first_satisfied.rb

# find first callback with satisfied dependencies
    def first_satisfied(r, known_callbacks)
      remaining_names = r.map { |cb| cb.name }
      res = r.find do |cb|
        cb.dependencies.each do |dep|
          fail "Unknown #{phase.inspect} extension dependency: #{dep.inspect}" unless known_callbacks.index(dep)
        end
        satisfied = cb.dependencies.find { |dep| remaining_names.index(dep) } == nil
        cb if satisfied
      end
      r.delete res
    end