/*
 * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/HTML/Navigable.h>
#include <LibWeb/HTML/SessionHistoryTraversalQueue.h>

namespace Web::HTML {

JS_DEFINE_ALLOCATOR(SessionHistoryTraversalQueue);
JS_DEFINE_ALLOCATOR(SessionHistoryTraversalQueueEntry);

JS::NonnullGCPtr<SessionHistoryTraversalQueueEntry> SessionHistoryTraversalQueueEntry::create(JS::VM& vm, Function<void()> steps, JS::GCPtr<HTML::Navigable> target_navigable)
{
    return vm.heap().allocate_without_realm<SessionHistoryTraversalQueueEntry>(JS::create_heap_function(vm.heap(), move(steps)), target_navigable);
}

void SessionHistoryTraversalQueueEntry::visit_edges(JS::Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_steps);
    visitor.visit(m_target_navigable);
}

SessionHistoryTraversalQueue::SessionHistoryTraversalQueue()
{
    m_timer = Core::Timer::create_single_shot(0, [this] {
        if (m_is_task_running && m_queue.size() > 0) {
            m_timer->start();
            return;
        }
        while (m_queue.size() > 0) {
            m_is_task_running = true;
            auto entry = m_queue.take_first();
            entry->execute_steps();
            m_is_task_running = false;
        }
    }).release_value_but_fixme_should_propagate_errors();
}

void SessionHistoryTraversalQueue::visit_edges(JS::Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    for (auto const& entry : m_queue) {
        visitor.visit(entry);
    }
}

void SessionHistoryTraversalQueue::append(Function<void()> steps)
{
    m_queue.append(SessionHistoryTraversalQueueEntry::create(vm(), move(steps), nullptr));
    if (!m_timer->is_active()) {
        m_timer->start();
    }
}

void SessionHistoryTraversalQueue::append_sync(Function<void()> steps, JS::GCPtr<Navigable> target_navigable)
{
    m_queue.append(SessionHistoryTraversalQueueEntry::create(vm(), move(steps), target_navigable));
    if (!m_timer->is_active()) {
        m_timer->start();
    }
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#sync-navigations-jump-queue
JS::GCPtr<SessionHistoryTraversalQueueEntry> SessionHistoryTraversalQueue::first_synchronous_navigation_steps_with_target_navigable_not_contained_in(Vector<JS::GCPtr<Navigable>> const& list)
{
    auto index = m_queue.find_first_index_if([&list](auto const& entry) -> bool {
        return (entry->target_navigable() != nullptr) && !list.contains_slow(entry->target_navigable());
    });
    if (index.has_value())
        return m_queue.take(*index);
    return {};
}

}