mod_tracker.h

#pragma once
#ifndef CATA_SRC_MOD_TRACKER_H
#define CATA_SRC_MOD_TRACKER_H

#include <string>

#include "cata_void.h"
#include "debug.h"
#include "demangle.h"
#include "type_id.h"


/**
 * Mod Tracking:
 *
 * These functions live here to provide various JSON-loaded entities
 * with the ids of the mods that they are from.
 *
 * To subscribe, a JSON-loaded entity simply needs to have a
 * 'std::vector<std::pair<(string or int)_id<T>, mod_id> src;' member.
 * (As well as storing their id in an 'id' member of either string or int id type)
 * If 'src' or 'id' is private, the subscriber must add 'mod_tracker' as a friend to access those members
 *
 * If the entity is loaded normally with generic_factory, no further changes are needed.
 * If the entity is not loaded with generic_factory, 'assign_src()' must be called sometime
 * after the 'id' member has been assigned.
 */

class mod_error : public std::runtime_error
{
    public:
        explicit mod_error( const std::string &msg ) : std::runtime_error( msg ) {}
};

struct mod_tracker {
    /** Template magic to determine if the conditions above are satisfied */
    template<typename T, typename = cata::void_t<>>
    struct has_src_member : std::false_type {};

    template<typename T>
struct has_src_member<T, cata::void_t<decltype( std::declval<T &>().src.emplace_back( std::declval<T &>().id, mod_id() ) )>> :
    std::true_type {};


    /** Dummy function, for if those conditions are not satisfied */
    template < typename T, typename std::enable_if_t < !has_src_member<T>::value > * = nullptr >
    static void assign_src( T &, const std::string & ) {
    }

    /** If those conditions are satisfied, keep track of where this item has been modified */
    template<typename T, typename std::enable_if_t<has_src_member<T>::value > * = nullptr>
    static void assign_src( T &def, const std::string &src ) {
        // We need to make sure we're keeping where this entity has been loaded
        // If the id this was last loaded with is not this one, discard the history and start again
        if( !def.src.empty() && def.src.back().first != def.id ) {
            def.src.clear();
        }
        def.src.emplace_back( def.id, mod_id( src ) );
    }

    /** Dummy function, for if those conditions are not satisfied */
    template < typename T, typename std::enable_if_t < !has_src_member<T>::value > * = nullptr >
    static void check_duplicate_entries( const T &n, const T & ) {
        static bool reported = false;
        // We don't need to complain more than once, it's spammy.
        if( reported ) {
            return;
        }
        reported = true;
        DebugLog( D_INFO, D_MAIN ) << __FILE__ << ":" << __LINE__ << ": " << "Tried check if '" <<
                                   n.id.str() << "' had a duplicate, but type '" << demangle( typeid( T ).name() ) <<
                                   "' does not track object sources";
    }

    /** If those conditions are satisfied, keep track of where this item has been modified */
    template<typename T, typename std::enable_if_t<has_src_member<T>::value > * = nullptr>
    static void check_duplicate_entries( const T &n, const T &o ) {
        // We need to make sure we're keeping where this entity has been loaded
        // If the id this was last loaded with is not this one, discard the history and start again
        if( n.src.back() == o.src.back() ) {
            throw mod_error( string_format( "%s (%s) has two definitions from the same source (%s)!",
                                            n.id.str(), demangle( typeid( T ).name() ), n.src.back().second.str() ) );
        }
    }

};

#endif // CATA_SRC_MOD_TRACKER_H