<?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\Fedi;

use Std\Lib\Activitypub;

/**
 * 受付ボックス（共有の/ap/inboxとユーザー毎の/ap/users/{名前}/inbox）に届いたアクティビティの処理
 *
 * 署名の検証は呼ぶ側（Fediverseコントローラー）で行う。
 * ローカルのユーザーからのアクティビティ（Delivery::enqueue）も、HTTPを使わずにここで処理する。
 */
final class Inbox {
  /**
   * アクティビティを処理する
   *
   * @param array $activity  アクティビティ（署名検証済み）
   * @param bool $local  このサイトのユーザーからか
   * @return array  [HTTPステータス, レスポンスの本文]
   */
  public static function handle(array $activity, bool $local = false): array {
    $actor = Fedi::id($activity['actor'] ?? null);
    $type = (string)($activity['type'] ?? '');
    if ($actor === null) return [400, ['error' => 'actorがありません']];
    // ローカルのアクターを名乗るリモートのアクティビティは受け付けない
    if (!$local && Fedi::isLocal($actor)) return [403, ['error' => '不正なactor']];
    if (Actor::isDomainBlocked($actor)) return [403, ['error' => 'ブロックされています']];

    try {
      return match ($type) {
        'Follow' => self::follow($activity, $actor),
        'Accept' => self::accept($activity, $actor, true),
        'Reject' => self::accept($activity, $actor, false),
        'Undo' => self::undo($activity, $actor),
        'Create' => self::create($activity, $actor, $local),
        'Update' => self::update($activity, $actor),
        'Delete' => self::delete($activity, $actor),
        'Like' => self::like($activity, $actor),
        'Announce' => self::announce($activity, $actor, $local),
        'Block' => self::block($activity, $actor),
        'Flag' => self::flag($activity, $actor),
        default => [202, ['status' => '未対応なアクティビティタイプ: '.$type]],
      };
    } catch (\Throwable $e) {
      logger(\LogType::ActivityPub, "受付ボックスの処理に失敗（{$type}）：".$e->getMessage());
      return [500, ['error' => '処理に失敗']];
    }
  }

  //////

  private static function follow(array $a, string $actor): array {
    $target = Fedi::id($a['object'] ?? null);
    if ($target === Fedi::blogActorUrl()) return (new Activitypub())->handleInbox($a);
    $username = $target ? Fedi::localUsername($target) : null;
    if ($username === null || Fedi::localActor($username) === null) return [404, ['error' => 'アカウントが見つかりません']];

    if (Actor::isBlocked($username, $actor)) {
      Social::rejectFollow($username, $a);
      return [202, ['status' => '拒否しました']];
    }
    if (Actor::isFollowedBy($username, $actor)) {
      // 既にフォロワー：もう一度Acceptを返す（相手が状態を失った場合）
      Social::acceptFollow($username, $a);
      return [202, ['status' => 'OK']];
    }
    if (Actor::settings($username)['locked']) {
      Fedi::update(Fedi::userPath($username, 'requests.json'), fn($l) => [$actor => ['activity' => $a, 'at' => time()]] + $l);
      Actor::notify($username, 'follow_request', $actor);
      return [202, ['status' => '承認待ち']];
    }
    Social::acceptFollow($username, $a);
    return [202, ['status' => 'OK']];
  }

  /**
   * 自分が送ったFollowへのAccept・Reject
   * Rejectはフォロワーを外された場合（Followが自分の場合）もある
   */
  private static function accept(array $a, string $actor, bool $accepted): array {
    $obj = $a['object'] ?? null;
    $followId = Fedi::id($obj);
    $follower = is_array($obj) ? Fedi::id($obj['actor'] ?? null) : null;

    foreach (Social::localUsernames() as $u) {
      $me = Fedi::actorUrl($u);
      $f = Actor::following($u)[$actor] ?? null;
      if ($f === null) continue;
      if ($follower !== null && $follower !== $me) continue;
      if ($follower === null && $followId !== $f['id']) continue;
      Fedi::update(Fedi::userPath($u, 'following.json'), function($l) use ($actor, $accepted) {
        if ($accepted) $l[$actor]['state'] = 'accepted';
        else unset($l[$actor]);
        return $l;
      });
      // 相手の最近の投稿をホームに入れる（取得はcronで。ここで待たせると相手のサーバーが再送する）
      if ($accepted) Delivery::queueBackfill($actor);
    }
    return [202, ['status' => 'OK']];
  }

  private static function undo(array $a, string $actor): array {
    $inner = $a['object'] ?? null;
    if (is_string($inner)) $inner = self::findOwnActivity($inner, $actor);
    if (!is_array($inner)) return [202, ['status' => '無視しました']];
    // 他人のアクティビティは取り消せない
    if (Fedi::id($inner['actor'] ?? null) !== $actor) return [202, ['status' => '無視しました']];

    switch ($inner['type'] ?? '') {
      case 'Follow':
        $target = Fedi::id($inner['object'] ?? null);
        if ($target === Fedi::blogActorUrl()) return (new Activitypub())->handleInbox($a);
        $username = $target ? Fedi::localUsername($target) : null;
        if ($username !== null) {
          Fedi::update(Fedi::userPath($username, 'followers.json'), function($l) use ($actor) { unset($l[$actor]); return $l; });
          Fedi::update(Fedi::userPath($username, 'requests.json'), function($l) use ($actor) { unset($l[$actor]); return $l; });
        }
        break;
      case 'Like':
        self::modifyLocalNote(Fedi::id($inner['object'] ?? null), function($n) use ($actor) { unset($n['likes'][$actor]); return $n; });
        break;
      case 'Announce':
        $obj = Fedi::id($inner['object'] ?? null);
        self::modifyLocalNote($obj, function($n) use ($actor) { unset($n['boosts'][$actor]); return $n; });
        if ($obj) Timeline::remove($obj, $actor);
        break;
    }
    return [202, ['status' => 'OK']];
  }

  private static function create(array $a, string $actor, bool $local): array {
    $obj = $a['object'] ?? null;
    if (is_string($obj)) $obj = Remote::object($obj);
    if (!is_array($obj) || !in_array($obj['type'] ?? '', ['Note', 'Article', 'Question', 'Page'], true)) return [202, ['status' => '無視しました']];
    if (Fedi::id($obj['attributedTo'] ?? null) !== $actor) return [403, ['error' => '作者が違います']];
    $id = Fedi::id($obj['id'] ?? null);
    if ($id === null || Fedi::domainOf($id) !== Fedi::domainOf($actor)) return [403, ['error' => '不正なID']];

    $addressed = self::addressedLocalUsers($obj);
    $parent = Fedi::id($obj['inReplyTo'] ?? null);
    $parentIds = $parent ? Fedi::localNoteId($parent) : null;

    if (!$local) {
      // 誰にも関係の無い投稿は保存しない（スパム対策）
      $followers = self::localFollowersOf($actor);
      if (empty($addressed) && empty($followers) && $parentIds === null) return [202, ['status' => '無視しました']];
      $obj['_receivedAt'] = time();
      Remote::store($obj);
      Timeline::add($obj);
      // 表示用にアクターをキャッシュする（1日1回まで取得）
      Remote::actor($actor);
    }

    // 返信と通知
    if ($parentIds !== null) {
      Notes::modify($parentIds[1], function($n) use ($id) {
        if (!in_array($id, $n['replies'] ?? [], true)) $n['replies'][] = $id;
        return $n;
      });
      if ($parentIds[0] !== Fedi::localUsername($actor)) Actor::notify($parentIds[0], 'reply', $actor, $id);
    }
    foreach ($addressed as $u) {
      if ($parentIds !== null && $u === $parentIds[0]) continue;
      if (Fedi::localUsername($actor) === $u || Actor::isBlocked($u, $actor)) continue;
      Actor::notify($u, 'mention', $actor, $id);
    }
    return [202, ['status' => 'OK']];
  }

  private static function update(array $a, string $actor): array {
    $obj = $a['object'] ?? null;
    if (!is_array($obj)) return [202, ['status' => '無視しました']];
    if (Remote::isActor($obj)) {
      if (($obj['id'] ?? null) === $actor) Remote::cacheActor($obj);
      return [202, ['status' => 'OK']];
    }
    $id = Fedi::id($obj['id'] ?? null);
    if ($id === null || Fedi::isLocal($id)) return [202, ['status' => 'OK']];
    $old = Remote::stored($id);
    if (!$old || Fedi::id($old['attributedTo'] ?? null) !== $actor || Fedi::id($obj['attributedTo'] ?? null) !== $actor) {
      return [202, ['status' => '無視しました']];
    }
    $obj['_receivedAt'] = $old['_receivedAt'] ?? time();
    Remote::store($obj);
    Timeline::refresh($obj);
    return [202, ['status' => 'OK']];
  }

  private static function delete(array $a, string $actor): array {
    $id = Fedi::id($a['object'] ?? null);
    if ($id === null) return [202, ['status' => '無視しました']];

    if ($id === $actor) {
      // アカウントの削除：全部から消す
      $blog = (new Activitypub())->handleInbox($a);
      foreach (Social::localUsernames() as $u) {
        foreach (['followers.json', 'following.json', 'requests.json'] as $f) {
          Fedi::update(Fedi::userPath($u, $f), function($l) use ($actor) { unset($l[$actor]); return $l; });
        }
      }
      foreach (Timeline::entries() as $e) {
        if ($e['author'] === $actor && !$e['local']) Remote::forget($e['object']);
      }
      Timeline::removeActor($actor);
      Remote::forgetActor($actor);
      return [202, ['status' => 'OK']];
    }

    $stored = Remote::stored($id);
    if ($stored && Fedi::id($stored['attributedTo'] ?? null) === $actor) {
      Remote::forget($id);
      Timeline::remove($id);
      $parent = Fedi::id($stored['inReplyTo'] ?? null);
      self::modifyLocalNote($parent, function($n) use ($id) {
        $n['replies'] = array_values(array_diff($n['replies'] ?? [], [$id]));
        return $n;
      });
    }
    return [202, ['status' => 'OK']];
  }

  private static function like(array $a, string $actor): array {
    $obj = Fedi::id($a['object'] ?? null);
    $ids = $obj ? Fedi::localNoteId($obj) : null;
    if ($ids === null) return [202, ['status' => '無視しました']];
    if (Actor::isBlocked($ids[0], $actor)) return [202, ['status' => '無視しました']];
    $id = Fedi::id($a['id'] ?? null) ?? '';
    self::modifyLocalNote($obj, function($n) use ($actor, $id) { $n['likes'][$actor] = $id; return $n; });
    if (Fedi::localUsername($actor) !== $ids[0]) Actor::notify($ids[0], 'like', $actor, $obj);
    return [202, ['status' => 'OK']];
  }

  private static function announce(array $a, string $actor, bool $local): array {
    $objId = Fedi::id($a['object'] ?? null);
    if ($objId === null) return [202, ['status' => '無視しました']];
    $ids = Fedi::localNoteId($objId);
    $id = Fedi::id($a['id'] ?? null) ?? '';

    if ($ids !== null && !Actor::isBlocked($ids[0], $actor)) {
      self::modifyLocalNote($objId, function($n) use ($actor, $id) { $n['boosts'][$actor] = $id; return $n; });
      if (Fedi::localUsername($actor) !== $ids[0]) Actor::notify($ids[0], 'boost', $actor, $objId);
    }
    // フォローしている人のブーストはタイムラインに載せる
    if (!$local && !empty(self::localFollowersOf($actor))) {
      // 埋め込まれたオブジェクトは偽装出来るので、IDから取得する
      $obj = Remote::object($objId);
      if ($obj && in_array(Fedi::visibility(Fedi::ids($obj['to'] ?? []), Fedi::ids($obj['cc'] ?? [])), ['public', 'unlisted'], true)) {
        if (!Fedi::isLocal($objId)) Remote::store($obj);
        Timeline::add($obj, $actor, strtotime((string)($a['published'] ?? '')) ?: time());
      }
    }
    return [202, ['status' => 'OK']];
  }

  private static function block(array $a, string $actor): array {
    $target = Fedi::id($a['object'] ?? null);
    $username = $target ? Fedi::localUsername($target) : null;
    if ($username === null) return [202, ['status' => '無視しました']];
    foreach (['followers.json', 'following.json', 'requests.json'] as $f) {
      Fedi::update(Fedi::userPath($username, $f), function($l) use ($actor) { unset($l[$actor]); return $l; });
    }
    return [202, ['status' => 'OK']];
  }

  private static function flag(array $a, string $actor): array {
    $objects = Fedi::ids($a['object'] ?? []);
    if (empty($objects)) return [202, ['status' => '無視しました']];
    Fedi::update(Fedi::path('reports.json'), function($l) use ($a, $actor, $objects) {
      array_unshift($l, ['id' => Fedi::newId(), 'from' => $actor, 'actor' => $objects[0], 'objects' => array_slice($objects, 1),
                         'content' => mb_substr(Html::text((string)($a['content'] ?? '')), 0, 1000), 'at' => time(),
                         'remote' => true, 'resolved' => false]);
      return array_slice($l, 0, 500);
    });
    return [202, ['status' => 'OK']];
  }

  //////

  /**
   * このアクターをフォローしているローカルのユーザー
   */
  public static function localFollowersOf(string $actor): array {
    $out = [];
    foreach (Social::localUsernames() as $u) {
      if (Actor::isFollowing($u, $actor)) $out[] = $u;
    }
    return $out;
  }

  /**
   * 投稿の宛先（to・cc・メンション）に含まれるローカルのユーザー
   */
  private static function addressedLocalUsers(array $obj): array {
    $targets = array_merge(Fedi::ids($obj['to'] ?? []), Fedi::ids($obj['cc'] ?? []));
    foreach ($obj['tag'] ?? [] as $t) {
      if (is_array($t) && ($t['type'] ?? '') === 'Mention' && is_string($t['href'] ?? null)) $targets[] = $t['href'];
    }
    $out = [];
    foreach (array_unique($targets) as $t) {
      $u = Fedi::localUsername($t);
      if ($u !== null && Fedi::localActor($u) !== null) $out[] = $u;
    }
    return array_values(array_unique($out));
  }

  private static function modifyLocalNote(?string $objectId, callable $fn): void {
    $ids = $objectId ? Fedi::localNoteId($objectId) : null;
    if ($ids) Notes::modify($ids[1], $fn);
  }

  /**
   * UndoのobjectがIDだけの場合：このアクターの以前のアクティビティを探す（いいね・ブースト・フォロー）
   */
  private static function findOwnActivity(string $id, string $actor): ?array {
    foreach (Timeline::entries() as $e) {
      if (!$e['local'] || $e['type'] !== 'note') continue;
      $ids = Fedi::localNoteId($e['object']);
      $n = $ids ? Notes::get($ids[1]) : null;
      if (!$n) continue;
      if (($n['likes'][$actor] ?? null) === $id) return ['type' => 'Like', 'actor' => $actor, 'object' => $e['object']];
      if (($n['boosts'][$actor] ?? null) === $id) return ['type' => 'Announce', 'actor' => $actor, 'object' => $e['object']];
    }
    return null;
  }
}