json.tpp

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#include <alpaqa/config/config.hpp>
#include <alpaqa/params/json.hpp>
#include <alpaqa/util/demangled-typename.hpp>
#include <alpaqa/util/string-util.hpp>
 
#include <nlohmann/json.hpp>
#include <stdexcept>
 
namespace alpaqa::params {
 
using config_t = DefaultConfig;
 
namespace detail {
std::string join_sorted_keys(const auto &members) {
    auto keys = std::views::keys(members);
    std::vector<std::string> sorted_keys{keys.begin(), keys.end()};
    util::sort_case_insensitive(sorted_keys);
    return util::join(sorted_keys, {.sep = ", ", .empty = "∅"});
}
} // namespace detail
 
template <class T>
    requires requires { attribute_table<T, json>::table; }
void set_param(T &t, const json &j) {
    if (!j.is_object())
        throw invalid_json_param("Invalid value " + to_string(j) +
                                 " for type '" + demangled_typename(typeid(T)) +
                                 "' (expected object, but got " +
                                 j.type_name() + ')');
    // Dictionary of members
    const auto &members = attribute_table<T, json>::table;
    // Loop over all items in the JSON object
    for (auto &&el : j.items()) {
        const auto &key = el.key();
        auto it         = members.find(key);
        // If member was not found
        if (it == members.end()) {
            // Perhaps it's an alias to another member?
            if constexpr (requires { attribute_alias_table<T, json>::table; }) {
                const auto &aliases = attribute_alias_table<T, json>::table;
                auto alias_it       = aliases.find(key);
                // If it's not an alias either, raise an error
                if (alias_it == aliases.end()) {
                    throw invalid_json_param(
                        "Invalid key '" + key + "' for type '" +
                        demangled_typename(typeid(T)) +
                        "',\n  possible keys are: " +
                        detail::join_sorted_keys(members) + " (aliases: " +
                        detail::join_sorted_keys(aliases) + ")");
                }
                // Resolve the alias and make sure that the target exists
                it = members.find(alias_it->second);
                if (it == members.end())
                    throw std::logic_error(
                        "Alias '" + std::string(alias_it->first) +
                        "' refers to nonexistent option '" +
                        std::string(alias_it->second) + "' in '" +
                        demangled_typename(typeid(T)) + "'");
            }
            // If there are no aliases, then it's always an error
            else {
                auto keys = std::views::keys(members);
                std::vector<std::string> sorted_keys{keys.begin(), keys.end()};
                util::sort_case_insensitive(sorted_keys);
                throw invalid_json_param("Invalid key '" + key +
                                         "' for type '" +
                                         demangled_typename(typeid(T)) +
                                         "',\n  possible keys are: " +
                                         detail::join_sorted_keys(members));
            }
        }
        // Member was found, invoke its setter (and possibly recurse)
        try {
            it->second.set(t, el.value());
        } catch (invalid_json_param &e) {
            // Keep a backtrace of the JSON keys for error reporting
            e.backtrace.push_back(key);
            throw;
        }
    }
}
 
template <class T>
    requires requires { attribute_table<T, json>::table; }
void get_param(const T &t, json &s) {
    s             = json::object();
    const auto &m = attribute_table<T, json>::table;
    for (auto &&[k, v] : m)
        v.get(t, s[k]);
}
 
} // namespace alpaqa::params