Class: Jekyll::Pseudo::Grammar

Inherits:
Object
  • Object
show all
Defined in:
lib/jekyll-pseudo/grammar.rb

Instance Method Summary collapse

Instance Method Details

#format(txt, brush) ⇒ Object

parse a block of text, using the given brush to format output (works in a single pass)



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# File 'lib/jekyll-pseudo/grammar.rb', line 5

def format(txt, brush)
  results = []

  mappings = [
    [/\#(.*$)/, :comment],
    [/\b([A-Z]\w+)/, :sym],
    [/(\w+)(?=[({\[])/, :fn],
    [/(\".*?\")/, :string],
    [/(<-|->|\+\+|<=|>=|--)/, :op],  # try these operators first
    [/([-()\[\]{}=<>+*])/, :op],     # and these second
    [/\b([a-z][a-zA-Z0-9]*)(_[a-zA-Z0-9]+)?/, :var],
    [/^(\s+)/, :indent]
  ]

  # replace tabs with three spaces
  txt.gsub! /^\t/, '   '

  # count leading whitespace
  ws = txt.scan(/^ */).map do |leading|
    leading.size
  end
  leading = (ws.min or 0)

  # remove leading whitespace of the given length
  if leading > 0
    r = /^ {#{leading}}/
    txt.gsub! r, ''
  end

  # lazy man's parser (we don't do any of that silly backtracking)
  cursor = 0
  while true
    matches = mappings.map do |pair|
      [pair[0].match(txt, cursor), pair[1]]
    end

    upto = matches.min_by do |pair|
      matchdata = pair[0]
      if matchdata == nil
        txt.size
      else
        matchdata.begin(0)
      end
    end

    if upto[0] != nil
      results << brush.plain(txt.slice(cursor, upto[0].begin(0)-cursor))

      # which match?
      captures = upto[0].captures
      results << brush.method(upto[1]).call(*captures)
      cursor = upto[0].end(0)
    else
      # no matches remaining
      results << brush.plain(txt.slice(cursor, txt.size))
      break
    end
  end

  return results.join('')
end