style_parser.rb

# Used to parse through an scss stylesheet to make editing of that stylesheet simpler
# Ex. Given a file called style.scss
#
# // @name Masthead Background Color
# // @type color
# // @description Background color of the masthead.
# $masthead_bg_color: #444;
#
# sp = StyleParser.new(contents of style.scss)
#
# # Reading
# sp.masthead_bg_color.value # returns "#444"
# sp.masthead_bg_color.name # returns "Masthead Background Color"
# sp.masthead_bg_color.type # returns "color"
# sp.masthead_bg_color.description # returns "Background color of the masthead."
#
# # Writing
# sp.masthead_bg_color.value = "#555"
# sp.render # returns all the text above except masthead_bg_color is now #555;

# Useful stuff:
# string = "my name is"
# string.index("name") # returns 3
# File.open("test.txt").each_with_index do |...| # to go to the line we want
# How to get the lines surrounding certain text: http://stackoverflow.com/questions/2760759/ruby-equivalent-to-grep-c-5-to-get-context-of-lines-around-the-match 
class StyleParser
  def initialize(text)
    @text = text
    @variables = {}

    @eol = '\n'
    @context_lines = 3
    @comment = /\/\//
    @context = "(^(?:#{@comment}\s@.*#{@eol}){#{@context_lines}})"
  end

  # Works this way: http://rubular.com/r/jWSYvfVrjj
  # From http://rubular.com/r/jWSYvfVrjj
  # Derived from http://stackoverflow.com/questions/2760759/ruby-equivalent-to-grep-c-5-to-get-context-of-lines-around-the-match
  def get_context(s)
    regexp = /.*\${1}#{s}:.*;[#{@eol}]*/
    @text =~ /^#{@context}(#{regexp})/
    before, match = $1, $2
    #puts "Before: #{before}; match #{match};"
    "#{before}#{match}"
  end

  def update_attributes(args)
    args.each do |k, v|
      send(k) # Instantiate it, so it will exist in @variables
      @variables[k].value = v unless @variables[k].nil? || v.nil?
    end
  end

  def render
    @variables.each do |key, var|
      @text.gsub!(/^\$#{key}: .+;/, %Q($#{key}: #{var.value};))
    end
    @text
  end

  def method_missing(method_name)
    if method_name.to_s =~ /[\w]+/
      context = get_context(method_name)

      # If there's no context (no variable with the proper
      # commented metadata), then it should not be accessible
      # and it won't come out in the form
      if context.blank?
        nil
      else
        @variables[method_name] ||= StyleVariable.new(method_name, context, @comment)
      end
    end
  end
end

style_variable.rb

class StyleVariable
  METADATA = %w(name kind description)

  def initialize(var, text, comment)
    @var = var
    @text = text
    @comment = comment
  end

  def method_missing(method_name)
    if METADATA.include? method_name.to_s
      content_of(method_name.to_s)
    end
  end

  def value
    @text.each do |string|
      string =~ /^\${1}#{@var}: (.+);/
      return $1 if $1
    end
  end

  def value=(val)
    @text.gsub!(/^\$#{@var}: .+;/, "$#{@var}: #{val};")
  end

  private

  def content_of(variable)
    @text.each do |string|
      string =~ /^#{@comment} @([\w]+[^\s]) (.+)/
      return $2 if $1 == variable
    end
  end
end