<?php

declare(strict_types=1);
namespace Belevo\EnelixEMS;

/** Lossless archival of fully acknowledged OLD outbox days. No device/API calls. */
final class NetzfahrplanV4Datenarchiv
{
    public static function run(string $directory, array $cursor, int $now): array
    {
        $day=$cursor['day']??'';
        if ($day==='') return ['archived'=>0];
        if (!is_string($day)||!preg_match('/^raw-[0-9]{8}\.jsonl$/D',$day)
            ||!is_int($cursor['offset']??null)||$cursor['offset']<0
            ||is_link($directory)||realpath($directory)!==$directory) {
            throw new \RuntimeException('Invalid archive cursor/directory');
        }
        $cutoff='raw-'.gmdate('Ymd',$now-7*86400).'.jsonl';
        $archive=$directory.'/archive';
        if (is_link($archive)) throw new \RuntimeException('Archive symlink refused');
        if (!is_dir($archive)&&!mkdir($archive,0700)) throw new \RuntimeException('Archive directory unavailable');
        if ((fileperms($archive)&0007)!==0) throw new \RuntimeException('Archive must remain private');
        $lockPath=$directory.'/.writer.lock';
        if (is_link($lockPath)) throw new \RuntimeException('Writer lock symlink refused');
        $lock=fopen($lockPath,'c+b');
        if ($lock===false) throw new \RuntimeException('Archive lock unavailable');
        $done=[];
        try {
            if (!flock($lock,LOCK_EX|LOCK_NB)) return ['archived'=>0,'status'=>'writer_busy'];
            foreach (glob($directory.'/raw-*.jsonl')?:[] as $file) {
                $name=basename($file);
                if (!preg_match('/^raw-[0-9]{8}\.jsonl$/D',$name)||$name>=$day||$name>=$cutoff) continue;
                if (is_link($file)||realpath($file)!==$file||!is_file($file)) throw new \RuntimeException('Unexpected journal');
                $before=stat($file);
                if (!$before||$before['size']>67108864) throw new \RuntimeException('Archive input bounds');
                $digest=hash_file('sha256',$file);
                if (!is_string($digest)) throw new \RuntimeException('Cannot hash journal');
                $target=$archive.'/'.$name.'.'.$digest.'.gz';
                if (is_link($target)) throw new \RuntimeException('Archive target symlink');
                if (!is_file($target)) {
                    $tmp=tempnam($archive,'.pending-');
                    if ($tmp===false) throw new \RuntimeException('Cannot create archive');
                    try {
                        chmod($tmp,0600);$in=fopen($file,'rb');$gz=gzopen($tmp,'wb6');
                        if ($in===false||$gz===false) {if(is_resource($in))fclose($in);if(is_resource($gz))gzclose($gz);throw new \RuntimeException('Cannot open archive streams');}
                        try {
                            while (!feof($in)) {
                                $block=fread($in,65536);
                                if ($block===false) throw new \RuntimeException('Archive read failed');
                                $offset=0;
                                while($offset<strlen($block)) {$n=gzwrite($gz,substr($block,$offset));if($n===false||$n===0)throw new \RuntimeException('Archive write failed');$offset+=$n;}
                            }
                        } finally {fclose($in);gzclose($gz);}
                        $sync=fopen($tmp,'r+b');
                        if ($sync===false) throw new \RuntimeException('Cannot sync archive');
                        try {if(!fsync($sync))throw new \RuntimeException('Archive sync failed');} finally {fclose($sync);}
                        if (!rename($tmp,$target)) throw new \RuntimeException('Archive rename failed');
                    } finally {if(is_file($tmp))unlink($tmp);}
                }
                $gz=gzopen($target,'rb');if($gz===false)throw new \RuntimeException('Cannot verify archive');
                $hash=hash_init('sha256');$bytes=0;
                try {while(!gzeof($gz)){$block=gzread($gz,65536);if($block===false)throw new \RuntimeException('Archive verification read failed');$bytes+=strlen($block);if($bytes>$before['size'])throw new \RuntimeException('Oversized decompressed archive');hash_update($hash,$block);}}
                finally {gzclose($gz);}
                clearstatcache(true,$file);$after=stat($file);
                if ($bytes!==$before['size']||hash_final($hash)!==$digest||!$after
                    ||$after['size']!==$before['size']||$after['ino']!==$before['ino']||$after['mtime']!==$before['mtime']
                    ||hash_file('sha256',$file)!==$digest) throw new \RuntimeException('Archive mismatch; original retained');
                $directoryHandle=fopen($archive,'r');
                if ($directoryHandle===false) throw new \RuntimeException('Cannot sync archive directory');
                try {if(!fsync($directoryHandle))throw new \RuntimeException('Archive directory sync failed');} finally {fclose($directoryHandle);}
                if (!unlink($file)) throw new \RuntimeException('Verified original could not be retired');
                $done[]=$name;
                if (count($done)>=2) break;
            }
        } finally {flock($lock,LOCK_UN);fclose($lock);}
        return ['archived'=>count($done),'compressedOriginalsRetained'=>true,'unacknowledgedDaysTouched'=>false];
    }
}