/*
 * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Bindings/DOMExceptionWrapper.h>
#include <LibWeb/Bindings/IDLAbstractOperations.h>
#include <LibWeb/Bindings/NodeWrapper.h>
#include <LibWeb/Bindings/NodeWrapperFactory.h>
#include <LibWeb/DOM/Node.h>
#include <LibWeb/DOM/NodeIterator.h>

namespace Web::DOM {

NodeIterator::NodeIterator(Node& root)
    : m_root(root)
    , m_reference(root)
{
}

// https://dom.spec.whatwg.org/#dom-document-createnodeiterator
NonnullRefPtr<NodeIterator> NodeIterator::create(Node& root, unsigned what_to_show, RefPtr<NodeFilter> filter)
{
    // 1. Let iterator be a new NodeIterator object.
    // 2. Set iterator’s root and iterator’s reference to root.
    auto iterator = adopt_ref(*new NodeIterator(root));

    // 3. Set iterator’s pointer before reference to true.
    iterator->m_pointer_before_reference = true;

    // 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 = move(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<RefPtr<Node>> NodeIterator::traverse(Direction direction)
{
    // 1. Let node be iterator’s reference.
    auto node = m_reference;

    // 2. Let beforeNode be iterator’s pointer before reference.
    auto before_node = m_pointer_before_reference;

    // 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 (!before_node) {
                auto* next_node = node->next_in_pre_order(m_root.ptr());
                if (!next_node)
                    return RefPtr<Node> {};
                node = *next_node;
            } else {
                // If beforeNode is true, then set it to false.
                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 (before_node) {
                if (node == m_root.ptr())
                    return nullptr;
                auto* previous_node = node->previous_in_pre_order();
                if (!previous_node)
                    return RefPtr<Node> {};
                node = *previous_node;
            } else {
                // If beforeNode is false, then set it to true.
                before_node = true;
            }
        }

        // 2. Let result be the result of filtering node within iterator.
        auto result = filter(*node);
        if (result.is_throw_completion())
            return result.release_error();

        // 3. If result is FILTER_ACCEPT, then break.
        if (result.value() == NodeFilter::FILTER_ACCEPT)
            break;
    }

    // 4. Set iterator’s reference to node.
    m_reference = node;

    // 5. Set iterator’s pointer before reference to beforeNode.
    m_pointer_before_reference = before_node;

    // 6. Return node.
    return RefPtr<Node> { node };
}

// https://dom.spec.whatwg.org/#concept-node-filter
JS::ThrowCompletionOr<NodeFilter::Result> NodeIterator::filter(Node& node)
{
    VERIFY(wrapper());
    auto& global_object = wrapper()->global_object();

    // 1. If traverser’s active flag is set, then throw an "InvalidStateError" DOMException.
    if (m_active)
        return JS::throw_completion(wrap(global_object, InvalidStateError::create("NodeIterator is already active")));

    // 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::FILTER_SKIP;

    // 4. If traverser’s filter is null, then return FILTER_ACCEPT.
    if (!m_filter)
        return NodeFilter::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 = Bindings::IDL::call_user_object_operation(m_filter->callback(), "acceptNode", {}, wrap(global_object, 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(global_object));
    return static_cast<NodeFilter::Result>(result_value);
}

// https://dom.spec.whatwg.org/#dom-nodeiterator-nextnode
JS::ThrowCompletionOr<RefPtr<Node>> NodeIterator::next_node()
{
    return traverse(Direction::Next);
}

// https://dom.spec.whatwg.org/#dom-nodeiterator-previousnode
JS::ThrowCompletionOr<RefPtr<Node>> NodeIterator::previous_node()
{
    return traverse(Direction::Previous);
}

}