# Chi-like syntactic sugar layer on top of stdlib http.ServeMux

> Source: <https://gist.github.com/alexaandru/747f9d7bdfb1fa35140b359bf23fa820>
> Published: 2024-02-14 16:40:44+00:00

chi.go

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// Chi-like syntactic sugar layer on top of stdlib http.ServeMux.

package main

import (

	"net/http"

	"slices"

)

type (

	middleware func(http.Handler) http.Handler

	router     struct {

		*http.ServeMux

		chain []middleware

	}

)

func NewRouter(mx ...middleware) *router {

	return &router{ServeMux: &http.ServeMux{}, chain: mx}

}

func (r *router) Use(mx ...middleware) {

	r.chain = append(r.chain, mx...)

}

func (r *router) Group(fn func(r *router)) {

	fn(&router{ServeMux: r.ServeMux, chain: slices.Clone(r.chain)})

}

func (r *router) Get(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodGet, path, fn, mx)

}

func (r *router) Post(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodPost, path, fn, mx)

}

func (r *router) Put(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodPut, path, fn, mx)

}

func (r *router) Delete(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodDelete, path, fn, mx)

}

func (r *router) Head(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodHead, path, fn, mx)

}

func (r *router) Options(path string, fn http.HandlerFunc, mx ...middleware) {

	r.handle(http.MethodOptions, path, fn, mx)

}

func (r *router) handle(method, path string, fn http.HandlerFunc, mx []middleware) {

	r.Handle(method+" "+path, r.wrap(fn, mx))

}

func (r *router) wrap(fn http.HandlerFunc, mx []middleware) (out http.Handler) {

	out, mx = http.Handler(fn), append(slices.Clone(r.chain), mx...)

	slices.Reverse(mx)

	for _, m := range mx {

		out = m(out)

	}

	return

}

example.go

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package main

import (

	"fmt"

	"log"

	"net/http"

)

func mid(i int) middleware {

	return func(next http.Handler) http.Handler {

		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

			fmt.Println("mid", i, "start")

			next.ServeHTTP(w, r)

			fmt.Println("mid", i, "done")

		})

	}

}

func someHandler(w http.ResponseWriter, r *http.Request) {

	fmt.Println("[the handler ran here]")

	fmt.Fprintln(w, "Hello world of", r.URL.Path)

}

func main() {

	r := NewRouter(mid(0))

	r.Group(func(r *router) {

		r.Use(mid(1), mid(2))

		r.Get("/foo", someHandler)

	})

	r.Group(func(r *router) {

		r.Use(mid(3))

		r.Get("/bar", someHandler, mid(4))

		r.Get("/baz", someHandler, mid(5))

	})

	r.Post("/foobar", someHandler)

	log.Fatal(http.ListenAndServe(":3000", r))

}