<?php
/*************************************************************
# 076 License

Copyright (c) テクニカル諏訪子

Permission is hereby granted to any person obtaining a copy of the software
Little Beast (the "Software") to use, modify, merge, copy, publish, distribute,
sublicense, and/or sell copies of the Software, subject to the following conditions:

    1. **Origin Attribution**:
       - You must not misrepresent the origin of the Software; you must not claim
         you created the original Software.
       - If the Software is used in a product, you must either:
         a. Provide clear attribution in the product's documentation, user interface,
            or other visible areas, **OR**
         b. Pay the original developers a fee they specify in writing.
    2. **Usage Restriction**:
       - The Software, or any derivative works, dependencies, or libraries
         incorporating it, must not be used for censorship or to suppress freedom of
         speech, expression, or creativity. Prohibited uses include, but are not
         limited to:
         - Censorship of so-called "hate speech", visuals, non-mainstream opinions,
           ideas, or objective reality.
         - Tools or systems designed to restrict access to information or
           artistic works.
    3. **Notice Preservation**:
       - This license and the above copyright notice must remain intact in all copies
         of the source code.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
namespace Std\Lib\Git;

/**
 * リポジトリの整理（git gc の基本）：到達出来るオブジェクトを1つのパックにまとめ、古い不要なファイルを消す
 *
 * プッシュで増えたルーズオブジェクトと小さいパックをまとめる。cronで定期的に実行すると良い。
 * 新しい差分は作らない（既存のパックの差分は再利用する）。
 */
final class Maintenance {
  /**
   * @param int $pruneAge  到達出来ないオブジェクト・パックを消すまでの秒数（既定は2週間、受信中の物を消さない様に）
   * @return array  objects（パックにしたオブジェクトの数）、removedLoose、removedPacks
   */
  public static function gc(Repository $repo, int $pruneAge = 1209600): array {
    $lock = $repo->path.'/gc.pid';
    $fh = @fopen($lock, 'c');
    if ($fh === false || !flock($fh, LOCK_EX | LOCK_NB)) throw new GitException('別のgcが実行中です');
    try {
      $tips = array_values($repo->refs->all());
      $head = $repo->refs->resolve('HEAD');
      if ($head !== null) $tips[] = $head;
      $tips = array_values(array_unique($tips));
      $objects = empty($tips) ? [] : (new Walk($repo))->objects($tips, []);
      $old = $repo->objects->packs(true);
      $newPack = null;
      if (!empty($objects)) {
        $tmp = $repo->objects->dir().'/pack/tmp_gc_'.bin2hex(random_bytes(6));
        $out = fopen($tmp, 'w+b');
        try {
          (new PackWriter($repo))->write($objects, fn(string $b) => fwrite($out, $b));
          rewind($out);
          $res = (new PackIndexer($repo))->receive($out, 0);
          $newPack = $res['pack'];
        } finally {
          fclose($out);
          @unlink($tmp);
        }
      }
      $cutoff = time() - $pruneAge;
      $removedPacks = 0;
      foreach ($old as $path => $pack) {
        if ($path === $newPack || !str_starts_with($path, $repo->objects->dir().'/')) continue;
        // 全部が新しいパックに有るか、古い（到達出来ない物だけ）なら消す
        $all = true;
        foreach ($pack->ids() as $id) if (!isset($objects[$id])) {
          $all = false;
          break;
        }
        if (!$all && filemtime($path) >= $cutoff) continue;
        if (is_file(substr($path, 0, -5).'.keep')) continue;
        unset($pack);
        foreach (['.idx', '.rev', '.pack'] as $ext) @unlink(substr($path, 0, -5).$ext);
        $removedPacks++;
      }
      $removedLoose = 0;
      foreach (glob($repo->objects->dir().'/[0-9a-f][0-9a-f]/*') ?: [] as $f) {
        $id = basename(dirname($f)).basename($f);
        if (!$repo->isId($id)) continue;
        if (isset($objects[$id]) || filemtime($f) < $cutoff) {
          if (@unlink($f)) $removedLoose++;
        }
      }
      foreach (glob($repo->objects->dir().'/[0-9a-f][0-9a-f]', GLOB_ONLYDIR) ?: [] as $d) @rmdir($d);
      // 残った一時ファイル
      foreach (glob($repo->objects->dir().'/pack/tmp_*') ?: [] as $f) if (filemtime($f) < $cutoff) @unlink($f);
      return ['objects' => count($objects), 'removedLoose' => $removedLoose, 'removedPacks' => $removedPacks];
    } finally {
      flock($fh, LOCK_UN);
      fclose($fh);
      @unlink($lock);
    }
  }
}