1 files changed, 50 insertions, 0 deletions
diff --git a/nihil.config/read.cc b/nihil.config/read.cc
new file mode 100644
index 0000000..48484fb
--- /dev/null
+++ b/nihil.config/read.cc
@@ -0,0 +1,50 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <coroutine>
+#include <expected>
+#include <filesystem>
+#include <format>
+#include <iterator>
+#include <string>
+
+module nihil.config;
+
+import nihil.error;
+import nihil.monad;
+import nihil.posix;
+import nihil.ucl;
+
+namespace nihil::config {
+
+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.
+
+	std::string config_text;
+	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 {};
+		auto errstr = std::format("cannot read {}", filename.string());
+		co_return std::unexpected(error(errstr, 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