Middleware is functions that have access to the http request, the http response, and the next function in the application' s request-response cycle.

Types of the Middleware chain

• case respond(Response): Respond to the content immediately with given Response
• case next(Request, Response): Chain to the next middleware or the route.
• case error(Error): Abort the middleware chain and pass the error to app.catch Handler.

You can choose 2 types of middleware registration ways from handy or creating Middleware struct.

Register Middleware by Handy Style

app.use { request, response, responder in
    do {
        if let data = try File.synchronousRead("/path/to/file") {
            response.data(data)
            responder(.respond(response)) // respond to the read file content
        } else {
            responder(.next(request, response)) // Chaining to the next middleware or route
        }
    } catch {
        responder(.error(error)) // Go to `catch` handler
    }
}

Register Middleware By Middleware Protocol Confirmed Style

struct FooMiddleware: Middleware {
    func respond(_ request: Request, _ response: Response, _ responder: @escaping (Chainer) -> Void) {
        do {
            if let data = try File.synchronousRead("/path/to/file") {
                response.data(data)
                responder(.respond(response))
            } else {
                responder(.next(request, response))
            }
        } catch {
            responder(.error(error))
        }
    }
}

app.use(FooMiddleware())