LibWeb: Implement Animatable::animate()

Userland/Libraries/LibWeb/Animations/Animatable.cpp

@@ -5,17 +5,52 @@
  */
 
 #include <LibWeb/Animations/Animatable.h>
-#include <LibWeb/WebIDL/ExceptionOr.h>
+#include <LibWeb/Animations/Animation.h>
+#include <LibWeb/Animations/DocumentTimeline.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/Element.h>
 
 namespace Web::Animations {
 
 // https://www.w3.org/TR/web-animations-1/#dom-animatable-animate
 WebIDL::ExceptionOr<JS::NonnullGCPtr<Animation>> Animatable::animate(Optional<JS::Handle<JS::Object>> keyframes, Variant<Empty, double, KeyframeAnimationOptions> options)
 {
-    // FIXME: Implement this
-    (void)keyframes;
-    (void)options;
-    return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Element.animate is not implemented"sv };
+    // 1. Let target be the object on which this method was called.
+    JS::NonnullGCPtr target { *static_cast<DOM::Element*>(this) };
+    auto& realm = target->realm();
+
+    // 2. Construct a new KeyframeEffect object, effect, in the relevant Realm of target by using the same procedure as
+    //    the KeyframeEffect(target, keyframes, options) constructor, passing target as the target argument, and the
+    //    keyframes and options arguments as supplied.
+    //
+    //    If the above procedure causes an exception to be thrown, propagate the exception and abort this procedure.
+    auto effect = TRY(options.visit(
+        [&](Empty) { return KeyframeEffect::construct_impl(realm, target, keyframes); },
+        [&](auto const& value) { return KeyframeEffect::construct_impl(realm, target, keyframes, value); }));
+
+    // 3. If options is a KeyframeAnimationOptions object, let timeline be the timeline member of options or, if
+    //    timeline member of options is missing, be the default document timeline of the node document of the element
+    //    on which this method was called.
+    JS::GCPtr<AnimationTimeline> timeline;
+    if (options.has<KeyframeAnimationOptions>())
+        timeline = options.get<KeyframeAnimationOptions>().timeline;
+    if (!timeline)
+        timeline = target->document().timeline();
+
+    // 4. Construct a new Animation object, animation, in the relevant Realm of target by using the same procedure as
+    //    the Animation() constructor, passing effect and timeline as arguments of the same name.
+    auto animation = TRY(Animation::construct_impl(realm, effect, timeline));
+
+    // 5. If options is a KeyframeAnimationOptions object, assign the value of the id member of options to animation’s
+    //    id attribute.
+    if (options.has<KeyframeAnimationOptions>())
+        animation->set_id(options.get<KeyframeAnimationOptions>().id);
+
+    //  6. Run the procedure to play an animation for animation with the auto-rewind flag set to true.
+    TRY(animation->play_an_animation(Animation::AutoRewind::Yes));
+
+    // 7. Return animation.
+    return animation;
 }
 
 // https://www.w3.org/TR/web-animations-1/#dom-animatable-getanimations