<?php
/**
 * Template Engine for rendering customizable templates.
 *
 * Supports template overrides via theme and admin customization.
 *
 * @package GeniusCommerce
 */

namespace GeniusCommerce;

defined( 'ABSPATH' ) || exit;

/**
 * GC_Template_Engine class.
 *
 * Provides template rendering with theme override support.
 */
class GC_Template_Engine {

	/**
	 * Template directory within the plugin.
	 *
	 * @var string
	 */
	private string $plugin_template_dir;

	/**
	 * Template directory within themes.
	 *
	 * @var string
	 */
	private string $theme_template_dir = 'genius-commerce/templates';

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

	/**
	 * Render a template with given arguments.
	 *
	 * Template lookup order:
	 * 1. Child theme: /genius-commerce/templates/{template}
	 * 2. Parent theme: /genius-commerce/templates/{template}
	 * 3. Admin custom template (stored in options)
	 * 4. Plugin default: /templates/{template}
	 *
	 * @param string $template_name Template file name (e.g., 'discount-price.php').
	 * @param array  $args          Variables to extract into template scope.
	 * @return string Rendered template HTML.
	 */
	public function render( string $template_name, array $args = array() ): string {
		// Theme templates have highest priority - render PHP file directly.
		if ( $this->is_theme_override( $template_name ) ) {
			$theme_path = $this->get_theme_template_path( $template_name );
			return $this->render_file( $theme_path, $args );
		}

		// Check for admin custom template (stored as option).
		$custom_template = $this->get_custom_template( $template_name );

		if ( null !== $custom_template ) {
			return $this->render_string( $custom_template, $args );
		}

		// Fall back to plugin default template.
		$template_path = $this->plugin_template_dir . $template_name;

		if ( ! file_exists( $template_path ) ) {
			Genius_Commerce::log(
				sprintf( 'Template not found: %s', $template_name ),
				'error'
			);
			return '';
		}

		// Render PHP template file.
		return $this->render_file( $template_path, $args );
	}

	/**
	 * Locate a template file.
	 *
	 * @param string $template_name Template file name.
	 * @return string|null Full path to template or null if not found.
	 */
	public function locate_template( string $template_name ): ?string {
		// Check theme directories.
		$theme_template = locate_template(
			array(
				$this->theme_template_dir . '/' . $template_name,
			)
		);

		if ( $theme_template ) {
			return $theme_template;
		}

		// Check plugin directory.
		$plugin_template = $this->plugin_template_dir . $template_name;

		if ( file_exists( $plugin_template ) ) {
			return $plugin_template;
		}

		return null;
	}

	/**
	 * Render a PHP template file.
	 *
	 * @param string $template_path Full path to template file.
	 * @param array  $args          Variables to extract into template scope.
	 * @return string Rendered HTML.
	 */
	private function render_file( string $template_path, array $args ): string {
		// Validate the resolved path is within allowed directories to prevent file inclusion attacks.
		$real_path = realpath( $template_path );
		$allowed_dirs = array(
			realpath( $this->plugin_template_dir ),
			realpath( get_stylesheet_directory() ),
			realpath( get_template_directory() ),
		);

		$is_allowed = false;
		foreach ( array_filter( $allowed_dirs ) as $dir ) {
			if ( 0 === strpos( $real_path, $dir ) ) {
				$is_allowed = true;
				break;
			}
		}

		if ( ! $real_path || ! $is_allowed ) {
			Genius_Commerce::log(
				sprintf( 'Template path not allowed: %s', $template_path ),
				'error'
			);
			return '';
		}

		// Extract variables into scope.
		// phpcs:ignore WordPress.PHP.DontExtract.extract_extract
		extract( $args, EXTR_SKIP );

		ob_start();
		include $real_path;
		return ob_get_clean();
	}

	/**
	 * Render a template string with placeholder replacement.
	 *
	 * Supports mustache-style placeholders: {{variable_name}}
	 *
	 * @param string $template Template string with placeholders.
	 * @param array  $args     Variables to replace placeholders with.
	 * @return string Rendered HTML.
	 */
	private function render_string( string $template, array $args ): string {
		$output = $template;

		foreach ( $args as $key => $value ) {
			// Skip non-scalar values.
			if ( ! is_scalar( $value ) ) {
				continue;
			}

			$placeholder = '{{' . $key . '}}';
			$output      = str_replace( $placeholder, esc_html( (string) $value ), $output );
		}

		// Allow HTML in certain placeholders (prices contain markup).
		$html_placeholders = array(
			'original_price',
			'discount_price',
			'discount_amount',
			'original_html',
		);

		foreach ( $html_placeholders as $key ) {
			if ( isset( $args[ $key ] ) ) {
				$placeholder = '{{' . $key . '_html}}';
				$output      = str_replace( $placeholder, wp_kses_post( (string) $args[ $key ] ), $output );
			}
		}

		return $output;
	}

	/**
	 * Get the default template content for admin editor.
	 *
	 * @param string $template_name Template file name.
	 * @return string Template content or empty string.
	 */
	public function get_default_template_content( string $template_name ): string {
		$template_path = $this->plugin_template_dir . $template_name;

		if ( ! file_exists( $template_path ) ) {
			return '';
		}

		// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents
		return file_get_contents( $template_path );
	}

	/**
	 * Save custom template content.
	 *
	 * @param string $template_name Template file name.
	 * @param string $content       Custom template content.
	 * @return bool True on success.
	 */
	public function save_custom_template( string $template_name, string $content ): bool {
		$option_key = 'genius_commerce_template_' . sanitize_key( str_replace( '.php', '', $template_name ) );

		// Empty content resets to default.
		if ( empty( trim( $content ) ) ) {
			delete_option( $option_key );
			return true;
		}

		// Sanitize content but allow safe HTML.
		$allowed_html = array(
			'div'   => array(
				'class' => array(),
				'id'    => array(),
				'style' => array(),
			),
			'span'  => array(
				'class' => array(),
				'id'    => array(),
				'style' => array(),
			),
			'del'   => array(
				'class' => array(),
			),
			'ins'   => array(
				'class' => array(),
			),
			'strong' => array(),
			'em'    => array(),
			'small' => array(
				'class' => array(),
			),
			'br'    => array(),
			'p'     => array(
				'class' => array(),
			),
		);

		$sanitized = wp_kses( $content, $allowed_html );

		return update_option( $option_key, $sanitized );
	}

	/**
	 * Get custom template content if exists.
	 *
	 * @param string $template_name Template file name.
	 * @return string|null Custom content or null if using default.
	 */
	public function get_custom_template( string $template_name ): ?string {
		$option_key = 'genius_commerce_template_' . sanitize_key( str_replace( '.php', '', $template_name ) );
		$custom     = get_option( $option_key, '' );

		return ! empty( $custom ) ? $custom : null;
	}

	/**
	 * Check if a template is overridden by the theme.
	 *
	 * @param string $template_name Template file name.
	 * @return bool True if theme override exists.
	 */
	public function is_theme_override( string $template_name ): bool {
		$theme_template = locate_template(
			array(
				$this->theme_template_dir . '/' . $template_name,
			)
		);

		return ! empty( $theme_template );
	}

	/**
	 * Get the full path to a theme template override.
	 *
	 * @param string $template_name Template file name.
	 * @return string|null Full path to theme template or null if not found.
	 */
	public function get_theme_template_path( string $template_name ): ?string {
		$theme_template = locate_template(
			array(
				$this->theme_template_dir . '/' . $template_name,
			)
		);

		return ! empty( $theme_template ) ? $theme_template : null;
	}

	/**
	 * Get the source of the active template.
	 *
	 * @param string $template_name Template file name.
	 * @return string Source: 'theme', 'admin', or 'plugin'.
	 */
	public function get_template_source( string $template_name ): string {
		if ( $this->is_theme_override( $template_name ) ) {
			return 'theme';
		}

		$custom = $this->get_custom_template( $template_name );
		if ( null !== $custom ) {
			return 'admin';
		}

		return 'plugin';
	}

	/**
	 * Get the active template path for debugging/testing.
	 *
	 * @param string $template_name Template file name.
	 * @return string|null Path or database key for the active template.
	 */
	public function get_active_template_path( string $template_name ): ?string {
		if ( $this->is_theme_override( $template_name ) ) {
			return $this->get_theme_template_path( $template_name );
		}

		if ( null !== $this->get_custom_template( $template_name ) ) {
			return 'database:genius_commerce_template_' . sanitize_key( str_replace( '.php', '', $template_name ) );
		}

		$plugin_path = $this->plugin_template_dir . $template_name;
		return file_exists( $plugin_path ) ? $plugin_path : null;
	}

	/**
	 * Get the theme template directory path.
	 *
	 * @return string Theme template directory (relative to theme root).
	 */
	public function get_theme_template_dir(): string {
		return $this->theme_template_dir;
	}
}