Made 'extensionless' middleware more modular/useful

config/parsing.go

@@ -24,7 +24,7 @@ func (p *parser) begin() error {
 // combination.
 func (p *parser) address() error {
 	if p.tkn() == "}" || p.tkn() == "{" {
-		return p.err("Syntax", "'"+p.tkn()+"' is not a listening address or EOF")
+		return p.err("Syntax", "'"+p.tkn()+"' is not EOF or address")
 	}
 	p.cfg.Host, p.cfg.Port = parseAddress(p.tkn())
 	return nil

middleware/extensionless/extensionless.go

@@ -15,47 +15,81 @@ import (
 // New creates a new instance of middleware that assumes extensions
 // so the site can use cleaner, extensionless URLs
 func New(c middleware.Controller) (middleware.Middleware, error) {
+	root := c.Root()
+
+	extensions, err := parse(c)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(next http.HandlerFunc) http.HandlerFunc {
+		return Extensionless{
+			Next:       next,
+			Extensions: extensions,
+			Root:       root,
+		}.ServeHTTP
+	}, nil
+}
+
+// Extensionless is an http.Handler that can assume an extension from clean URLs.
+// It tries extensions in the order listed in Extensions.
+type Extensionless struct {
+	Next       http.HandlerFunc
+	Extensions []string
+	Root       string
+}
+
+// ServeHTTP implements the http.Handler interface.
+func (e Extensionless) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if !hasExt(r) {
+		for _, ext := range e.Extensions {
+			if resourceExists(e.Root, r.URL.Path+ext) {
+				r.URL.Path = r.URL.Path + ext
+				break
+			}
+		}
+	}
+	e.Next(w, r)
+}
+
+// parse sets up an instance of Extensionless middleware
+// from a middleware controller and returns a list of extensions.
+func parse(c middleware.Controller) ([]string, error) {
 	var extensions []string
-	var root = c.Root() // TODO: Big gotcha! Save this now before it goes away! We can't get this later during a request!
 
 	for c.Next() {
+		// At least one extension is required
 		if !c.NextArg() {
-			return nil, c.ArgErr()
+			return extensions, c.ArgErr()
 		}
 		extensions = append(extensions, c.Val())
+
+		// Tack on any other extensions that may have been listed
 		for c.NextArg() {
 			extensions = append(extensions, c.Val())
 		}
 	}
 
-	resourceExists := func(path string) bool {
-		_, err := os.Stat(root + path)
-		// technically we should use os.IsNotExist(err)
-		// but we don't handle any other kinds of errors anyway
-		return err == nil
-	}
+	return extensions, nil
+}
 
-	hasExt := func(r *http.Request) bool {
-		if r.URL.Path[len(r.URL.Path)-1] == '/' {
-			// directory
-			return true
-		}
-		lastSep := strings.LastIndex(r.URL.Path, "/")
-		lastDot := strings.LastIndex(r.URL.Path, ".")
-		return lastDot > lastSep
-	}
+// resourceExists returns true if the file specified at
+// root + path exists; false otherwise.
+func resourceExists(root, path string) bool {
+	_, err := os.Stat(root + path)
+	// technically we should use os.IsNotExist(err)
+	// but we don't handle any other kinds of errors anyway
+	return err == nil
+}
 
-	return func(next http.HandlerFunc) http.HandlerFunc {
-		return func(w http.ResponseWriter, r *http.Request) {
-			if !hasExt(r) {
-				for _, ext := range extensions {
-					if resourceExists(r.URL.Path + ext) {
-						r.URL.Path = r.URL.Path + ext
-						break
-					}
-				}
-			}
-			next(w, r)
-		}
-	}, nil
+// hasExt returns true if the HTTP request r has an extension,
+// false otherwise.
+func hasExt(r *http.Request) bool {
+	if r.URL.Path[len(r.URL.Path)-1] == '/' {
+		// directory
+		return true
+	}
+	lastSep := strings.LastIndex(r.URL.Path, "/")
+	lastDot := strings.LastIndex(r.URL.Path, ".")
+	return lastDot > lastSep
 }