<?php
/**
 * Phone number masking helpers shared by the account UI and the
 * phone-match verification endpoint.
 *
 * The hidden middle segment adapts to the number: domestic 11-digit
 * numbers hide 4 digits (138****1234), longer international numbers
 * hide length-7 digits (min 4), so the digit-entry UI renders one box
 * per hidden digit.
 *
 * @package AKSRT
 */

if (!defined('ABSPATH')) {
	exit;
}

/**
 * Split a bound phone number into visible prefix / hidden middle / visible suffix.
 *
 * Works on the digit core of the number (a leading "+" is ignored for the split
 * but reported back). Returns null when the number holds fewer than 8 digits —
 * such numbers cannot be verified by middle-digit entry.
 *
 * @return array{prefix:string,hidden:string,suffix:string,hidden_length:int,leading_plus:bool}|null
 */
function aksrt_phone_mask_parts(string $phone): ?array {
	$phone = trim($phone);
	if ($phone === '') {
		return null;
	}

	$leading_plus = $phone[0] === '+';
	$core = preg_replace('/\D+/', '', $phone);
	$length = strlen($core);
	if ($length < 8) {
		return null;
	}

	$hidden_length = min(11, max(4, $length - 7));
	$suffix_length = $length - 3 - $hidden_length;
	if ($suffix_length < 1) {
		return null;
	}

	return [
		'prefix'        => substr($core, 0, 3),
		'hidden'        => substr($core, 3, $hidden_length),
		'suffix'        => substr($core, $length - $suffix_length),
		'hidden_length' => $hidden_length,
		'leading_plus'  => $leading_plus,
	];
}

/**
 * Masked display form of a phone number, e.g. 138****1234 or +861******1234.
 * Falls back to the raw number when it cannot be masked.
 */
function aksrt_phone_mask_display(string $phone): string {
	$parts = aksrt_phone_mask_parts($phone);
	if ($parts === null) {
		return $phone;
	}

	$mask = str_repeat('*', (int) $parts['hidden_length']);
	$display = $parts['prefix'] . $mask . $parts['suffix'];
	return $parts['leading_plus'] ? '+' . $display : $display;
}