Rewrite

url-rewrite-single-page-apps/index.js

@@ -1,14 +1,33 @@
+/**
+ * Given a URI this will return the suffix which should be appended in cases where the URI does not include a filename or extension.
+ * @see https://github.com/aws-samples/amazon-cloudfront-functions/tree/main/url-rewrite-single-page-apps
+ */
+function uriSuffix(uri) {
+    // Iterate over the given URI in reverse order looking for '/' or '.' as a means to determine if the
+    // last path element represents a file (indicated by a file extension).
+    var count = uri.length - 1;
+    for (var indx = count; indx >= 0; --indx) {
+        var achar = uri[indx];
+        // If we find a '/' append 'index.html' as the last path element
+        if (achar === '/') {
+            return indx === count ? 'index.html' : '/index.html';
+        }
+        // Otherwise if we find a '.' we assume the last path element is a file and return empty string
+        // (no URI modification needed).
+        else if (achar === '.') {
+            return '';
+        }
+    }
+
+    // If we did not encounter a '/' or '.', default.
+    return '/index.html';
+}
+
 function handler(event) {
     var request = event.request;
-    var uri = request.uri;
-
-    // Check whether the URI is missing a file name.
-    if (uri.endsWith('/')) {
-        request.uri += 'index.html';
-    } 
-    // Check whether the URI is missing a file extension.
-    else if (!uri.includes('.')) {
-        request.uri += '/index.html';
+    var suffix = uriSuffix(request.uri);
+    if (suffix.length) {
+        request.uri += suffix;
     }
 
     return request;