/*

 * Copyright 2023 GNOME Foundation Inc.

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Authors:

 *  - Philip Withnall <pwithnall@gnome.org>

 */

#include "glib.h"

#include "gdatetime-private.h"

/**

 * _g_era_date_compare:

 * @date1: first date

 * @date2: second date

 *

 * Compare two #GEraDates for ordering, taking into account negative and

 * positive infinity.

 *

 * Returns: strcmp()-style integer, `<0` indicates `date1 < date2`, `0`

 *   indicates `date1 == date2`, `>0` indicates `date1 > date2`

 * Since: 2.80

 */

int

_g_era_date_compare (const GEraDate *date1,

                     const GEraDate *date2)

{

  if (date1->type == G_ERA_DATE_SET &&

      date2->type == G_ERA_DATE_SET)

    {

      if (date1->year != date2->year)

        return date1->year - date2->year;

      if (date1->month != date2->month)

        return date1->month - date2->month;

      return date1->day - date2->day;

    }

  if (date1->type == date2->type)

    return 0;

  if (date1->type == G_ERA_DATE_MINUS_INFINITY || date2->type == G_ERA_DATE_PLUS_INFINITY)

    return -1;

  if (date1->type == G_ERA_DATE_PLUS_INFINITY || date2->type == G_ERA_DATE_MINUS_INFINITY)

    return 1;

  g_assert_not_reached ();

}

static gboolean

parse_era_date (const char *str,

                const char *endptr,

                GEraDate   *out_date)

{

  const char *str_endptr = NULL;

  int year_multiplier;

  guint64 year, month, day;

  year_multiplier = (str[0] == '-') ? -1 : 1;

  if (str[0] == '-' || str[0] == '+')

    str++;

  year = g_ascii_strtoull (str, (gchar **) &str_endptr, 10);

  g_assert (str_endptr <= endptr);

  if (str_endptr == endptr || *str_endptr != '/' || year > G_MAXINT)

    return FALSE;

  str = str_endptr + 1;

  month = g_ascii_strtoull (str, (gchar **) &str_endptr, 10);

  g_assert (str_endptr <= endptr);

  if (str_endptr == endptr || *str_endptr != '/' || month < 1 || month > 12)

    return FALSE;

  str = str_endptr + 1;

  day = g_ascii_strtoull (str, (gchar **) &str_endptr, 10);

  g_assert (str_endptr <= endptr);

  if (str_endptr != endptr || day < 1 || day > 31)

    return FALSE;

  /* Success */

  out_date->type = G_ERA_DATE_SET;

  out_date->year = year_multiplier * year;

  out_date->month = month;

  out_date->day = day;

  return TRUE;

}

/**

 * _g_era_description_segment_ref:

 * @segment: a #GEraDescriptionSegment

 *

 * Increase the ref count of @segment.

 *

 * Returns: (transfer full): @segment

 * Since: 2.80

 */

GEraDescriptionSegment *

_g_era_description_segment_ref (GEraDescriptionSegment *segment)

{

  g_atomic_ref_count_inc (&segment->ref_count);

  return segment;

}

/**

 * _g_era_description_segment_unref:

 * @segment: (transfer full): a #GEraDescriptionSegment to unref

 *

 * Decreases the ref count of @segment.

 *

 * Since: 2.80

 */

void

_g_era_description_segment_unref (GEraDescriptionSegment *segment)

{

  if (g_atomic_ref_count_dec (&segment->ref_count))

    {

      g_free (segment->era_format);

      g_free (segment->era_name);

      g_free (segment);

    }

}

/**

 * _g_era_description_parse:

 * @desc: an `ERA` description string from `nl_langinfo()`

 *

 * Parse an ERA description string. See [`nl_langinfo(3)`](man:nl_langinfo(3)).

 *

 * Example description string for th_TH.UTF-8:

 * ```

 * +:1:-543/01/01:+*:พ.ศ.:%EC %Ey

 * ```

 *

 * @desc must be in UTF-8, so all conversion from the locale encoding must

 * happen before this function is called. The resulting `era_name` and

 * `era_format` in the returned segments will be in UTF-8.

 *

 * Returns: (transfer full) (nullable) (element-type GEraDescriptionSegment):

 *   array of one or more parsed era segments, or %NULL if parsing failed

 * Since: 2.80

 */

GPtrArray *

_g_era_description_parse (const char *desc)

{

  GPtrArray *segments = g_ptr_array_new_with_free_func ((GDestroyNotify) _g_era_description_segment_unref);

  for (const char *p = desc; *p != '\0';)

    {

      const char *next_colon, *endptr = NULL;

      GEraDescriptionSegment *segment = NULL;

      char direction;

      guint64 offset;

      GEraDate start_date, end_date;

      char *era_name = NULL, *era_format = NULL;

      /* direction */

      direction = *p++;

      if (direction != '+' && direction != '-')

        goto error;

      if (*p++ != ':')

        goto error;

      /* offset */

      next_colon = strchr (p, ':');

      if (next_colon == NULL)

        goto error;

      offset = g_ascii_strtoull (p, (gchar **) &endptr, 10);

      if (endptr != next_colon)

        goto error;

      p = next_colon + 1;

      /* start_date */

      next_colon = strchr (p, ':');

      if (next_colon == NULL)

        goto error;

      if (!parse_era_date (p, next_colon, &start_date))

        goto error;

      p = next_colon + 1;

      /* end_date */

      next_colon = strchr (p, ':');

      if (next_colon == NULL)

        goto error;

      if (strncmp (p, "-*", 2) == 0)

        end_date.type = G_ERA_DATE_MINUS_INFINITY;

      else if (strncmp (p, "+*", 2) == 0)

        end_date.type = G_ERA_DATE_PLUS_INFINITY;

      else if (!parse_era_date (p, next_colon, &end_date))

        goto error;

      p = next_colon + 1;

      /* era_name */

      next_colon = strchr (p, ':');

      if (next_colon == NULL)

        goto error;

      if (next_colon - p == 0)

        goto error;

      era_name = g_strndup (p, next_colon - p);

      p = next_colon + 1;

      /* era_format; either the final field in the segment (followed by a

       * semicolon) or the description (followed by nul) */

      next_colon = strchr (p, ';');

      if (next_colon == NULL)

        next_colon = p + strlen (p);

      if (next_colon - p == 0)

        {

          g_free (era_name);

          goto error;

        }

      era_format = g_strndup (p, next_colon - p);

      if (*next_colon == ';')

        p = next_colon + 1;

      else

        p = next_colon;

      /* Successfully parsed that segment. */

      segment = g_new0 (GEraDescriptionSegment, 1);

      g_atomic_ref_count_init (&segment->ref_count);

      segment->offset = offset;

      segment->start_date = start_date;

      segment->end_date = end_date;

      segment->direction_multiplier =

          ((_g_era_date_compare (&segment->start_date, &segment->end_date) <= 0) ? 1 : -1) *

          ((direction == '-') ? -1 : 1);

      segment->era_name = g_steal_pointer (&era_name);

      segment->era_format = g_steal_pointer (&era_format);

      g_ptr_array_add (segments, g_steal_pointer (&segment));

    }

  return g_steal_pointer (&segments);

error:

  g_ptr_array_unref (segments);

  return NULL;

}