Update Meta cdn redirect function with latest code (#5206)

This incorporates :
https://github.com/pytorch/test-infra/blob/main/aws/websites/download.pytorch.org/pep503_whl_redirect.js
Also adds Country based redirect, currently set to 'CA' for testing
purposes

aws/websites/download.pytorch.org/meta_cdn_whl_redirect.js

@@ -1,22 +1,66 @@
 function handler(event) {
     var request = event.request;
+    const headers = request.headers;
     var uri = request.uri;
+    var uri_parts = uri.split('/');
+    var last_uri_part = uri_parts[uri_parts.length -1];
+    var rocm_pattern = /^rocm[0-9]+\.[0-9]+$/
     var CDN_TEST_PATH = '/whl/cdntest/';
 
-    // if we are requesting for whl files in cdntest path - perform the translation to meta CDN
+    // if we are requesting for whl files in cdntest path:
+    // - redirect to download.pytorch.org in case of CN
+    // - default perform the translation to meta CDN
     if( uri.startsWith(CDN_TEST_PATH) && uri.endsWith('.whl') ) {
-        var uri_suffix = uri.slice(CDN_TEST_PATH.length).split('/').join('%2F');
-        var meta_cdn_path = 'https://scontent.xx.fbcdn.net/mci_ab/uap/?ab_b=m&ab_page=PyTorchBinary&ab_entry=tree%2Fwhl%2Ftest%2F'
+        var uri_suffix = uri.slice(CDN_TEST_PATH.length);
+        var redirect_value = '';
+
+        if (headers['cloudfront-viewer-country']) {
+            const countryCode = Symbol.for(headers['cloudfront-viewer-country'].value);
+            if (countryCode === Symbol.for('CA')) {
+                redirect_value = 'https://download.pytorch.org/whl/test/'+uri_suffix;
+            }
+        }
+        if(redirect_value == '') {
+            var meta_cdn_path = 'https://scontent.xx.fbcdn.net/mci_ab/uap/?ab_b=m&ab_page=PyTorchBinary&ab_entry=tree%2Fwhl%2Ftest%2F'
+            redirect_value = meta_cdn_path+uri_suffix.split('/').join('%2F');
+        }
 
         const response = {
                 statusCode: 302,
                 statusDescription: 'Found',
                 headers:
-                    { "location": { "value": meta_cdn_path+uri_suffix } }
+                    { "location": { "value": redirect_value } }
                 }
 
         return response;
+    }
 
+    if (uri.startsWith('/whl')) {
+        // Check whether the URI is missing a file name.
+        if (uri.endsWith('/')) {
+            request.uri += 'index.html';
+        // Check whether the URI is folder like
+        // I.e. does not have dots in path or rocm\d.\d or 1.8 (for lts)
+        // For example /whl/cpu/torch
+        } else if (last_uri_part.indexOf('.') == -1
+                || last_uri_part.match(rocm_pattern)
+                || uri == "/whl/lts/1.8") {
+            request.uri += '/index.html';
+        }
     }
+
+    // Similar behavior for libtorch
+    if (uri.startsWith('/libtorch')) {
+        // Check whether the URI is missing a file name.
+        if (uri.endsWith('/')) {
+            request.uri += 'index.html';
+        // Check whether the URI is folder like
+        // I.e. does not have dots in path
+        // For example /libtorch/cpu
+        } else if (last_uri_part.indexOf('.') == -1) {
+            request.uri += '/index.html';
+        }
+    }
+
     return request;
 }