<?php
<?
// Hooks only for version 5 only, may be for previous version also works
if (!defined('WPCF7_VERSION') OR intval(WPCF7_VERSION) !== 5)
{
    return;
}

add_filter( 'wpcf7_validate_text', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_text*', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_email', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_email*', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_url', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_url*', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_tel', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_tel*', 'wpcf7_text_allowed_chars_validation_filter', 11, 2 );

/**
 * @param WPCF7_Validation $result
 * @param WPCF7_FormTag $tag
 * @return mixed
 */
function wpcf7_text_allowed_chars_validation_filter($result, $tag)
{
    $name = $tag->name;

    $value = isset($_POST[$name])
        ? trim(wp_unslash(strtr((string)$_POST[$name], "\n", " ")))
        : '';

    if ($validation_patterns = $tag->get_option('valid-chars'))
    {
        $validation_patterns = wpcf7_field_validation_patterns_filter($validation_patterns);
    }

    if ($validation_patterns)
    {
        if (!wpcf7_validate_field_with_pattern($validation_patterns, $value))
        {
            $result->invalidate($tag, wpcf7_get_message(wpcf7_get_field_invalidation_pattern_message($validation_patterns)));
        }
    }

    return $result;
}

function wpcf7_get_default_validation_patterns()
{
    return $patterns = [
        'letters' => 'A-ZА-Я\s_\-',
        'digits' => '\d'
    ];
}

function wpcf7_field_validation_patterns_filter($patterns = [])
{
    $valid_patterns = wpcf7_get_default_validation_patterns();

    return array_filter($patterns, function ($pattern) use ($valid_patterns)
    {
        return !empty($valid_patterns[$pattern]);
    });
}

function wpcf7_get_field_invalidation_pattern_message($patterns = [])
{
    $is_letters_invalid = in_array('letters', $patterns);
    $is_digits_invalid = in_array('digits', $patterns);

    if ($is_letters_invalid AND $is_digits_invalid)
    {
        return 'invalid_letters_digits';
    }
    elseif ($is_letters_invalid)
    {
        return 'invalid_letters';
    }
    elseif ($is_digits_invalid)
    {
        return 'invalid_digits';
    }
}

/**
 * @param string[] $validation_patterns
 * @param string $value
 * @return bool
 */
function wpcf7_validate_field_with_pattern($validation_patterns = [], $value)
{
    $validation_patterns = array_filter((array)$validation_patterns);

    if (!$validation_patterns)
    {
        return TRUE;
    }

    $patterns = wpcf7_get_default_validation_patterns();

    $pattern = [];

    foreach ($validation_patterns AS $pattern_name)
    {
        if (isset($patterns[$pattern_name]))
        {
            $pattern[] = $patterns[$pattern_name];
        }
    }

    $pattern = implode('', $pattern);

    return preg_match("/^[$pattern]+$/iu", $value);
}

add_filter('wpcf7_messages', function ($messages)
{
    $messages['invalid_letters_digits'] = [
        'description' => __('Allowed letters and digits only.', 'THEME_DOMAIN'),
        'default'     => __('Letters and didgits only.', 'THEME_DOMAIN'),
    ];

    $messages['invalid_letters'] = [
        'description' => __('Allowed letters only.', 'THEME_DOMAIN'),
        'default'     => __('Letters only.', 'THEME_DOMAIN'),
    ];

    $messages['invalid_digits'] = [
        'description' => __('Allowed digits only.', 'THEME_DOMAIN'),
        'default'     => __('Digits only.', 'THEME_DOMAIN'),
    ];

    return $messages;
});