/*

 * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <LibJS/Runtime/Object.h>

#include <LibWeb/DOM/NodeFilter.h>

namespace Web::DOM {

// https://dom.spec.whatwg.org/#nodeiterator

class NodeIterator final : public Bindings::PlatformObject {

    WEB_PLATFORM_OBJECT(NodeIterator, Bindings::PlatformObject);

    JS_DECLARE_ALLOCATOR(NodeIterator);

public:

    static WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeIterator>> create(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter>);

    virtual ~NodeIterator() override;

    JS::NonnullGCPtr<Node> root() { return m_root; }

    JS::NonnullGCPtr<Node> reference_node() { return m_reference.node; }

    bool pointer_before_reference_node() const { return m_reference.is_before_node; }

    unsigned what_to_show() const { return m_what_to_show; }

    NodeFilter* filter() { return m_filter.ptr(); }

    JS::ThrowCompletionOr<JS::GCPtr<Node>> next_node();

    JS::ThrowCompletionOr<JS::GCPtr<Node>> previous_node();

    void detach();

    void run_pre_removing_steps(Node&);

private:

    explicit NodeIterator(Node& root);

    virtual void initialize(JS::Realm&) override;

    virtual void visit_edges(Cell::Visitor&) override;

    virtual void finalize() override;

    enum class Direction {

        Next,

        Previous,

    };

    JS::ThrowCompletionOr<JS::GCPtr<Node>> traverse(Direction);

    JS::ThrowCompletionOr<NodeFilter::Result> filter(Node&);

    // https://dom.spec.whatwg.org/#concept-traversal-root

    JS::NonnullGCPtr<Node> m_root;

    struct NodePointer {

        JS::NonnullGCPtr<Node> node;

        // https://dom.spec.whatwg.org/#nodeiterator-pointer-before-reference

        bool is_before_node { true };

    };

    void run_pre_removing_steps_with_node_pointer(Node&, NodePointer&);

    // https://dom.spec.whatwg.org/#nodeiterator-reference

    NodePointer m_reference;

    // While traversal is ongoing, we keep track of the current node pointer.

    // This allows us to adjust it during traversal if calling the filter ends up removing the node from the DOM.

    Optional<NodePointer> m_traversal_pointer;

    // https://dom.spec.whatwg.org/#concept-traversal-whattoshow

    unsigned m_what_to_show { 0 };

    // https://dom.spec.whatwg.org/#concept-traversal-filter

    JS::GCPtr<NodeFilter> m_filter;

    // https://dom.spec.whatwg.org/#concept-traversal-active

    bool m_active { false };

};

}