@spec formula(ct :: binary() | t()) :: :error | binary()

Produces the single formula out of cron record. Might be useful for some external check that requires the single validation call.

Examples

iex> formula = Tarearbol.Crontab.formula("42 3 28 08 *").formula
...> formula |> String.split(" && ") |> Enum.sort()
["(day == 28)", "(hour == 3)", "(minute == 42)", "(month == 8)", "(rem(day_of_week, 1) == 0)"]

iex> Tarearbol.Crontab.formula("423 * * * *")
{:error, [minute: {:could_not_parse_field, ["423"]}]}

@spec next(dt :: nil | DateTime.t(), input :: binary(), opts :: keyword()) ::
  DateTime.t()

Returns the next DateTime the respective cron record points to with a precision given as the third argument (default: :second.)

If the first parameter is not given, it assumes the next after now.

Examples

iex> dt = DateTime.from_unix!(1567091960)
~U[2019-08-29 15:19:20Z]
iex> Tarearbol.Crontab.next(dt, "42 3 28 08 *")
[
  origin: ~U[2019-08-29 15:19:20Z],
  next: ~U[2020-08-28 03:42:00Z],
  second: 31494160
]

where origin contains the timestamp to lookup the next for, next is the DateTime instance of the next event and second is the {precision, difference_in_that_precision}.

@spec next_as_list(dt :: nil | DateTime.t(), input :: binary(), opts :: keyword()) ::
  keyword()

Returns the list of all the events after dt (default: DateTime.utc_now/0.)

This function calculates the outcome greedily and, while it might be slightly faster than Tarearbol.Crontab.next_as_stream/3, it should not be used for frequently recurring cron records (like "* * * * *".)

@spec next_as_stream(dt :: nil | DateTime.t(), input :: binary(), opts :: keyword()) ::
  Enumerable.t()

Returns the stream of all the events after dt (default: DateTime.utc_now/0.)

This function calculates the outcome lazily, returning a stream.

See Tarearbol.Crontab.next_as_list/3 for greedy evaluation.

@spec parse(input :: binary()) :: t()

Parses the cron string into human-readable representation.

This function is exported for debugging purposes only, normally one would call prepare/1 instead.

Input format: "minute hour day/month month day/week".

Examples:

iex> Tarearbol.Crontab.parse "10-30/5 */4 1 */1 6,7"
%Tarearbol.Crontab{
  day: "(day == 1)",
  day_of_week: "(day_of_week == 6 || day_of_week == 7)",
  hour: "(rem(hour, 4) == 0)",
  minute: "(rem(minute, 5) == 0 && minute >= 10 && minute <= 30)",
  month: "(rem(month, 1) == 0)"
}

In case of malformed input:

iex> Tarearbol.Crontab.parse "10-30/5 */4 1 */1 6d,7"
%Tarearbol.Crontab{
  day: "(day == 1)",
  day_of_week: {:error, {:could_not_parse_integer, "6d"}},
  hour: "(rem(hour, 4) == 0)",
  minute: "(rem(minute, 5) == 0 && minute >= 10 && minute <= 30)",
  month: "(rem(month, 1) == 0)"
}

@spec prepare(input :: binary() | t()) :: t()

Parses the cron string into Tarearbol.Crontab.t() struct.

Input format: "minute hour day/month month day/week".

@spec to_cron(dt :: Time.t()) :: binary()

Converts the Time instance into daily-execution cron string