Cocktail

Cocktail is an Elixir date recurrence library based on iCalendar events. Its primary use case currently is to expand schedules with recurrence rules into streams of occurrences. For example: say you wanted to represent a repeating schedule of events that occurred every other week, on Mondays, Wednesdays and Fridays, at 10am and 4pm.

iex> schedule = Cocktail.Schedule.new(~N[2017-01-02 10:00:00])
...> schedule = Cocktail.Schedule.add_recurrence_rule(schedule, :weekly, interval: 2, days: [:monday, :wednesday, :friday], hours: [10, 16])
#Cocktail.Schedule<Every 2 weeks on Mondays, Wednesdays and Fridays on the 10th and 16th hours of the day>

Then to get a list of the first 10 occurrences of this schedule, you would do:

...> stream = Cocktail.Schedule.occurrences(schedule)
...> Enum.take(stream, 10)
[~N[2017-01-02 10:00:00], ~N[2017-01-02 16:00:00], ~N[2017-01-04 10:00:00],
 ~N[2017-01-04 16:00:00], ~N[2017-01-06 10:00:00], ~N[2017-01-06 16:00:00],
 ~N[2017-01-16 10:00:00], ~N[2017-01-16 16:00:00], ~N[2017-01-18 10:00:00],
 ~N[2017-01-18 16:00:00]]

Installation

Cocktail is available in Hex and can be installed by adding cocktail to your list of dependencies in mix.exs:

def deps do
  [
    {:cocktail, "~> 0.10"}
  ]
end

Documentation

Detailed documentation with all available options can be found at https://hexdocs.pm/cocktail.

Quick-start Guide

Schedules

Everything starts with a Cocktail.Schedule; create one like this:

iex> schedule = Cocktail.schedule(start_time, opts)
#Cocktail.Schedule<>

# or
...> schedule = Cocktail.Schedule.new(start_time, opts)
#Cocktail.Schedule<>

• start_time - Either a DateTime or a NaiveDateTime representing the beginning of your schedule.
• opts:
  • duration - (optional) How long each occurrence is, in seconds.

Recurrence Rules

Schedules are pretty useless on their own. To have them do something useful, you add recurrence rules to them. Currently, Cocktail supports:

• Monthly
• Weekly
• Daily
• Hourly
• Minutely
• Secondly

On top of these basic recurrence frequencies, you can add various options. Let's see some examples:

iex> every_other_day = Cocktail.Schedule.add_recurrence_rule(schedule, :daily, interval: 2)
#Cocktail.Schedule<Every 2 days>

...> weekly_on_mo_we_fr = Cocktail.Schedule.add_recurrence_rule(schedule, :weekly, days: [:monday, :wednesday, :friday])
#Cocktail.Schedule<Weekly on Mondays, Wednesdays and Fridays>

...> daily_at_9am_and_5pm = Cocktail.Schedule.add_recurrence_rule(schedule, :daily, hours: [9, 17])
#Cocktail.Schedule<Daily on the 9th and 17th hours of the day>

For more details about frequencies and options, see Cocktail.Schedule.add_recurrence_rule/3

Occurrences

Once you've got a schedule set up the way you want, you can generate a stream of occurrences that match the schedule like so:

iex> occurrences = Cocktail.Schedule.occurrences(schedule)
#Function<60.51599720/2 in Stream.unfold/2>
...> Enum.take(occurrences, 3)
[~N[2017-01-01 00:00:00], ~N[2017-01-02 00:00:00], ~N[2017-01-03 00:00:00]]

The type of each occurrence depends on what start time type you used, and wether or not you supplied a duration when creating the schedule.

Duration

If you add the duration option when creating a schedule, you'll get Cocktail.Span structs as occurrences, with :from and :until fields of the same type as your start time.

iex> schedule = Cocktail.schedule(~N[2017-01-01 00:00:00], duration: 3600) |> Cocktail.Schedule.add_recurrence_rule(:daily)
#Cocktail.Schedule<Daily>
...> occurrences = Cocktail.Schedule.occurrences(schedule)
#Function<60.51599720/2 in Stream.unfold/2>
...> Enum.take(occurrences, 3)
[%Cocktail.Span{from: ~N[2017-01-01 00:00:00], until: ~N[2017-01-01 01:00:00]},
 %Cocktail.Span{from: ~N[2017-01-02 00:00:00], until: ~N[2017-01-02 01:00:00]},
 %Cocktail.Span{from: ~N[2017-01-03 00:00:00], until: ~N[2017-01-03 01:00:00]}]

Recurrence Times and Exception Times

You can also add one-off recurrence times that don't fit into a normal recurrence pattern, and exception times if you want to exclude a time that would normally be included because of a recurrence rule:

iex> schedule = Cocktail.schedule(~N[2017-01-01 08:00:00]) |> Cocktail.Schedule.add_recurrence_rule(:daily)
#Cocktail.Schedule<Daily>
...> schedule = [~N[2017-01-01 09:00:00], ~N[2017-01-02 11:00:00], ~N[2017-01-03 17:00:00]] |> Enum.reduce(schedule, &Cocktail.Schedule.add_recurrence_time(&2, &1))
#Cocktail.Schedule<Daily>
...> schedule = Cocktail.Schedule.add_exception_time(schedule, ~N[2017-01-02 08:00:00])
#Cocktail.Schedule<Daily>
...> Cocktail.Schedule.occurrences(schedule) |> Enum.take(6)
[~N[2017-01-01 08:00:00], ~N[2017-01-01 09:00:00], ~N[2017-01-02 11:00:00],
 ~N[2017-01-03 08:00:00], ~N[2017-01-03 17:00:00], ~N[2017-01-04 08:00:00]]

iCalendar

You can convert schedules to and from the iCalendar format like this:

iex> i_calendar = Cocktail.Schedule.to_i_calendar(schedule)
"DTSTART:20170101T000000\nRRULE:FREQ=DAILY"

...> Cocktail.Schedule.from_i_calendar(i_calendar)
{:ok, #Cocktail.Schedule<Daily>}

Roadmap

• investigate and fix DST bugs when using zoned DateTime
• support all iCalendar RRULE options
• support week-start option
• support iCalendar EXRULE
• convert to/from JSON representation

Credits

Cocktail is heavily inspired by and based on a very similar Ruby library, ice_cube.

License

MIT