router.go

package main

// demonstrates how to create a simple http router compartible with std net/http lib
import (
	"net/http"
	"strings"
)

type Handle func(http.ResponseWriter, *http.Request)

type Router struct {
	handler map[string]Handle
}

func NewRouter() *Router {
	r := new(Router)
	r.handler = make(map[string]Handle)
	return r
}

func (r *Router) Get(path string, h Handle) {
	r.Handle(http.MethodGet, path, h)
}

func (r *Router) Post(path string, h Handle) {
	r.Handle(http.MethodPost, path, h)
}

func (r *Router) Put(path string, h Handle) {
	r.Handle(http.MethodPut, path, h)
}

func key(method, path string) string {
	return method + ":" + path
}

//ServeHTTP handles all connections from http clients
func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	fn, ok := r.handler[key(req.Method, req.URL.Path)]
	if !ok {
		// do something here like say invalid url path
		w.Write([]byte("Invalid URL Context path specified"))
		return
	}
	fn(w, req)
}

func (r *Router) Handle(method, path string, handle Handle) {

	if method == "" {
		panic("method must not be empty")
	}

	if len(path) < 1 || path[0] != '/' {
		panic("method must begin with a forward slash /")
	}

	if handle == nil {
		panic("handle must not be nil")
	}

	r.handler[key(method, path)] = handle
}

func main() {
  // Usage is simple as below. 
  // This does not cater for param slicing and shouldn't be used for production.
	router := NewRouter()
	router.Get("/users", func(w http.ResponseWriter, r *http.Request) {
		// do whatever you want with the request/response
		w.Write([]byte("This is a list of get items"))
	})

	router.Get("/users/:name", func(w http.ResponseWriter, r *http.Request) {
		// do whatever you want with the request/response
		name := strings.TrimPrefix(r.URL.Path, "/users/")
		w.Write([]byte("This is your " + name))
	})

	router.Post("/users", func(w http.ResponseWriter, r *http.Request) {
		// do whatever you want with the request/response
    panic("implement me")
	})

	http.ListenAndServe(":3000", router)
}