1 files changed, 77 insertions, 0 deletions
diff --git a/lib/exTpl/Context.php b/lib/exTpl/Context.php
new file mode 100644
index 0000000..309174f
--- /dev/null
+++ b/lib/exTpl/Context.php
@@ -0,0 +1,77 @@
+<?php
+/**
+ * Context.php - template parser symbol table
+ *
+ * A Context object represents the symbol table used to resolve
+ *  symbol names to their values in the local scope. Each context
+ *  may inherit symbol definitions from its parent context.
+ *
+ * @copyright 2013  Elmar Ludwig
+ * @license GPL2 or any later version
+ */
+
+namespace exTpl;
+
+use Closure;
+
+class Context
+{
+    private array $bindings;
+    private Closure|null $escape;
+    private Context|null $parent;
+
+    /**
+     * Initializes a new Context instance with the given bindings.
+     *
+     * @param array $bindings symbol table
+     * @param Context|null $parent parent context (or NULL)
+     */
+    public function __construct(array $bindings, Context $parent = null)
+    {
+        $this->bindings = $bindings;
+        $this->parent   = $parent;
+    }
+
+    /**
+     * Looks up the value of a symbol in this context and returns it.
+     * The reserved symbol "this" is an alias for the current context.
+     *
+     * @param string $key symbol name
+     */
+    public function lookup(string $key): mixed
+    {
+        if (isset($this->bindings[$key])) {
+            return $this->bindings[$key];
+        } else if ($this->parent) {
+            return $this->parent->lookup($key);
+        }
+
+        return null;
+    }
+
+    /**
+     * Enables or disables automatic escaping for template values.
+     *
+     * @param callable|null $escape escape callback or null
+     */
+    public function autoescape(?callable $escape): void
+    {
+        $this->escape = $escape ? $escape(...) : null;
+    }
+
+    /**
+     * Escapes the given value using the configured strategy.
+     *
+     * @param mixed $value expression value
+     */
+    public function escape(mixed $value): mixed
+    {
+        if (isset($this->escape)) {
+            $value = call_user_func($this->escape, $value);
+        } else if ($this->parent) {
+            $value = $this->parent->escape($value);
+        }
+
+        return $value;
+    }
+}