/*
 * This source code is released into the public domain.
 */

module;

#include <expected>
#include <filesystem>
#include <iterator>
#include <ranges>
#include <span>
#include <system_error>

#include <fcntl.h>
#include <unistd.h>

export module nihil.posix:read_file;

import nihil.error;
import nihil.monad;
import :fd;
import :open;

namespace nihil {

/*
 * Read the contents of a file into an output iterator. 
 */
export [[nodiscard]] auto
read_file(std::filesystem::path const &filename,
	  std::output_iterator<char> auto &&iter)
	-> std::expected<void, error>
{
	auto file = co_await open(filename, O_RDONLY);

	auto constexpr bufsize = std::size_t{1024};
	auto buffer = std::array<char, bufsize>{};

	for (;;) {
		auto read_buf = co_await(read(file, buffer));
		if (read_buf.empty())
			co_return {};

		std::ranges::copy(read_buf, iter);
	}
}

} // namespace nihil