<?php
/**
 * Eigenständiger ZIP-Writer ohne php_zip Erweiterung.
 * Implementiert ZIP-Format (PKZIP 2.0) direkt in PHP.
 */
class SimpleZip
{
    private string $path;
    private        $fh;
    private array  $entries = [];
    private int    $offset  = 0;

    public function __construct(string $path)
    {
        $this->path = $path;
        $this->fh   = fopen($path, 'wb');
        if (!$this->fh) throw new RuntimeException("Kann ZIP nicht erstellen: $path");
    }

    public function addFromString(string $localName, string $data): void
    {
        $this->addData($localName, $data, time());
    }

    public function addFile(string $filePath, string $localName): void
    {
        $data    = file_get_contents($filePath);
        $mtime   = filemtime($filePath);
        $this->addData($localName, $data, $mtime);
    }

    private function addData(string $localName, string $data, int $mtime): void
    {
        $localName  = str_replace('\\', '/', $localName);
        $crc        = crc32($data);
        $size       = strlen($data);
        $compressed = gzdeflate($data, 6);
        $compSize   = strlen($compressed);

        // Lokaler Header
        $dosTime = $this->dosTime(filemtime($filePath));
        $nameLen = strlen($localName);

        $localHeader = pack('VvvvvVVVvv',
            0x04034b50,  // Signatur
            20,          // Version needed
            0,           // Flags
            8,           // Deflate
            $dosTime,    // Mod time
            $crc,
            $compSize,
            $size,
            $nameLen,
            0            // Extra length
        ) . $localName;

        fwrite($this->fh, $localHeader);
        fwrite($this->fh, $compressed);

        $this->entries[] = [
            'name'     => $localName,
            'crc'      => $crc,
            'size'     => $size,
            'compSize' => $compSize,
            'offset'   => $this->offset,
            'dosTime'  => $dosTime,
        ];

        $this->offset += strlen($localHeader) + $compSize;
    }

    public function close(): void
    {
        $cdOffset = $this->offset;
        $cdSize   = 0;

        foreach ($this->entries as $e) {
            $nameLen = strlen($e['name']);
            $cd = pack('VvvvvVVVvvvvvVV',
                0x02014b50,  // CD Signatur
                20,          // Version made by
                20,          // Version needed
                0,           // Flags
                8,           // Deflate
                $e['dosTime'],
                $e['crc'],
                $e['compSize'],
                $e['size'],
                $nameLen,
                0,           // Extra length
                0,           // Comment length
                0,           // Disk start
                0,           // Internal attr
                0,           // External attr
                $e['offset']
            ) . $e['name'];

            fwrite($this->fh, $cd);
            $cdSize += strlen($cd);
        }

        // End of central directory
        $count = count($this->entries);
        fwrite($this->fh, pack('VvvvvVVv',
            0x06054b50,  // EOCD Signatur
            0,           // Disk number
            0,           // Disk with CD
            $count,      // Entries on disk
            $count,      // Total entries
            $cdSize,
            $cdOffset,
            0            // Comment length
        ));

        fclose($this->fh);
    }

    private function dosTime(int $unixTime): int
    {
        $d = getdate($unixTime);
        return (($d['year'] - 1980) << 25)
             | ($d['mon']  << 21)
             | ($d['mday'] << 16)
             | ($d['hours']   << 11)
             | ($d['minutes'] << 5)
             | ($d['seconds'] >> 1);
    }
}