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//! Library for parsing cron expressions with timezone support.
//!
//! Example:
//! ```
//! use chrono::{TimeZone, Utc};
//! use chrono_tz::Europe::Lisbon;
//! use cron_parser::parse;
//!
//! if let Ok(next) = parse("*/5 * * * *", &Utc::now()) {
//! println!("when: {}", next);
//! }
//!
//! // passing a custom timestamp
//! if let Ok(next) = parse("0 0 29 2 *", &Utc.timestamp_opt(1893456000, 0).unwrap()) {
//! println!("next leap year: {}", next);
//! assert_eq!(next.timestamp(), 1961625600);
//! }
//!
//! assert!(parse("2-3,9,*/15,1-8,11,9,4,5 * * * *", &Utc::now()).is_ok());
//! assert!(parse("* * * * */Fri", &Utc::now()).is_err());
//!
//! // use custom timezone
//! assert!(parse("*/5 * * * *", &Utc::now().with_timezone(&Lisbon)).is_ok());
//! ```
use chrono::{DateTime, Datelike, Duration, TimeZone, Timelike, Utc};
use std::{collections::BTreeSet, error::Error, fmt, num, str::FromStr};
#[derive(Debug)]
pub enum ParseError {
InvalidCron,
InvalidRange,
InvalidValue,
ParseIntError(num::ParseIntError),
TryFromIntError(num::TryFromIntError),
}
enum Dow {
Sun = 0,
Mon = 1,
Tue = 2,
Wed = 3,
Thu = 4,
Fri = 5,
Sat = 6,
}
impl FromStr for Dow {
type Err = ();
fn from_str(s: &str) -> Result<Self, Self::Err> {
match &*s.to_uppercase() {
"SUN" => Ok(Self::Sun),
"MON" => Ok(Self::Mon),
"TUE" => Ok(Self::Tue),
"WED" => Ok(Self::Wed),
"THU" => Ok(Self::Thu),
"FRI" => Ok(Self::Fri),
"SAT" => Ok(Self::Sat),
_ => Err(()),
}
}
}
impl fmt::Display for ParseError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
Self::InvalidCron => write!(f, "invalid cron"),
Self::InvalidRange => write!(f, "invalid input"),
Self::InvalidValue => write!(f, "invalid value"),
Self::ParseIntError(ref err) => err.fmt(f),
Self::TryFromIntError(ref err) => err.fmt(f),
}
}
}
impl Error for ParseError {}
impl From<num::ParseIntError> for ParseError {
#[must_use]
fn from(err: num::ParseIntError) -> Self {
Self::ParseIntError(err)
}
}
impl From<num::TryFromIntError> for ParseError {
#[must_use]
fn from(err: num::TryFromIntError) -> Self {
Self::TryFromIntError(err)
}
}
/// Parse cron expression
/// ```text
///
/// ┌───────────────────── minute (0 - 59)
/// │ ┌─────────────────── hour (0 - 23)
/// │ │ ┌───────────────── dom (1 - 31) day of month
/// │ │ │ ┌─────────────── month (1 - 12)
/// │ │ │ │ ┌───────────── dow (0 - 6 or Sun - Sat) day of week (Sunday to Saturday)
/// │ │ │ │ │
/// │ │ │ │ │
/// │ │ │ │ │
/// * * * * * <command to execute>
/// ```
///
/// Example
/// ```
/// use cron_parser::parse;
/// use chrono::Utc;
///
/// assert!(parse("*/5 * * * *", &Utc::now()).is_ok());
///
/// // use custom timezone
/// use chrono_tz::US::Pacific;
/// assert!(parse("*/5 * * * *", &Utc::now().with_timezone(&Pacific)).is_ok());
/// ```
/// # Errors
/// [`ParseError`](enum.ParseError.html)
pub fn parse<TZ: TimeZone>(cron: &str, dt: &DateTime<TZ>) -> Result<DateTime<TZ>, ParseError> {
let tz = dt.timezone();
// TODO handle unwrap
let mut next = Utc.from_local_datetime(&dt.naive_local()).unwrap() + Duration::minutes(1);
let fields: Vec<&str> = cron.split_whitespace().collect();
if fields.len() != 5 {
return Err(ParseError::InvalidCron);
}
next = Utc
.with_ymd_and_hms(
next.year(),
next.month(),
next.day(),
next.hour(),
next.minute(),
0,
)
.unwrap();
let result = loop {
// only try until next leap year
if next.year() - dt.year() > 4 {
return Err(ParseError::InvalidCron);
}
// * * * <month> *
let month = parse_field(fields[3], 1, 12)?;
if !month.contains(&next.month()) {
if next.month() == 12 {
next = Utc
.with_ymd_and_hms(next.year() + 1, 1, 1, 0, 0, 0)
.unwrap();
} else {
next = Utc
.with_ymd_and_hms(next.year(), next.month() + 1, 1, 0, 0, 0)
.unwrap();
}
continue;
}
// * * <dom> * *
let do_m = parse_field(fields[2], 1, 31)?;
if !do_m.contains(&next.day()) {
next += Duration::days(1);
next = Utc
.with_ymd_and_hms(next.year(), next.month(), next.day(), 0, 0, 0)
.unwrap();
continue;
}
// * <hour> * * *
let hour = parse_field(fields[1], 0, 23)?;
if !hour.contains(&next.hour()) {
next += Duration::hours(1);
next = Utc
.with_ymd_and_hms(next.year(), next.month(), next.day(), next.hour(), 0, 0)
.unwrap();
continue;
}
// <minute> * * * *
let minute = parse_field(fields[0], 0, 59)?;
if !minute.contains(&next.minute()) {
next += Duration::minutes(1);
continue;
}
// * * * * <dow>
let do_w = parse_field(fields[4], 0, 6)?;
if !do_w.contains(&next.weekday().num_days_from_sunday()) {
next += Duration::days(1);
continue;
}
// Valid datetime for the timezone
if let Some(dt) = tz.from_local_datetime(&next.naive_local()).latest() {
break dt;
}
next += Duration::minutes(1);
};
Ok(result)
}
/// `parse_field`
/// Allowed special characters:
/// * `*` any value
/// * `,` value list separator
/// * `-` range of values
/// * `/` step values
///
/// ```text
/// minutes min: 0, max: 59
/// hours min: 0, max: 23
/// days min: 1, max: 31
/// month min: 1, max: 12
/// dow min: 0, max: 6 or min: Sun, max Sat
///
/// Day of week (dow):
/// Sun = 0
/// Mon = 1
/// Tue = 2
/// Wed = 3
/// Thu = 4
/// Fri = 5
/// Sat = 6
/// ```
///
/// The field column can have a `*` or a list of elements separated by commas.
/// An element is either a number in the ranges or two numbers in the range
/// separated by a hyphen, slashes can be combined with ranges to specify
/// step values
///
/// Example
/// ```
/// use cron_parser::parse_field;
/// use std::collections::BTreeSet;
///
/// // every 3 months
/// assert_eq!(parse_field("*/3", 1, 12).unwrap(),
/// BTreeSet::<u32>::from([1,4,7,10].iter().cloned().collect::<BTreeSet<u32>>()));
///
/// // day 31
/// assert_eq!(parse_field("31", 1, 31).unwrap(),
/// BTreeSet::<u32>::from([31].iter().cloned().collect::<BTreeSet<u32>>()));
///
/// // every minute from 40 through 50
/// assert_eq!(parse_field("40-50", 0, 59).unwrap(),
/// BTreeSet::<u32>::from([40,41,42,43,44,45,46,47,48,49,50].iter().cloned().collect::<BTreeSet<u32>>()));
///
/// // at hour 3,15,23
/// assert_eq!(parse_field("15,3,23", 0, 23).unwrap(),
/// BTreeSet::<u32>::from([3,15,23].iter().cloned().collect::<BTreeSet<u32>>()));
/// ```
/// # Errors
/// [`ParseError`](enum.ParseError.html)
pub fn parse_field(field: &str, min: u32, max: u32) -> Result<BTreeSet<u32>, ParseError> {
// set of integers
let mut values = BTreeSet::<u32>::new();
// split fields by ','
let fields: Vec<&str> = field.split(',').filter(|s| !s.is_empty()).collect();
// iterate over the fields and match against allowed characters
for field in fields {
match field {
// any
"*" => {
for i in min..=max {
values.insert(i);
}
}
// step values
f if field.starts_with("*/") => {
let f: u32 = f.trim_start_matches("*/").parse()?;
if f > max {
return Err(ParseError::InvalidValue);
}
for i in (min..=max).step_by(f as usize) {
values.insert(i);
}
}
// range of values, it can have days of week like Wed-Fri
f if f.contains('-') => {
let tmp_fields: Vec<&str> = f.split('-').collect();
if tmp_fields.len() != 2 {
return Err(ParseError::InvalidRange);
}
let mut fields: Vec<u32> = Vec::new();
if let Ok(dow) = Dow::from_str(tmp_fields[0]) {
fields.push(dow as u32);
} else {
fields.push(tmp_fields[0].parse::<u32>()?);
};
if let Ok(dow) = Dow::from_str(tmp_fields[1]) {
fields.push(dow as u32);
} else {
fields.push(tmp_fields[1].parse::<u32>()?);
}
if fields[0] > fields[1] || fields[1] > max {
return Err(ParseError::InvalidRange);
}
for i in fields[0]..=fields[1] {
values.insert(i);
}
}
// integers or days of week any other will return an error
_ => {
if let Ok(dow) = Dow::from_str(field) {
values.insert(dow as u32);
} else {
let f = field.parse::<u32>()?;
if f > max {
return Err(ParseError::InvalidValue);
}
values.insert(f);
}
}
}
}
Ok(values)
}