/*

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

 *

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

 */

#include <LibWeb/Bindings/NodeIteratorPrototype.h>

#include <LibWeb/DOM/Document.h>

#include <LibWeb/DOM/Node.h>

#include <LibWeb/DOM/NodeIterator.h>

#include <LibWeb/WebIDL/AbstractOperations.h>

namespace Web::DOM {

JS_DEFINE_ALLOCATOR(NodeIterator);

NodeIterator::NodeIterator(Node& root)

    : PlatformObject(root.realm())

    , m_root(root)

    , m_reference({ root })

{

    root.document().register_node_iterator({}, *this);

}

NodeIterator::~NodeIterator() = default;

void NodeIterator::initialize(JS::Realm& realm)

{

    Base::initialize(realm);

    WEB_SET_PROTOTYPE_FOR_INTERFACE(NodeIterator);

}

void NodeIterator::finalize()

{

    Base::finalize();

    m_root->document().unregister_node_iterator({}, *this);

}

void NodeIterator::visit_edges(Cell::Visitor& visitor)

{

    Base::visit_edges(visitor);

    visitor.visit(m_filter);

    visitor.visit(m_root);

    visitor.visit(m_reference.node);

    if (m_traversal_pointer.has_value())

        visitor.visit(m_traversal_pointer->node);

}

// https://dom.spec.whatwg.org/#dom-document-createnodeiterator

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

{

    // 1. Let iterator be a new NodeIterator object.

    // 2. Set iterator’s root and iterator’s reference to root.

    // 3. Set iterator’s pointer before reference to true.

    auto& realm = root.realm();

    auto iterator = realm.heap().allocate<NodeIterator>(realm, root);

    // 4. Set iterator’s whatToShow to whatToShow.

    iterator->m_what_to_show = what_to_show;

    // 5. Set iterator’s filter to filter.

    iterator->m_filter = filter;

    // 6. Return iterator.

    return iterator;

}

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

void NodeIterator::detach()

{

    // The detach() method steps are to do nothing.

    // Its functionality (disabling a NodeIterator object) was removed, but the method itself is preserved for compatibility.

}

// https://dom.spec.whatwg.org/#concept-nodeiterator-traverse

JS::ThrowCompletionOr<JS::GCPtr<Node>> NodeIterator::traverse(Direction direction)

{

    // 1. Let node be iterator’s reference.

    // 2. Let beforeNode be iterator’s pointer before reference.

    m_traversal_pointer = m_reference;

    JS::GCPtr<Node> candidate;

    // 3. While true:

    while (true) {

        // 4. Branch on direction:

        if (direction == Direction::Next) {

            // next

            // If beforeNode is false, then set node to the first node following node in iterator’s iterator collection.

            // If there is no such node, then return null.

            if (!m_traversal_pointer->is_before_node) {

                auto* next_node = m_traversal_pointer->node->next_in_pre_order(m_root.ptr());

                if (!next_node)

                    return nullptr;

                m_traversal_pointer->node = *next_node;

            } else {

                // If beforeNode is true, then set it to false.

                m_traversal_pointer->is_before_node = false;

            }

        } else {

            // previous

            // If beforeNode is true, then set node to the first node preceding node in iterator’s iterator collection.

            // If there is no such node, then return null.

            if (m_traversal_pointer->is_before_node) {

                if (m_traversal_pointer->node.ptr() == m_root.ptr())

                    return nullptr;

                auto* previous_node = m_traversal_pointer->node->previous_in_pre_order();

                if (!previous_node)

                    return nullptr;

                m_traversal_pointer->node = *previous_node;

            } else {

                // If beforeNode is false, then set it to true.

                m_traversal_pointer->is_before_node = true;

            }

        }

        // NOTE: If the NodeFilter deletes the iterator's current traversal pointer,

        //       we will automatically retarget it. However, in that case, we're expected

        //       to return the node passed to the filter, not the adjusted traversal pointer's

        //       node after the filter returns!

        candidate = m_traversal_pointer->node;

        // 2. Let result be the result of filtering node within iterator.

        auto result = TRY(filter(*m_traversal_pointer->node));

        // 3. If result is FILTER_ACCEPT, then break.

        if (result == NodeFilter::Result::FILTER_ACCEPT)

            break;

    }

    // 4. Set iterator’s reference to node.

    // 5. Set iterator’s pointer before reference to beforeNode.

    m_reference = m_traversal_pointer.release_value();

    // 6. Return node.

    return candidate;

}

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

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

{

    // 1. If traverser’s active flag is set, then throw an "InvalidStateError" DOMException.

    if (m_active)

        return throw_completion(WebIDL::InvalidStateError::create(realm(), "NodeIterator is already active"_string));

    // 2. Let n be node’s nodeType attribute value − 1.

    auto n = node.node_type() - 1;

    // 3. If the nth bit (where 0 is the least significant bit) of traverser’s whatToShow is not set, then return FILTER_SKIP.

    if (!(m_what_to_show & (1u << n)))

        return NodeFilter::Result::FILTER_SKIP;

    // 4. If traverser’s filter is null, then return FILTER_ACCEPT.

    if (!m_filter)

        return NodeFilter::Result::FILTER_ACCEPT;

    // 5. Set traverser’s active flag.

    m_active = true;

    // 6. Let result be the return value of call a user object’s operation with traverser’s filter, "acceptNode", and « node ».

    //    If this throws an exception, then unset traverser’s active flag and rethrow the exception.

    auto result = WebIDL::call_user_object_operation(m_filter->callback(), "acceptNode"_string, {}, &node);

    if (result.is_abrupt()) {

        m_active = false;

        return result;

    }

    // 7. Unset traverser’s active flag.

    m_active = false;

    // 8. Return result.

    auto result_value = TRY(result.value()->to_i32(vm()));

    return static_cast<NodeFilter::Result>(result_value);

}

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

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

{

    return traverse(Direction::Next);

}

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

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

{

    return traverse(Direction::Previous);

}

void NodeIterator::run_pre_removing_steps_with_node_pointer(Node& to_be_removed_node, NodePointer& pointer)

{

    // NOTE: This function tries to match the behavior of other engines, but not the DOM specification

    //       as it's a known issue that the spec doesn't match how major browsers behave.

    //       Spec bug: https://github.com/whatwg/dom/issues/907

    if (!to_be_removed_node.is_descendant_of(root()))

        return;

    if (!to_be_removed_node.is_inclusive_ancestor_of(pointer.node))

        return;

    if (pointer.is_before_node) {

        if (auto* node = to_be_removed_node.next_in_pre_order(root())) {

            while (node && node->is_descendant_of(to_be_removed_node))

                node = node->next_in_pre_order(root());

            if (node)

                pointer.node = *node;

            return;

        }

        if (auto* node = to_be_removed_node.previous_in_pre_order()) {

            if (to_be_removed_node.is_ancestor_of(pointer.node)) {

                while (node && node->is_descendant_of(to_be_removed_node))

                    node = node->previous_in_pre_order();

            }

            if (node) {

                pointer = {

                    .node = *node,

                    .is_before_node = false,

                };

            }

        }

        return;

    }

    if (auto* node = to_be_removed_node.previous_in_pre_order()) {

        if (to_be_removed_node.is_ancestor_of(pointer.node)) {

            while (node && node->is_descendant_of(to_be_removed_node))

                node = node->previous_in_pre_order();

        }

        if (node)

            pointer.node = *node;

        return;

    }

    auto* node = to_be_removed_node.next_in_pre_order(root());

    if (to_be_removed_node.is_ancestor_of(pointer.node)) {

        while (node && node->is_descendant_of(to_be_removed_node))

            node = node->previous_in_pre_order();

    }

    if (node)

        pointer.node = *node;

}

// https://dom.spec.whatwg.org/#nodeiterator-pre-removing-steps

void NodeIterator::run_pre_removing_steps(Node& to_be_removed_node)

{

    // NOTE: If we're in the middle of traversal, we have to adjust the traversal pointer in response to node removal.

    if (m_traversal_pointer.has_value())

        run_pre_removing_steps_with_node_pointer(to_be_removed_node, *m_traversal_pointer);

    run_pre_removing_steps_with_node_pointer(to_be_removed_node, m_reference);

}

}