Contents

require_relative './processor_error'
require_relative './syntax_error'
require_relative './tokens'

class MacroProcessor

  def initialize(params)
    @params = params
  end

  def parse(text)
    @tokens = Tokens.new(text)
    @tokens.advance
    result = words
    expect(Tokens::EOF)
    result
  end

  private

  def words
    result = []
    while @tokens.peek != Tokens::EOF
      result << word
    end
    result.join
  end

  def word
    result = @tokens.peek
    @tokens.advance
    if result == '~' and accept('{')
      @tokens.push_back(macro)
      result = word
    end
    result
  end

  def macro
    args = []
    loop do
      args << word
      break if @tokens.peek == '}' || @tokens.peek == Tokens::EOF
    end
    expect('}')
    execute(args.join.split(' '))
  end

  def execute(args)
    if args[0] == 'include'
      return lookup(:filestore).contents_of(args[1])
    else
      return lookup(args[0])
    end
  end

  def lookup(field_name)
    value = @params[field_name] || @params[field_name.to_sym]
    raise ProcessorError.new(field_name) unless value
    value
  end

  def accept(s)
    if (@tokens.peek == s)
      @tokens.advance
      true
    else
      false
    end
  end

  def expect(s)
    return true if accept(s)
    raise SyntaxError.new(s, @tokens.peek)
    false
  end

end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
ns-macro-processor-0.0.1	lib/macro_processor.rb