Read a JSON file containing breakpoints, and return a Sass list.

breakpoints.json

{
  "desktop": {
    "min": 801
  },
  "tablet": {
    "min": 481,
    "max": 800
  },
  "phone": {
    "max": 480
  }
}

compass.rb

module Sass::Script::Functions
  # Public: Get breakpoints from a json file, converted into a Sass list.
  # https://gist.github.com/brianmcallister/9009230
  #
  # filename - Name of the file to read.
  #
  # Examples
  #
  #   If 'breakpoints.json' looks like this:
  #   {'desktop': {'min': 801}, 'tablet': {'max': 800, 'min': 481},
  #   'phone': {'max': 480}}
  #
  #   You'll get the following:
  #
  #   $breakpoints: get_breakpoints();
  #   #=> desktop 801, tablet 800, 481, phone 480
  #
  # Returns a Sass list of breakpoints.
  def get_breakpoints(filename = Sass::Script::String.new('breakpoints.json'))
    assert_type filename, :String
    
    # Get the file contents.
    path = "#{@options[:custom][:javascripts_dir]}/libs/#{filename}"
    file = IO.read(path)
    
    # Convert the JSON into a Sass list.
    breakpoints = ::JSON.parse(file)
    list = []
    
    breakpoints.each do |b|
      name = Sass::Script::String.new(b[0])
      values = []
      
      values << if b[1]['min'].nil?
        Sass::Script::Null.new()
      else
        Sass::Script::Number.new(b[1]['min'], ['px'])
      end
      
      values << if b[1]['max'].nil?
        Sass::Script::Null.new()
      else
        Sass::Script::Number.new(b[1]['max'], ['px'])
      end

      values = Sass::Script::List.new(values, :comma)
      list << Sass::Script::List.new([name, values], :space)
    end

    return Sass::Script::List.new(list, :comma)
  end
  declare :get_breakpoints, %w(:filename)
end