WatchEntityComponnent.java

    public static <A> nz.sodium.Cell<Option<A>> watchEntityComponentOp(
        nz.sodium.Cell<Option<EcsReadOnlySceneContext>> cSceneCtxOp,
        nz.sodium.Stream<EcsSceneChanges> sSceneChanges,
        int entityId,
        EcsComponent<A> ecsComponent
    ) {
        nz.sodium.StreamLoop<Option<A>> slEntityComponentOp = new sodium.StreamLoop<>();
        nz.sodium.Cell<Option<A>> cEntityComponentOp =
            slEntityComponentOp
                .hold(
                    cSceneCtxOp.sample()
                        .bind(
                            (EcsReadOnlySceneContext sceneCtx) ->
                                sceneCtx.getComponent(entityId, ecsComponent)
                        )
                );
        slEntityComponentOp.loop(
            sodium.Stream.filterOptional(
                sSceneChanges.snapshot(
                    cEntityComponentOp,
                    cSceneCtxOp,
                    (EcsSceneChanges sceneChanges, Option<A> entityComponentOp, Option<EcsReadOnlySceneContext> sceneCtxOp) -> {
                        Option<Option<A>> _nextEntityComponentOpOp = Option.none();
                        for (EcsSceneChange sceneChange : sceneChanges.changes()) {
                            Option<Option<A>> lastEntityComponentOpOp = _nextEntityComponentOpOp;
                            _nextEntityComponentOpOp = sceneChange.match(new EcsSceneChange.CasesAdapter<Option<Option<A>>>(lastEntityComponentOpOp) {
                                @Override
                                public Option<Option<A>> newScene() {
                                    return sceneCtxOp.map((EcsReadOnlySceneContext sceneCtx) -> sceneCtx.getComponent(entityId, ecsComponent));
                                }
                                @Override
                                public Option<Option<A>> setComponents(int entityId2, EcsComponentValue[] components) {
                                    if (entityId2 != entityId) {
                                        return lastEntityComponentOpOp;
                                    }
                                    for (EcsComponentValue componentValue : components) {
                                        for (A component : componentValue.value(ecsComponent)) {
                                            return Option.some(Option.some(component));
                                        }
                                    }
                                    return lastEntityComponentOpOp;
                                }
                                @Override
                                public Option<Option<A>> unsetComponents(int entityId2, EcsComponentType[] componentTypes) {
                                    if (entityId2 != entityId) {
                                        return lastEntityComponentOpOp;
                                    }
                                    for (EcsComponentType componentType : componentTypes) {
                                        if (componentType.equals(ecsComponent.type())) {
                                            return Option.some(Option.none());
                                        }
                                    }
                                    return lastEntityComponentOpOp;
                                }
                            });
                        }
                        return fj.data.Java8.Option_Optional(_nextEntityComponentOpOp);
                    }
                )
            )
        );
        return cEntityComponentOp;
    }