class ComponentElement

class ComponentElement extends RenderElementBase {
    use DoTrustedCallbackTrait;
    
    /**
     * Expands a component into an inline template with an attachment.
     *
     * @param array $element
     *   The element to process. See main class documentation for properties.
     *
     * @return array
     *   The form element.
     *
     * @throws \Drupal\Core\Render\Component\Exception\InvalidComponentDataException
     */
    public function preRenderComponent(array $element) : array {
        $props = $element['#props'];
        $props_alter_callbacks = $element['#propsAlter'];
        // This callback can be used to prepare the context. For instance to replace
        // tokens in the props.
        $props = array_reduce($props_alter_callbacks, fn(array $carry, callable $callback) => $this->doTrustedCallback($callback, [
            $carry,
        ], '%s is not trusted'), $props);
        $inline_template = $this->generateComponentTemplate($element['#component'], $element['#slots'], $element['#slotsAlter'], $props);
        $element['inline-template'] = [
            '#type' => 'inline_template',
            '#template' => $inline_template,
            '#context' => $props,
        ];
        return $element;
    }
    
    /**
     * Generates the template to render the component.
     *
     * @param string $id
     *   The component id.
     * @param array $slots
     *   The contents of any potential embed blocks.
     * @param array $slots_alter_callbacks
     *   The potential callables for altering slots.
     * @param array $context
     *   Inline template context.
     *
     * @return string
     *   The template.
     *
     * @throws \Drupal\Core\Render\Component\Exception\InvalidComponentDataException
     *   When slots are not render arrays.
     */
    private function generateComponentTemplate(string $id, array $slots, array $slots_alter_callbacks, array &$context) : string {
        $template = '{# This template was dynamically generated by single-directory components #}' . PHP_EOL;
        $template .= sprintf('{%% embed \'%s\' %%}', $id);
        $template .= PHP_EOL;
        foreach ($slots as $slot_name => $slot_value) {
            if (\is_scalar($slot_value)) {
                $slot_value = [
                    "#plain_text" => (string) $slot_value,
                ];
            }
            if (!Element::isRenderArray($slot_value)) {
                $message = sprintf('Unable to render component "%s". A render array or a scalar is expected for the slot "%s" when using the render element with the "#slots" property', $id, $slot_name);
                throw new InvalidComponentDataException($message);
            }
            $context[$slot_name] = array_reduce($slots_alter_callbacks, fn(array $carry, callable $callback) => $this->doTrustedCallback($callback, [
                $carry,
                $context,
            ], '%s is not trusted'), $slot_value);
            $template .= "  {% block {$slot_name} %}" . PHP_EOL . "    {{ {$slot_name} }}" . PHP_EOL . "  {% endblock %}" . PHP_EOL;
        }
        $template .= '{% endembed %}' . PHP_EOL;
        return $template;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() : array {
        return [
            '#pre_render' => [
                [
                    $this,
                    'preRenderComponent',
                ],
            ],
            '#component' => '',
            '#props' => [],
            '#slots' => [],
            '#propsAlter' => [],
            '#slotsAlter' => [],
        ];
    }

}