add 404 handler (#57)

internal/router/router.go

@@ -42,6 +42,8 @@ type Router interface {
 	AttachHandler(method string, path string, f gin.HandlerFunc)
 	// Attach a gin middleware to the router that will be used globally
 	AttachMiddleware(handler gin.HandlerFunc)
+	// Attach 404 NoRoute handler
+	AttachNoRouteHandler(handler gin.HandlerFunc)
 	// Start the router
 	Start()
 	// Stop the router
@@ -109,6 +111,11 @@ func (r *router) AttachMiddleware(middleware gin.HandlerFunc) {
 	r.engine.Use(middleware)
 }
 
+// AttachNoRouteHandler attaches a gin.HandlerFunc to NoRoute to handle 404's
+func (r *router) AttachNoRouteHandler(handler gin.HandlerFunc) {
+	r.engine.NoRoute(handler)
+}
+
 // New returns a new Router with the specified configuration, using the given logrus logger.
 func New(config *config.Config, logger *logrus.Logger) (Router, error) {
 	lvl, err := logrus.ParseLevel(config.LogLevel)

internal/web/base.go

@@ -68,6 +68,22 @@ func (m *Module) baseHandler(c *gin.Context) {
 	})
 }
 
+func (m *Module) NotFoundHandler(c *gin.Context) {
+	l := m.log.WithField("func", "404")
+	l.Trace("serving 404 html")
+
+	instance, err := m.processor.InstanceGet(m.config.Host)
+	if err != nil {
+		l.Debugf("error getting instance from processor: %s", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "internal server error"})
+		return
+	}
+
+	c.HTML(404, "404.tmpl", gin.H{
+		"instance": instance,
+	})
+}
+
 // Route satisfies the RESTAPIModule interface
 func (m *Module) Route(s router.Router) error {
 
@@ -81,5 +97,9 @@ func (m *Module) Route(s router.Router) error {
 
 	// serve front-page
 	s.AttachHandler(http.MethodGet, "/", m.baseHandler)
+
+	// 404 handler
+	s.AttachNoRouteHandler(m.NotFoundHandler)
+
 	return nil
 }

web/template/404.tmpl

@@ -0,0 +1,11 @@
+{{ template "header.tmpl" .}}
+
+<aside class="left logo">
+	<img src="/assets/sloth.png" alt="Clipart styled sloth logo">
+</aside>
+<section>
+	<h1>404: Page Not Found</h1>
+	If you believe this was an error, you can <a href="/{{.instance.ContactAccount}}">contact an admin</a>
+</section>
+
+{{ template "footer.tmpl" .}}