<?php
/**
 * Message templates: {placeholder} substitution with one rule — a line whose optional
 * placeholders (tracking, items, …) are all empty is dropped, so "Tracking: {tracking_number}"
 * disappears on an order without tracking instead of reading "Tracking: ". Messages are sent as plain text, never as HTML,
 * so nothing a customer typed into an order can turn into markup.
 *
 * @package Orderchirp
 */

namespace Orderchirp;

defined( 'ABSPATH' ) || exit;

final class Template {

	/**
	 * Telegram's limit for one message.
	 */
	const MAX_LENGTH = 4096;

	/**
	 * The placeholders the owner can use, with what each one means.
	 *
	 * @return array<string,string>
	 */
	public static function placeholders() {
		return array(
			'first_name'        => __( 'Customer first name', 'orderchirp' ),
			'last_name'         => __( 'Customer last name', 'orderchirp' ),
			'order_number'      => __( 'Order number', 'orderchirp' ),
			'order_total'       => __( 'Order total with currency', 'orderchirp' ),
			'order_status'      => __( 'Order status', 'orderchirp' ),
			'order_date'        => __( 'Order date', 'orderchirp' ),
			'items'             => __( 'Items, one per line', 'orderchirp' ),
			'item_count'        => __( 'Number of items', 'orderchirp' ),
			'payment_method'    => __( 'Payment method', 'orderchirp' ),
			'order_url'         => __( 'Link to the order', 'orderchirp' ),
			'tracking_number'   => __( 'Tracking number (when a tracking plugin added one)', 'orderchirp' ),
			'tracking_provider' => __( 'Carrier name (when known)', 'orderchirp' ),
			'tracking_url'      => __( 'Tracking link (when known)', 'orderchirp' ),
			'shop_name'         => __( 'Your shop name', 'orderchirp' ),
		);
	}

	/**
	 * Placeholders whose line is dropped when they are all empty. Only these: a missing first
	 * name must not take "Hi {first_name}, thanks for your order" away with it.
	 *
	 * @var string[]
	 */
	const OPTIONAL = array( 'tracking_number', 'tracking_provider', 'tracking_url', 'items', 'payment_method', 'order_url' );

	/**
	 * Render a template.
	 *
	 * @param string               $text Template text.
	 * @param array<string,string> $vars Values by placeholder name; unknown placeholders stay as typed.
	 * @return string
	 */
	public static function render( $text, array $vars ) {
		$text = str_replace( array( "\r\n", "\r" ), "\n", (string) $text );
		$out  = array();
		foreach ( explode( "\n", $text ) as $line ) {
			preg_match_all( '/\{([a-z_]+)\}/', $line, $found );
			$names = array_values( array_intersect( array_unique( $found[1] ), array_keys( $vars ) ) );
			if ( $names && array_intersect( $names, self::OPTIONAL ) ) {
				$all_empty = true;
				foreach ( $names as $name ) {
					if ( '' !== trim( (string) $vars[ $name ] ) ) {
						$all_empty = false;
						break;
					}
				}
				if ( $all_empty ) {
					continue;
				}
			}
			$rendered = preg_replace_callback(
				'/\{([a-z_]+)\}/',
				static function ( $m ) use ( $vars ) {
					return array_key_exists( $m[1], $vars ) ? trim( (string) $vars[ $m[1] ] ) : $m[0];
				},
				$line
			);
			// Two placeholders with one of them empty leave a double space behind.
			$out[] = rtrim( (string) preg_replace( '/ {2,}/', ' ', (string) $rendered ) );
		}
		$message = trim( implode( "\n", $out ) );
		$message = (string) preg_replace( "/\n{3,}/", "\n\n", $message );
		return self::truncate( $message );
	}

	/**
	 * Cut to Telegram's limit on a character (not byte) boundary.
	 *
	 * @param string $message Message.
	 * @return string
	 */
	public static function truncate( $message ) {
		if ( function_exists( 'mb_strlen' ) && mb_strlen( $message, 'UTF-8' ) > self::MAX_LENGTH ) {
			return mb_substr( $message, 0, self::MAX_LENGTH - 1, 'UTF-8' ) . '…';
		}
		return $message;
	}
}