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module;
#include <boost/json.hpp>
#include <boost/system/system_error.hpp>
module routemon:config$impl;
import std;
import :config;
import :log;
import :util;
namespace json = boost::json;
namespace routemon::config {
class location
{
std::optional<std::pair<std::string_view, util::not_null<location const*>>>
next_;
auto append_to(std::string& s) const -> void
{
if (next_)
{
next_->second->append_to(s);
s += next_->first;
s += ".";
}
}
public:
location() = default;
explicit location(location const& next, std::string_view entry)
: next_{std::make_pair(entry, util::not_null{&next})}
{
}
[[nodiscard]] auto to_string() const -> std::string
{
if (!next_)
return "";
auto s = std::string{};
next_->second->append_to(s);
s += next_->first;
return s;
}
auto sub(std::string_view entry) const& -> location
{
return location{*this, entry};
}
};
class object_reader
{
location loc_;
json::object const& obj_;
std::unordered_set<std::string> visited_;
public:
object_reader(json::value const& jv, location loc)
try : loc_{std::move(loc)}, obj_{jv.as_object()} {}
catch (boost::system::system_error const&)
{
throw std::runtime_error{std::format(
"expected an object at {}", loc.to_string())};
}
auto check_unused() const -> void
{
for (auto const& kv : obj_)
{
if (!visited_.contains(std::string{kv.key()}))
{
throw std::runtime_error{std::format(
"unexpected key {}", loc_.sub(kv.key()).to_string())};
}
}
}
template <class T>
auto allow_at(std::string_view key) -> std::optional<T>
{
visited_.emplace(key);
auto const loc = loc_.sub(key);
if (auto const jv = obj_.try_at(key); jv && !jv->is_null())
{
try
{
return json::value_to<T>(*jv, loc);
}
catch (boost::system::system_error const& e)
{
throw std::runtime_error{std::format(
"failed to read {}: {}", loc.to_string(), e.code().message())};
}
}
else
{
return std::nullopt;
}
}
template <class T>
auto expect_at(std::string_view key) -> T
{
if (auto&& mv = allow_at<T>(key); mv)
{
return std::forward<T>(*mv);
}
else
{
throw std::runtime_error{std::format(
"did not find expected key {}", loc_.sub(key).to_string())};
}
}
};
auto as_checked_object(
json::value const& jv, location const& loc,
std::invocable<object_reader&> auto const& f)
-> decltype(f(std::declval<object_reader&>()))
{
auto r = object_reader{jv, loc};
auto&& v = f(r);
r.check_unused();
return std::forward<decltype(f(r))>(v);
}
auto tag_invoke(
json::value_to_tag<rwgps> const&, json::value const& jv,
location const& loc) -> rwgps
{
return as_checked_object(
jv, loc,
[](object_reader& r) -> rwgps
{
return {
.api_key_filename = r.expect_at<std::string>("api_key_filename"),
.auth_token_filename =
r.expect_at<std::string>("auth_token_filename"),
};
});
}
auto tag_invoke(
json::value_to_tag<situations> const&, json::value const& jv,
location const& loc) -> situations
{
return as_checked_object(
jv, loc,
[](object_reader& r) -> situations
{
return {
.datex2_filename = r.expect_at<std::string>("datex2_filename"),
};
});
}
auto tag_invoke(
json::value_to_tag<database> const&, json::value const& jv,
location const& loc) -> database
{
return as_checked_object(
jv, loc,
[](object_reader& r) -> database
{
return {
.sqlite3_filename = r.expect_at<std::string>("sqlite3_filename"),
};
});
}
auto tag_invoke(
json::value_to_tag<http_server> const&, json::value const& jv,
location const& loc) -> http_server
{
return as_checked_object(
jv, loc,
[](object_reader& r) -> http_server
{
return {
.allow_origins =
r.expect_at<std::vector<std::string>>("allow_origins"),
};
});
}
auto tag_invoke(
json::value_to_tag<logger> const&, json::value const& jv,
location const& loc) -> logger
{
return as_checked_object(
jv, loc,
[obj_loc = loc](object_reader& r) -> logger
{
auto const level_str = r.expect_at<std::string>("level");
auto level = log::level{};
if (level_str == "debug")
level = log::level::debug;
else if (level_str == "info")
level = log::level::info;
else if (level_str == "warn")
level = log::level::warn;
else if (level_str == "error")
level = log::level::error;
else
throw std::runtime_error{std::format(
"unable to parse log level {:?} at {}: expected one "
"of {{debug, info, warn, error}}",
level_str, obj_loc.sub("level").to_string())};
return logger{level};
});
}
auto json_value_to_app(json::value const& jv) -> app
{
return as_checked_object(
jv, location{},
[](object_reader& r) -> app
{
return {
.rwgps = r.allow_at<rwgps>("rwgps"),
.situations = r.expect_at<situations>("situations"),
.database = r.expect_at<database>("database"),
.http_server = r.expect_at<http_server>("http_server"),
.logger = r.expect_at<logger>("logger"),
};
});
}
auto load_file(std::string const& filename) -> app
{
// TODO: migrate away from json::value_to w/ tag_invoke.
// Boost.JSON does not properly propagate custom exceptions accross
// json::value_to calls when certain containers are involved
// (std::{optional,variant,vector}).
auto f = std::ifstream{filename, std::ios::binary};
if (!f.is_open())
throw std::runtime_error{std::format("failed to open {}", filename)};
auto jv = json::value{};
try
{
jv = json::parse(f);
}
catch (boost::system::system_error const& e)
{
throw std::runtime_error{std::format(
"failed to parse: {}", e.code().message())};
}
return json_value_to_app(jv);
}
} // namespace routemon::config
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