class ComponentValidator

final class ComponentValidator {
    
    /**
     * The schema validator.
     *
     * This property will only be set if the validator library is available.
     *
     * @var \JsonSchema\Validator|null
     */
    protected ?Validator $validator = NULL;
    
    /**
     * Sets the validator service if available.
     */
    public function setValidator(Validator $validator = NULL) : void {
        if ($validator) {
            $this->validator = $validator;
            return;
        }
        if (class_exists(Validator::class)) {
            $this->validator = new Validator();
        }
    }
    
    /**
     * Validates the component metadata file.
     *
     * A valid component metadata file can be validated against the
     * metadata-author.schema.json, plus the ability of classes and interfaces
     * in the `type` property.
     *
     * @param array $definition
     *   The definition to validate.
     * @param bool $enforce_schemas
     *   TRUE if schema definitions are mandatory.
     *
     * @return bool
     *   TRUE if the component is valid.
     *
     * @throws \Drupal\sdc\Exception\InvalidComponentException
     */
    public function validateDefinition(array $definition, bool $enforce_schemas) : bool {
        // First ensure there are no name collisions between props and slots.
        $prop_names = array_keys($definition['props']['properties'] ?? []);
        $slot_names = array_keys($definition['slots'] ?? []);
        $collisions = array_intersect($prop_names, $slot_names);
        if ($collisions) {
            $message = sprintf('The component "%s" declared [%s] both as a prop and as a slot. Make sure to use different names.', $definition['id'], implode(', ', $collisions));
            throw new InvalidComponentException($message);
        }
        // If the validator isn't set, then the validation library is not installed.
        if (!$this->validator) {
            return TRUE;
        }
        // Detect the props with a type class, and validate that the class exists.
        $schema = $definition['props'] ?? NULL;
        if (!$schema) {
            if ($enforce_schemas) {
                throw new InvalidComponentException(sprintf('The component "%s" does not provide schema information. Schema definitions are mandatory for components declared in modules. For components declared in themes, schema definitions are only mandatory if the "enforce_prop_schemas" key is set to "true" in the theme info file.', $definition['id']));
            }
            return TRUE;
        }
        // If there are no props, force casting to object instead of array.
        if (($schema['properties'] ?? NULL) === []) {
            $schema['properties'] = new \stdClass();
        }
        $classes_per_prop = $this->getClassProps($schema);
        $missing_class_errors = [];
        foreach ($classes_per_prop as $prop_name => $class_types) {
            // For each possible type, check if it is a class.
            $missing_classes = array_filter($class_types, static fn(string $class) => !class_exists($class) && !interface_exists($class));
            $missing_class_errors = [
                $missing_class_errors,
                array_map(static fn(string $class) => sprintf('Unable to find class/interface "%s" specified in the prop "%s" for the component "%s".', $class, $prop_name, $definition['id']), $missing_classes),
            ];
        }
        // Remove the non JSON Schema types for validation down below.
        $definition['props'] = $this->nullifyClassPropsSchema($schema, $classes_per_prop);
        $definition_object = Validator::arrayToObjectRecursive($definition);
        $this->validator
            ->validate($definition_object, (object) [
            '$ref' => 'file://' . dirname(__DIR__) . '/metadata-full.schema.json',
        ]);
        if (empty($missing_class_errors) && $this->validator
            ->isValid()) {
            return TRUE;
        }
        $message_parts = array_map(static fn(array $error): string => sprintf("[%s] %s", $error['property'], $error['message']), $this->validator
            ->getErrors());
        $message_parts = [
            $message_parts,
            $missing_class_errors,
        ];
        $message = implode("/n", $message_parts);
        // Throw the exception with the error message.
        throw new InvalidComponentException($message);
    }
    
    /**
     * Validates that the props provided to the component.
     *
     * Valid props are compliant with the schema definition in the component
     * metadata file.
     *
     * @param array $context
     *   The Twig context that contains the prop data.
     * @param \Drupal\sdc\Plugin\Component $component
     *   The component to validate the props against.
     *
     * @return bool
     *   TRUE if the props adhere to the component definition.
     *
     * @throws \Drupal\sdc\Exception\InvalidComponentException
     */
    public function validateProps(array $context, Component $component) : bool {
        // If the validator isn't set, then the validation library is not installed.
        if (!$this->validator) {
            return TRUE;
        }
        $component_id = $component->getPluginId();
        $schema = $component->metadata->schema;
        if (!$schema) {
            if ($component->metadata->mandatorySchemas) {
                throw new InvalidComponentException(sprintf('The component "%s" does not provide schema information. Schema definitions are mandatory for components declared in modules. For components declared in themes, schema definitions are only mandatory if the "enforce_prop_schemas" key is set to "true" in the theme info file.', $component_id));
            }
            return TRUE;
        }
        if (empty($schema['properties'])) {
            // If there are no properties in the schema there is nothing to validate.
            return TRUE;
        }
        $prop_names = array_keys($schema['properties']);
        $props_raw = array_intersect_key($context, array_flip($prop_names));
        // Validator::arrayToObjectRecursive stringifies the props using the JSON
        // encoder. Before that happens, we want to validate classes. Once the
        // classes are validated, we remove them as potential problems for the JSON
        // Schema validation.
        [
            $schema,
            $props_raw,
        ] = $this->validateClassProps($schema, $props_raw, $component_id);
        $schema = Validator::arrayToObjectRecursive($schema);
        $props = Validator::arrayToObjectRecursive($props_raw);
        $validator = new Validator();
        $validator->validate($props, $schema, Constraint::CHECK_MODE_TYPE_CAST);
        $validator->getErrors();
        if ($validator->isValid()) {
            return TRUE;
        }
        // Dismiss type errors if the prop received a render array.
        $errors = array_filter($validator->getErrors(), function (array $error) use ($context) : bool {
            if (($error['constraint'] ?? '') !== 'type') {
                return TRUE;
            }
            return !Utilities::isRenderArray($context[$error['property']] ?? NULL);
        });
        if (empty($errors)) {
            return TRUE;
        }
        $message_parts = array_map(static function (array $error) : string {
            // We check the error message instead of values and definitions here
            // because it's hard to access both given the possible complexity of a
            // schema. Since this is a small non critical DX improvement error
            // message checking should be sufficient.
            if (str_contains($error['message'], 'NULL value found, but a ')) {
                $error['message'] .= '. This may be because the property is empty instead of having data present. If possible fix the source data, use the |default() twig filter, or update the schema to allow multiple types.';
            }
            return sprintf("[%s] %s", $error['property'], $error['message']);
        }, $errors);
        $message = implode("/n", $message_parts);
        throw new InvalidComponentException($message);
    }
    
    /**
     * Validates the props that are not JSON Schema.
     *
     * This validates that the props are instances of the class/interface declared
     * in the metadata file.
     *
     * @param array $props_schema
     *   The schema for all the props in the component.
     * @param array $props_raw
     *   The props provided to the component.
     * @param string $component_id
     *   The component ID. Used for error reporting.
     *
     * @return array
     *   A tuple containing the new $props_schema and the new $props_raw. We
     *   mutate the schema to be `type: null` and the prop value to be `NULL` for
     *   the props that are validated as class objects. This is done so these
     *   props can pass validation later on when validating against the JSON
     *   Schema. We can do this because we have already validated these props
     *   manually.
     *
     * @throws \Drupal\sdc\Exception\InvalidComponentException
     */
    private function validateClassProps(array $props_schema, array $props_raw, string $component_id) : array {
        $error_messages = [];
        $classes_per_prop = $this->getClassProps($props_schema);
        $properties = $props_schema['properties'] ?? [];
        foreach ($properties as $prop_name => $prop_def) {
            $class_types = $classes_per_prop[$prop_name] ?? [];
            $prop = $props_raw[$prop_name] ?? NULL;
            if (empty($class_types) || is_null($prop)) {
                continue;
            }
            $is_valid = array_reduce($class_types, static fn(bool $valid, string $class_name) => $valid || $prop instanceof $class_name, FALSE);
            if (!$is_valid) {
                $error_messages[] = sprintf('Data provided to prop "%s" for component "%s" is not a valid instance of "%s"', $prop_name, $component_id, implode(', ', $class_types));
            }
            // Remove the non JSON Schema types for later JSON Schema validation.
            $props_raw[$prop_name] = NULL;
        }
        $props_schema = $this->nullifyClassPropsSchema($props_schema, $classes_per_prop);
        if (!empty($error_messages)) {
            $message = implode("/n", $error_messages);
            throw new InvalidComponentException($message);
        }
        return [
            $props_schema,
            $props_raw,
        ];
    }
    
    /**
     * Gets the props that are not JSON based.
     *
     * @param array $props_schema
     *   The schema for the props.
     *
     * @return array
     *   The class props.
     */
    private function getClassProps(array $props_schema) : array {
        $classes_per_prop = [];
        foreach ($props_schema['properties'] ?? [] as $prop_name => $prop_def) {
            $type = $prop_def['type'] ?? 'null';
            $types = is_string($type) ? [
                $type,
            ] : $type;
            // For each possible type, check if it is a class.
            $class_types = array_filter($types, static fn(string $type) => !in_array($type, [
                'array',
                'boolean',
                'integer',
                'null',
                'number',
                'object',
                'string',
            ]));
            $classes_per_prop[$prop_name] = $class_types;
        }
        return array_filter($classes_per_prop);
    }
    
    /**
     * Utility method to ensure the schema for class props is set to 'null'.
     *
     * @param array $schema_props
     *   The schema for all the props.
     * @param array $classes_per_prop
     *   Associative array that associates prop names with their prop classes.
     *
     * @return array
     *   The new schema.
     */
    private function nullifyClassPropsSchema(array $schema_props, array $classes_per_prop) : array {
        foreach ($schema_props['properties'] as $prop_name => $prop_def) {
            $class_types = $classes_per_prop[$prop_name] ?? [];
            // Remove the non JSON Schema types for later JSON Schema validation.
            $types = (array) ($prop_def['type'] ?? [
                'null',
            ]);
            $types = array_diff($types, $class_types);
            $types = empty($types) ? [
                'null',
            ] : $types;
            $schema_props['properties'][$prop_name]['type'] = $types;
        }
        return $schema_props;
    }

}