// This source code is released into the public domain.
export module nihil.config:read;

import nihil.std;
import nihil.core;
import nihil.posix;
import nihil.ucl;

import :option;
import :store;

namespace nihil::config {

// Load the configuration from a file.
export [[nodiscard]] auto
read_from(std::filesystem::path const &filename) -> std::expected<void, error>
{
	// TODO: nihil.ucl should have a way to load UCL from a filename.

	auto config_text = std::string();
	auto err = read_file(filename, std::back_inserter(config_text));
	if (!err) {
		// Ignore ENOENT, it simply means we haven't created the
		// config file yet, so default values will be used.
		if (err.error().root_cause() == std::errc::no_such_file_or_directory)
			co_return {};
		co_return std::unexpected(error(std::format("cannot read {}", filename.string()), err.error()));
	}

	// Parse the UCL.
	auto uclconfig = co_await ucl::parse(config_text);

	for (auto &&[key, value] : uclconfig) {
		auto *opt = co_await store::get().fetch(key);
		co_await opt->ucl(value);
	}

	co_return {};
}

} // namespace nihil::config