<?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;

/**
 * git-receive-pack（プッシュ）。HTTP（stateless）とSSH
 *
 * 対応：report-status、delete-refs、side-band-64k、quiet、atomic、ofs-delta、no-thin（相手はシンパックを送らない）。
 * 受け取ったオブジェクトは確認し（壊れたオブジェクト、足りないオブジェクト）、参照はロックして更新する。
 */
final class ReceivePack {
  private string $agent;
  private int $unpackLimit;
  private Output $out;
  private bool $sideband = false;

  /**
   * @param array $opt  agent、unpackLimit（これより少ないオブジェクトはルーズにする、既定100）、
   *                    check（fn(array $commands): ?string、全部の更新の前、エラーのメッセージで全部拒否）、
   *                    update（fn(string $ref, string $old, string $new): ?string、参照毎、エラーならその参照を拒否）、
   *                    after（fn(array $commands)、更新した参照 [ref, old, new]、結果を送った後）、
   *                    intercept（fn(string $ref): bool、trueの参照は書かずにprocessに渡す。AGitのrefs/for/等）、
   *                    process（fn(array $commands): array、成功した参照 [ref, old, new]、結果を送る前。返した行はクライアントに表示する）、
   *                    denyNonFastForwards、denyDeletes（既定はconfigのreceive.*）
   */
  public function __construct(private Repository $repo, private array $opt = []) {
    $this->agent = (string)($opt['agent'] ?? 'LittleBeast');
    $this->unpackLimit = (int)($opt['unpackLimit'] ?? $repo->config->getInt('receive.unpacklimit', $repo->config->getInt('transfer.unpacklimit', 100)));
  }

  /**
   * 参照の広告
   *
   * @param resource $out
   */
  public function advertise($out, bool $http): void {
    $o = new Output($out, $http);
    $s = $http ? PktLine::encode("# service=git-receive-pack\n").PktLine::flush() : '';
    $caps = "report-status delete-refs side-band-64k quiet atomic ofs-delta no-thin object-format={$this->repo->hashAlgo} agent={$this->agent}";
    $first = true;
    foreach ($this->repo->refs->all() as $name => $id) {
      $s .= PktLine::encode("{$id} {$name}".($first ? "\0".$caps : '')."\n");
      $first = false;
    }
    if ($first) $s .= PktLine::encode($this->repo->zeroId()." capabilities^{}\0{$caps}\n");
    $o->write($s.PktLine::flush());
    $o->flush();
  }

  /**
   * プッシュを処理する
   *
   * @param resource $in
   * @param resource $out
   * @return array  更新した参照 [ref, old, new]
   */
  public function serve($in, $out, bool $statelessRpc): array {
    $this->out = new Output($out, $statelessRpc);
    if (!$statelessRpc) $this->advertise($out, false);
    $pkt = new PktLine($in);
    $commands = [];
    $caps = [];
    $zero = $this->repo->zeroId();
    while (true) {
      $l = $pkt->read();
      if ($l === null || $l === PktLine::FLUSH) break;
      if (!is_string($l)) continue;
      if (str_starts_with($l, 'shallow ')) continue;
      $nul = strpos($l, "\0");
      if ($nul !== false) {
        $caps = explode(' ', trim(substr($l, $nul + 1)));
        $l = substr($l, 0, $nul);
      }
      if (!preg_match('/^([0-9a-f]+) ([0-9a-f]+) (.+)$/', $l, $m) || !$this->repo->isId($m[1]) || !$this->repo->isId($m[2])) {
        throw new GitException("不正なコマンド：{$l}");
      }
      $commands[] = ['ref' => $m[3], 'old' => $m[1], 'new' => $m[2], 'error' => null];
    }
    if (empty($commands)) return [];
    foreach ($caps as $c) {
      if (str_starts_with($c, 'object-format=') && substr($c, 14) !== $this->repo->hashAlgo) throw new GitException('オブジェクトの形式が違います');
    }
    $this->sideband = in_array('side-band-64k', $caps, true);
    $quiet = in_array('quiet', $caps, true);
    $atomic = in_array('atomic', $caps, true);
    $report = in_array('report-status', $caps, true);

    // パック（削除だけなら無い）
    $unpack = 'ok';
    $received = ['objects' => [], 'links' => []];
    $needPack = false;
    foreach ($commands as $c) if ($c['new'] !== $zero) $needPack = true;
    if ($needPack) {
      try {
        $progress = $quiet || !$this->sideband ? null : function(string $what, int $done, int $total): void {
          $this->out->write(PktLine::band(2, "{$what}：{$done}/{$total}".($done === $total ? "\n" : "\r")));
          $this->out->flush();
        };
        $received = (new PackIndexer($this->repo))->receive($in, $this->unpackLimit, $progress);
        // 足りないオブジェクト
        foreach (array_keys($received['links']) as $id) {
          if (!$this->repo->objects->exists($id)) throw new GitException("必要なオブジェクトが有りません：{$id}");
        }
      } catch (GitException $e) {
        $unpack = $e->getMessage();
      }
    }
    if ($unpack !== 'ok') {
      foreach ($commands as $i => $c) $commands[$i]['error'] = 'unpacker error';
    } else {
      $commands = $this->check($commands, $received['objects']);
      if ($atomic && count(array_filter($commands, fn($c) => $c['error'] !== null)) > 0) {
        foreach ($commands as $i => $c) $commands[$i]['error'] ??= 'atomic push failed';
      }
      $commands = $this->apply($commands, $atomic);
      // 参照の処理（プルリクエスト等）とクライアントへのメッセージ
      if (isset($this->opt['process'])) {
        $ok = array_values(array_map(fn($c) => [$c['ref'], $c['old'], $c['new']], array_filter($commands, fn($c) => $c['error'] === null)));
        $lines = empty($ok) ? [] : ($this->opt['process'])($ok);
        if ($this->sideband && !empty($lines)) {
          foreach ($lines as $line) $this->out->write(PktLine::band(2, rtrim((string)$line, "\n")."\n"));
          $this->out->flush();
        }
      }
    }

    if ($report) {
      $s = PktLine::encode('unpack '.($unpack === 'ok' ? 'ok' : str_replace("\n", ' ', $unpack))."\n");
      foreach ($commands as $c) $s .= PktLine::encode($c['error'] === null ? "ok {$c['ref']}\n" : "ng {$c['ref']} ".str_replace("\n", ' ', $c['error'])."\n");
      $s .= PktLine::flush();
      $this->out->write($this->sideband ? PktLine::band(1, $s) : $s);
    }
    if ($this->sideband) $this->out->write(PktLine::flush());
    $this->out->flush();

    $done = [];
    foreach ($commands as $c) if ($c['error'] === null) $done[] = [$c['ref'], $c['old'], $c['new']];
    if (!empty($done) && isset($this->opt['after'])) ($this->opt['after'])($done);
    return $done;
  }

  /** 更新出来るか確かめる */
  private function check(array $commands, array $received): array {
    $zero = $this->repo->zeroId();
    $denyFf = (bool)($this->opt['denyNonFastForwards'] ?? $this->repo->config->getBool('receive.denynonfastforwards'));
    $denyDel = (bool)($this->opt['denyDeletes'] ?? $this->repo->config->getBool('receive.denydeletes'));
    if (isset($this->opt['check'])) {
      $err = ($this->opt['check'])(array_map(fn($c) => [$c['ref'], $c['old'], $c['new']], $commands));
      if ($err !== null) {
        foreach ($commands as $i => $c) $commands[$i]['error'] = $err;
        return $commands;
      }
    }
    $walk = new Walk($this->repo);
    foreach ($commands as $i => $c) {
      $err = null;
      $ref = $c['ref'];
      $type = $c['new'] === $zero ? null : ($received[$c['new']] ?? $this->repo->objects->info($c['new'])[0] ?? null);
      if (!Refs::validName($ref) || !str_starts_with($ref, 'refs/') || $ref === 'HEAD') $err = 'funny refname';
      else if ($c['new'] !== $zero && $type === null) $err = 'missing necessary objects';
      else if (str_starts_with($ref, 'refs/heads/') && $c['new'] !== $zero && $type !== 'commit') $err = 'branch must point to a commit';
      else if ($c['new'] === $zero && $denyDel) $err = 'deletion prohibited';
      else if ($c['new'] === $zero && $c['old'] === $zero) $err = 'nothing to delete';
      else if ($denyFf && $c['old'] !== $zero && $c['new'] !== $zero && $this->repo->objects->exists($c['old'])
               && !$walk->isAncestor($c['old'], $c['new'])) $err = 'non-fast-forward';
      if ($err === null && isset($this->opt['update'])) $err = ($this->opt['update'])($ref, $c['old'], $c['new']);
      $commands[$i]['error'] = $err;
    }
    return $commands;
  }

  /** 参照を更新する（古い値が変わっていれば失敗） */
  private function apply(array $commands, bool $atomic): array {
    $zero = $this->repo->zeroId();
    // interceptの参照は書かない
    $skip = fn(array $c) => isset($this->opt['intercept']) && ($this->opt['intercept'])($c['ref']);
    $ok = array_filter($commands, fn($c) => $c['error'] === null && !$skip($c));
    if (empty($ok)) return $commands;
    $tx = fn(array $c) => [$c['ref'], $c['new'] === $zero ? null : $c['new'], $c['old']];
    if ($atomic) {
      try {
        $this->repo->refs->transaction(array_map($tx, $ok));
      } catch (GitException $e) {
        foreach ($commands as $i => $c) $commands[$i]['error'] ??= 'failed to update ref';
      }
      return $commands;
    }
    foreach ($commands as $i => $c) {
      if ($c['error'] !== null || $skip($c)) continue;
      try {
        $this->repo->refs->transaction([$tx($c)]);
      } catch (GitException $e) {
        $commands[$i]['error'] = str_contains($e->getMessage(), '変わって') ? 'fetch first' : 'failed to update ref';
      }
    }
    return $commands;
  }
}