/*
 * Copyright (c) 2021, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/ByteReader.h>
#include <AK/MemoryStream.h>
#include <LibCore/Socket.h>
#include <LibCore/System.h>
#include <LibIPC/Decoder.h>
#include <LibIPC/Encoder.h>
#include <LibIPC/File.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Bindings/MessagePortPrototype.h>
#include <LibWeb/DOM/EventDispatcher.h>
#include <LibWeb/HTML/EventNames.h>
#include <LibWeb/HTML/MessageEvent.h>
#include <LibWeb/HTML/MessagePort.h>
#include <LibWeb/HTML/Scripting/TemporaryExecutionContext.h>
#include <LibWeb/HTML/StructuredSerializeOptions.h>
#include <LibWeb/HTML/WorkerGlobalScope.h>

namespace Web::HTML {

constexpr u8 IPC_FILE_TAG = 0xA5;

JS_DEFINE_ALLOCATOR(MessagePort);

static HashTable<JS::RawGCPtr<MessagePort>>& all_message_ports()
{
    static HashTable<JS::RawGCPtr<MessagePort>> ports;
    return ports;
}

JS::NonnullGCPtr<MessagePort> MessagePort::create(JS::Realm& realm)
{
    return realm.heap().allocate<MessagePort>(realm, realm);
}

MessagePort::MessagePort(JS::Realm& realm)
    : DOM::EventTarget(realm)
{
    all_message_ports().set(this);
}

MessagePort::~MessagePort()
{
    all_message_ports().remove(this);
    disentangle();
}

void MessagePort::for_each_message_port(Function<void(MessagePort&)> callback)
{
    for (auto port : all_message_ports())
        callback(*port);
}

void MessagePort::initialize(JS::Realm& realm)
{
    Base::initialize(realm);
    WEB_SET_PROTOTYPE_FOR_INTERFACE(MessagePort);
}

void MessagePort::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_remote_port);

    // FIXME: This is incorrect!! We *should* be visiting the worker event target,
    //        but CI hangs if we do: https://github.com/SerenityOS/serenity/issues/23899
    visitor.ignore(m_worker_event_target);
}

void MessagePort::set_worker_event_target(JS::NonnullGCPtr<DOM::EventTarget> target)
{
    m_worker_event_target = target;
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#message-ports:transfer-steps
WebIDL::ExceptionOr<void> MessagePort::transfer_steps(HTML::TransferDataHolder& data_holder)
{
    // 1. Set value's has been shipped flag to true.
    m_has_been_shipped = true;

    // FIXME: 2. Set dataHolder.[[PortMessageQueue]] to value's port message queue.
    // FIXME: Support delivery of messages that haven't been delivered yet on the other side

    // 3. If value is entangled with another port remotePort, then:
    if (is_entangled()) {
        // 1. Set remotePort's has been shipped flag to true.
        m_remote_port->m_has_been_shipped = true;

        // 2. Set dataHolder.[[RemotePort]] to remotePort.
        auto fd = MUST(m_socket->release_fd());
        m_socket = nullptr;
        data_holder.fds.append(IPC::File::adopt_fd(fd));
        data_holder.data.append(IPC_FILE_TAG);
    }

    // 4. Otherwise, set dataHolder.[[RemotePort]] to null.
    else {
        data_holder.data.append(0);
    }

    return {};
}

WebIDL::ExceptionOr<void> MessagePort::transfer_receiving_steps(HTML::TransferDataHolder& data_holder)
{
    // 1. Set value's has been shipped flag to true.
    m_has_been_shipped = true;

    // FIXME 2. Move all the tasks that are to fire message events in dataHolder.[[PortMessageQueue]] to the port message queue of value,
    //     if any, leaving value's port message queue in its initial disabled state, and, if value's relevant global object is a Window,
    //     associating the moved tasks with value's relevant global object's associated Document.

    // 3. If dataHolder.[[RemotePort]] is not null, then entangle dataHolder.[[RemotePort]] and value.
    //     (This will disentangle dataHolder.[[RemotePort]] from the original port that was transferred.)
    auto fd_tag = data_holder.data.take_first();
    if (fd_tag == IPC_FILE_TAG) {
        auto fd = data_holder.fds.take_first();
        m_socket = MUST(Core::LocalSocket::adopt_fd(fd.take_fd()));

        m_socket->on_ready_to_read = [strong_this = JS::make_handle(this)]() {
            strong_this->read_from_socket();
        };
    } else if (fd_tag != 0) {
        dbgln("Unexpected byte {:x} in MessagePort transfer data", fd_tag);
        VERIFY_NOT_REACHED();
    }

    return {};
}

void MessagePort::disentangle()
{
    if (m_remote_port)
        m_remote_port->m_remote_port = nullptr;
    m_remote_port = nullptr;

    m_socket = nullptr;

    m_worker_event_target = nullptr;
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#entangle
void MessagePort::entangle_with(MessagePort& remote_port)
{
    if (m_remote_port.ptr() == &remote_port)
        return;

    // 1. If one of the ports is already entangled, then disentangle it and the port that it was entangled with.
    if (is_entangled())
        disentangle();
    if (remote_port.is_entangled())
        remote_port.disentangle();

    // 2. Associate the two ports to be entangled, so that they form the two parts of a new channel.
    //    (There is no MessageChannel object that represents this channel.)
    remote_port.m_remote_port = this;
    m_remote_port = &remote_port;

    auto create_paired_sockets = []() -> Array<NonnullOwnPtr<Core::LocalSocket>, 2> {
        int fds[2] = {};
        MUST(Core::System::socketpair(AF_LOCAL, SOCK_STREAM, 0, fds));
        auto socket0 = MUST(Core::LocalSocket::adopt_fd(fds[0]));
        MUST(socket0->set_blocking(false));
        MUST(socket0->set_close_on_exec(true));
        auto socket1 = MUST(Core::LocalSocket::adopt_fd(fds[1]));
        MUST(socket1->set_blocking(false));
        MUST(socket1->set_close_on_exec(true));

        return Array { move(socket0), move(socket1) };
    };

    auto sockets = create_paired_sockets();
    m_socket = move(sockets[0]);
    m_remote_port->m_socket = move(sockets[1]);

    m_socket->on_ready_to_read = [strong_this = JS::make_handle(this)]() {
        strong_this->read_from_socket();
    };

    m_remote_port->m_socket->on_ready_to_read = [remote_port = JS::make_handle(m_remote_port)]() {
        remote_port->read_from_socket();
    };
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#dom-messageport-postmessage-options
WebIDL::ExceptionOr<void> MessagePort::post_message(JS::Value message, Vector<JS::Handle<JS::Object>> const& transfer)
{
    // 1. Let targetPort be the port with which this MessagePort is entangled, if any; otherwise let it be null.
    JS::GCPtr<MessagePort> target_port = m_remote_port;

    // 2. Let options be «[ "transfer" → transfer ]».
    auto options = StructuredSerializeOptions { transfer };

    // 3. Run the message port post message steps providing this, targetPort, message and options.
    return message_port_post_message_steps(target_port, message, options);
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#dom-messageport-postmessage
WebIDL::ExceptionOr<void> MessagePort::post_message(JS::Value message, StructuredSerializeOptions const& options)
{
    // 1. Let targetPort be the port with which this MessagePort is entangled, if any; otherwise let it be null.
    JS::GCPtr<MessagePort> target_port = m_remote_port;

    // 2. Run the message port post message steps providing targetPort, message and options.
    return message_port_post_message_steps(target_port, message, options);
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#message-port-post-message-steps
WebIDL::ExceptionOr<void> MessagePort::message_port_post_message_steps(JS::GCPtr<MessagePort> target_port, JS::Value message, StructuredSerializeOptions const& options)
{
    auto& realm = this->realm();
    auto& vm = this->vm();

    // 1. Let transfer be options["transfer"].
    auto const& transfer = options.transfer;

    // 2. If transfer contains this MessagePort, then throw a "DataCloneError" DOMException.
    for (auto const& handle : transfer) {
        if (handle == this)
            return WebIDL::DataCloneError::create(realm, "Cannot transfer a MessagePort to itself"_string);
    }

    // 3. Let doomed be false.
    bool doomed = false;

    // 4. If targetPort is not null and transfer contains targetPort, then set doomed to true and optionally report to a developer console that the target port was posted to itself, causing the communication channel to be lost.
    if (target_port) {
        for (auto const& handle : transfer) {
            if (handle == target_port.ptr()) {
                doomed = true;
                dbgln("FIXME: Report to a developer console that the target port was posted to itself, causing the communication channel to be lost");
            }
        }
    }

    // 5. Let serializeWithTransferResult be StructuredSerializeWithTransfer(message, transfer). Rethrow any exceptions.
    auto serialize_with_transfer_result = TRY(structured_serialize_with_transfer(vm, message, transfer));

    // 6. If targetPort is null, or if doomed is true, then return.
    // IMPLEMENTATION DEFINED: Actually check the socket here, not the target port.
    //     If there's no target message port in the same realm, we still want to send the message over IPC
    if (!m_socket || doomed) {
        return {};
    }

    // 7. Add a task that runs the following steps to the port message queue of targetPort:
    post_port_message(move(serialize_with_transfer_result));

    return {};
}

ErrorOr<void> MessagePort::send_message_on_socket(SerializedTransferRecord const& serialize_with_transfer_result)
{
    IPC::MessageBuffer buffer;
    IPC::Encoder encoder(buffer);
    MUST(encoder.encode(serialize_with_transfer_result));

    TRY(buffer.transfer_message(*m_socket));
    return {};
}

void MessagePort::post_port_message(SerializedTransferRecord serialize_with_transfer_result)
{
    // FIXME: Use the correct task source?
    queue_global_task(Task::Source::PostedMessage, relevant_global_object(*this), JS::create_heap_function(heap(), [this, serialize_with_transfer_result = move(serialize_with_transfer_result)]() mutable {
        if (!m_socket || !m_socket->is_open())
            return;
        if (auto result = send_message_on_socket(serialize_with_transfer_result); result.is_error()) {
            dbgln("Failed to post message: {}", result.error());
            disentangle();
        }
    }));
}

ErrorOr<MessagePort::ParseDecision> MessagePort::parse_message()
{
    static constexpr size_t HEADER_SIZE = sizeof(u32);

    auto num_bytes_ready = m_buffered_data.size();
    switch (m_socket_state) {
    case SocketState::Header: {
        if (num_bytes_ready < HEADER_SIZE)
            return ParseDecision::NotEnoughData;

        m_socket_incoming_message_size = ByteReader::load32(m_buffered_data.data());
        // NOTE: We don't decrement the number of ready bytes because we want to remove the entire
        //       message + header from the buffer in one go on success
        m_socket_state = SocketState::Data;
        [[fallthrough]];
    }
    case SocketState::Data: {
        if (num_bytes_ready < HEADER_SIZE + m_socket_incoming_message_size)
            return ParseDecision::NotEnoughData;

        auto payload = m_buffered_data.span().slice(HEADER_SIZE, m_socket_incoming_message_size);

        FixedMemoryStream stream { payload, FixedMemoryStream::Mode::ReadOnly };
        IPC::Decoder decoder { stream, m_unprocessed_fds };

        auto serialized_transfer_record = TRY(decoder.decode<SerializedTransferRecord>());

        // Make sure to advance our state machine before dispatching the MessageEvent,
        // as dispatching events can run arbitrary JS (and cause us to receive another message!)
        m_socket_state = SocketState::Header;

        m_buffered_data.remove(0, HEADER_SIZE + m_socket_incoming_message_size);

        post_message_task_steps(serialized_transfer_record);

        break;
    }
    case SocketState::Error:
        return Error::from_errno(ENOMSG);
    }

    return ParseDecision::ParseNextMessage;
}

void MessagePort::read_from_socket()
{
    u8 buffer[4096] {};

    Vector<int> fds;
    // FIXME: What if pending bytes is > 4096? Should we loop here?
    auto maybe_bytes = m_socket->receive_message(buffer, MSG_NOSIGNAL, fds);
    if (maybe_bytes.is_error()) {
        dbgln("MessagePort::read_from_socket(): Failed to receive message: {}", maybe_bytes.error());
        return;
    }
    auto bytes = maybe_bytes.release_value();

    m_buffered_data.append(bytes.data(), bytes.size());

    for (auto fd : fds)
        m_unprocessed_fds.enqueue(IPC::File::adopt_fd(fd));

    while (true) {
        auto parse_decision_or_error = parse_message();
        if (parse_decision_or_error.is_error()) {
            dbgln("MessagePort::read_from_socket(): Failed to parse message: {}", parse_decision_or_error.error());
            return;
        }
        if (parse_decision_or_error.value() == ParseDecision::NotEnoughData)
            break;
    }
}

void MessagePort::post_message_task_steps(SerializedTransferRecord& serialize_with_transfer_result)
{
    // 1. Let finalTargetPort be the MessagePort in whose port message queue the task now finds itself.
    // NOTE: This can be different from targetPort, if targetPort itself was transferred and thus all its tasks moved along with it.
    auto* final_target_port = this;

    // IMPLEMENTATION DEFINED:
    // https://html.spec.whatwg.org/multipage/workers.html#dedicated-workers-and-the-worker-interface
    //      Worker objects act as if they had an implicit MessagePort associated with them.
    //      All messages received by that port must immediately be retargeted at the Worker object.
    // We therefore set a special event target for those implicit ports on the Worker and the WorkerGlobalScope objects
    EventTarget* message_event_target = final_target_port;
    if (m_worker_event_target != nullptr) {
        message_event_target = m_worker_event_target;
    }

    // 2. Let targetRealm be finalTargetPort's relevant realm.
    auto& target_realm = relevant_realm(*final_target_port);
    auto& target_vm = target_realm.vm();

    // 3. Let deserializeRecord be StructuredDeserializeWithTransfer(serializeWithTransferResult, targetRealm).
    TemporaryExecutionContext context { relevant_settings_object(*final_target_port) };
    auto deserialize_record_or_error = structured_deserialize_with_transfer(target_vm, serialize_with_transfer_result);
    if (deserialize_record_or_error.is_error()) {
        // If this throws an exception, catch it, fire an event named messageerror at finalTargetPort, using MessageEvent, and then return.
        auto exception = deserialize_record_or_error.release_error();
        MessageEventInit event_init {};
        message_event_target->dispatch_event(MessageEvent::create(target_realm, HTML::EventNames::messageerror, event_init));
        return;
    }
    auto deserialize_record = deserialize_record_or_error.release_value();

    // 4. Let messageClone be deserializeRecord.[[Deserialized]].
    auto message_clone = deserialize_record.deserialized;

    // 5. Let newPorts be a new frozen array consisting of all MessagePort objects in deserializeRecord.[[TransferredValues]], if any, maintaining their relative order.
    // FIXME: Use a FrozenArray
    Vector<JS::Handle<MessagePort>> new_ports;
    for (auto const& object : deserialize_record.transferred_values) {
        if (is<HTML::MessagePort>(*object)) {
            new_ports.append(verify_cast<MessagePort>(*object));
        }
    }

    // 6. Fire an event named message at finalTargetPort, using MessageEvent, with the data attribute initialized to messageClone and the ports attribute initialized to newPorts.
    MessageEventInit event_init {};
    event_init.data = message_clone;
    event_init.ports = move(new_ports);
    message_event_target->dispatch_event(MessageEvent::create(target_realm, HTML::EventNames::message, event_init));
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#dom-messageport-start
void MessagePort::start()
{
    if (!is_entangled())
        return;

    VERIFY(m_socket);

    // TODO: The start() method steps are to enable this's port message queue, if it is not already enabled.
}

// https://html.spec.whatwg.org/multipage/web-messaging.html#dom-messageport-close
void MessagePort::close()
{
    // 1. Set this MessagePort object's [[Detached]] internal slot value to true.
    set_detached(true);

    // 2. If this MessagePort object is entangled, disentangle it.
    if (is_entangled())
        disentangle();
}

#undef __ENUMERATE
#define __ENUMERATE(attribute_name, event_name)                         \
    void MessagePort::set_##attribute_name(WebIDL::CallbackType* value) \
    {                                                                   \
        set_event_handler_attribute(event_name, value);                 \
    }                                                                   \
    WebIDL::CallbackType* MessagePort::attribute_name()                 \
    {                                                                   \
        return event_handler_attribute(event_name);                     \
    }
ENUMERATE_MESSAGE_PORT_EVENT_HANDLERS(__ENUMERATE)
#undef __ENUMERATE

}