<?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;

/**
 * 参照（HEAD、refs/heads/、refs/tags/等）：ルーズとpacked-refs
 *
 * 変更はロックファイル（.lock）で行い、古い値を確かめられる（他の更新と競合しない様に）。
 */
final class Refs {
  private ?array $packed = null;
  private ?array $peeled = null;

  public function __construct(private Repository $repo) {}

  /** 参照の名前が正しいか（git check-ref-format） */
  public static function validName(string $name): bool {
    if ($name === 'HEAD') return true;
    if (!str_starts_with($name, 'refs/') || str_ends_with($name, '/') || str_ends_with($name, '.') || str_ends_with($name, '.lock')) return false;
    if (preg_match('#[\x00-\x20\x7f~^:?*\[\\\\]|\.\.|//|@\{|/\.|^\.#', $name)) return false;
    foreach (explode('/', $name) as $part) if ($part === '' || $part[0] === '.') return false;
    return $name !== '@';
  }

  private function packed(): array {
    if ($this->packed !== null) return $this->packed;
    $this->packed = [];
    $this->peeled = [];
    $file = $this->repo->path.'/packed-refs';
    if (!is_file($file)) return $this->packed;
    $last = null;
    foreach (preg_split('/\r?\n/', (string)file_get_contents($file)) as $line) {
      if ($line === '' || $line[0] === '#') continue;
      if ($line[0] === '^') {
        if ($last !== null) $this->peeled[$last] = substr($line, 1);
        continue;
      }
      $sp = strpos($line, ' ');
      if ($sp === false) continue;
      $last = substr($line, $sp + 1);
      $this->packed[$last] = substr($line, 0, $sp);
    }
    return $this->packed;
  }

  /**
   * 参照の中身（解決しない）
   *
   * @return string|null  ID又は「ref: 名前」
   */
  public function readRaw(string $name): ?string {
    if (!self::validName($name)) return null;
    $file = $this->repo->path.'/'.$name;
    if (is_file($file)) {
      $v = trim((string)file_get_contents($file));
      return $v === '' ? null : $v;
    }
    return $this->packed()[$name] ?? null;
  }

  /** シンボリック参照の先（HEAD → refs/heads/main）、シンボリックでなければnull */
  public function symbolic(string $name): ?string {
    $v = $this->readRaw($name);
    return $v !== null && str_starts_with($v, 'ref: ') ? trim(substr($v, 5)) : null;
  }

  /**
   * 参照をIDに解決する（シンボリック参照を辿る）
   */
  public function resolve(string $name): ?string {
    for ($i = 0; $i < 10; $i++) {
      $v = $this->readRaw($name);
      if ($v === null) return null;
      if (!str_starts_with($v, 'ref: ')) return $this->repo->isId($v) ? strtolower($v) : null;
      $name = trim(substr($v, 5));
    }
    return null;
  }

  /**
   * 短い名前（main、v1.0、origin/main）を完全な名前にする
   */
  public function dwim(string $short): ?string {
    foreach ([$short, "refs/{$short}", "refs/tags/{$short}", "refs/heads/{$short}", "refs/remotes/{$short}", "refs/remotes/{$short}/HEAD"] as $n) {
      if ($this->readRaw($n) !== null) return $n;
    }
    return null;
  }

  /**
   * 全部の参照（HEADを除く、名前の順）
   *
   * @param string $prefix  名前の始まり（例：refs/heads/）
   * @return array  名前 => ID
   */
  public function all(string $prefix = 'refs/'): array {
    $out = [];
    foreach ($this->packed() as $name => $id) if (str_starts_with($name, $prefix)) $out[$name] = $id;
    $base = $this->repo->path.'/';
    $dir = $base.rtrim(str_contains($prefix, '/') ? substr($prefix, 0, strrpos($prefix, '/')) : $prefix, '/');
    if (is_dir($dir)) {
      $it = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($dir, \FilesystemIterator::SKIP_DOTS));
      foreach ($it as $f) {
        if (!$f->isFile()) continue;
        $name = str_replace('\\', '/', substr($f->getPathname(), strlen($base)));
        if (!str_starts_with($name, $prefix) || !self::validName($name)) continue;
        $v = trim((string)file_get_contents($f->getPathname()));
        if (str_starts_with($v, 'ref: ')) {
          $r = $this->resolve($name);
          if ($r !== null) $out[$name] = $r;
        } else if ($this->repo->isId($v)) {
          $out[$name] = strtolower($v);
        }
      }
    }
    ksort($out, SORT_STRING);
    return $out;
  }

  /** packed-refsの剥いた値（注釈付きタグの先）。無ければnull */
  public function peeledFromPack(string $name): ?string {
    $this->packed();
    return $this->peeled[$name] ?? null;
  }

  /**
   * 参照を更新する
   *
   * @param string $name  参照の名前
   * @param string|null $new  新しいID（nullなら削除）
   * @param string|null $old  今のID（確かめる。0ばかりのIDは「無い事」、nullなら確かめない）
   * @throws GitException  競合した場合等
   */
  public function update(string $name, ?string $new, ?string $old = null): void {
    $this->transaction([[$name, $new, $old]]);
  }

  /**
   * 複数の参照を全部更新するか、全部しない
   *
   * @param array $updates  [名前, 新しいID又はnull, 今のID又はnull]
   */
  public function transaction(array $updates): void {
    $locks = [];
    $zero = $this->repo->zeroId();
    try {
      // HEAD等のシンボリック参照は先を更新する
      foreach ($updates as $i => [$name, $new, $old]) {
        $target = $name;
        for ($d = 0; $d < 10 && ($s = $this->symbolic($target)) !== null; $d++) $target = $s;
        if (!self::validName($target) || $target === 'HEAD') throw new GitException("不正な参照の名前：{$name}");
        if ($new !== null && !$this->repo->isId($new)) throw new GitException("不正なID：{$new}");
        $updates[$i][0] = $target;
        $lock = $this->repo->path.'/'.$target.'.lock';
        $this->repo->mkdir(dirname($lock));
        // ディレクトリと同じ名前の参照（refs/heads/aとrefs/heads/a/b）は作れない
        if (is_dir($this->repo->path.'/'.$target)) throw new GitException("参照の名前が他の参照と重なります：{$target}");
        $fh = @fopen($lock, 'x');
        if ($fh === false) throw new GitException("参照がロックされています：{$target}");
        $locks[$target] = [$fh, $lock];
      }
      $this->packed = null;
      foreach ($updates as [$name, $new, $old]) {
        if ($old === null) continue;
        $cur = $this->resolve($name);
        if ($old === $zero ? $cur !== null : $cur !== strtolower($old)) throw new GitException("参照が変わっています：{$name}");
      }
      $deletes = [];
      foreach ($updates as [$name, $new]) {
        [$fh, $lock] = $locks[$name];
        if ($new === null) {
          $deletes[] = $name;
          continue;
        }
        fwrite($fh, strtolower($new)."\n");
      }
      if (!empty($deletes)) $this->removePacked($deletes);
      foreach ($updates as [$name, $new]) {
        [$fh, $lock] = $locks[$name];
        fclose($fh);
        $file = $this->repo->path.'/'.$name;
        if ($new === null) {
          @unlink($lock);
          @unlink($file);
          $this->pruneDirs(dirname($file));
        } else {
          if (!@rename($lock, $file)) throw new GitException("参照を書けません：{$name}");
          $this->repo->chmodFile($file);
        }
        unset($locks[$name]);
      }
    } finally {
      foreach ($locks as [$fh, $lock]) {
        if (is_resource($fh)) fclose($fh);
        @unlink($lock);
      }
      $this->packed = null;
    }
  }

  /** packed-refsから消す */
  private function removePacked(array $names): void {
    $file = $this->repo->path.'/packed-refs';
    if (!is_file($file)) return;
    $lock = $file.'.lock';
    $fh = @fopen($lock, 'x');
    if ($fh === false) throw new GitException('packed-refsがロックされています');
    $out = [];
    $skip = false;
    foreach (preg_split('/\r?\n/', (string)file_get_contents($file)) as $line) {
      if ($line === '') continue;
      if ($line[0] === '^') {
        if (!$skip) $out[] = $line;
        continue;
      }
      $sp = strpos($line, ' ');
      $skip = $sp !== false && $line[0] !== '#' && in_array(substr($line, $sp + 1), $names, true);
      if (!$skip) $out[] = $line;
    }
    fwrite($fh, implode("\n", $out)."\n");
    fclose($fh);
    if (!@rename($lock, $file)) {
      @unlink($lock);
      throw new GitException('packed-refsを書けません');
    }
  }

  /** 空になった参照のディレクトリを消す（refs/heads等は残す） */
  private function pruneDirs(string $dir): void {
    $base = $this->repo->path.'/refs';
    while (strlen($dir) > strlen($base) && !in_array(basename($dir), ['heads', 'tags'], true) && dirname($dir) !== $base) {
      if (!@rmdir($dir)) break;
      $dir = dirname($dir);
    }
  }

  /** シンボリック参照を設定する（例：HEADをrefs/heads/mainに） */
  public function setSymbolic(string $name, string $target): void {
    if (!self::validName($name) || !self::validName($target)) throw new GitException("不正な参照の名前：{$target}");
    $this->repo->writeFile($this->repo->path.'/'.$name, "ref: {$target}\n");
  }
}