meta {
  name: Unlock Topic
  type: http
  seq: 4
}

delete {
  url: {{appview_url}}/api/mod/lock/123456
}

headers {
  Content-Type: application/json
}

body:json {
  {
    "reason": "Discussion can continue constructively"
  }
}

assert {
  res.status: eq 200
  res.body.success: eq true
  res.body.action: eq space.atbb.modAction.unlock
}

docs {
  Unlocks a previously locked topic (reversal moderation action).

  Requires authentication via session cookie and `space.atbb.permission.lockTopics` permission.

  Path parameters:
  - topicId: string (required) - Database ID of the topic post to unlock (in URL path)

  Body parameters:
  - reason: string (required) - Reason for unlocking (1-3000 characters, cannot be empty)

  Returns:
  {
    "success": true,
    "action": "space.atbb.modAction.unlock",
    "postId": "123456",
    "postUri": "at://user-did/space.atbb.post/rkey",
    "uri": "at://forum-did/space.atbb.modAction/rkey",
    "cid": "bafyrei...",
    "alreadyActive": false
  }

  If topic is already unlocked, returns 200 with `alreadyActive: true` (idempotent).

  Writes a modAction record to the Forum DID's PDS with:
  - action: "space.atbb.modAction.unlock"
  - subject: { post: { uri, cid } }
  - reason: provided reason
  - createdBy: moderator's DID

  Error codes:
  - 400: Invalid input (invalid topicId format, missing/empty reason, malformed JSON)
  - 401: Unauthorized (not authenticated)
  - 403: Forbidden (lacks lockTopics permission)
  - 404: Post not found
  - 500: ForumAgent not available (server configuration issue)
  - 503: ForumAgent not authenticated or unable to reach Forum PDS (retry later)

  Notes:
  - Unlock writes a distinct "unlock" action type (different from lock)
  - Read-path logic determines current lock state by checking most recent action chronologically
  - Additive reversal model: unlock writes new record, doesn't delete lock record
}