#include "node.h"

#include <ivy/lang/ast.h>

enum ivy_status iterate_regular(
	struct ivy_ast_node *node, struct ivy_ast_node_iterator *it,
	ivy_ast_node_iteration_callback callback)
{
#if 0
	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);

		if (!node) {
			/* this should never happen. */
			return IVY_ERR_INTERNAL_FAILURE;
		}

		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);
	}
#endif

	return IVY_OK;
}

enum ivy_status iterate_postorder(
	struct ivy_ast_node *node, struct ivy_ast_node_iterator *it,
	ivy_ast_node_iteration_callback callback)
{
	/* general iteration strategy:
	 * 1. create a queue.
	 * 2. push `node` to the end of the queue.
	 * 3. for each node N in the queue:
	 * 	1. collect N's children.
	 * 	2. insert the children into the queue between N and the node
	 * 	   immediately following N.
	 * 4. the loop in step 3 continues over all nodes added within the loop,
	 *    and stops when all nodes have been visited.
	 * 5. iterate over the completed queue in reverse order, calling
	 *    `callback` on each one.
	 *
	 * NOTES:
	 *  - not sure how this will work for package definitions.
	 *  - should probably use this just for the executable parts of the AST,
	 *    not for nodes defining classes, function metadata, etc.
	 */
	b_queue_push_back(&it->it_queue, &node->n_it.it_entry);
	node->n_it.it_depth = 0;

	b_queue_entry *entry = b_queue_first(&it->it_queue);

	while (entry) {
		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);

		if (!node) {
			/* this should never happen. */
			return IVY_ERR_INTERNAL_FAILURE;
		}

		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);
		}

		entry = b_queue_next(entry);
	}

	while (!b_queue_empty(&it->it_queue)) {
		b_queue_entry *entry = b_queue_pop_back(&it->it_queue);
		if (!entry) {
			break;
		}

		node = b_unbox(struct ivy_ast_node, entry, n_it);

		if (!node) {
			/* this should never happen. */
			return IVY_ERR_INTERNAL_FAILURE;
		}

		// callback(node, it);
	}

	return IVY_OK;
}

enum ivy_status ivy_ast_node_iterate(
	struct ivy_ast_node *node, struct ivy_ast_node_iterator *it,
	ivy_ast_node_iteration_callback callback, void *arg)
{
	b_queue_push_back(&it->it_queue, &node->n_it.it_entry);
	node->n_it.it_depth = 0;

	b_queue_entry *entry = b_queue_first(&it->it_queue);

	while (entry) {
		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);

		if (!node) {
			/* this should never happen. */
			return IVY_ERR_INTERNAL_FAILURE;
		}

		enum ivy_status status
			= callback(node, IVY_AST_ITERATION_PRE, it, arg);
		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);
		}

		entry = b_queue_next(entry);
	}

	while (!b_queue_empty(&it->it_queue)) {
		b_queue_entry *entry = b_queue_pop_back(&it->it_queue);
		if (!entry) {
			break;
		}

		node = b_unbox(struct ivy_ast_node, entry, n_it);

		if (!node) {
			/* this should never happen. */
			return IVY_ERR_INTERNAL_FAILURE;
		}

		enum ivy_status status
			= callback(node, IVY_AST_ITERATION_POST, it, arg);
		if (status != IVY_OK) {
			return status;
		}
	}

	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;
}