class ComponentNodeVisitor

final class ComponentNodeVisitor implements NodeVisitorInterface {
    
    /**
     * Creates a new ComponentNodeVisitor object.
     *
     * @param \Drupal\sdc\ComponentPluginManager $pluginManager
     *   The plugin manager for components.
     */
    public function __construct(ComponentPluginManager $pluginManager) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function enterNode(Node $node, Environment $env) : Node {
        return $node;
    }
    
    /**
     * {@inheritdoc}
     */
    public function leaveNode(Node $node, Environment $env) : ?Node {
        if (!$node instanceof ModuleNode) {
            return $node;
        }
        $component = $this->getComponent($node);
        if (!$component) {
            return $node;
        }
        $line = $node->getTemplateLine();
        $print_nodes = [];
        $component_id = $component->getPluginId();
        $emoji = static::emojiForString($component_id);
        if ($env->isDebug()) {
            $print_nodes[] = new PrintNode(new ConstantExpression(sprintf('<!-- %s Component start: %s -->', $emoji, $component_id), $line), $line);
        }
        $print_nodes[] = new PrintNode(new FunctionExpression('attach_library', new Node([
            new ConstantExpression($component->getLibraryName(), $line),
        ]), $line), $line);
        $print_nodes[] = new PrintNode(new FunctionExpression('sdc_additional_context', new Node([
            new ConstantExpression($component_id, $line),
        ]), $line), $line);
        $print_nodes[] = new PrintNode(new FunctionExpression('sdc_validate_props', new Node([
            new ConstantExpression($component_id, $line),
        ]), $line), $line);
        // Append the print nodes to the display_start node.
        $node->setNode('display_start', new Node([
            $node->getNode('display_start'),
            $print_nodes,
        ]));
        if ($env->isDebug()) {
            // Append the closing comment to the display_end node.
            $node->setNode('display_end', new Node([
                new PrintNode(new ConstantExpression(sprintf('<!-- %s Component end: %s -->', $emoji, $component_id), $line), $line),
                $node->getNode('display_end'),
            ]));
        }
        // Slots can be validated at compile time, we don't need to add nodes to
        // execute functions during display with the actual data.
        $this->validateSlots($component, $node->getNode('blocks'));
        return $node;
    }
    
    /**
     * Finds the SDC for the current module node.
     *
     * @param \Twig\Node\Node $node
     *   The node.
     *
     * @return \Drupal\sdc\Plugin\Component|null
     *   The component, if any.
     */
    protected function getComponent(Node $node) : ?Component {
        $component_id = $node->getTemplateName();
        if (!preg_match('/^[a-z]([a-zA-Z0-9_-]*[a-zA-Z0-9])*:[a-z]([a-zA-Z0-9_-]*[a-zA-Z0-9])*$/', $component_id)) {
            return NULL;
        }
        try {
            return $this->pluginManager
                ->find($component_id);
        } catch (ComponentNotFoundException $e) {
            return NULL;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getPriority() : int {
        return 250;
    }
    
    /**
     * Performs a cheap validation of the slots in the template.
     *
     * It validates them against the JSON Schema provided in the component
     * definition file and massaged in the ComponentMetadata class. We don't use
     * the JSON Schema validator because we just want to validate required and
     * undeclared slots. This cheap validation lets us validate during runtime
     * even in production.
     *
     * @throws \Drupal\sdc\Exception\InvalidComponentException
     *   When the slots don't pass validation.
     */
    protected function validateSlots(Component $component, Node $node) : void {
        $metadata = $component->metadata;
        if (!$metadata->mandatorySchemas) {
            return;
        }
        $slot_definitions = $metadata->slots;
        $ids_available = array_keys($slot_definitions);
        $undocumented_ids = [];
        try {
            $it = $node->getIterator();
        } catch (\Exception $e) {
            return;
        }
        if ($it instanceof \SeekableIterator) {
            while ($it->valid()) {
                $provided_id = $it->key();
                if (!in_array($provided_id, $ids_available, TRUE)) {
                    $undocumented_ids[] = $provided_id;
                }
                $it->next();
            }
        }
        // Now build the error message.
        $error_messages = [];
        if (!empty($undocumented_ids)) {
            $error_messages[] = sprintf('We found an unexpected slot that is not declared: [%s]. Declare them in "%s.component.yml".', implode(', ', $undocumented_ids), $component->machineName);
        }
        if (!empty($error_messages)) {
            $message = implode("\n", $error_messages);
            throw new InvalidComponentException($message);
        }
    }
    
    /**
     * Chooses an emoji representative for the input string.
     *
     * @param string $input
     *   The input string.
     *
     * @return string
     *   The emoji code.
     */
    protected static function emojiForString(string $input) : string {
        // Compute a cheap and reproducible float between 0 and 1 for based on the
        // component ID.
        $max_length = 40;
        $input = strtolower($input);
        $input = strtr($input, '-_:', '000');
        $input = substr($input, 0, $max_length);
        $chars = str_split($input);
        $chars = array_pad($chars, 20, '0');
        $sum = array_reduce($chars, static fn(int $total, string $char) => $total + ord($char), 0);
        $num = $sum / 4880;
        // Compute an int between 129338 and 129431, which is the sequential emoji
        // range we are interested in. We chose this range because all integers in
        // between correspond to an emoji. These emojis depict sports, food, and
        // animals.
        $html_entity = floor(129338 + $num * (129431 - 129338));
        $emoji = mb_convert_encoding("&#{$html_entity};", 'UTF-8', 'HTML-ENTITIES');
        return is_string($emoji) ? $emoji : '';
    }

}