Middleware.swift

protocol MiddlewareType {
  func intercept(request: Request, nextResponder: ResponderType) throws -> Response
}

protocol RequestMiddlewareType: MiddlewareType {
  func intercept(request: Request) throws -> Request
}

extension RequestMiddlewareType {
  func intercept(request: Request, nextResponder: ResponderType) throws -> Response {
    let interceptedRequest = try self.intercept(request)
    return try nextResponder.respond(request)
  }
}

protocol ResponseMiddlewareType: MiddlewareType {
  func intercept(response: Response) throws -> Response
}

extension ResponseMiddlewareType {
  func intercept(request: Request, nextResponder: ResponderType) throws -> Response {
    let response = try nextResponder.respond(request)
    return try self.intercept(response)
  }
}

protocol FailureRecoveryMiddlewareType: MiddlewareType {
  func intercept(error: ErrorType) -> Response
}

extension FailureRecoveryMiddlewareType {
  func intercept(request: Request, nextResponder: ResponderType) throws -> Response {
    do {
      return try nextResponder.respond(request)
    } catch {
      return self.intercept(error)
    }
  }
}

enum EarlyReturnMiddlewareResult {
  case PassForward(Request)
  case EarlyReturn(Response)
}

protocol EarlyReturnMiddlewareType: MiddlewareType {
  func intercept(request: Request) throws -> EarlyReturnMiddlewareResult
}

extension EarlyReturnMiddlewareType {
  func intercept(request: Request, nextResponder: ResponderType) throws -> Response {
    switch try self.intercept(request) {
    case .PassForward(let request):
      return try nextResponder.respond(request)
    case .EarlyReturn(let response):
      return response
    }
  }
}

route.get("/", middleware: logger, errorHandler, authenticator, contentNegotiator, templateRender, responder: responder)