/* Copyright (C) 2008  Emmanuel Varoquaux

   This file is part of XOS.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

#include "time.h"

#include <stdio.h>

struct output_struct {
  char *s;
  size_t max;
};

static const char *abbr_weekday_name[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
static const char *full_weekday_name[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
static const char *abbr_month_name[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
static const char *full_month_name[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

static void output_init(struct output_struct *output, char *s, size_t max)
{
  output->s = s;
  output->max = max;
}

static int output_add(struct output_struct *output, char c)
{
  if (!output->max)
    return 0;
  *output->s++ = c;
  output->max--;
  return 1;
}

static int output_adds(struct output_struct *output, const char *s)
{
  while (*s) {
    if (!output->max)
      return 0;
    *output->s++ = *s;
    output->max--;
    s++;
  }
  return 1;
}

size_t __attribute__ ((weak, visibility ("default"))) strftime(char *s, size_t max, const char *format, const struct tm *tm)
{
  struct output_struct output;
  int state;
  char modifier;
  char c;
  char buf[256];

  __tzset();
  output_init(&output, s, max);
  state = 0;
  modifier = 0;
  do {
    c = *format++;
    switch (state) {
    case 0:
      if (c == '%') {
        state = 1;
        modifier = 0;
        continue;
      }
      if (!output_add(&output, c))
        return 0;
      continue;
    case 1:
      if (c == 'E' || c == '0') {
        modifier = c;
        state = 2;
        continue;
      }
    case 2:
      switch (c) {
      case 'a':
        if (!output_adds(&output, abbr_weekday_name[tm->tm_wday]))
          return 0;
        break;
      case 'A':
        if (!output_adds(&output, full_weekday_name[tm->tm_wday]))
          return 0;
        break;
      case 'b':
        if (!output_adds(&output, abbr_month_name[tm->tm_mon]))
          return 0;
        break;
      case 'B':
        if (!output_adds(&output, full_month_name[tm->tm_mon]))
          return 0;
        break;
      case 'c':
        sprintf(buf, "%s %s %2d %02d:%02d:%02d %d", abbr_weekday_name[tm->tm_wday], abbr_month_name[tm->tm_mon], tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec, 1900 + tm->tm_year);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'C':
        sprintf(buf, "%02d", (1900 + tm->tm_year) / 100);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'd':
        sprintf(buf, "%02d", tm->tm_mday);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'D':
        sprintf(buf, "%02d/%02d/%02d", 1 + tm->tm_mon, tm->tm_mday, tm->tm_year % 100);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'e':
        sprintf(buf, "%2d", tm->tm_mday);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'F':
        sprintf(buf, "%d-%02d-%02d", 1900 + tm->tm_year, 1 + tm->tm_mon, tm->tm_mday);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'h':
        if (!output_adds(&output, abbr_month_name[tm->tm_mon]))
          return 0;
        break;
      case 'H':
        sprintf(buf, "%02d", tm->tm_hour);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'I':
        sprintf(buf, "%02d", ((tm->tm_hour + 11) % 12) + 1);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'j':
        sprintf(buf, "%03d", 1 + tm->tm_yday);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'm':
        sprintf(buf, "%02d", 1 + tm->tm_mon);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'M':
        sprintf(buf, "%02d", tm->tm_min);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'n':
        if (!output_add(&output, '\n'))
          return 0;
        break;
      case 'p':
        if (!output_adds(&output, tm->tm_hour < 12 ? "AM" : "PM"))
          return 0;
        break;
      case 'r':
        sprintf(buf, "%02d:%02d:%02d %s", ((tm->tm_hour + 11) % 12) + 1, tm->tm_min, tm->tm_sec, tm->tm_hour < 12 ? "AM" : "PM");
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'R':
        sprintf(buf, "%02d:%02d", tm->tm_hour, tm->tm_min);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'S':
        sprintf(buf, "%02d", tm->tm_sec);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 't':
        if (!output_add(&output, '\t'))
          return 0;
        break;
      case 'T':
        sprintf(buf, "%02d:%02d:%02d", tm->tm_hour, tm->tm_min, tm->tm_sec);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'u':
        sprintf(buf, "%d", (tm->tm_wday + 6) % 7 + 1);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'w':
        sprintf(buf, "%d", tm->tm_wday);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'x':
        sprintf(buf, "%02d/%02d/%02d", 1 + tm->tm_mon, tm->tm_mday, tm->tm_year % 100);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'X':
        sprintf(buf, "%02d:%02d:%02d", tm->tm_hour, tm->tm_min, tm->tm_sec);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'y':
        sprintf(buf, "%02d", tm->tm_year % 100);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'Y':
        sprintf(buf, "%d", 1900 + tm->tm_year);
        if (!output_adds(&output, buf))
          return 0;
        break;
      case 'z':
        if (tm->tm_isdst >= 0) {
          sprintf(buf, "%+.4ld", -(tm->tm_isdst ? __current_tz->dst->offset : __current_tz->offset) / 36);
          if (!output_adds(&output, buf))
            return 0;
        }
        break;
      case 'Z':
        if (tm->tm_isdst >= 0)
          if (!output_adds(&output, tm->tm_isdst ? __current_tz->dst->name : __current_tz->name))
            return 0;
        break;
      case '%':
        if (!output_add(&output, '%'))
          return 0;
        break;
      default:
        if (!output_add(&output, '%'))
          return 0;
        if (modifier)
          if (!output_add(&output, modifier))
            return 0;
        if (!output_add(&output, c))
          return 0;
      }
      state = 0;
      continue;
    }
  }
  while (c);
  return max - output.max - 1;
}