/** 
 * Copyright (c) 2016 rxi
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MIT license. See LICENSE for details.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "luaobj.h"


int luaobj_newclass(lua_State *L, const char *name, const char *extends, 
                    int (*constructor)(lua_State*), luaL_Reg* reg
) {
  /* Creates and pushes a new metatable which represents a class containing the
   * functions in the `reg` argument. If the `extends` argument is not NULL
   * this class will use the specified class as a super class */

  /* Build metatable */ 
  luaL_newmetatable(L, name);
  /* Add type name string */
  lua_pushstring(L, "__type");
  lua_pushstring(L, name);
  lua_rawset(L, -3);
  /* Make and add func table */
  lua_newtable(L);
  luaL_setfuncs(L, reg, 0); 
  lua_pushstring(L, "__index");
  lua_pushvalue(L, -2);
  lua_rawset(L, -4);
  /* Handle extended */
  if (extends) {
    luaL_getmetatable(L, extends);
    /* Pull metatable functions from base class */
    char *mtfields[] = { "__gc", "__tostring", NULL };
    int i;
    for (i = 0; mtfields[i]; i++) {
      lua_getfield(L, -1, mtfields[i]);
      lua_setfield(L, -4, mtfields[i]);
    }
    lua_setmetatable(L, -2);
  }
  lua_pop(L, 1);              /* Pop func table */
  luaL_setfuncs(L, reg, 0);   /* Set metatable's funcs */
  lua_pop(L, 1);              /* Pop metatable */

  /* Return constructor */
  lua_pushcfunction(L, constructor);

  return 1;
}


void luaobj_setclass(lua_State *L, uint32_t type, char *name) {
  /* Sets the the metatable of the member at the top of the stack to the
   * class-metatable of the given `name` */
  luaobj_head_t *udata = lua_touserdata(L, -1);
  udata->type = type;
  luaL_getmetatable(L, name);
  if (lua_isnil(L, -1)) {
    luaL_error(
      L, "missing metatable: assure class '%s' is inited in love.c\n", name);
  }
  lua_setmetatable(L, -2);
}


void *luaobj_newudata(lua_State *L, int size) {
  /* Creates a udata of the requested size, plus space for the luaobj_head_t
   * header. Returns the pointer to the udata's body */
  int s = size + sizeof(luaobj_head_t);
  luaobj_head_t *udata = lua_newuserdata(L, s);
  udata->type = 0;
  return udata + 1;
}


void *luaobj_checkudata(lua_State *L, int index, uint32_t type) {
  /* Checks the header of a luaobj udata at the given index, taking into
   * account super-classes it may have extended. Returns the udata's body if
   * it is of the correct class, else errors out */
  index = lua_absindex(L, index);
  luaobj_head_t *udata = lua_touserdata(L, index);
  if (!udata || !(udata->type & type)) {
    luaL_argerror(L, index, "bad type");
  }
  return udata + 1;
}