module Cucumber::CiEnvironment::VariableExpression

def evaluate(expression, env)
  return nil if expression.nil?
  begin
    expression.gsub(/\${(.*?)(?:(?<!\\)\/(.*)\/(.*))?}/) do
      variable = $1
      pattern = $2
      replacement = $3
      value = get_value(variable, env)
      raise "Undefined variable #{variable}" if value.nil?
      if pattern.nil?
        value
      else
        regexp = Regexp.new(pattern.gsub('\/', '/'))
        match = value.match(regexp)
        raise "No match for variable #{variable}" if match.nil?
        match[1..-1].each_with_index do |group, i|
          replacement = replacement.gsub("\\#{i+1}", group)
        end
        replacement
      end
    end
  rescue
    nil
  end
end

def get_value(variable, env)
  if variable.index('*')
    env.each do |name, value|
      return value if Regexp.new(variable.gsub('*', '.*')) =~ name
    end
  end
  env[variable]
end