Clarify getLegacyScript per feedback.

Author: jzohrab

migration.rst

@@ -312,14 +312,41 @@ somewhat like this::
 
     class LegacyBridge
     {
-        public static function handleRequest(Request $request, Response $response, string $publicDirectory): ?string
+
+        /**
+         * Map the incoming request to the right file.  This is the
+         * key function of the LegacyBridge.
+         *
+         * Sample code only.  Your implementation will vary, depending on the
+         * architecture of the legacy code and how it's executed.
+         *
+         * If your mapping is complicated, you may want to write unit tests
+         * to verify your logic, hence this is public static.
+         */
+        public static function getLegacyScript(string $requestPathInfo): string
         {
-            // Figure out how to map to the needed script file
-            // from the existing application.
-            function getScript($requestPathInfo) { ... }
+            $legacyRoot = __DIR__ . '/../';
+
+            // Map a route to a legacy script:
+            if ($requestPathInfo == '/customer/') {
+                return "{$legacyRoot}src/customers/list.php";
+            }
+
+            // Map a direct file call, e.g. an ajax call:
+            if ($requestPathInfo == 'inc/ajax_cust_details.php) {
+                return "{$legacyRoot}inc/ajax_cust_details.php";
+            }
 
+            // ... etc.
+
+            throw new \Exception("Unhandled legacy mapping for $requestPathInfo");
+        }
+
+
+        public static function handleRequest(Request $request, Response $response, string $publicDirectory): ?string
+        {
             $p = $request->getPathInfo();
-            $legacyScriptFilename = getScript($p);
+            $legacyScriptFilename = LegacyBridge::getLegacyScript($p);
 
             // Possibly (re-)set some env vars (e.g. to handle forms
             // posting to PHP_SELF):