#include <time.h>
#include <string.h>

#define lib_os_c
#define LUA_LIB

/*
** list of valid conversion specifiers for the 'strftime' function
*/
#if !defined(LUA_STRFTIMEOPTIONS)

#if !defined(LUA_USE_POSIX)
#define LUA_STRFTIMEOPTIONS     { "aAbBcdHIjmMpSUwWxXyYz%", "" }
#else
#define LUA_STRFTIMEOPTIONS \
        { "aAbBcCdDeFgGhHIjmMnprRStTuUVwWxXyYzZ%", "" \
          "", "E", "cCxXyY",  \
          "O", "deHImMSuUVwWy" }
#endif

#endif

/*
** By default, Lua uses gmtime/localtime, except when POSIX is available,
** where it uses gmtime_r/localtime_r
*/
#if defined(LUA_USE_GMTIME_R)

#define l_gmtime(t,r)           gmtime_r(t,r)
#define l_localtime(t,r)        localtime_r(t,r)

#elif !defined(l_gmtime)

#define l_gmtime(t,r)           ((void)r, gmtime(t))
#define l_localtime(t,r)        ((void)r, localtime(t))

#endif

#include "lua.h"
#include "lauxlib.h"
#include "lj_err.h"

static int os_clock(lua_State *L) {
  lua_Number clk = ((lua_Number)clock())*(1.0/(lua_Number)CLOCKS_PER_SEC);
  lua_pushnumber(L, clk);
  return 1;
}

/*
** {======================================================
** Time/Date operations
** { year=%Y, month=%m, day=%d, hour=%H, min=%M, sec=%S,
**   wday=%w+1, yday=%j, isdst=? }
** =======================================================
*/

static void setfield (lua_State *L, const char *key, int value) {
  lua_pushinteger(L, value);
  lua_setfield(L, -2, key);
}

static void setboolfield (lua_State *L, const char *key, int value) {
  if (value < 0)  /* undefined? */
    return;  /* does not set field */
  lua_pushboolean(L, value);
  lua_setfield(L, -2, key);
}

static int getboolfield(lua_State *L, const char *key) {
  int res;
  lua_getfield(L, -1, key);
  res = lua_isnil(L, -1) ? -1 : lua_toboolean(L, -1);
  lua_pop(L, 1);
  return res;
}

static int getfield(lua_State *L, const char *key, int d) {
  int res;
  lua_getfield(L, -1, key);
  if (lua_isnumber(L, -1)) {
    res = (int)lua_tointeger(L, -1);
  } else {
    if (d < 0)
      lj_err_callerv(L, LJ_ERR_OSDATEF, key);
    res = d;
  }
  lua_pop(L, 1);
  return res;
}

static const char *checkoption (lua_State *L, const char *conv, char *buff) {
  static const char *const options[] = LUA_STRFTIMEOPTIONS;
  unsigned int i;
  for (i = 0; i < sizeof(options)/sizeof(options[0]); i += 2) {
    if (*conv != '\0' && strchr(options[i], *conv) != NULL) {
      buff[1] = *conv;
      if (*options[i + 1] == '\0') {  /* one-char conversion specifier? */
        buff[2] = '\0';  /* end buffer */
        return conv + 1;
      }
      else if (*(conv + 1) != '\0' &&
               strchr(options[i + 1], *(conv + 1)) != NULL) {
        buff[2] = *(conv + 1);  /* valid two-char conversion specifier */
        buff[3] = '\0';  /* end buffer */
        return conv + 2;
      }
    }
  }
  luaL_argerror(L, 1,
    lua_pushfstring(L, "invalid conversion specifier '%%%s'", conv));
  return conv;  /* to avoid warnings */
}

static int os_date (lua_State *L) {
  const char *s = luaL_optstring(L, 1, "%c");
  time_t t = luaL_opt(L, (time_t)luaL_checknumber, 2, time(NULL));
  struct tm tmr, *stm;
  if (*s == '!') {  /* UTC? */
    stm = l_gmtime(&t, &tmr);
    s++;  /* skip `!' */
  }
  else
    stm = l_localtime(&t, &tmr);
  if (stm == NULL)  /* invalid date? */
    lua_pushnil(L);
  else if (strcmp(s, "*t") == 0) {
    lua_createtable(L, 0, 9);  /* 9 = number of fields */
    setfield(L, "sec", stm->tm_sec);
    setfield(L, "min", stm->tm_min);
    setfield(L, "hour", stm->tm_hour);
    setfield(L, "day", stm->tm_mday);
    setfield(L, "month", stm->tm_mon+1);
    setfield(L, "year", stm->tm_year+1900);
    setfield(L, "wday", stm->tm_wday+1);
    setfield(L, "yday", stm->tm_yday+1);
    setboolfield(L, "isdst", stm->tm_isdst);
  }
  else {
    char cc[4];
    luaL_Buffer b;
    cc[0] = '%';
    luaL_buffinit(L, &b);
    while (*s) {
      if (*s != '%')  /* no conversion specifier? */
        luaL_addchar(&b, *s++);
      else {
        size_t reslen;
        char buff[200];  /* should be big enough for any conversion result */
        s = checkoption(L, s + 1, cc);
        reslen = strftime(buff, sizeof(buff), cc, stm);
        luaL_addlstring(&b, buff, reslen);
      }
    }
    luaL_pushresult(&b);
  }
  return 1;
}

static int os_time(lua_State *L) {
  time_t t;
  if (lua_isnoneornil(L, 1)) {  /* called without args? */
    t = time(NULL);  /* get current time */
  } else {
    struct tm ts;
    luaL_checktype(L, 1, LUA_TTABLE);
    lua_settop(L, 1);  /* make sure table is at the top */
    ts.tm_sec = getfield(L, "sec", 0);
    ts.tm_min = getfield(L, "min", 0);
    ts.tm_hour = getfield(L, "hour", 12);
    ts.tm_mday = getfield(L, "day", -1);
    ts.tm_mon = getfield(L, "month", -1) - 1;
    ts.tm_year = getfield(L, "year", -1) - 1900;
    ts.tm_isdst = getboolfield(L, "isdst");
    t = mktime(&ts);
  }
  if (t == (time_t)(-1))
    lua_pushnil(L);
  else
    lua_pushnumber(L, (lua_Number)t);
  return 1;
}

static int os_difftime(lua_State *L) {
  lua_pushnumber(L, difftime((time_t)(luaL_checknumber(L, 1)),
           (time_t)(luaL_optnumber(L, 2, (lua_Number)0))));
  return 1;
}

static const luaL_Reg libluaos[] = {
  {"clock", os_clock},
  {"time", os_time},
  {"difftime", os_difftime},
  {"date", os_date},

  {NULL, NULL}
};

int
luaopen_luaos(lua_State *L) {
//  luaL_checkversion(L);
  luaL_register(L, "perf", libluaos);
  return 1;
}