#include <string.h>

#include <lua.h>
#include <lauxlib.h>
#include "luaopen.h"

static int ip_encode(lua_State *L) {
  const unsigned char *s = luaL_checklstring(L, 1, NULL);
  char *p, b[6];
  size_t l, o = 4, n = strtol(s, &p, 10);
  if (!n) return 0;
  while (--o) {
    if (n > 255 || *p != '.' || *(p + 1) == '.' ) return 0;
    b[l++] = (char)n;
    n = strtol(p + 1, &p, 10);
  }
  if (n > 255 || !n || *p) return 0;
  b[l++] = (char)n;
  if (lua_type(L, 2) != LUA_TNONE) {
    n = luaL_checkinteger(L, 2);
    if (n > 65536 || !n) return 0;
    b[l++] = n / 256;
    b[l++] = n % 256;
  }
  lua_pushlstring(L, b, l);
  return 1;
}

static int ip_decode(lua_State *L) {
  size_t i, l, n;
  const unsigned char *s = luaL_checklstring(L, 1, &n);
  if (n != 4 && n != 6) return 0;
  char b[15];
  l = sprintf(b, "%d", *s);
  for (i = 0; i < 3; ++i) l += sprintf(b + l, ".%d", s[i]);
  lua_pushlstring(L, b, l);
  if (n == 4) return 1;
  lua_pushinteger(L, s[4] * 256 + s[5]);
  return 2;
}

static struct luaL_Reg funcs[] = {
  {"encode", ip_encode},
  {"decode", ip_decode},
  {NULL, NULL}
};

int luaopen_ipconv(lua_State *L) {
    luaL_newmetatable(L, "ipconv");
    luaL_newlib(L, funcs);
    return 1;
}