add auth middleware

Signed-off-by: Tobias Erbshäußer <tobias@tesoft.dev>

backend/api.go

@@ -1,15 +1,36 @@
 package main
 
-import "net/http"
+import (
+	"context"
+	"net/http"
+)
 
 type ApiHandler struct {
+	db        *Database
+	authToken *string
 }
 
-func NewApiHandler() *ApiHandler {
-	// TODO
-	return &ApiHandler{}
+const authTokenCookieName = "auth-token"
+const isAuthorizedContextKey = "is-authorized"
+
+func (h *ApiHandler) ProcessAuth(next http.Handler, required bool) http.Handler {
+	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		isAuthorized := false
+		cookie, _ := request.Cookie(authTokenCookieName)
+		if cookie != nil {
+			isAuthorized = h.authToken != nil && *h.authToken == cookie.Value
+		}
+
+		if !isAuthorized && required {
+			http.Error(writer, "authentication required", http.StatusUnauthorized)
+			return
+		}
+
+		next.ServeHTTP(writer, request.WithContext(context.WithValue(request.Context(), isAuthorizedContextKey, isAuthorized)))
+	})
 }
 
-func (api *ApiHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	// TODO
+func IsAuthorized(request *http.Request) bool {
+	value := request.Context().Value(isAuthorizedContextKey)
+	return value != nil && value.(bool)
 }