<?php

declare(strict_types=1);
function v4UnifiedWrite(string $path,string $text,int $mode=0644):void
{
    $tmp=tempnam(dirname($path),'.v4-rc-');if($tmp===false)throw new RuntimeException('Temporaere Datei fehlt.');
    try {if(file_put_contents($tmp,$text,LOCK_EX)!==strlen($text)||!chmod($tmp,$mode)||!rename($tmp,$path))throw new RuntimeException('Datei konnte nicht geschrieben werden.');}
    finally {if(is_file($tmp))unlink($tmp);}
}
function v4UnifiedFiles(string $stage,string $target):array
{
    $m=json_decode(file_get_contents($stage.'/MANIFEST.json'),true,64,JSON_THROW_ON_ERROR);
    $names=['libs/NetzfahrplanV4Datenarchiv.php','libs/NetzfahrplanV4Bilanzierung.php','libs/ManagerNetzfahrplanV4DatenTrait.php'];
    if($m['scope']!=='unified_native_data_only'||array_keys($m['files'])!==$names)throw new RuntimeException('Falscher Installationsumfang.');
    $old=[];$new=[];$complete=true;
    foreach($names as$name){
        $p=$target.'/'.$name;$s=$stage.'/source/'.$name;
        if(is_link($p)||is_link($s)||realpath(dirname($p))!==realpath($target).'/libs')throw new RuntimeException('Unerwarteter Dateipfad.');
        $new[$name]=file_get_contents($s);token_get_all($new[$name],TOKEN_PARSE);
        if(hash('sha256',$new[$name])!==$m['files'][$name]['after'])throw new RuntimeException('Vorbereitete Datei geaendert.');
        $old[$name]=is_file($p)?file_get_contents($p):null;$h=$old[$name]===null?null:hash('sha256',$old[$name]);
        if($h!==$m['files'][$name]['after'])$complete=false;
        if($h!==$m['files'][$name]['before']&&$h!==$m['files'][$name]['after'])throw new RuntimeException('Parallele Modulaenderung; nichts ueberschrieben.');
    }
    if($complete)return ['status'=>'already_installed'];
    foreach($names as$name)if(($old[$name]===null?null:hash('sha256',$old[$name]))!==$m['files'][$name]['before'])throw new RuntimeException('Teilstand zuerst pruefen.');
    $backup=$stage.'/backups/'.gmdate('YmdTHis').'-'.bin2hex(random_bytes(4));
    if(!mkdir($backup.'/libs',0700,true))throw new RuntimeException('Sicherung fehlt.');
    foreach($names as$name)if($old[$name]!==null)v4UnifiedWrite($backup.'/'.$name,$old[$name],0600);
    v4UnifiedWrite($backup.'/MANIFEST.json',json_encode($m,JSON_THROW_ON_ERROR|JSON_PRETTY_PRINT),0600);
    $written=[];
    try {foreach($names as$name){$p=$target.'/'.$name;if((is_file($p)?file_get_contents($p):null)!==$old[$name])throw new RuntimeException('Parallele Dateiaenderung.');v4UnifiedWrite($p,$new[$name]);$written[]=$name;}}
    catch(Throwable $e){foreach(array_reverse($written)as$name){$p=$target.'/'.$name;if(hash_file('sha256',$p)!==$m['files'][$name]['after'])continue;if($old[$name]===null)unlink($p);else v4UnifiedWrite($p,$old[$name]);}throw $e;}
    return ['status'=>'installed','backup'=>$backup];
}