# frozen_string_literal: true

Puppet::Parser::Functions.newfunction(
  :reverse_each,
  :type => :rvalue,
  :arity => -1,
  :doc => <<~DOC
    Reverses the order of the elements of something that is iterable and optionally runs a
    [lambda](https://puppet.com/docs/puppet/latest/lang_lambdas.html) for each
    element.

    This function takes one to two arguments:

    1. An `Iterable` that the function will iterate over.
    2. An optional lambda, which the function calls for each element in the first argument. It must
       request one parameter.

    **Example:** Using the `reverse_each` function

    ```puppet
    $data.reverse_each |$parameter| { <PUPPET CODE BLOCK> }
    ```

    or

    ```puppet
    $reverse_data = $data.reverse_each
    ```

    or

    ```puppet
    reverse_each($data) |$parameter| { <PUPPET CODE BLOCK> }
    ```

    or

    ```puppet
    $reverse_data = reverse_each($data)
    ```

    When no second argument is present, Puppet returns an `Iterable` that represents the reverse
    order of its first argument. This allows methods on `Iterable` to be chained.

    When a lambda is given as the second argument, Puppet iterates the first argument in reverse
    order and passes each value in turn to the lambda, then returns `undef`.

    **Example:** Using the `reverse_each` function with an array and a one-parameter lambda

    ``` puppet
    # Puppet will log a notice for each of the three items
    # in $data in reverse order.
    $data = [1,2,3]
    $data.reverse_each |$item| { notice($item) }
    ```

    When no second argument is present, Puppet returns a new `Iterable` which allows it to
    be directly chained into another function that takes an `Iterable` as an argument.

    **Example:** Using the `reverse_each` function chained with a `map` function.

    ```puppet
    # For the array $data, return an array containing each
    # value multiplied by 10 in reverse order
    $data = [1,2,3]
    $transformed_data = $data.reverse_each.map |$item| { $item * 10 }
    # $transformed_data is set to [30,20,10]
    ```

    **Example:** Using `reverse_each` function chained with a `map` in alternative syntax

    ```puppet
    # For the array $data, return an array containing each
    # value multiplied by 10 in reverse order
    $data = [1,2,3]
    $transformed_data = map(reverse_each($data)) |$item| { $item * 10 }
    # $transformed_data is set to [30,20,10]
    ```

    * Since 4.4.0

  DOC
) do |_args|
  Puppet::Parser::Functions::Error.is4x('reverse_each')
end