/*
  Copyright 2019-2021 David Robillard <d@drobilla.net>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include "read_utils.h"
#include "string_utils.h"
#include "time_utils.h"
#include "timezone.h"
#include "write_utils.h"

#include "exess/exess.h"

#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

ExessResult
read_nanoseconds(uint32_t* const out, const char* const str)
{
  size_t i               = 0;
  char   frac_digits[10] = {'0', '0', '0', '0', '0', '0', '0', '0', '0', 0};
  for (unsigned j = 0u; j < 9u && is_digit(str[i]); ++j) {
    frac_digits[j] = str[i++];
  }

  return result(exess_read_uint(out, frac_digits).status, i);
}

ExessResult
exess_read_time(ExessTime* const out, const char* const str)
{
  memset(out, 0, sizeof(*out));

  // Read hour
  size_t      i = skip_whitespace(str);
  ExessResult r = read_two_digit_number(&out->hour, 0, 24, str + i);
  if (r.status) {
    return result(r.status, i + r.count);
  }

  // Read hour-minute delimiter
  i += r.count;
  if (str[i] != ':') {
    return result(EXESS_EXPECTED_COLON, i);
  }

  // Read minute
  ++i;
  r = read_two_digit_number(&out->minute, 0, 59, str + i);
  if (r.status) {
    return result(r.status, i + r.count);
  }

  // Read minute-second delimiter
  i += r.count;
  if (str[i] != ':') {
    return result(EXESS_EXPECTED_COLON, i);
  }

  // Read second
  ++i;
  r = read_two_digit_number(&out->second, 0, 59, str + i);
  i += r.count;
  if (r.status) {
    return result(r.status, i);
  }

  // Read nanoseconds if present
  if (str[i] == '.') {
    ++i;
    r = read_nanoseconds(&out->nanosecond, str + i);
    i += r.count;
  }

  // Read timezone if present
  if (!is_end(str[i])) {
    r = exess_read_timezone(&out->zone, str + i);
    i += r.count;
  } else {
    out->zone.quarter_hours = EXESS_LOCAL;
  }

  return end_read(r.status, str, i);
}

size_t
write_nanoseconds(const uint32_t nanosecond,
                  const size_t   buf_size,
                  char* const    buf,
                  const size_t   i)
{
  assert(nanosecond <= 999999999);

  if (nanosecond == 0) {
    return 0;
  }

  char frac_digits[10] = {'0', '0', '0', '0', '0', '0', '0', '0', '0', 0};

  // Write digits right to left, but replace trailing zeros with null
  uint32_t remaining     = nanosecond;
  uint32_t n_trailing    = 0;
  bool     wrote_nonzero = false;
  for (uint32_t j = 0; remaining > 0; ++j) {
    const char digit = (char)('0' + (remaining % 10));
    if (!wrote_nonzero && digit == '0') {
      frac_digits[8 - j] = '\0';
      ++n_trailing;
    } else {
      frac_digits[8 - j] = digit;
    }

    wrote_nonzero = wrote_nonzero || digit != '0';
    remaining /= 10;
  }

  size_t n = write_char('.', buf_size, buf, i);

  n += write_string(9 - n_trailing, frac_digits, buf_size, buf, i + n);

  return n;
}

ExessResult
write_time(const ExessTime value,
           const size_t    buf_size,
           char* const     buf,
           const size_t    offset)
{
  if (value.hour > 24 || value.minute > 59 || value.second > 59 ||
      value.nanosecond > 999999999 ||
      (value.hour == 24 &&
       (value.minute != 0 || value.second != 0 || value.nanosecond != 0))) {
    return result(EXESS_BAD_VALUE, 0);
  }

  size_t o = offset;

  // Write integral hour, minute, and second
  o += write_two_digit_number(value.hour, buf_size, buf, o);
  o += write_char(':', buf_size, buf, o);
  o += write_two_digit_number(value.minute, buf_size, buf, o);
  o += write_char(':', buf_size, buf, o);
  o += write_two_digit_number(value.second, buf_size, buf, o);
  o += write_nanoseconds(value.nanosecond, buf_size, buf, o);

  const ExessResult r = write_timezone(value.zone, buf_size, buf, o);

  return result(r.status, o - offset + r.count);
}

ExessResult
exess_write_time(const ExessTime value, const size_t buf_size, char* const buf)
{
  const ExessResult r = write_time(value, buf_size, buf, 0);

  return end_write(r.status, buf_size, buf, r.count);
}