Refactor. Add Swagger UI docs.

Change from Gorilla mux to net/http

internal/api/authentication.go

@@ -10,47 +10,43 @@ import (
 	"github.com/golang-jwt/jwt/v4"
 )
 
-func authentication(next http.Handler, publicKey ed25519.PublicKey) http.Handler {
+var publicKey ed25519.PublicKey
+
+func isAuthenticated(r *http.Request) error {
 	cacheLock := sync.RWMutex{}
 	cache := map[string]*jwt.Token{}
 
-	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		authheader := r.Header.Get("Authorization")
-		if authheader == "" || !strings.HasPrefix(authheader, "Bearer ") {
-			http.Error(rw, "Use JWT Authentication", http.StatusUnauthorized)
-			return
+	authheader := r.Header.Get("Authorization")
+	if authheader == "" || !strings.HasPrefix(authheader, "Bearer ") {
+		return errors.New("Use JWT Authentication")
+	}
+
+	rawtoken := authheader[len("Bearer "):]
+	cacheLock.RLock()
+	token, ok := cache[rawtoken]
+	cacheLock.RUnlock()
+	if ok && token.Claims.Valid() == nil {
+		return nil
+	}
+
+	// The actual token is ignored for now.
+	// In case expiration and so on are specified, the Parse function
+	// already returns an error for expired tokens.
+	var err error
+	token, err = jwt.Parse(rawtoken, func(t *jwt.Token) (interface{}, error) {
+		if t.Method != jwt.SigningMethodEdDSA {
+			return nil, errors.New("only Ed25519/EdDSA supported")
 		}
 
-		rawtoken := authheader[len("Bearer "):]
-		cacheLock.RLock()
-		token, ok := cache[rawtoken]
-		cacheLock.RUnlock()
-		if ok && token.Claims.Valid() == nil {
-			next.ServeHTTP(rw, r)
-			return
-		}
-
-		// The actual token is ignored for now.
-		// In case expiration and so on are specified, the Parse function
-		// already returns an error for expired tokens.
-		var err error
-		token, err = jwt.Parse(rawtoken, func(t *jwt.Token) (interface{}, error) {
-			if t.Method != jwt.SigningMethodEdDSA {
-				return nil, errors.New("only Ed25519/EdDSA supported")
-			}
-
-			return publicKey, nil
-		})
-		if err != nil {
-			http.Error(rw, err.Error(), http.StatusUnauthorized)
-			return
-		}
-
-		cacheLock.Lock()
-		cache[rawtoken] = token
-		cacheLock.Unlock()
-
-		// Let request through...
-		next.ServeHTTP(rw, r)
+		return publicKey, nil
 	})
+	if err != nil {
+		return err
+	}
+
+	cacheLock.Lock()
+	cache[rawtoken] = token
+	cacheLock.Unlock()
+
+	return nil
 }