module Skylight
  class Middleware

    class BodyProxy
      def initialize(body, &block)
        @body, @block, @closed = body, block, false
      end

      def respond_to?(*args)
        return false if args.first.to_s =~ /^to_ary$/
        super or @body.respond_to?(*args)
      end

      def close
        return if @closed
        @closed = true
        begin
          @body.close if @body.respond_to? :close
        ensure
          @block.call
        end
      end

      def closed?
        @closed
      end

      # N.B. This method is a special case to address the bug described by #434.
      # We are applying this special case for #each only. Future bugs of this
      # class will be handled by requesting users to patch their ruby
      # implementation, to save adding too many methods in this class.
      def each(*args, &block)
        @body.each(*args, &block)
      end

      def method_missing(*args, &block)
        super if args.first.to_s =~ /^to_ary$/
        @body.__send__(*args, &block)
      end
    end

    def initialize(app)
      @app = app
    end

    def call(env)
      begin
        trace = Skylight.trace "Rack", 'app.rack.request'
        resp = @app.call(env)
        resp[2] = BodyProxy.new(resp[2]) { trace.submit } if trace
        resp
      rescue Exception
        trace.submit if trace
        raise
      ensure
        trace.release if trace
      end
    end
  end
end