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/*
* This source code is released into the public domain.
*/
module;
/*
* The configuration store. There should only be one of these.
*/
#include <coroutine>
#include <format>
#include <map>
export module nihil.config:store;
import nihil;
import :error;
import :option;
namespace nihil::config {
// Exception thrown on an attempt to fetch an undefined option.
export struct unknown_option final : error {
std::string varname;
unknown_option(std::string_view varname_)
: error("unknown configuration variable '{}'", varname_)
, varname(varname_)
{}
};
export struct store final {
/*
* Get the global config store.
*/
static auto get() -> store& {
if (instance == nullptr)
instance = new store;
return *instance;
}
/*
* Initialise the global config store.
*/
#if 0
void init(context const &ctx) {
std::string config_text;
// Load the configuration text.
auto config_path = ctx.dbdir / "config.ucl";
try {
read_file(config_path, std::back_inserter(config_text));
} catch (io_error const &exc) {
// Ignore ENOENT, it simply means we haven't created the
// config file yet, so default values will be used.
if (exc.error == std::errc::no_such_file_or_directory)
return;
throw;
}
// Parse the UCL.
std::string err;
auto uclconfig = ucl::Ucl::parse(config_text, err);
if (!uclconfig)
throw error("{0}: {1}", config_path, err);
auto const &cfg = get();
for (auto const &uclvalue : uclconfig) {
auto &value = cfg.fetch(uclvalue.key());
switch (uclvalue.type()) {
case UCL_INT:
value.integer(uclvalue.int_value());
break;
case UCL_STRING:
value.string(uclvalue.string_value());
break;
default:
throw error(
"INTERNAL ERROR: unknown value type {0}",
static_cast<int>(uclvalue.type()));
}
}
}
#endif
/*
* Register a new value with the config store.
*/
auto register_option(this store &self, option *object) -> void
{
auto [it, okay] = self.options.insert(
std::pair{object->name(), object});
if (okay)
return;
throw error("INTERNAL ERROR: attempt to register "
"duplicate config value '{0}'",
object->name());
}
/*
* Fetch an existing value in the config store.
*/
auto fetch(this store const &self, std::string_view name)
-> option &
{
if (auto it = self.options.find(name); it != self.options.end())
return *it->second;
throw unknown_option(name);
}
/*
* Fetch all values in the configuration store.
*/
auto all(this auto &&self) -> nihil::generator<option const &>
{
for (auto &&it : self.options)
co_yield *it.second;
}
/*
* Write all config values (except defaults) to disk.
*/
#if 0
void store::write_all(this store const &self, context const &ctx) {
// The UCL C++ API doesn't seem to support creating new objects
// from scratch, so we use the C API here. We should probably
// provider a better wrapper for this.
auto ucl = ::ucl_object_typed_new(UCL_OBJECT);
auto ucl_guard = guard([ucl] { ::ucl_object_unref(ucl); });
// Add all the options to the UCL object.
for (auto const &option : self.fetch_all()) {
if (option.is_default)
continue;
option.add_to_ucl(ucl);
}
// Dump the UCL object to a string.
auto *ucl_c_text = reinterpret_cast<char *>(
::ucl_object_emit(ucl, UCL_EMIT_CONFIG));
//NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
auto ucl_text_guard = guard([ucl_c_text] { ::free(ucl_c_text); });
std::string ucl_text(ucl_c_text);
// Write the object to a file.
auto config_path = ctx.dbdir / "config.ucl";
try {
safe_write_file(config_path, ucl_text);
} catch (io_error const &exc) {
throw error("{}", exc.what());
}
}
#endif
// Not movable or copyable.
store(store const &) = delete;
store(store &&) = delete;
store& operator=(store const &) = delete;
store& operator=(store &&) = delete;
private:
/*
* The global configuration store, created by init() and accessed via
* get().
*/
inline static store *instance = nullptr;
std::map<std::string_view, option *> options;
store() = default;
};
} // namespace nihil::config
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