Custom validation for ACF Repeater Field values

validate-acf-field-repeater.php

add_filter('acf/validate_value/name=voucher', 'acf_validate_vocher_code_unique', 10, 4);

function acf_validate_vocher_code_unique($valid, $value, $field, $input_name) {

        // Bail early if value is already invalid.
        if ($valid !== true) {
            return $valid;
        }
        
        $result = validate_voucher_unqiue($value);
        if( !empty($result) ){
            return $result;
        }

        global $post;
        $vochers = get_all_voucher_range($post->ID);
        
        $result = self::validate_voucher_unqiue_all_tercarios($value, $vochers);
        if (!empty($result)) {
            return 'Overlapping Value for Voucher Codes. Overlap present in ' . $result;
        } else {
            return $valid;
        }
        return $valid;
    }

    function get_all_voucher_range($current_post) {
        //get your custom posts ids as an array
        $posts = get_posts(
                array(
                    'post_type' => self::$post_type,
                    'post_status' => 'publish',
                    'posts_per_page' => -1,
                    'exclude' => array($current_post),
                    'fields' => 'ids'
                )
        );
        $rows = [];
        foreach ($posts as $post_id) {
            $rows[$post_id] = get_field('voucher', $post_id);
        }
        return $rows;
    }
    
    function validate_voucher_unqiue($current_rows) {
        $value_range = [];
        foreach ($current_rows as $current_row) {
            $current = array_values($current_row);
            $current_start = $current[0];
            $current_end = $current[1];
            if($current_end < $current_start){
                return 'End value should be bigger than Start Value';
            }
            /** This logic is worst for huge range of data **/
            $value_range = array_merge ( $value_range, range($current_start, $current_end));
            
        }
        
        if (count($value_range) !== count(array_unique($value_range))){
            return 'Overlapping Voucher codes range found in this range';
        }
        
        return false;
    }

    public static function validate_voucher_unqiue_all_tercarios($current_rows, $all_vouchers) {
        foreach ($current_rows as $current_row) {
            $current = array_values($current_row);
            $current_start = $current[0];
            $current_end = $current[1];

            foreach ($all_vouchers as $post_id => $voucher) {
                foreach ($voucher as $voucher_row) {
                    $start = $voucher_row['de'];
                    if (!empty($current_start) && !empty($current_end) && !empty($start)) {
                        if (($current_start <= $start) && ($start <= $current_end)) {
                            return get_edit_post_link($post_id);
                        }
                    }

                    $end = $voucher_row['ate'];
                    if (!empty($current_start) && !empty($current_end) && !empty($end)) {
                        if (($current_start <= $end) && ($end <= $current_end)) {
                            return get_edit_post_link($post_id);
                        }
                    }
                }
            }
        }

        return false;
    }

thanks for that approach.
i developed an other validation for a relay price table based on this:
https://gist.github.com/AndreKelling/8968ff5195f7b7ad78356d2fa820045d