/*
 * Copyright (c) 2023-2024, Matthew Olsson <mattco@serenityos.org>.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Animations/Animation.h>
#include <LibWeb/Animations/AnimationTimeline.h>
#include <LibWeb/Bindings/AnimationTimeline.h>
#include <LibWeb/DOM/Document.h>

namespace Web::Animations {

GC_DEFINE_ALLOCATOR(AnimationTimeline);

// https://drafts.csswg.org/web-animations-1/#dom-animationtimeline-currenttime
Optional<TimeValue> AnimationTimeline::current_time() const
{
    // Returns the current time for this timeline or null if this timeline is inactive.
    if (is_inactive())
        return {};
    return m_current_time;
}

void AnimationTimeline::set_current_time(Optional<TimeValue> value)
{
    if (m_is_monotonically_increasing && m_current_time.has_value() && (!value.has_value() || *value < *m_current_time)) {
        dbgln("AnimationTimeline::set_current_time({}): monotonically increasing timeline can only move forward", value);
        return;
    }

    m_current_time = value;

    update_associated_animations_and_dispatch_events();
}

void AnimationTimeline::update_associated_animations_and_dispatch_events()
{
    // https://drafts.csswg.org/web-animations-1/#animation-frame-loop
    // Note: Due to the hierarchical nature of the timing model, updating the current time of a timeline also involves:
    // - Updating the current time of any animations associated with the timeline.
    // - Running the update an animation's finished state procedure for any animations whose current time has been
    //   updated.
    // - Queueing animation events for any such animations.
    for (auto& animation : m_associated_animations)
        animation.update();

    auto animations = GC::RootVector<GC::Ref<Animations::Animation>> { heap() };
    for (auto& animation : m_associated_animations)
        animations.append(animation);
    for (auto& animation : animations)
        m_associated_document->dispatch_events_for_animation_if_necessary(animation);
}

// https://drafts.csswg.org/web-animations-2/#timeline-duration
NullableCSSNumberish AnimationTimeline::duration_for_bindings() const
{
    // The duration of a timeline gives the maximum value a timeline may generate for its current time. This value is
    // used to calculate the intrinsic iteration duration for the target effect of an animation that is associated with
    // the timeline when the effect’s iteration duration is "auto". The value is computed such that the effect fills the
    // available time. For a monotonic timeline, there is no upper bound on current time, and timeline duration is
    // unresolved. For a non-monotonic (e.g. scroll) timeline, the duration has a fixed upper bound. In this case, the
    // timeline is a progress-based timeline, and its timeline duration is 100%.
    return NullableCSSNumberish::from_optional_css_numberish_time(realm(), duration());
}

// https://drafts.csswg.org/web-animations-1/#timeline
bool AnimationTimeline::is_inactive() const
{
    // A timeline is considered to be inactive when its time value is unresolved, and active otherwise.
    return !m_current_time.has_value();
}

AnimationTimeline::AnimationTimeline(JS::Realm& realm, GC::Ref<DOM::Document> document)
    : Bindings::PlatformObject(realm)
    , m_associated_document(document)
{
}

void AnimationTimeline::finalize()
{
    Base::finalize();
    m_associated_document->disassociate_with_timeline(*this);
}

void AnimationTimeline::initialize(JS::Realm& realm)
{
    WEB_SET_PROTOTYPE_FOR_INTERFACE(AnimationTimeline);
    Base::initialize(realm);
    m_associated_document->associate_with_timeline(*this);
}

void AnimationTimeline::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_associated_document);
    // We intentionally don't visit m_associated_animations here to avoid keeping Animations alive solely because they
    // are associated with a timeline. Animations are disassociated from timelines in Animation::finalize() so we don't
    // need to worry about dangling references.
}

}