<?php
/**
 * Variable replacement pipeline with format-correct escaping.
 *
 * @package Bookline
 */

declare( strict_types=1 );

namespace Bookline\Domain\Notification;

/**
 * Substitutes `{{key}}` tokens into template strings.
 *
 * @since 0.1.0
 */
final class TemplateRenderer {

	/**
	 * Replace tokens with escaped values.
	 *
	 * @param string       $template Template with {{tokens}}.
	 * @param VariableBag  $bag      Values.
	 * @param EscapeFormat $format   Escape format.
	 *
	 * @since 0.1.0
	 */
	public function replace( string $template, VariableBag $bag, EscapeFormat $format ): string {
		return (string) preg_replace_callback(
			'/\{\{\s*([a-z0-9_.]+)\s*\}\}/i',
			static function ( array $matches ) use ( $bag, $format ): string {
				$raw = $bag->get( $matches[1], '' );
				return self::escape( $raw, $format );
			},
			$template
		);
	}

	/**
	 * Escape a value for the target format.
	 *
	 * @param string       $value  Raw value.
	 * @param EscapeFormat $format Format.
	 *
	 * @since 0.1.0
	 */
	public static function escape( string $value, EscapeFormat $format ): string {
		return match ( $format ) {
			EscapeFormat::Html => self::escape_html( $value ),
			EscapeFormat::Text => $value,
			EscapeFormat::Url  => rawurlencode( $value ),
		};
	}

	/**
	 * HTML-escape without requiring WordPress bootstrap.
	 *
	 * @param string $value Raw.
	 */
	private static function escape_html( string $value ): string {
		if ( function_exists( 'esc_html' ) ) {
			return esc_html( $value );
		}
		return htmlspecialchars( $value, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8' );
	}
}