module;

#include <simd>

module tricks;

import std;

namespace brc {

std::size_t find_delim(std::string_view string, char target) {
	constexpr auto width = std::simd::vec<std::uint8_t>::size();
	const auto needle = std::simd::vec<std::uint8_t>(static_cast<std::uint8_t>(target));

	auto i = std::size_t(0);
	for (; i + width <= string.size(); i += width) {
		const auto chunk = std::simd::vec<std::uint8_t>(
			std::span<const std::uint8_t, width>(reinterpret_cast<const std::uint8_t*>(string.data() + i), width));

		const auto mask = chunk == needle;
		if (const auto bits = mask.to_bitset(); bits.any()) {
			return i + std::countr_zero(bits.to_ullong());
		}
	}

	for (; i < string.size(); ++i) {
		if (string[i] == target) return i;
	}
	return string.size();
}

std::inplace_vector<std::size_t, 4> find_delim_batch(std::string_view string, char target) {
	constexpr auto BatchSize = 4;
	auto sizes = std::inplace_vector<std::size_t, BatchSize>();

	constexpr auto width = std::simd::vec<std::uint8_t>::size();
	const auto needle = std::simd::vec<std::uint8_t>(static_cast<std::uint8_t>(target));

	std::size_t i = 0;

	for (; i + width <= string.size() && sizes.size() < BatchSize; i += width) {
		const auto chunk = std::simd::vec<std::uint8_t>(
			std::span<const std::uint8_t, width>(reinterpret_cast<const std::uint8_t*>(string.data() + i), width));

		const auto mask = chunk == needle;
		auto bits = mask.to_bitset().to_ullong();

		while (bits != 0 && sizes.size() < BatchSize) {
			const auto bit_pos = std::countr_zero(bits);
			sizes.push_back(i + bit_pos);
			bits &= bits - 1;
		}
	}

	for (; i < string.size() && sizes.size() < BatchSize; ++i) {
		if (string[i] == target) {
			sizes.push_back(i);
		}
	}

	return sizes;
}

}  // namespace brc