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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 <filesystem>
#include <format>
#include <map>
export module nihil.config:store;
import :error;
import :option;
namespace nihil::config {
// Exception thrown on an attempt to fetch an undefined option.
export struct unknown_option final : error {
unknown_option(std::string_view option_name)
: error(std::format("unknown configuration variable '{}'",
option_name))
, _option_name(option_name)
{}
auto option_name(this unknown_option const &self) -> std::string_view
{
return self._option_name;
}
private:
std::string _option_name;
};
struct store final {
/*
* Get the global config store.
*/
static auto get() -> store& {
if (instance == nullptr)
instance = new store;
return *instance;
}
/*
* 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)
throw error(std::format(
"INTERNAL ERROR: attempt to register "
"duplicate config value '{0}'",
object->name()));
}
/*
* Remove a value from the config store.
*/
auto unregister_option(this store &self, option *object) -> void
{
auto it = self.options.find(object->name());
if (it == self.options.end())
throw error(std::format(
"INTERNAL ERROR: attempt to unregister "
"non-existent config value '{}'",
object->name()));
self.options.erase(it);
}
/*
* 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;
}
// 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;
};
/*
* The public API.
*/
export auto get_option(std::string_view option_name) -> option &
{
return store::get().fetch(option_name);
}
} // namespace nihil::config
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