sundial

Sundial

Sundial is a library written in pure Rust which partially implements the iCalendar spec to support parsing of RRules.

Current high level features to be supported in this project

• Ability to parse an RRule to a json representation

• Ability to extract an RRule implementation from a given json

• Ability to generate next iteration/iterations given an RRule string

RFC5545 spec features supported

Since the library is designed purely to support the RRules section of the spec at the moment, features will be added iteratively for each type of RRule support (note: all frequency types fully support: COUNT, INTERVAL, DTSTART and UNTIL):

Timezones support is provided via chrono_tz and all supported timezones in chrono-tz are supported out of the box. At the moment this library does not support custom timezones.

Usage:

The packages compiles to a native binary and can be run simply as a simple sys call.

To view help:

./sundial -h

To parse and get the iter dates from an rrule string:

./sundial --rrule 'Enter your rrule string here'

example, running the following:

./sundial 'FREQ=WEEKLY;INTERVAL=2;COUNT=12;BYHOUR=0;BYMINUTE=0;DTSTART=20190101T030000'

gives the results:

[
  "2019-01-15T00:00:00+00:00",
  "2019-01-29T00:00:00+00:00",
  "2019-02-12T00:00:00+00:00",
  "2019-02-26T00:00:00+00:00",
  "2019-03-12T00:00:00+00:00",
  "2019-03-26T00:00:00+00:00",
  "2019-04-09T00:00:00+00:00",
  "2019-04-23T00:00:00+00:00",
  "2019-05-07T00:00:00+00:00",
  "2019-05-21T00:00:00+00:00",
  "2019-06-04T00:00:00+00:00",
  "2019-06-18T00:00:00+00:00"
]

We also support specifying count and until as OPTIONAL command line arguments (please not these will override COUNT and UNTIL parts of the provided rrule string if it contains any):

./sundial --rrule <rrule_string> -ct 25 -ul 20220123T030000

OR

./sundial --rrule <rrule_string> --count 25 --until 20220123T030000

This will give you the results of the rrule string intervals bounded by the count value of 25 or until 23/12/2022 3 am UTC, whichever comes first.

Note that we currently only support parsing the until value argument as UTC date.

Using Date Cutoffs

Sundial supports specifying the fact that the given rrule string might not have an updated DTSTART part and that we would like to have the dates from using current date as the cutoff date.

This can be done by adding the optional --cutoff cli parameter.

To illustrate,

if we run 15th April 2019 at midnight:

./sundial FREQ=WEEKLY;INTERVAL=1;COUNT=3;BYDAY=TU;BYHOUR=23;BYMINUTE=54;BYSECOND=0;TZID=Australia/Melbourne;DTSTART=20180110T034500

without specifying the cutoff parameter, sundial will assume the DTSTART (10th January 2019) as the date to start sending results from, giving us:

["2018-01-16T23:54:00+11:00", "2018-01-23T23:54:00+11:00", "2018-01-30T23:54:00+11:00"]

however, if we specify the cutoff parameter,

./sundial FREQ=WEEKLY;INTERVAL=1;COUNT=3;BYDAY=TU;BYHOUR=23;BYMINUTE=54;BYSECOND=0;TZID=Australia/Melbourne;DTSTART=20180110T034500 --cutoff

sundial will keep on calculating until we start off on a date that is greater than or equal to current run date (in this case 15th April 2019 at midnight) and send a count of dates starting from that date, resulting in:

["2019-04-16T23:54:00+10:00", "2019-04-23T23:54:00+10:00", "2019-04-30T23:54:00+10:00"]

Running tests

To run the full test suite:

$ cargo test --all

from the repository root.

Useful Resources

• RRule Demo