/*

 * Copyright (c) 2024, Matthew Olsson <mattco@serenityos.org>

 * Copyright (c) 2024, Sam Atkins <sam@ladybird.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibWeb/Animations/DocumentTimeline.h>

#include <LibWeb/Bindings/CSSTransitionPrototype.h>

#include <LibWeb/Bindings/Intrinsics.h>

#include <LibWeb/CSS/CSSStyleDeclaration.h>

#include <LibWeb/CSS/CSSTransition.h>

#include <LibWeb/CSS/Interpolation.h>

#include <LibWeb/DOM/Document.h>

#include <LibWeb/DOM/Element.h>

#include <LibWeb/HTML/Scripting/TemporaryExecutionContext.h>

namespace Web::CSS {

JS_DEFINE_ALLOCATOR(CSSTransition);

JS::NonnullGCPtr<CSSTransition> CSSTransition::start_a_transition(DOM::Element& element, PropertyID property_id, size_t transition_generation,

    double start_time, double end_time, NonnullRefPtr<CSSStyleValue const> start_value, NonnullRefPtr<CSSStyleValue const> end_value,

    NonnullRefPtr<CSSStyleValue const> reversing_adjusted_start_value, double reversing_shortening_factor)

{

    auto& realm = element.realm();

    return realm.heap().allocate<CSSTransition>(realm, realm, element, property_id, transition_generation, start_time, end_time, start_value, end_value, reversing_adjusted_start_value, reversing_shortening_factor);

}

Animations::AnimationClass CSSTransition::animation_class() const

{

    return Animations::AnimationClass::CSSTransition;

}

Optional<int> CSSTransition::class_specific_composite_order(JS::NonnullGCPtr<Animations::Animation> other_animation) const

{

    auto other = JS::NonnullGCPtr { verify_cast<CSSTransition>(*other_animation) };

    // Within the set of CSS Transitions, two animations A and B are sorted in composite order (first to last) as

    // follows:

    // 1. If neither A nor B has an owning element, sort based on their relative position in the global animation list.

    if (!owning_element() && !other->owning_element())

        return global_animation_list_order() - other->global_animation_list_order();

    // 2. Otherwise, if only one of A or B has an owning element, let the animation with an owning element sort first.

    if (owning_element() && !other->owning_element())

        return -1;

    if (!owning_element() && other->owning_element())

        return 1;

    // 3. Otherwise, if the owning element of A and B differs, sort A and B by tree order of their corresponding owning

    //    elements. With regard to pseudo-elements, the sort order is as follows:

    //    - element

    //    - ::marker

    //    - ::before

    //    - any other pseudo-elements not mentioned specifically in this list, sorted in ascending order by the Unicode

    //      codepoints that make up each selector

    //    - ::after

    //    - element children

    if (owning_element().ptr() != other->owning_element().ptr()) {

        // FIXME: Actually sort by tree order

        return {};

    }

    // 4. Otherwise, if A and B have different transition generation values, sort by their corresponding transition

    //    generation in ascending order.

    if (m_transition_generation != other->m_transition_generation)

        return m_transition_generation - other->m_transition_generation;

    // FIXME:

    // 5. Otherwise, sort A and B in ascending order by the Unicode codepoints that make up the expanded transition

    //    property name of each transition (i.e. without attempting case conversion and such that ‘-moz-column-width’

    //    sorts before ‘column-width’).

    return {};

}

CSSTransition::CSSTransition(JS::Realm& realm, DOM::Element& element, PropertyID property_id, size_t transition_generation,

    double start_time, double end_time, NonnullRefPtr<CSSStyleValue const> start_value, NonnullRefPtr<CSSStyleValue const> end_value,

    NonnullRefPtr<CSSStyleValue const> reversing_adjusted_start_value, double reversing_shortening_factor)

    : Animations::Animation(realm)

    , m_transition_property(property_id)

    , m_transition_generation(transition_generation)

    , m_start_time(start_time)

    , m_end_time(end_time)

    , m_start_value(move(start_value))

    , m_end_value(move(end_value))

    , m_reversing_adjusted_start_value(move(reversing_adjusted_start_value))

    , m_reversing_shortening_factor(reversing_shortening_factor)

    , m_keyframe_effect(Animations::KeyframeEffect::create(realm))

{

    // FIXME:

    // Transitions generated using the markup defined in this specification are not added to the global animation list

    // when they are created. Instead, these animations are appended to the global animation list at the first moment

    // when they transition out of the idle play state after being disassociated from their owning element. Transitions

    // that have been disassociated from their owning element but are still idle do not have a defined composite order.

    set_start_time(start_time - element.document().timeline()->current_time().value());

    // Construct a KeyframesEffect for our animation

    m_keyframe_effect->set_target(&element);

    m_keyframe_effect->set_start_delay(start_time);

    m_keyframe_effect->set_iteration_duration(m_end_time - start_time);

    m_keyframe_effect->set_timing_function(element.property_transition_attributes(property_id)->timing_function);

    auto key_frame_set = adopt_ref(*new Animations::KeyframeEffect::KeyFrameSet);

    Animations::KeyframeEffect::KeyFrameSet::ResolvedKeyFrame initial_keyframe;

    initial_keyframe.properties.set(property_id, m_start_value);

    Animations::KeyframeEffect::KeyFrameSet::ResolvedKeyFrame final_keyframe;

    final_keyframe.properties.set(property_id, m_end_value);

    key_frame_set->keyframes_by_key.insert(0, initial_keyframe);

    key_frame_set->keyframes_by_key.insert(100 * Animations::KeyframeEffect::AnimationKeyFrameKeyScaleFactor, final_keyframe);

    m_keyframe_effect->set_key_frame_set(key_frame_set);

    set_timeline(element.document().timeline());

    set_owning_element(element);

    set_effect(m_keyframe_effect);

    element.associate_with_animation(*this);

    element.set_transition(m_transition_property, *this);

    HTML::TemporaryExecutionContext context(element.document().relevant_settings_object());

    play().release_value_but_fixme_should_propagate_errors();

}

void CSSTransition::initialize(JS::Realm& realm)

{

    Base::initialize(realm);

    WEB_SET_PROTOTYPE_FOR_INTERFACE(CSSTransition);

}

void CSSTransition::visit_edges(Cell::Visitor& visitor)

{

    Base::visit_edges(visitor);

    visitor.visit(m_cached_declaration);

    visitor.visit(m_keyframe_effect);

}

double CSSTransition::timing_function_output_at_time(double t) const

{

    auto progress = (t - transition_start_time()) / (transition_end_time() - transition_start_time());

    // FIXME: Is this before_flag value correct?

    bool before_flag = t < transition_start_time();

    return m_keyframe_effect->timing_function().evaluate_at(progress, before_flag);

}

NonnullRefPtr<CSSStyleValue const> CSSTransition::value_at_time(double t) const

{

    // https://drafts.csswg.org/css-transitions/#application

    auto progress = timing_function_output_at_time(t);

    auto result = interpolate_property(*m_keyframe_effect->target(), m_transition_property, m_start_value, m_end_value, progress);

    if (result)

        return result.release_nonnull();

    return m_start_value;

}

}