# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
openapi: 3.1.0
info:
  title: Matrix Client-Server Room Knocking API
  version: 1.0.0
paths:
  "/knock/{roomIdOrAlias}":
    post:
      x-addedInMatrixVersion: "1.1"
      summary: Knock on a room, requesting permission to join.
      description: |-
        *Note that this API takes either a room ID or alias, unlike other membership APIs.*

        This API "knocks" on the room to ask for permission to join, if the user
        is allowed to knock on the room. Acceptance of the knock happens out of
        band from this API, meaning that the client will have to watch for updates
        regarding the acceptance/rejection of the knock.

        If the room history settings allow, the user will still be able to see
        history of the room while being in the "knock" state. The user will have
        to accept the invitation to join the room (acceptance of knock) to see
        messages reliably. See the `/join` endpoints for more information about
        history visibility to the user.

        The knock will appear as an entry in the response of the
        [`/sync`](/client-server-api/#get_matrixclientv3sync) API.
      operationId: knockRoom
      security:
        - accessToken: []
      parameters:
        - in: path
          name: roomIdOrAlias
          description: The room identifier or alias to knock upon.
          required: true
          example: "#monkeys:matrix.org"
          schema:
            type: string
        - in: query
          name: server_name
          description: |-
            The servers to attempt to knock on the room through. One of the servers
            must be participating in the room.
          example:
            - matrix.org
            - elsewhere.ca
          schema:
            type: array
            items:
              type: string
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                reason:
                  type: string
                  description: |-
                    Optional reason to be included as the `reason` on the subsequent
                    membership event.
                  example: Looking for support
        required: true
      responses:
        "200":
          description: |-
            The room has been knocked upon.

            The knocked room ID must be returned in the `room_id` field.
          content:
            application/json:
              schema:
                type: object
                properties:
                  room_id:
                    type: string
                    description: The knocked room ID.
                required:
                  - room_id
              examples:
                response:
                  value: {
                    "room_id": "!d41d8cd:matrix.org"
                  }
        "403":
          description: |-
            You do not have permission to knock on the room. A meaningful `errcode`
            and description error text will be returned. Example reasons for rejection are:

            - The room is not set up for knocking.
            - The user has been banned from the room.
          content:
            application/json:
              schema:
                $ref: definitions/errors/error.yaml
              examples:
                response:
                  value: {
                    "errcode": "M_FORBIDDEN",
                    "error": "You are not allowed to knock on this room."
                  }
        "404":
          description: The room could not be found or resolved to a room ID.
          content:
            application/json:
              schema:
                $ref: definitions/errors/error.yaml
              examples:
                response:
                  value: {
                    "errcode": "M_NOT_FOUND",
                    "error": "That room does not appear to exist."
                  }
        "429":
          description: This request was rate-limited.
          content:
            application/json:
              schema:
                $ref: definitions/errors/rate_limited.yaml
      tags:
        - Room membership
servers:
  - url: "{protocol}://{hostname}{basePath}"
    variables:
      protocol:
        enum:
          - http
          - https
        default: https
      hostname:
        default: localhost:8008
      basePath:
        default: /_matrix/client/v3
components:
  securitySchemes:
    $ref: definitions/security.yaml