lang: ast: implement ast iteration

iteration is implementing without recursion, instead using type-specific callbacks to construct a queue of nodes to iterate through. ast priting is implemented using this functionality.

lang/ast/iterate.c

@@ -0,0 +1,48 @@
+#include <ivy/lang/ast.h>
+#include "node.h"
+
+enum ivy_status ivy_ast_node_iterate(
+	struct ivy_ast_node *node,
+	struct ivy_ast_node_iterator *it,
+	ivy_ast_node_iteration_callback callback)
+{
+	memset(it, 0x0, sizeof *it);
+	b_queue_push_back(&it->it_queue, &node->n_it.it_entry);
+	node->n_it.it_depth = 0;
+
+	while (!b_queue_empty(&it->it_queue)) {
+		b_queue_entry *entry = b_queue_first(&it->it_queue);
+		struct ivy_ast_node_iterator_entry *it_entry = b_unbox(struct ivy_ast_node_iterator_entry, entry, it_entry);
+		node = b_unbox(struct ivy_ast_node, it_entry, n_it);
+
+		enum ivy_status status = callback(node, it);
+		if (status != IVY_OK) {
+			return status;
+		}
+
+		const struct ast_node_type *type = get_ast_node_type(node->n_type);
+		if (type->n_collect_children) {
+			it->it_insert_after = entry;
+			type->n_collect_children(node, it);
+		}
+
+		b_queue_delete(&it->it_queue, entry);
+	}
+
+	return IVY_OK;
+}
+
+void ast_node_iterator_enqueue_node(
+	struct ivy_ast_node_iterator *it,
+	struct ivy_ast_node *parent,
+	struct ivy_ast_node *node)
+{
+	if (it->it_insert_after) {
+		b_queue_insert_after(&it->it_queue, &node->n_it.it_entry, it->it_insert_after);
+	} else {
+		b_queue_push_back(&it->it_queue, &node->n_it.it_entry);
+	}
+
+	node->n_it.it_depth = parent->n_it.it_depth + 1;
+	it->it_insert_after = &node->n_it.it_entry;
+}