1package middleware
2
3import (
4	"context"
5	"net/http"
6	"strings"
7
8	"github.com/go-chi/chi"
9)
10
11var (
12	// URLFormatCtxKey is the context.Context key to store the URL format data
13	// for a request.
14	URLFormatCtxKey = &contextKey{"URLFormat"}
15)
16
17// URLFormat is a middleware that parses the url extension from a request path and stores it
18// on the context as a string under the key `middleware.URLFormatCtxKey`. The middleware will
19// trim the suffix from the routing path and continue routing.
20//
21// Routers should not include a url parameter for the suffix when using this middleware.
22//
23// Sample usage.. for url paths: `/articles/1`, `/articles/1.json` and `/articles/1.xml`
24//
25//  func routes() http.Handler {
26//    r := chi.NewRouter()
27//    r.Use(middleware.URLFormat)
28//
29//    r.Get("/articles/{id}", ListArticles)
30//
31//    return r
32//  }
33//
34//  func ListArticles(w http.ResponseWriter, r *http.Request) {
35// 	  urlFormat, _ := r.Context().Value(middleware.URLFormatCtxKey).(string)
36//
37// 	  switch urlFormat {
38// 	  case "json":
39// 	  	render.JSON(w, r, articles)
40// 	  case "xml:"
41// 	  	render.XML(w, r, articles)
42// 	  default:
43// 	  	render.JSON(w, r, articles)
44// 	  }
45// }
46//
47func URLFormat(next http.Handler) http.Handler {
48	fn := func(w http.ResponseWriter, r *http.Request) {
49		ctx := r.Context()
50
51		var format string
52		path := r.URL.Path
53
54		if strings.Index(path, ".") > 0 {
55			base := strings.LastIndex(path, "/")
56			idx := strings.Index(path[base:], ".")
57
58			if idx > 0 {
59				idx += base
60				format = path[idx+1:]
61
62				rctx := chi.RouteContext(r.Context())
63				rctx.RoutePath = path[:idx]
64			}
65		}
66
67		r = r.WithContext(context.WithValue(ctx, URLFormatCtxKey, format))
68
69		next.ServeHTTP(w, r)
70	}
71	return http.HandlerFunc(fn)
72}
73