#12 - form live preview

modules/Templating/RsvTemplateEngine.php

@@ -49,18 +49,27 @@ class RsvTemplateEngine {
 
     /**
      * Lists a template's problems without rendering it (empty = valid): empty
-     * interpolations, unregistered custom elements, and attributes an element
-     * does not declare.
+     * interpolations, references to unknown symbols, unregistered custom
+     * elements, and attributes an element does not declare.
      *
+     * @param list<string>|null $symbols When given, the roots an interpolation may
+     *        reference; a path rooted outside the set is reported as unknown. Null
+     *        skips the reference check (any path is accepted).
      * @return list<string>
      */
-    public function validate(string $source): array {
+    public function validate(string $source, ?array $symbols = null): array {
         $errors = [];
 
         if (preg_match_all('/{{\s*([^}]*?)\s*}}/', $source, $matches)) {
             foreach ($matches[1] as $path) {
-                if (trim($path) === '') {
+                $expr = trim($path);
+                if ($expr === '') {
                     $errors[] = 'Empty interpolation: {{ }}';
+                    continue;
+                }
+                $root = $this->tokens($expr)[0] ?? null;
+                if ($symbols !== null && $root !== null && !in_array($root, $symbols, true)) {
+                    $errors[] = "Unknown reference: {{ {$expr} }}";
                 }
             }
         }
@@ -148,14 +157,9 @@ class RsvTemplateEngine {
      * @param array<string, mixed> $data
      */
     private function resolve(string $path, array $data): mixed {
-        $tokens  = preg_split('/[\.\[\]]+/', $path, -1, PREG_SPLIT_NO_EMPTY) ?: [];
         $current = $data;
 
-        foreach ($tokens as $token) {
-            if ($token === '$') {
-                continue; // root sigil
-            }
-            $token = trim($token, "'\""); // strip bracket-notation quotes
+        foreach ($this->tokens($path) as $token) {
             if (!is_array($current) || !array_key_exists($token, $current)) {
                 return null;
             }
@@ -165,6 +169,24 @@ class RsvTemplateEngine {
         return $current;
     }
 
+    /**
+     * Splits a JSON Path into its key tokens, dropping the root sigil and
+     * bracket-notation quotes — e.g. "$.items[0]" yields ['items', '0'].
+     *
+     * @return list<string>
+     */
+    private function tokens(string $path): array {
+        $raw    = preg_split('/[\.\[\]]+/', $path, -1, PREG_SPLIT_NO_EMPTY) ?: [];
+        $tokens = [];
+        foreach ($raw as $token) {
+            if ($token === '$') {
+                continue; // root sigil
+            }
+            $tokens[] = trim($token, "'\""); // strip bracket-notation quotes
+        }
+        return $tokens;
+    }
+
     // -------------------------------------------------------------------------
     // DOM helpers
     // -------------------------------------------------------------------------