values_at.rb

values_at.rb

#
# values_at.rb
#
# Copyright 2012-2014 Krzysztof Wilczynski
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

module Puppet::Parser::Functions
  newfunction(:values_at, :type => :rvalue, :doc => <<-EOS
Returns

Prototype:

    values_at()

Where

For example:

  Given the following statements:

  The result will be as follows:

    EOS
  ) do |arguments|

    raise Puppet::ParseError, "values_at(): Wrong number of " +
      "arguments given (#{arguments.size} for 1)" if arguments.size < 1

    array = arguments.shift

    raise Puppet::ParseError, 'values_at(): Requires ' +
      'an array to work with' unless array.is_a?(Array)

    indices = *arguments # Get them all ...

    # Anything to collect?  If not then just return empty array ...
    return [] if array.nil? || array.empty?

    # This is to detect single empty string as first arguments ...
    raise Puppet::ParseError, 'values_at(): Requires ' +
      'a numeric value or range to work with' if indices.nil? || indices.empty?

    indices_list = []

    indices.each do |value|
      # This should cover all the generic numeric types present in Puppet ...
      unless value.class.ancestors.include?(Numeric) || value.is_a?(String)
        raise Puppet::ParseError, 'values_at(): Requires ' +
          'a numeric value or range to work with'
      end

      type_error = false

      if value.is_a?(String)
        type_error = true if value.empty?

        # We support rages given as a..b, a...b and a-b which resembles a..b ...
        if m = value.match(/^(-?\d+)(\.{2,3}|\-)(-?\d+)$/)
          start = m[1]
          stop  = m[3]
          range = m[2]

          start = start.to_i
          stop  = stop.to_i

          range = case range
            when /^(\.{2}|\-)$/ then (start .. stop)
            when /^\.{3}$/      then (start ... stop) # Exclusive of last element ...
          end

          indices_list += range.to_a
        elsif value.match(/^-?(?:\d+)(?:\.\d+){1}$/) # Floating point
          type_error = true
        elsif value.match(/^-?\d+$/) # Integer
          # In Puppet numbers are often string-encoded ...
          indices_list << value.to_i
        else
          raise Puppet::ParseError, 'values_at(): Unknown type of ' +
            'value for indices given'
        end

        raise Puppet::ParseError, 'values_at(): Requires ' +
          'an integer value to work with' if type_error
      else
        indices_list << value
      end
    end

    #
    # We remove nil values as they make no sense in Puppet DSL
    # and turn them into :undef value.
    #
    array.values_at(*indices_list).map {|i| i.nil? ? :undef : i }
  end
end

# vim: set ts=2 sw=2 et :
# encoding: utf-8

Testing locally:

matti@acrux ~/test/lib $ ls -l puppet/parser/functions/
total 8
-rw-r--r-- 1 matti users 3795 wrz  8 19:30 dump.rb
-rw-r--r-- 1 matti users 3201 wrz  8 20:00 values_at.rb
matti@acrux ~/test/lib $ cat - | RUBYLIB=. puppet apply
$a = [1, 2, 3]
notice dump(values_at($a, 1, '2-3', 2, -1))
notice dump(values_at($a, 3, 2, 1, 0))
notice dump(values_at($a, '0..3'))
notice dump(values_at($a, '0...3'))
Notice: Scope(Class[main]): ["2", "3", :undef, "3", "3"]
Notice: Scope(Class[main]): [:undef, "3", "2", "1"]
Notice: Scope(Class[main]): ["1", "2", "3", :undef]
Notice: Scope(Class[main]): ["1", "2", "3"]
Notice: Compiled catalog for acrux.romke.net in environment production in 0.02 seconds
Notice: Finished catalog run in 1.32 seconds