1 files changed, 63 insertions, 0 deletions
diff --git a/nihil.config/read.ccm b/nihil.config/read.ccm
new file mode 100644
index 0000000..8d6c202
--- /dev/null
+++ b/nihil.config/read.ccm
@@ -0,0 +1,63 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <filesystem>
+#include <format>
+#include <iterator>
+#include <string>
+
+export module nihil.config:read;
+
+import nihil;
+import nihil.ucl;
+
+import :error;
+import :store;
+
+namespace nihil::config {
+
+/*
+ * Load the configuration from a file.  Throws config::error on failure.
+ */
+export auto read_from(std::filesystem::path const &filename) -> void
+{
+	// 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() == std::errc::no_such_file_or_directory)
+			return;
+		throw error(std::format("{}: {}",
+			    filename.string(),
+			    err.error().message()));
+	}
+
+	// Parse the UCL.
+	try {
+		auto uclconfig = ucl::parse(config_text);
+
+		for (auto &&[key, value] : uclconfig) {
+			auto &opt = store::get().fetch(key);
+			opt.from_ucl(value);
+		}
+	} catch (unknown_option const &) {
+		// This is probably an old option which has been removed;
+		// ignore it, and we'll remove the bad option next time
+		// we write the config.
+	} catch (error const &err) {
+		// Include the filename in any other config errors.
+		throw error(std::format("{}: {}", filename.string(),
+					err.what()));
+	} catch (ucl::error const &err) {
+		throw error(std::format("{}: {}", filename.string(),
+					err.what()));
+	}
+}
+
+} // namespace nihil::config