<?php
function resoto_register_custom_control() {
    /**
     * Pro customizer section.
     *
     * @since  1.0.0
     * @access public
     */
    class Resoto_Upgrade_Pro_Customize_Section_Pro extends WP_Customize_Section {

        /**
         * The type of customize section being rendered.
         *
         * @since  1.0.0
         * @access public
         * @var    string
         */
        public $type = 'upgrade-button';

        /**
         * Custom button text to output.
         *
         * @since  1.0.0
         * @access public
         * @var    string
         */
        public $pro_text = '';

        /**
         * Custom pro button URL.
         *
         * @since  1.0.0
         * @access public
         * @var    string
         */
        public $pro_url = '';

        /**
         * Add custom parameters to pass to the JS via JSON.
         *
         * @since  1.0.0
         * @access public
         * @return void
         */
        public function json() {
            $json = parent::json();

            $json['pro_text'] = $this->pro_text;
            $json['pro_url']  = esc_url( $this->pro_url );

            return $json;
        }

        /**
         * Outputs the Underscore.js template.
         *
         * @since  1.0.0
         * @access public
         * @return void
         */
        protected function render_template() { ?>

            <li id="accordion-section-{{ data.id }}" class="accordion-section control-section control-section-{{ data.type }} cannot-expand">

                <h3 class="accordion-section-title">
                    {{ data.title }}

                    <# if ( data.pro_text && data.pro_url ) { #>
                        <a href="{{ data.pro_url }}" class="button button-secondary alignright" target="_blank">{{ data.pro_text }}</a>
                    <# } #>
                </h3>
            </li>
        <?php }
    }
}
add_action('customize_register', 'resoto_register_custom_control');