<?php
defined( 'ABSPATH' ) || exit;

class XFee_Plugin {

    private static $instance = null;

    public static function instance(): self {
        if ( null === self::$instance ) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    private function __construct() {
        $this->includes();
        $this->init_hooks();
    }

    private function includes(): void {
        // Model + fee engine: needed on both frontend and admin.
        require_once XFEE_PLUGIN_PATH . 'admin/model.php';
        require_once XFEE_PLUGIN_PATH . 'front/class-fee.php';

        if ( is_admin() ) {
            require_once XFEE_PLUGIN_PATH . 'system/library/ocm/autoloader.php';
            require_once XFEE_PLUGIN_PATH . 'admin/controller.php';
            new XFee_Back( new XFee_Model() );
        }
    }

    private function init_hooks(): void {
        // Translations load automatically on WP 4.6+ (slug = text domain = "extnify-fee"),
        // so no load_plugin_textdomain() call is needed.
        //
        // Fees are added to the cart/checkout totals via woocommerce_cart_calculate_fees.
        // The engine reads the shared methods table and calls WC()->cart->add_fee().
        add_action( 'woocommerce_cart_calculate_fees', array( $this, 'calculate_fees' ) );
    }

    /**
     * Apply matching fees to the cart. WooCommerce fires this during totals
     * calculation (cart + checkout); the fee engine owns all the logic.
     */
    public function calculate_fees( $cart ): void {
        if ( is_admin() && ! defined( 'DOING_AJAX' ) ) {
            return;
        }
        if ( ! $cart instanceof WC_Cart || $cart->is_empty() ) {
            return;
        }
        ( new XFee_Fee() )->apply( $cart );
    }

}