# Scans a string and returns an array of one or more converted values as directed by a given format string.args
# See the documenation of Ruby's String::scanf method for details about the supported formats (which
# are similar but not identical to the formats used in Puppet's `sprintf` function.
#
# This function takes two mandatory arguments: the first is the String to convert, and the second
# the format String. A parameterized block may optionally be given, which is called with the result
# that is produced by scanf if no block is present, the result of the block is then returned by
# the function.
#
# The result of the scan is an Array, with each sucessfully scanned and transformed value.args The scanning
# stops if a scan is unsuccesful and the scanned result up to that point is returned. If there was no
# succesful scan at all, the result is an empty Array. The optional code block is typically used to
# assert that the scan was succesful, and either produce the same input, or perform unwrapping of
# the result
#
# @example scanning an integer in string form (result is an array with
#   integer, or empty if  unsuccessful)
#    "42".scanf("%i")
#
# @example scanning and processing resulting array to assert result and unwrap
#
#     "42".scanf("%i") |$x| {
#       unless $x[0] =~ Integer {
#         fail "Expected a well formed integer value, got '$x[0]'"
#       }
#       $x[0]
#     }
#
# @since 4.0.0
#
Puppet::Functions.create_function(:scanf) do
  require 'scanf'

  dispatch :scanf do
    param 'String', :data
    param 'String', :format
    optional_block_param
  end

  def scanf(data, format)
    result = data.scanf(format)
    if block_given?
      result = yield(result)
    end
    result
  end
end
