Class: Less::Engine

Inherits:
String
  • Object
show all
Defined in:
lib/less/engine.rb

Constant Summary collapse

REGEXP = 
{
  :path     => /([#.][->#.\w ]+)?( ?> ?)?@([-\w]+)/,     # #header > .title > @var
  :selector => /[-\w #.>*:]/,                            # .cow .milk > a
  :variable => /@([-\w]+)/,                              # @milk-white
  :property => /@[-\w]+|[-a-z]+/                         # font-size
}

Instance Method Summary collapse

Constructor Details

#initialize(s) ⇒ Engine

Returns a new instance of Engine.



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# File 'lib/less/engine.rb', line 10

def initialize s
  super
  @tree = Tree.new self.hashify
end

Instance Method Details

#compile ⇒ Object Also known as: render 



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# File 'lib/less/engine.rb', line 15

def compile     
  #
  # Parse the variables and mixins
  #
  # We use symbolic keys, such as :mixins, to store LESS-only data,
  # each branch has its own :mixins => [], and :variables => {}
  # Once a declaration has been recognised as LESS-specific, it is copied 
  # in the appropriate data structure in that branch. The declaration itself
  # can then be deleted.
  #
  @tree = @tree.traverse :leaf do |key, value, path, node|
    matched = if match = key.match( REGEXP[:variable] )          
      node[:variables] ||= Tree.new
      node[:variables][ match.captures.first ] = value
    elsif value == :mixin
      node[:mixins] ||= []          
      node[:mixins] << key
    end
    node.delete key if matched # Delete the property if it's LESS-specific
  end
  
  #
  # Evaluate mixins
  #
  @tree = @tree.traverse :branch do |path, node|
    if node.include? :mixins
      node[:mixins].each do |m|
        @tree.find( :mixin, m.delete(' ').split('>') ).each {|k, v| node[ k ] = v }
      end
    end
  end
  
  # Call `evaluate` on variables, such as '@dark: @light / 2'
  @tree = @tree.traverse :branch do |path, node|
    node.vars.each do |key, value|
      evaluate key, value, node.vars
    end if node.vars?
  end
  
  # Call `evaluate` on css properties, such as 'font-size: @big'
  @tree = @tree.traverse :leaf do |key, value, path, node|
    evaluate key, value, node
  end
  
  #
  # Evaluate operations (2+2)
  #
  # Units are: 1px, 1em, 1%, #111
  @tree = @tree.traverse :leaf do |key, value, path, node|
    if value.match /[-+\/*]/
      if (unit = value.scan(/(%)|\d+(px)|\d+(em)|(#)/i).flatten.compact.uniq).size <= 1
        unit = unit.join            
        value = if unit == '#'
          evaluate = lambda do |v| 
            result = eval v
            unit + ( result.zero?? '000' : result.to_s(16) )
          end
          value.gsub(/#([a-z0-9]+)/i) do
            hex = $1 * ( $1.size < 6 ? 6 / $1.size : 1 )
            hex.to_i(16)
          end.delete unit
        else
          evaluate = lambda {|v| eval( v ).to_s + unit }
          value.gsub(/px|em|%/, '')
        end.to_s                
        next if value.match /[a-z]/i
        node[ key ] = evaluate.call value
      else
        raise MixedUnitsError
      end
    end
  end
end

#evaluate(key, value, node) ⇒ Object

Evaluate variables



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# File 'lib/less/engine.rb', line 93

def evaluate key, value, node               
  if value.is_a? String and value.include? '@'       # There's a var to evaluate    
    value.scan REGEXP[:path] do |p|
      p = p.join.delete ' '
      var = if p.include? '>'
        @tree.find :var, p.split('>')                # Try finding it in a specific namespace
      else
        node.var( p ) || @tree.var( p )              # Try local first, then global
      end

      if var
        node[ key ] = value.gsub REGEXP[:path], var  # Substitute variable with value
      else
        node.delete key                              # Discard the declaration if the variable wasn't found
      end
    end    
  end
end

#hashify ⇒ Object 



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# File 'lib/less/engine.rb', line 116

def hashify
#
# Parse the LESS structure into a hash
#
###
  #   less:     color: black;
  #   hashify: "color" => "black"
  #
  hash = self.gsub(/\/\/.*\n/, '').                                                   # Comments //
              gsub(/\/\*.*?\//m, '').                                                 # Comments /*
              gsub(/"/, "'").                                                         # " => '
              gsub(/("|')(.+?)(\1)/) { $1 + CGI.escape( $2 ) + $1 }.                  # Escape string values
              gsub(/(#{REGEXP[:property]}):[ \t]*(.+?);/, '"\\1" => "\\2",').         # Declarations
              gsub(/\}/, "},").                                                       # Closing }
              gsub(/([ \t]*)(#{REGEXP[:selector]}+?)[ \t\n]*\{/m, '\\1"\\2" => {').   # Selectors
              gsub(/([.#][->\w .#]+);/, '"\\1" => :mixin,')                           # Mixins
  eval "{" + hash + "}"                                                               # Return {hash}
end

#to_css ⇒ Object 



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# File 'lib/less/engine.rb', line 112

def to_css
  self.compile.to_css
end