Getting Started

Usecases

Tempus library provides an easy way to handle and manipulate time slots.

TYime slot is the base concept behind the library. It is basically the struct, containing from and to instances of DateTime. One might provide the list of slots, as Enum or as a Stream, and check whether another time slot and/or DateTime instance is overlapped or disjoined. Also one might get the next “available” slot(s) providing an origin, as well as next busy slot(s).

It might be used e. g. to calculate the working days between now and some day in the future, providing the list of holidays, and the stream of weekends.

Initializing Slots

Tempus.Slots module leverages AVLTree. It exposes add/2, merge/2 and inverse/2 functions to add slots, merge the slots with another slot(s) and/or Stream, and inverse the slots respecively. Typically one starts with something like

slots = [
  Tempus.Slot.wrap(~D|2020-08-07|),
  Tempus.Slot.wrap(~D|2020-08-10|),
  %Tempus.Slot{
      from: ~U|2020-08-07 01:00:00Z|, to: ~U|2020-08-08 01:00:00Z|}
] |> Enum.into(%Tempus.Slots{})

When updated, Tempus.Slots joins the newly added slot(s) into the set of existing ones, so thet at any moment there is no overlapped slots. This happens when new slot is added with Tempus.Slots.add/2 and when the enumerable is collected.

Consuming Streams

Tempus.Slots is optimized for reads, that’s why internally it keeps slots as an Enum. It only allows to merge Stream into the existing Tempus.Slots and the stream will be terminated within the range of the Enum already presented. Below is the example of consuming the stream.

holidays = [~D|2020-08-06|, ~D|2020-08-13|]
weekends = Stream.map([~D|2020-08-08|, ~D|2020-08-20|], & &1)
schedule = holidays |> Enum.into(%Slots{}) |> Slots.merge(weekends)

#⇒ #Slots<[
#    #Slot<[
#      from: ~U[2020-08-06 00:00:00.000000Z],
#      to: ~U[2020-08-06 23:59:59.999999Z]
#    ]>,
#    #Slot<[
#      from: ~U[2020-08-08 00:00:00.000000Z],
#      to: ~U[2020-08-08 23:59:59.999999Z]
#    ]>,
#    #Slot<[
#      from: ~U[2020-08-13 00:00:00.000000Z],
#      to: ~U[2020-08-13 23:59:59.999999Z]
#    ]>
#  ]>

Checking State

With a help of Tempus.next_busy/2 and Tempus.next_free/2, one might get the next busy and/or free slot(s). To calculate the first free slot in 5 business days after 2020-08-05, the following is to be done.

holidays = [~D|2020-08-07|, ~D|2020-08-13|] # ...
weekends = [~D|2020-08-08|, ~D|2020-08-09|] # ...

holidays
|> Enum.into(%Slots{})
|> Tempus.Slots.merge(weekends)
|> Tempus.days_ahead(~D|2020-08-05|, 5)
|> hd()
#⇒ "2020-08-14"