From 5298b4bcfa27ac7ebc479b6c139f2da0f5ea3f59 Mon Sep 17 00:00:00 2001
From: Willy Kloucek <wkloucek@owncloud.com>
Date: Mon, 13 Sep 2021 19:22:27 +0200
Subject: [PATCH] redirect to root when file not found

---
 .../redirect-invalid-links-to-oC-web.md       |  5 +++
 web/pkg/service/v0/service.go                 | 43 ++++++++++++++++---
 2 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 changelog/unreleased/redirect-invalid-links-to-oC-web.md

diff --git a/changelog/unreleased/redirect-invalid-links-to-oC-web.md b/changelog/unreleased/redirect-invalid-links-to-oC-web.md
new file mode 100644
index 000000000..a7b17cf10
--- /dev/null
+++ b/changelog/unreleased/redirect-invalid-links-to-oC-web.md
@@ -0,0 +1,5 @@
+Enhancement: redirect invalid links to oC Web
+
+Invalid links (eg. https://foo.bar/index.php/apps/pdfviewer) will be redirect to ownCloud Web instead of displaying a blank page with a "not found" message.
+
+https://github.com/owncloud/ocis/pull/2493
diff --git a/web/pkg/service/v0/service.go b/web/pkg/service/v0/service.go
index 7498fc809..ac022cb6d 100644
--- a/web/pkg/service/v0/service.go
+++ b/web/pkg/service/v0/service.go
@@ -133,14 +133,15 @@ func (p Web) Static(ttl int) http.HandlerFunc {
 	if !strings.HasSuffix(rootWithSlash, "/") {
 		rootWithSlash = rootWithSlash + "/"
 	}
-
+	assets := assets.New(
+		assets.Logger(p.logger),
+		assets.Config(p.config),
+	)
 	static := http.StripPrefix(
 		rootWithSlash,
-		http.FileServer(
-			assets.New(
-				assets.Logger(p.logger),
-				assets.Config(p.config),
-			),
+		interceptNotFound(
+			http.FileServer(assets),
+			rootWithSlash,
 		),
 	)
 
@@ -182,3 +183,33 @@ func (p Web) Static(ttl int) http.HandlerFunc {
 		static.ServeHTTP(w, r)
 	}
 }
+
+func interceptNotFound(h http.Handler, root string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		notFoundInterceptor := &NotFoundInterceptor{ResponseWriter: w}
+		h.ServeHTTP(notFoundInterceptor, r)
+		if notFoundInterceptor.status == http.StatusNotFound {
+			http.Redirect(w, r, root, http.StatusTemporaryRedirect)
+			// TODO: replace the redirect with a not found page containing a link to the Web UI
+		}
+	}
+}
+
+type NotFoundInterceptor struct {
+	http.ResponseWriter
+	status int
+}
+
+func (w *NotFoundInterceptor) WriteHeader(status int) {
+	w.status = status
+	if status != http.StatusNotFound {
+		w.ResponseWriter.WriteHeader(status)
+	}
+}
+
+func (w *NotFoundInterceptor) Write(p []byte) (int, error) {
+	if w.status != http.StatusNotFound {
+		return w.ResponseWriter.Write(p)
+	}
+	return len(p), nil
+}