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) {
    const int db = lua_gettop(L) - 1;
    const int cname = lua_gettop(L);
    
    luaL_checktype(L, db, LUA_TTABLE);
    luaL_checktype(L, cname, LUA_TSTRING);
    lua_pushvalue(L, cname);
    lua_rawget(L, db);
    if (lua_istable(L, -1)) {
        return 1;
    } else if (!lua_isnil(L, -1)) {
        lua_pushfstring(L, "%s is not a class", lua_tostring(L, cname));
        lua_error(L);
    }
    lua_pop(L, 1);
    lua_newtable(L);
    int cls = lua_gettop(L);
    lua_pushvalue(L, cname);
    lua_pushvalue(L, cls);
    lua_rawset(L, db);
    lua_pushstring(L, "__index");
    lua_pushvalue(L, cls);
    lua_rawset(L, cls);
    lua_pushstring(L, "__class");
    lua_pushvalue(L, cname);
    lua_rawset(L, cls);
    lua_pushstring(L, "action");
    lua_newtable(L);
    lua_rawset(L, cls);

    // Remove arguments, leaving new table on stack.
    lua_replace(L, db);
    lua_settop(L, db);
    return 1;
}

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

int lpx_classdb_accessor(lua_State *L) {
    const int db = lua_gettop(L);
    luaL_checktype(L, db, LUA_TTABLE);
    lua_pushcclosure(L, 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) {
    const int db = lua_gettop(L);
    luaL_checktype(L, db, LUA_TTABLE);
    lua_pushnil(L);
    while (lua_next(L, db) != 0) {
        int cname = lua_gettop(L) - 1;
        int cls = lua_gettop(L);
        if (lua_istable(L, cls)) {
            lua_pushstring(L, "action");
            lua_rawget(L, cls);
            int actn = lua_gettop(L);
            if (lua_istable(L, actn)) {
                lua_pushvalue(L, actn);
                lpx_table_clear(L);
            } else {
                lua_pop(L, 1);
                lua_newtable(L);
            }
            lua_pushvalue(L, cls);
            lpx_table_clear(L);
            lua_pushstring(L, "__index");
            lua_pushvalue(L, cls);
            lua_rawset(L, cls);
            lua_pushstring(L, "__class");
            lua_pushvalue(L, cname);
            lua_rawset(L, cls);
            lua_pushstring(L, "action");
            lua_pushvalue(L, actn);
            lua_rawset(L, cls);
        }
        lua_settop(L, cname);
    }
    // Remove arguments, leave nothing on stack.
    lua_settop(L, db - 1);
    return 0;
}

// Create the global function 'class'.
//
//   This version of 'class' creates classes in the global environment.
//   Note that this is lua 5.1 specific.
//
static int lpx_create_global_class(lua_State *L) {
    lua_pushstring(L, "class");
    lua_pushvalue(L, LUA_GLOBALSINDEX);
    lpx_classdb_accessor(L);
    lua_rawset(L, LUA_GLOBALSINDEX);
}

static const struct luaL_Reg lpx_classdb_lib [] = {
    {"get", lpx_classdb_get},
    {"accessor", lpx_classdb_accessor},
    {"reset", lpx_classdb_reset},
    {NULL, NULL}  /* sentinel */
};

int luaopen_lpx_classdb(lua_State *L) {
    luaL_openlib(L, "classdb", lpx_classdb_lib, 0);
    lpx_create_global_class(L);
    return 1;
}