libvieter/include/vieter_cron.h

#ifndef VIETER_CRON
#define VIETER_CRON

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

typedef enum vieter_cron_parse_error {
  vieter_cron_parse_ok = 0,
  vieter_cron_parse_invalid_expression = 1,
  vieter_cron_parse_invalid_number = 2,
  vieter_cron_parse_out_of_range = 3,
  vieter_cron_parse_too_many_parts = 4,
  vieter_cron_parse_not_enough_parts = 5
} vieter_cron_parse_error;

typedef struct vieter_cron_expression {
  uint8_t *minutes;
  uint8_t *hours;
  uint8_t *days;
  uint8_t *months;
  uint8_t minute_count;
  uint8_t hour_count;
  uint8_t day_count;
  uint8_t month_count;
} vieter_cron_expression;

typedef struct vieter_cron_simple_time {
  int year;
  int month;
  int day;
  int hour;
  int minute;
} vieter_cron_simple_time;

/*
 * Allocate and initialize a new empty cron expression.
 */
vieter_cron_expression *vieter_cron_expr_init();

/*
 * Deallocate a cron expression.
 */
void vieter_cron_expr_free(vieter_cron_expression *ce);

/*
 * Given a cron expression and a reference time, calculate the next time after
 * the reference time that this expression matches.
 */
void vieter_cron_expr_next(vieter_cron_simple_time *out,
                           vieter_cron_expression *ce,
                           vieter_cron_simple_time *ref);

/*
 * Convencience wrapper around vieter_cron_expr_next that uses the current time
 * as the reference time.
 */
void vieter_cron_expr_next_from_now(vieter_cron_simple_time *out,
                                    vieter_cron_expression *ce);

/*
 * Try to parse a string into a cron expression. Note that the cron expression
 * is updated in-place, meaning it can contain invalid information if the
 * function returns an error. The cron expression should only be used if the
 * function succeeded.
 */
vieter_cron_parse_error vieter_cron_expr_parse(vieter_cron_expression *out,
                                               const char *expression);

#endif