openapi: 3.0.3

info:
  title: "Distributed Arcade"
  version: 0.3.0
  description: |-
    A super-fast high score gatherer using Rust and Redis.
    
    It allows the creation of _boards_, [sorted sets](https://redis.io/docs/data-types/sorted-sets/) that can be used to track the scores of players in videogames.
    
    It is written to be extremely fast and scalable: it should be able to receive bursts of many requests.
    
    Errors can be distinguished from successful requests via HTTP status codes >=400.
  contact:
    name: "Stefano Pigozzi"
    url: "https://www.steffo.eu"
    email: "me@steffo.eu"
  license:
    name: "GNU Affero General Public License v3.0 or later"
    url: https://github.com/Steffo99/distributed-arcade/blob/main/LICENSE.txt"

servers:
  - url: "https://arcade.steffo.eu"
    description: "Experimental production server"
  - url: "http://127.0.0.1:30000"
    description: "Local development server"

tags:
  - name: "Home"
    description: "Launch checklist"
  - name: "Board"
    description: "About boards"
  - name: "Score"
    description: "Submit scores"

paths:
  /:
    get:
      operationId: "getHome"
      summary: "Verify that the web server is working as expected"
      description: |-
        This method simply echoes back a response, and can be used to verify that the API web server is working.
      tags: ["Home"]
      responses:
        204:
          description: "Working as expected"
    post:
      operationId: "postHome"
      summary: "Verify that everything is working as expected"
      description: |-
        This method is like `GET /`, but it also `PING`s the Redis server to ensure it is working and configured properly.
      tags: ["Home"]
      responses:
        204:
          description: "Working as expected"
        500:
          description: "Did not receive `PONG` from redis"
          content:
            application/json:
              schema:
                type: string
                example: "Redis gave an unexpected response"
        502:
          $ref: "#/components/responses/RedisCmdFailed"
        504:
          $ref: "#/components/responses/RedisConnFailed"

  /board/:
    get:
      operationId: "getBoard"
      summary: "Get the scores of a board"
      description: |-
        This method requests a page of scores from a board using the [`ZSCAN`](https://redis.io/commands/zscan/) Redis command.
        
        An offset must be specified to start returning scores from a certain index.        
        The number of responses to return must be specified as well.
      tags: ["Board"]
      parameters:
        - $ref: "#/components/parameters/board"
        - $ref: "#/components/parameters/offset"
        - $ref: "#/components/parameters/size"
      responses:
        200:
          description: "Scores retrieved successfully"
          content:
            application/json:
              schema:
                type: array
                items:
                  type: object
                  description: "A score submitted by an user."
                  properties:
                    name:
                      type: string
                      description: "The name of the user who submitted the score."
                      example: "Steffo"
                    score:
                      type: number
                      description: "The submitted score."
                      example: 1234.56
        502:
          $ref: "#/components/responses/RedisCmdFailed"
        504:
          $ref: "#/components/responses/RedisConnFailed"
    post:
      operationId: "postBoard"
      summary: "Create a new board"
      description: |-
        This method creates a new board.
        
        It returns its _score submission token_ (`XBoardToken` in this spec), which is required to submit new scores to the board.
        
        Boards can use two different orders:
        
        - using the `Ascending` order, lower scores are better ranked than higher scores, like in racing games or golf;
        - using the `Descending` order, higher scores are better ranked than lower scores, like in arcade games or athletics.
        
        **WARNING: Once created, a board cannot be edited or deleted, and its token will not be accessible any longer!**
        
        Requires an authorization key, set as the `CREATE_TOKEN` environment variable of the server.
      tags: ["Board"]
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                name:
                  type: string
                  description: "The name of the board to create. It will be converted to kebab-case."
                  example: "gravityfusion"
                order:
                  type: string
                  example: "Descending"
                  description: "The ordering of the board, either ascending or descending."
                  enum:
                    - "Ascending"
                    - "Descending"
      security:
        - XCreateToken: []
      responses:
        201:
          description: "Board created successfully"
          content:
            application/json:
              schema:
                type: string
                example: "W4SbhbJ3tnGaIM1S"
          links:
            getScore:
              operationId: "getScore"
              parameters:
                board: "$response.body/name"
            putScore:
              operationId: "putScore"
              parameters:
                board: "$response.body/name"
        401:
          description: "Missing, invalid or malformed Authorization header"
          content:
            application/json:
              schema:
                type: string
                example: "Missing Authorization header"
        403:
          description: "Invalid create token"
          content:
            application/json:
              schema:
                type: string
                example: "Invalid create token"
        409:
          description: "Board already exists"
          content:
            application/json:
              schema:
                type: string
                example: "Board already exists"
        500:
          description: "Could not generate secure board token"
          content:
            application/json:
              schema:
                type: string
                example: "Could not generate secure board token"
        502:
          $ref: "#/components/responses/RedisCmdFailed"
        504:
          $ref: "#/components/responses/RedisConnFailed"

  /score/:
    get:
      operationId: "getScore"
      summary: "Get a score from a board"
      description: |-
        Retrieve the score and the position that the given user has on the leaderboard.
      tags: ["Score"]
      parameters:
        - $ref: "#/components/parameters/board"
        - $ref: "#/components/parameters/player"
      responses:
        200:
          description: "Score retrieved successfully"
          content:
            application/json:
              schema:
                type: object
                properties:
                  score:
                    type: number
                    description: "The score of the specified player."
                    example: 1234.56
                  rank:
                    type: integer
                    description: "The zero-indexed rank of the specified player. (You may probably want to add `1` before displaying it to an user.)"
                    example: 0
        502:
          $ref: "#/components/responses/RedisCmdFailed"
        504:
          $ref: "#/components/responses/RedisConnFailed"

    put:
      operationId: "putScore"
      summary: "Submit a score to a board"
      tags: ["Score"]
      parameters:
        - $ref: "#/components/parameters/board"
        - $ref: "#/components/parameters/player"
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: number
              description: "The score to submit to the board."
              example: 1234.56
      security:
        - XBoardToken: []
      responses:
        200:
          description: "Score discarded as it was worse than the previous one"
          content:
            application/json:
              schema:
                type: object
                properties:
                  score:
                    type: number
                    description: "The score of the specified player."
                    example: 1234.56
                  rank:
                    type: integer
                    description: "The zero-indexed rank of the specified player. (You may probably want to add `1` before displaying it to an user.)"
                    example: 0
        201:
          description: "Score submitted and updated"
          content:
            application/json:
              schema:
                type: object
                properties:
                  score:
                    type: number
                    description: "The score of the specified player."
                    example: 2468.13
                  rank:
                    type: integer
                    description: "The zero-indexed rank of the specified player. (You may probably want to add `1` before displaying it to an user.)"
                    example: 0
        401:
          description: "Missing, invalid or malformed Authorization header"
          content:
            application/json:
              schema:
                type: string
                example: "Missing Authorization header"
        403:
          description: "Invalid board token"
          content:
            application/json:
              schema:
                type: string
                example: "Invalid board token"
        502:
          $ref: "#/components/responses/RedisCmdFailed"
        504:
          $ref: "#/components/responses/RedisConnFailed"


components:
  securitySchemes:
    XCreateToken:
      type: http
      scheme: "bearer"
      bearerFormat: "setInEnvVars"
    XBoardToken:
      type: http
      scheme: "bearer"
      bearerFormat: "gVsuzIxgVfRx4RNl"

  parameters:
    board:
      name: "board"
      description: "The name of the board to operate on."
      in: query
      schema:
        type: string
    player:
      name: "player"
      description: "The name of the player to operate on."
      in: query
      schema:
        type: string
    offset:
      name: "offset"
      description: "The offset to start returning results from."
      in: query
      schema:
        type: integer
    size:
      name: "size"
      description: "How many results to return."
      in: query
      schema:
        type: integer
        minimum: 0
        maximum: 500

  responses:
    RedisCmdFailed:
      description: "Could not execute Redis command"
      content:
        application/json:
          schema:
            type: string
            example: "Could not execute Redis command"
    RedisConnFailed:
      description: "Could not connect to Redis"
      content:
        application/json:
          schema:
            type: string
            example: "Could not connect to Redis"