<?php
declare(strict_types=1);
defined( 'ABSPATH' ) || exit;

/** Strict decoder of the shipped exclusion option. All reasons retain the old
 * staff/test exemption semantics; this is NOT an objection/suppression source. */
final class OG_Exclusion_Source {
    const MAX_BYTES=1048576;
    const MAX_ENTRIES=500;
    const MAX_HASHES=500;
    public static function decode(?string $raw): array {
        if($raw===null){return array();}
        if(strlen($raw)>self::MAX_BYTES){throw new RuntimeException('exclusion_source_too_large');}
        $list=@unserialize($raw,array('allowed_classes'=>false));
        if(!is_array($list) || !array_is_list($list) || serialize($list)!==$raw){throw new RuntimeException('exclusion_source_invalid');}
        if(count($list)>self::MAX_ENTRIES){throw new RuntimeException('exclusion_source_too_large');}
        $hashes=array();
        foreach($list as $entry){
            if(!is_array($entry) || !in_array($entry['field']??null,array('email','phone','name'),true)){throw new RuntimeException('exclusion_source_invalid');}
            $values=array();
            if(array_key_exists('hashes',$entry)){
                if(!is_array($entry['hashes']) || !array_is_list($entry['hashes'])){throw new RuntimeException('exclusion_source_invalid');}
                if(count($entry['hashes'])>self::MAX_HASHES){throw new RuntimeException('exclusion_source_too_large');}
                $values=$entry['hashes'];
            }
            if(array_key_exists('hash',$entry)){$values[]=$entry['hash'];}
            if(!$values){throw new RuntimeException('exclusion_source_invalid');}
            foreach($values as $hash){
                if(!is_string($hash) || !preg_match('/^[a-f0-9]{64}$/D',$hash)){throw new RuntimeException('exclusion_source_invalid');}
                $hashes[$hash]=true;
                if(count($hashes)>self::MAX_HASHES){throw new RuntimeException('exclusion_source_too_large');}
            }
        }
        $result=array_keys($hashes);sort($result,SORT_STRING);return $result;
    }
}