A basic HTTP router

router.go

package router

import (
	"encoding/json"
	"html/template"
	"io/fs"
	"net/http"
)

var commonMiddleware = []Middleware{}

type Router struct {
	*http.ServeMux
	StaticFileSystem fs.FS

	Template *template.Template
}

func NewRouter(staticFileSystem fs.FS, template *template.Template) *Router {
	mux := http.NewServeMux()

	subFolderStaticFileSystem, err := fs.Sub(staticFileSystem, "static")
	if err != nil {
		panic(err)
	}
	// serve static files
	mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(subFolderStaticFileSystem))))

	return &Router{
		ServeMux:         mux,
		StaticFileSystem: staticFileSystem,
		Template:         template,
	}
}

func (r *Router) GET(path string, handler http.HandlerFunc) {
	// loop over common middleware reverse order
	for i := len(commonMiddleware) - 1; i >= 0; i-- {
		handler = commonMiddleware[i](handler).ServeHTTP
	}

	r.HandleFunc(path, func(w http.ResponseWriter, req *http.Request) {
		if req.Method != http.MethodGet {
			http.NotFound(w, req)
			return
		}
		handler(w, req)
	})
}

func (r *Router) POST(path string, handler http.HandlerFunc) {
	r.HandleFunc(path, func(w http.ResponseWriter, req *http.Request) {
		if req.Method != http.MethodPost {
			http.NotFound(w, req)
			return
		}
		handler(w, req)
	})
}

func (r *Router) JSON(w http.ResponseWriter, data interface{}, code int) {
	buf, err := json.Marshal(data)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	status := http.StatusOK
	if code != 0 {
		status = code
	}
	w.WriteHeader(status)
	w.Write(buf)
}

type Middleware func(http.Handler) http.Handler

// Use adds middleware to the router. You can list multiple middleware here,
// or make multiple calls. Middleware is applied in the order it is added.
func (r *Router) Use(middleware ...Middleware) {
	commonMiddleware = append(commonMiddleware, middleware...)
}