<?php
/**
 * AMP WP Component Factory Class
 *
 * @since 1.0.0
 */
class Amp_WP_Component extends Amp_WP_Component_Base {

    /**
     * Component instance
     *
     * @since 1.0.0
     *
     * @var Amp_WP_Component_Interface
     */
    private $component;

    /**
     * Component class name
     *
     * @since 1.0.0
     *
     * @var string
     */
    private $class_name;

    /**
     * Store components instance
     *
     * @since 1.0.0
     *
     * @var array
     */
    private static $instances;

    /**
     * Get self instance
     *
     * @param   string  $component_class component class name that implements Amp_WP_Component_Interface
     * @param   bool    $fresh  new fresh object?
     *
     * @since   1.0.0
     *
     * @return  Amp_WP_Component|bool Amp_WP_Component object on success or false on failure.
     */
    public static function instance($component_class, $fresh = false) {
        if (isset(self::$instances[$component_class]) && !$fresh) {
            return self::$instances[$component_class];
        }

        if (class_exists($component_class)) {
            return self::$instances[$component_class] = new Amp_WP_Component($component_class);
        }

        return false;
    }

    /**
     * Clean instance storage cache
     *
     * @since 1.0.0
     */
    public static function flush_instances() {
        self::$instances = array();
    }

    /**
     * Constructor.
     *
     * @since 1.0.0
     *
     * @param string $component_class
     */
    public function __construct($component_class) {
        $this->class_name = $component_class;
        $this->set_component_instance(new $this->class_name);
    }

    /**
     * Set a component class instance
     *
     * @param Amp_WP_Component_Interface $instance
     *
     * @since 1.0.0
     */
    public function set_component_instance(Amp_WP_Component_Interface $instance) {
        $this->component = $instance;
    }

    /**
     * Get a component instance
     *
     * @return Amp_WP_Component_Interface;
     *
     * @since 1.0.0
     */
    public function get_component_instance() {
        return $this->component;
    }

    /**
     * Execute component and Transform HTML content to AMP content
     *
     * @param string $content html content
     *
     * @since 1.0.0
     *
     * @return string transformed content
     */
    public function render($content) {
        return $this->component->transform($content);
    }

    /**
     * Get component config
     *
     * @see   Amp_WP_Component_Interface for more documentation
     *
     * @since 1.0.0
     *
     * @return array
     */
    public function get_config() {
        return wp_parse_args(
            $this->component->config(), array(
                'shortcodes' => array(),
                'scripts' => array(),
            )
        );
    }

    /**
     * Replaces the default shortcode with the component shortcode
     *
     * @since 1.0.0
     */
    public function register_shortcodes() {
        $config = $this->get_config();
        foreach ($config['shortcodes'] as $shortcode => $callback) {
            remove_shortcode($shortcode);
            add_shortcode($shortcode, $callback);
        }
    }

    /**
     * Magic method handler
     *
     * Make private/protected methods readable for fire component method via this object instance
     *
     * @param string $method
     * @param array  $args
     *
     * @since 1.0.0
     *
     * @return mixed
     */
    public function __call($method, $args) {
        $callback = array($this->component, $method);
        if (is_callable($callback)) {
            return call_user_func_array($callback, $args);
        }
    }

    /**
     * Enqueues component script.
     *
     * @param array $deps
     *
     * @since 1.0.0
     *
     * @return array
     */
    public function enqueue_amp_scripts($deps = array()) {
        $config = $this->get_config();
        foreach ($config['scripts'] as $name => $script) {
            amp_wp_enqueue_script($name, $script, $deps);
        }
        return $deps; // pass $deps to work with series call {@see Amp_WP::call_component_method}
    }

    /**
     * Determines the script should be enqueued!
     *
     * @since 1.0.0
     *
     * @return bool
     */
    public function can_enqueue_scripts() {
        return !empty($this->component->enable_enqueue_scripts);
    }

    /**
     * Enqueue AMP component script if amp tag exists in the page and script was not printed yet
     *
     * @param Amp_WP_Html_Util $dom
     *
     * @return Amp_WP_Html_Util
     */
    public function enqueue_amp_tags_script($dom) {
        $has_enqueue_scripts = $this->can_enqueue_scripts();

        if (!$has_enqueue_scripts) { // if script was not printed previously
            $config = $this->get_config();

            foreach ($config['scripts'] as $tag => $script) {
                if ($dom->getElementsByTagName($tag)->length) {
                    amp_wp_enqueue_script($tag, $script, array('ampproject'));
                }
            }
        }
        return $dom;
    }
}