<?php
/**
 * Template Override.
 *
 * Intercepts WooCommerce's PHP template rendering and replaces it
 * with Twig template output from the child theme's templates/ directory.
 *
 * Uses woocommerce_before_template_part / woocommerce_after_template_part
 * hooks to render the Twig version and discard the PHP include output.
 *
 * @package WcBootstrap
 * @since 0.1.0
 */

namespace WcBootstrap;

use WPBootstrap\Twig\TwigService;

class TemplateOverride {

    /**
     * Path to the child theme's templates directory.
     *
     * @var string
     */
    private string $templatePath;

    /**
     * Stack of template names with active output buffers.
     *
     * Handles nested template calls where one WC template triggers
     * another via wc_get_template() from within action hooks.
     *
     * @var string[]
     */
    private array $bufferStack = [];

    /**
     * Constructor.
     */
    public function __construct() {
        $this->templatePath = WC_BOOTSTRAP_PATH . 'templates/';
    }

    /**
     * Register the template override hooks.
     *
     * Only registers if the parent theme's TwigService is available.
     *
     * @return void
     */
    public function register(): void {
        if ( ! class_exists( TwigService::class ) ) {
            return;
        }

        add_action( 'woocommerce_before_template_part', [ $this, 'beforeTemplatePart' ], 10, 4 );
        add_action( 'woocommerce_after_template_part', [ $this, 'afterTemplatePart' ], 10, 4 );
    }

    /**
     * Before WooCommerce includes a PHP template.
     *
     * If a matching Twig template exists, renders it and starts output
     * buffering to capture (and later discard) the PHP template output.
     *
     * @param string $templateName Template name (e.g., 'cart/cart.php').
     * @param string $templatePath Template path override.
     * @param string $located      Full path to the located PHP template.
     * @param array  $args         Template context variables.
     * @return void
     */
    public function beforeTemplatePart( string $templateName, string $templatePath, string $located, array $args ): void {
        $twigTemplate = $this->resolveTwigTemplate( $templateName );

        if ( null === $twigTemplate ) {
            return; // No Twig override — let PHP render normally.
        }

        try {
            $twig    = TwigService::getInstance();
            $context = $args;

            // Inject the global $product into the Twig context.
            // WooCommerce PHP templates access it via `global $product;` but Twig
            // templates have isolated variable scopes and need it passed explicitly.
            if ( ! isset( $context['product'] ) && ! empty( $GLOBALS['product'] ) ) {
                $context['product'] = $GLOBALS['product'];
            }

            echo $twig->render( $twigTemplate, $context );

            // Buffer the upcoming PHP include so we can discard it.
            ob_start();
            $this->bufferStack[] = $templateName;
        } catch ( \Throwable $e ) {
            // Twig render failed — let PHP render as fallback.
            if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
                error_log( sprintf(
                    'WC Bootstrap: Twig render failed for %s — %s',
                    $templateName,
                    $e->getMessage()
                ) );
            }
        }
    }

    /**
     * After WooCommerce includes a PHP template.
     *
     * If we started buffering for this template, discards the PHP output.
     *
     * @param string $templateName Template name.
     * @param string $templatePath Template path override.
     * @param string $located      Full path to the located PHP template.
     * @param array  $args         Template context variables.
     * @return void
     */
    public function afterTemplatePart( string $templateName, string $templatePath, string $located, array $args ): void {
        if ( ! empty( $this->bufferStack ) && end( $this->bufferStack ) === $templateName ) {
            ob_end_clean(); // Discard PHP template output.
            array_pop( $this->bufferStack );
        }
    }

    /**
     * Resolve a WooCommerce template name to a Twig template path.
     *
     * Maps 'cart/cart.php' to 'cart/cart.html.twig' and checks that
     * the file exists in the child theme's templates/ directory.
     *
     * @param string $templateName WooCommerce template name.
     * @return string|null Twig template path relative to templates/, or null if not found.
     */
    private function resolveTwigTemplate( string $templateName ): ?string {
        $twigName = preg_replace( '/\.php$/', '.html.twig', $templateName );
        $fullPath = $this->templatePath . $twigName;

        if ( file_exists( $fullPath ) ) {
            return $twigName;
        }

        return null;
    }
}