integration/luprex/syscpp/lpx-classdb.cpp

#include "lpx-classdb.hpp"
#include "lpx-table.hpp"

// Get an entry from the class database.
//
//   DB, CLASSNAME
//   if classname is already present, and is a table, return it.
//   if classname is already present, and not a table, error.
//   if classname is not present, create and initialize it.
//
int lpx_classdb_get(lua_State *L) {
    LpxArg db, classname;
    LpxRet classtab;
    LpxVar action;
    LpxStackManager LSM(L, db, classname, classtab, action);

    LSM.checknometa(db);
    luaL_checktype(L, classname, LUA_TSTRING);
    LSM.rawget(classtab, db, classname);
    if (lua_istable(L, classtab)) {
        return LSM.retval();
    } else if (!lua_isnil(L, classtab)) {
        luaL_error(L, "%s is not a class", lua_tostring(L, classname));
    }
    LSM.newtable(classtab);
    LSM.rawset(db, classname, classtab);
    LSM.setfield(classtab, "__index", classtab);
    LSM.setfield(classtab, "__class", classname);
    LSM.newtable(action);
    LSM.setfield(classtab, "action", action);
    return LSM.retval();
}

// Curried version of classdb.get where db is stored in an upvalue.
//
static int lpx_classdb_class(lua_State *L) {
    lua_pushvalue(L, lua_upvalueindex(1));
    lua_insert(L, -2);
    return lpx_classdb_get(L);
}

int lpx_classdb_accessor(lua_State *L) {
    luaL_checktype(L, -1, LUA_TTABLE);
    lua_pushcclosure(L, LpxArgCheck<1, lpx_classdb_class>, 1);
    return 1;
}

// Reset a class database:
//
//   Clear out all classes.  Instead of replacing the class tables,
//   it simply deletes all keys.  That way, if somebody has a pointer
//   to a class, the pointer is not invalidated.
//
//   Caution: do not reset the global class database!
//
int lpx_classdb_reset(lua_State *L) {
    LpxArg db;
    LpxVar classname, classtab, action, key;
    LpxStackManager LSM(L, db, classname, classtab, action, key);

    luaL_checktype(L, db, LUA_TTABLE);
    LSM.setnil(classname);
    while (LSM.next(db, classname, classtab) != 0) {
        if (lua_istable(L, classtab)) {
            LSM.setstring(key, "action");
            LSM.rawget(action, classtab, key);
            if (lua_istable(L, action)) {
                lua_pushvalue(L, action);
                lpx_table_clear(L);
            } else {
                LSM.newtable(action);
            }
            lua_pushvalue(L, classtab);
            lpx_table_clear(L);
            LSM.setfield(classtab, "__index", classtab);
            LSM.setfield(classtab, "__class", classname);
            LSM.setfield(classtab, "action", action);
        }
    }
    return LSM.retval();
}

// Create a classdb.  That's just an empty table.
int lpx_classdb_create(lua_State *L) {
    lua_newtable(L);
    return 1;
}

void luaopen_lpx_classdb(lua_State *L) {
    LpxStackManager::reg(L, "classdb", "get", LpxArgCheck<2, lpx_classdb_get>);
    LpxStackManager::reg(L, "classdb", "accessor", LpxArgCheck<1, lpx_classdb_accessor>);
    LpxStackManager::reg(L, "classdb", "reset", LpxArgCheck<1, lpx_classdb_reset>);
    LpxStackManager::reg(L, "classdb", "create", LpxArgCheck<0, lpx_classdb_create>);

    // Insert the global function 'class', which is a closure with an upvalue.
    lua_pushstring(L, "class");
    lua_pushvalue(L, LUA_GLOBALSINDEX);
    lpx_classdb_accessor(L);
    lua_rawset(L, LUA_GLOBALSINDEX);
}