ladybird/Libraries/LibDevTools/Actors/WalkerActor.cpp

/*
 * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/JsonArray.h>
#include <AK/StringUtils.h>
#include <LibDevTools/Actors/AccessibilityNodeActor.h>
#include <LibDevTools/Actors/LayoutInspectorActor.h>
#include <LibDevTools/Actors/TabActor.h>
#include <LibDevTools/Actors/WalkerActor.h>
#include <LibDevTools/DevToolsDelegate.h>
#include <LibDevTools/DevToolsServer.h>
#include <LibWeb/DOM/NodeType.h>
#include <LibWebView/Mutation.h>

namespace DevTools {

NonnullRefPtr<WalkerActor> WalkerActor::create(DevToolsServer& devtools, String name, WeakPtr<TabActor> tab, JsonObject dom_tree)
{
    return adopt_ref(*new WalkerActor(devtools, move(name), move(tab), move(dom_tree)));
}

WalkerActor::WalkerActor(DevToolsServer& devtools, String name, WeakPtr<TabActor> tab, JsonObject dom_tree)
    : Actor(devtools, move(name))
    , m_tab(move(tab))
    , m_dom_tree(move(dom_tree))
{
    populate_dom_tree_cache();

    if (auto tab = m_tab.strong_ref()) {
        devtools.delegate().listen_for_dom_mutations(tab->description(),
            weak_callback(*this, [](auto& self, WebView::Mutation mutation) {
                self.new_dom_node_mutation(move(mutation));
            }));
    }
}

WalkerActor::~WalkerActor()
{
    if (auto tab = m_tab.strong_ref())
        devtools().delegate().stop_listening_for_dom_mutations(tab->description());
}

void WalkerActor::handle_message(Message const& message)
{
    JsonObject response;

    if (message.type == "children"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto ancestor_node = WalkerActor::dom_node_for(*this, *node);
        if (!ancestor_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        JsonArray nodes;

        if (auto children = ancestor_node->node.get_array("children"sv); children.has_value()) {
            children->for_each([&](JsonValue const& child) {
                nodes.must_append(serialize_node(child.as_object()));
            });
        }

        response.set("hasFirst"sv, !nodes.is_empty());
        response.set("hasLast"sv, !nodes.is_empty());
        response.set("nodes"sv, move(nodes));
        send_response(message, move(response));
        return;
    }

    if (message.type == "duplicateNode"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().clone_dom_node(dom_node->tab->description(), dom_node->identifier.id, default_async_handler(message));
        return;
    }

    if (message.type == "editTagName"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto tag_name = get_required_parameter<String>(message, "tagName"sv);
        if (!tag_name.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().set_dom_node_tag(dom_node->tab->description(), dom_node->identifier.id, *tag_name, default_async_handler(message));
        return;
    }

    if (message.type == "getLayoutInspector"sv) {
        if (!m_layout_inspector)
            m_layout_inspector = devtools().register_actor<LayoutInspectorActor>(m_tab, make_weak_ptr<WalkerActor>());

        JsonObject actor;
        actor.set("actor"sv, m_layout_inspector->name());

        response.set("actor"sv, move(actor));
        send_response(message, move(response));
        return;
    }

    if (message.type == "getMutations"sv) {
        response.set("mutations"sv, serialize_mutations());
        send_response(message, move(response));

        m_has_new_mutations_since_last_mutations_request = false;
        return;
    }

    if (message.type == "getNodeFromActor"sv) {
        auto path = get_required_parameter<JsonArray>(message, "path"sv);
        if (!path.has_value())
            return;

        auto actor_id = get_required_parameter<String>(message, "actorID"sv);
        if (!actor_id.has_value())
            return;

        // The ["rawAccessible","DOMNode"] path retrieves the DOM node corresponding to an AccessibilityNodeActor.
        if (path->size() == 2) {
            auto const& first = path->at(0);
            auto const& second = path->at(1);
            if (first.is_string() && first.as_string() == "rawAccessible"sv
                && second.is_string() && second.as_string() == "DOMNode"sv) {

                auto maybe_actor = devtools().actor_registry().find(actor_id.value());
                if (maybe_actor == devtools().actor_registry().end()) {
                    send_unknown_actor_error(message, actor_id.value());
                    return;
                }

                auto accessibility_actor = as<AccessibilityNodeActor>(maybe_actor->value.ptr());
                if (auto node_actor_name = m_dom_node_id_to_actor_map.get(accessibility_actor->node_identifier().id); node_actor_name.has_value()) {
                    auto dom_node = dom_node_for(this, node_actor_name.value());
                    if (!dom_node.has_value()) {
                        send_unknown_actor_error(message, node_actor_name.value());
                        return;
                    }

                    JsonObject node;
                    node.set("node"sv, serialize_node(dom_node->node));
                    node.set("newParents"sv, JsonArray {});

                    response.set("node"sv, move(node));
                    send_response(message, move(response));
                    return;
                }
            }
        }

        // Firefox asks for ["containerEl"] on a GridActor when the grid form did not include a containerNodeActorID.
        if (path->size() == 1 && path->at(0).is_string() && path->at(0).as_string() == "containerEl"sv) {
            auto maybe_actor = devtools().actor_registry().find(actor_id.value());
            if (maybe_actor == devtools().actor_registry().end()) {
                send_unknown_actor_error(message, actor_id.value());
                return;
            }

            if (auto* grid_actor = as_if<GridActor>(maybe_actor->value.ptr())) {
                if (auto node_actor_name = m_dom_node_id_to_actor_map.get(grid_actor->container_node_id()); node_actor_name.has_value()) {
                    auto dom_node = dom_node_for(this, node_actor_name.value());
                    if (!dom_node.has_value()) {
                        send_unknown_actor_error(message, node_actor_name.value());
                        return;
                    }

                    JsonObject node;
                    node.set("node"sv, serialize_node(dom_node->node));
                    node.set("newParents"sv, JsonArray {});

                    response.set("node"sv, move(node));
                    send_response(message, move(response));
                    return;
                }
            }
        }

        JsonObject error;
        error.set("error"sv, "unrecognizedNodePath"sv);
        error.set("message"sv, MUST(String::formatted("Unrecognized or missing path for getNodeFromActor: '{}'", message.data.serialized())));
        send_response(message, move(error));
        return;
    }

    if (message.type == "getOffsetParent"sv) {
        response.set("node"sv, JsonValue {});
        send_response(message, move(response));
        return;
    }

    if (message.type == "getParentGridNode"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        JsonValue parent_grid_node;
        if (auto parent_grid = parent_grid_node_for_node(dom_node->node); parent_grid.has_value())
            parent_grid_node = serialize_node(parent_grid.value());

        response.set("node"sv, move(parent_grid_node));
        send_response(message, move(response));
        return;
    }

    if (message.type == "innerHTML"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().get_dom_node_inner_html(dom_node->tab->description(), dom_node->identifier.id,
            async_handler(message, [](auto&, auto html, auto& response) {
                response.set("value"sv, move(html));
            }));

        return;
    }

    if (message.type == "insertAdjacentHTML") {
        // FIXME: This message also contains `value` and `position` parameters, containing the HTML to insert and the
        //        location to insert it. For the "Create New Node" action, this is always "<div></div>" and "beforeEnd",
        //        which is exactly what our WebView implementation currently supports.
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().create_child_element(dom_node->tab->description(), dom_node->identifier.id,
            async_handler<WalkerActor>(message, [](auto& self, auto node_id, auto& response) {
                JsonArray nodes;

                if (auto actor = self.m_dom_node_id_to_actor_map.get(node_id); actor.has_value()) {
                    if (auto dom_node = WalkerActor::dom_node_for(self, *actor); dom_node.has_value())
                        nodes.must_append(self.serialize_node(dom_node->node));
                }

                response.set("newParents"sv, JsonArray {});
                response.set("nodes"sv, move(nodes));
            }));

        return;
    }

    if (message.type == "insertBefore"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto parent = get_required_parameter<String>(message, "parent"sv);
        if (!parent.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        auto parent_dom_node = WalkerActor::dom_node_for(*this, *parent);
        if (!parent_dom_node.has_value()) {
            send_unknown_actor_error(message, *parent);
            return;
        }

        Optional<Web::UniqueNodeID> sibling_node_id;
        if (auto sibling = message.data.get_string("sibling"sv); sibling.has_value()) {
            auto sibling_dom_node = WalkerActor::dom_node_for(*this, *sibling);
            if (!sibling_dom_node.has_value()) {
                send_unknown_actor_error(message, *sibling);
                return;
            }

            sibling_node_id = sibling_dom_node->identifier.id;
        }

        devtools().delegate().insert_dom_node_before(dom_node->tab->description(), dom_node->identifier.id, parent_dom_node->identifier.id, sibling_node_id, default_async_handler(message));
        return;
    }

    if (message.type == "isInDOMTree"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        response.set("attached"sv, m_actor_to_dom_node_map.contains(*node));
        send_response(message, move(response));
        return;
    }

    if (message.type == "outerHTML"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().get_dom_node_outer_html(dom_node->tab->description(), dom_node->identifier.id,
            async_handler(message, [](auto&, auto html, auto& response) {
                response.set("value"sv, move(html));
            }));

        return;
    }

    if (message.type == "previousSibling"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        JsonValue previous_sibling;
        if (auto previous_sibling_node = previous_sibling_for_node(dom_node->node); previous_sibling_node.has_value())
            previous_sibling = serialize_node(*previous_sibling_node);

        response.set("node"sv, move(previous_sibling));
        send_response(message, move(response));
        return;
    }

    if (message.type == "querySelector"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto selector = get_required_parameter<String>(message, "selector"sv);
        if (!selector.has_value())
            return;

        auto ancestor_node = WalkerActor::dom_node_for(*this, *node);
        if (!ancestor_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        if (auto selected_node = find_node_by_selector(ancestor_node->node, *selector); selected_node.has_value()) {
            response.set("node"sv, serialize_node(*selected_node));

            if (auto parent = m_dom_node_to_parent_map.get(&selected_node.value()); parent.value() && parent.value() != &ancestor_node->node) {
                // FIXME: Should this be a stack of nodes leading to `ancestor_node`?
                JsonArray new_parents;
                new_parents.must_append(serialize_node(*parent.value()));

                response.set("newParents"sv, move(new_parents));
            }
        }

        send_response(message, move(response));
        return;
    }

    if (message.type == "removeNode"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        JsonValue next_sibling;
        if (auto next_sibling_node = next_sibling_for_node(dom_node->node); next_sibling_node.has_value())
            next_sibling = serialize_node(*next_sibling_node);

        auto parent_node = remove_node(dom_node->node);
        if (!parent_node.has_value())
            return;

        devtools().delegate().remove_dom_node(dom_node->tab->description(), dom_node->identifier.id,
            async_handler(message, [next_sibling = move(next_sibling)](auto&, auto, auto& response) mutable {
                response.set("nextSibling"sv, move(next_sibling));
            }));

        return;
    }

    if (message.type == "retainNode"sv) {
        send_response(message, move(response));
        return;
    }

    if (message.type == "setOuterHTML"sv) {
        auto node = get_required_parameter<String>(message, "node"sv);
        if (!node.has_value())
            return;

        auto value = get_required_parameter<String>(message, "value"sv);
        if (!value.has_value())
            return;

        auto dom_node = WalkerActor::dom_node_for(*this, *node);
        if (!dom_node.has_value()) {
            send_unknown_actor_error(message, *node);
            return;
        }

        devtools().delegate().set_dom_node_outer_html(dom_node->tab->description(), dom_node->identifier.id, value.release_value(), default_async_handler(message));
        return;
    }

    if (message.type == "watchRootNode"sv) {
        response.set("type"sv, "root-available"sv);
        response.set("node"sv, serialize_root());
        send_response(message, move(response));

        send_message({});
        return;
    }

    send_unrecognized_packet_type_error(message);
}

bool WalkerActor::is_suitable_for_dom_inspection(JsonValue const& node)
{
    if (!node.is_object())
        return true;

    auto const& object = node.as_object();

    if (!object.has_string("name"sv) || !object.has_string("type"sv))
        return false;

    if (auto text = object.get_string("text"sv); text.has_value()) {
        if (AK::StringUtils::is_whitespace(*text))
            return false;
    }
    if (auto data = object.get_string("data"sv); data.has_value()) {
        if (AK::StringUtils::is_whitespace(*data))
            return false;
    }

    return true;
}

JsonValue WalkerActor::serialize_root() const
{
    return serialize_node(m_dom_tree);
}

JsonValue WalkerActor::serialize_node(JsonObject const& node) const
{
    auto tab = m_tab.strong_ref();
    if (!tab)
        return {};

    auto actor = node.get_string("actor"sv);
    if (!actor.has_value())
        return {};

    auto name = node.get_string("name"sv).release_value();
    auto type = node.get_string("type"sv).release_value();

    auto dom_type = parse_dom_node_type(type);
    JsonValue node_value;

    auto is_top_level_document = &node == &m_dom_tree;
    auto is_displayed = !is_top_level_document && node.get_bool("visible"sv).value_or(false);
    auto is_scrollable = node.get_bool("scrollable"sv).value_or(false);

    auto is_shadow_root = false;
    auto is_after_pseudo_element = false;
    auto is_before_pseudo_element = false;
    auto is_marker_pseudo_element = false;

    if (dom_type == Web::DOM::NodeType::TEXT_NODE) {
        if (auto text = node.get_string("text"sv); text.has_value())
            node_value = text.release_value();
    } else if (dom_type == Web::DOM::NodeType::COMMENT_NODE) {
        if (auto data = node.get_string("data"sv); data.has_value())
            node_value = data.release_value();
    }

    if (type == "shadow-root"sv) {
        is_shadow_root = true;
    } else if (type == "pseudo-element"sv) {
        auto pseudo_element = node.get_integer<UnderlyingType<Web::CSS::PseudoElement>>("pseudo-element"sv).map([](auto value) {
            VERIFY(value < to_underlying(Web::CSS::PseudoElement::KnownPseudoElementCount));
            return static_cast<Web::CSS::PseudoElement>(value);
        });

        is_after_pseudo_element = pseudo_element == Web::CSS::PseudoElement::After;
        is_before_pseudo_element = pseudo_element == Web::CSS::PseudoElement::Before;
        is_marker_pseudo_element = pseudo_element == Web::CSS::PseudoElement::Marker;

        auto parent_id = node.get_integer<Web::UniqueNodeID::Type>("parent-id"sv).value();

        if (auto parent_actor = m_dom_node_id_to_actor_map.get(parent_id); parent_actor.has_value()) {
            if (auto parent_node = WalkerActor::dom_node_for(this, *parent_actor); parent_node.has_value()) {
                dom_type = parse_dom_node_type(parent_node->node.get_string("type"sv).value());
                is_displayed = !is_top_level_document && parent_node->node.get_bool("visible"sv).value_or(false);
            }
        }
    }

    size_t child_count = 0;
    if (auto children = node.get_array("children"sv); children.has_value())
        child_count = children->size();

    JsonArray attrs;

    if (auto attributes = node.get_object("attributes"sv); attributes.has_value()) {
        attributes->for_each_member([&](String const& name, JsonValue const& value) {
            if (!value.is_string())
                return;

            JsonObject attr;
            attr.set("name"sv, name);
            attr.set("value"sv, value.as_string());
            attrs.must_append(move(attr));
        });
    }

    JsonObject serialized;
    serialized.set("actor"sv, actor.release_value());
    serialized.set("attrs"sv, move(attrs));
    serialized.set("baseURI"sv, tab->description().url);
    serialized.set("causesOverflow"sv, false);
    serialized.set("containerType"sv, JsonValue {});
    serialized.set("displayName"sv, name.to_ascii_lowercase());
    serialized.set("displayType"sv, node.get_string("display"sv).value_or("block"_string));
    serialized.set("hasEventListeners"sv, false);
    serialized.set("isAfterPseudoElement"sv, is_after_pseudo_element);
    serialized.set("isAnonymous"sv, false);
    serialized.set("isBeforePseudoElement"sv, is_before_pseudo_element);
    serialized.set("isDirectShadowHostChild"sv, JsonValue {});
    serialized.set("isDisplayed"sv, is_displayed);
    serialized.set("isInHTMLDocument"sv, true);
    serialized.set("isMarkerPseudoElement"sv, is_marker_pseudo_element);
    serialized.set("isNativeAnonymous"sv, false);
    serialized.set("isScrollable"sv, is_scrollable);
    serialized.set("isShadowHost"sv, false);
    serialized.set("isShadowRoot"sv, is_shadow_root);
    serialized.set("isTopLevelDocument"sv, is_top_level_document);
    serialized.set("nodeName"sv, name);
    serialized.set("nodeType"sv, to_underlying(dom_type));
    serialized.set("nodeValue"sv, move(node_value));
    serialized.set("numChildren"sv, child_count);
    serialized.set("shadowRootMode"sv, JsonValue {});
    serialized.set("traits"sv, JsonObject {});

    // FIXME: De-duplicate this string. LibDevTools currently cannot depend on LibWeb.
    serialized.set("namespaceURI"sv, "http://www.w3.org/1999/xhtml"sv);

    if (!is_top_level_document) {
        if (auto parent = m_dom_node_to_parent_map.get(&node); parent.has_value() && parent.value()) {
            actor = parent.value()->get_string("actor"sv);
            if (!actor.has_value())
                return {};

            serialized.set("parent"sv, actor.release_value());
        }
    }

    return serialized;
}

Optional<Node> WalkerActor::dom_node_for(WeakPtr<WalkerActor> const& weak_walker, StringView actor)
{
    if (auto walker = weak_walker.strong_ref())
        return walker->dom_node(actor);
    return {};
}

Optional<Node> WalkerActor::dom_node(StringView actor)
{
    auto tab = m_tab.strong_ref();
    if (!tab)
        return {};

    auto maybe_dom_node = m_actor_to_dom_node_map.get(actor);
    if (!maybe_dom_node.has_value() || !maybe_dom_node.value())
        return {};

    auto const& dom_node = *maybe_dom_node.value();
    auto identifier = NodeIdentifier::for_node(dom_node);

    return Node { .node = dom_node, .identifier = move(identifier), .tab = tab.release_nonnull() };
}

Optional<String> WalkerActor::node_actor_name_for(Web::UniqueNodeID node_id) const
{
    return m_dom_node_id_to_actor_map.get(node_id).copy();
}

Optional<JsonObject const&> WalkerActor::find_node_by_selector(JsonObject const& node, StringView selector)
{
    auto matches = [&](auto const& candidate) {
        return candidate.get_string("name"sv)->equals_ignoring_ascii_case(selector);
    };

    if (matches(node))
        return node;

    if (auto children = node.get_array("children"sv); children.has_value()) {
        for (size_t i = 0; i < children->size(); ++i) {
            auto const& child = children->at(i);

            if (matches(child.as_object()))
                return child.as_object();

            if (auto result = find_node_by_selector(child.as_object(), selector); result.has_value())
                return result;
        }
    }

    return {};
}

enum class Direction {
    Previous,
    Next,
};
static Optional<JsonObject const&> sibling_for_node(JsonObject const& parent, JsonObject const& node, Direction direction)
{
    auto children = parent.get_array("children"sv);
    VERIFY(children.has_value());

    auto index = children->values().find_first_index_if([&](auto const& child) {
        return &child.as_object() == &node;
    });
    VERIFY(index.has_value());

    switch (direction) {
    case Direction::Previous:
        if (*index == 0)
            return {};
        index = *index - 1;
        break;

    case Direction::Next:
        if (*index == children->size() - 1)
            return {};
        index = *index + 1;
        break;
    }

    return children->at(*index).as_object();
}

Optional<JsonObject const&> WalkerActor::previous_sibling_for_node(JsonObject const& node)
{
    auto parent = m_dom_node_to_parent_map.get(&node);
    if (!parent.has_value() || !parent.value())
        return {};
    return sibling_for_node(*parent.value(), node, Direction::Previous);
}

Optional<JsonObject const&> WalkerActor::next_sibling_for_node(JsonObject const& node)
{
    auto parent = m_dom_node_to_parent_map.get(&node);
    if (!parent.has_value() || !parent.value())
        return {};
    return sibling_for_node(*parent.value(), node, Direction::Next);
}

Optional<JsonObject const&> WalkerActor::parent_grid_node_for_node(JsonObject const& node) const
{
    auto parent = m_dom_node_to_parent_map.get(&node);
    while (parent.has_value() && parent.value()) {
        auto display = parent.value()->get_string("display"sv);
        if (!display.has_value())
            return {};
        if (display->contains("grid"sv))
            return *parent.value();
        if (*display != "contents"sv)
            return {};

        parent = m_dom_node_to_parent_map.get(parent.value());
    }

    return {};
}

Optional<JsonObject const&> WalkerActor::remove_node(JsonObject const& node)
{
    auto maybe_parent = m_dom_node_to_parent_map.get(&node);
    if (!maybe_parent.has_value() || !maybe_parent.value())
        return {};
    auto const& parent = *maybe_parent.value();

    auto children = parent.get_array("children"sv);
    VERIFY(children.has_value());

    const_cast<JsonArray&>(*children).values().remove_first_matching([&](auto const& child) {
        return &child.as_object() == &node;
    });

    populate_dom_tree_cache();
    return parent;
}

void WalkerActor::new_dom_node_mutation(WebView::Mutation mutation)
{
    auto serialized_target = JsonValue::from_string(mutation.serialized_target);
    if (serialized_target.is_error() || !serialized_target.value().is_object()) {
        dbgln_if(DEVTOOLS_DEBUG, "Unable to parse serialized target as JSON object: {}", serialized_target.error());
        return;
    }

    if (!replace_node_in_tree(move(serialized_target.release_value().as_object()))) {
        dbgln_if(DEVTOOLS_DEBUG, "Unable to apply mutation to DOM tree");
        return;
    }

    m_dom_node_mutations.append(move(mutation));

    if (m_has_new_mutations_since_last_mutations_request)
        return;

    JsonObject message;
    message.set("type"sv, "newMutations"sv);
    send_message(move(message));

    m_has_new_mutations_since_last_mutations_request = true;
}

JsonValue WalkerActor::serialize_mutations()
{
    JsonArray mutations;
    mutations.ensure_capacity(m_dom_node_mutations.size());

    for (auto& mutation : m_dom_node_mutations) {
        auto target = m_dom_node_id_to_actor_map.get(mutation.target);
        if (!target.has_value())
            continue;

        JsonObject serialized;
        serialized.set("target"sv, target.release_value());
        serialized.set("type"sv, move(mutation.type));

        mutation.mutation.visit(
            [&](WebView::AttributeMutation& mutation) {
                serialized.set("attributeName"sv, move(mutation.attribute_name));

                if (mutation.new_value.has_value())
                    serialized.set("newValue"sv, mutation.new_value.release_value());
                else
                    serialized.set("newValue"sv, JsonValue {});
            },
            [&](WebView::CharacterDataMutation& mutation) {
                serialized.set("newValue"sv, move(mutation.new_value));
            },
            [&](WebView::ChildListMutation const& mutation) {
                JsonArray added;
                JsonArray removed;

                for (auto id : mutation.added) {
                    if (auto node = m_dom_node_id_to_actor_map.get(id); node.has_value())
                        added.must_append(node.release_value());
                }
                for (auto id : mutation.removed) {
                    if (auto node = m_dom_node_id_to_actor_map.get(id); node.has_value())
                        removed.must_append(node.release_value());
                }

                serialized.set("added"sv, move(added));
                serialized.set("removed"sv, move(removed));
                serialized.set("numChildren"sv, mutation.target_child_count);
            });

        mutations.must_append(move(serialized));
    }

    m_dom_node_mutations.clear();
    return mutations;
}

bool WalkerActor::replace_node_in_tree(JsonObject replacement)
{
    auto const& actor = actor_for_node(replacement);

    auto node = m_actor_to_dom_node_map.get(actor.name());
    if (!node.has_value() || !node.value())
        return false;

    const_cast<JsonObject&>(*node.value()) = move(replacement);
    populate_dom_tree_cache();

    return true;
}

void WalkerActor::populate_dom_tree_cache()
{
    m_dom_node_to_parent_map.clear();
    m_actor_to_dom_node_map.clear();
    m_dom_node_id_to_actor_map.clear();

    populate_dom_tree_cache(m_dom_tree, nullptr);
}

void WalkerActor::populate_dom_tree_cache(JsonObject& node, JsonObject const* parent)
{
    auto const& node_actor = actor_for_node(node);
    node.set("actor"sv, node_actor.name());

    m_dom_node_to_parent_map.set(&node, parent);
    m_actor_to_dom_node_map.set(node_actor.name(), &node);

    if (!node_actor.node_identifier().pseudo_element.has_value())
        m_dom_node_id_to_actor_map.set(node_actor.node_identifier().id, node_actor.name());

    auto children = node.get_array("children"sv);
    if (!children.has_value())
        return;

    children->values().remove_all_matching([&](JsonValue const& child) {
        return !is_suitable_for_dom_inspection(child);
    });

    children->for_each([&](JsonValue& child) {
        populate_dom_tree_cache(child.as_object(), &node);
    });
}

NodeActor const& WalkerActor::actor_for_node(JsonObject const& node)
{
    auto identifier = NodeIdentifier::for_node(node);

    if (auto it = m_node_actors.find(identifier); it != m_node_actors.end()) {
        if (auto node_actor = it->value.strong_ref())
            return *node_actor;
    }

    auto& node_actor = devtools().register_actor<NodeActor>(identifier, *this);
    m_node_actors.set(identifier, node_actor);

    return node_actor;
}

}