class Chronic::Handler

def match(tokens, definitions)
  token_index = 0
  @pattern.each do |element|
    name = element.to_s
    optional = name.reverse[0..0] == '?'
    name = name.chop if optional
    if element.instance_of? Symbol
      klass = constantize(name)
      match = tokens[token_index] && !tokens[token_index].tags.select { |o| o.kind_of?(klass) }.empty?
      return false if !match && !optional
      (token_index += 1; next) if match
      next if !match && optional
    elsif element.instance_of? String
      return true if optional && token_index == tokens.size
      sub_handlers = definitions[name.intern] || raise(ChronicPain, "Invalid subset #{name} specified")
      sub_handlers.each do |sub_handler|
        return true if sub_handler.match(tokens[token_index..tokens.size], definitions)
      end
      return false
    else
      raise(ChronicPain, "Invalid match type: #{element.class}")
    end
  end
  return false if token_index != tokens.size
  return true
end