Hll.Count(), 0);
}

TEST_CASE("hyperloglog.merge")
{
	constexpr uint64_t N = 50000;

	metrics::HyperLogLog<14> A;
	metrics::HyperLogLog<14> B;

	// A gets even numbers, B gets odd numbers
	for (uint64_t i = 0; i < N; ++i)
	{
		std::string Value = fmt::format("item_{}", i * 2);
		A.Add(Value);
	}
	for (uint64_t i = 0; i < N; ++i)
	{
		std::string Value = fmt::format("item_{}", i * 2 + 1);
		B.Add(Value);
	}

	A.Merge(B);

	uint64_t Estimate = A.Count();
	double	 Error	  = std::abs(static_cast<double>(Estimate) - static_cast<double>(N * 2)) / static_cast<double>(N * 2);

	CHECK(Error < 0.05);
}

TEST_SUITE_END();

}  // namespace zen::tests

#endif	// ZEN_WITH_TESTS