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UCLCSSA API v1 Specification

Introduction

This specification documents the UCLSSA API v1 for interoperability between clients and services. The specification builds atop of:

Relevant REST information may be found at Standards.REST.

This API specification is modeled after GitHub API v3.

Conventions Used in this Specification

The requirement level keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" used in this specification are intended to be interpreted according to RFC2119.

Relevant terminology from the HTTP/1.1 (RFC2616) standard is used where appropriate, such as header, body.

Current API Version

By default, all requests to https://api.uclcssa.cn SHALL dispatch to the v1 REST API. All requests SHOULD explicitly include the Accept HTTP header for stability against API changes.

Accept: application/vnd.uclcssa.v1+json

For more details, refer to Media Types.

Schema

All API communication MUST occur over HTTPS, at https://api.uclcssa.cn. The data interchange format used MUST be JSON.

For example, the response to a request to https://api.uclcssa.cn/users/testuser fetching headers should return

curl -i https://api.uclccsa.cn/users/testuser
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 13 Jun 2019 16:50:11 GMT
Content-Type: application/json; charset=utf-8
Content-Encoding: gzip
Content-Length: 5
Connection: keep-alive
Status: 200 OK
X-Media-Type: uclcssa.v1
X-Content-Type-Options: nosniff

Suitable HTTP headers SHOULD be used to convey additional information, such as authentication, caching, API versioning and access control. See HTTP Headers for more information.

Notes:

  • Date format SHOULD conform to HTTP-date in RFC7231
  • Content-Encoding SHOULD be specified to use gzip.
  • X-* headers are custom headers for additional metadata.
  • X-Media-Type: uclcssa.v1 specifies the API version as v1.
  • There are no rate limits yet - restricting traffic flow, e.g. for load-balancing is not yet considered in v1 API.
  • There are no caching support yet.
  • Content-Length specifies the size of the body in bytes, and MUST be included.

Blank fields MUST be included with value null instead of being omitted.

All timestamps MUST be returned in RFC3339 format.

Summary Representations

When requesting a list of certain resources, only their summary representations are returned for performance reasons.

For example, when trying to fetch a list of nearby restaurants, only the summary representations of the restaurants are returned.

Detailed Representations

When requesting an individual resource, such as a library, all of its attributes and detailed information are returned, depending on the requester's permissions.

Authentication

All authentication for restricting access to server resources MUST be handled via OAuth 2.0 mechanisms (hereafter abbreviated as OAuth2), standardized by RFC6749.

Tutorials for OAuth2 can be found at bubblecode.

The user SHOULD register with WeChat authentication. The user SHOULD be able to additionally bind their WeChat id to their UCL email address for personalized UCL API related capabilities, such as personal timetables.

Upon requesting any access-restricted resource, as such personal timetables, the client MUST send their OAuth2 token via the Authorization http header.

For example,

curl -H "Authorization: token {OAUTH-TOKEN}" https://api.uclcssa.cn

Failed Login Limit

Upon receiving invalid credentials, the server MUST return 401 Unauthorized status code to notify the client.

Upon 5 requests trying to authenticate via invalid credentials, the server MUST reject any authentication requests from the client for 10 minutes, beginning from the fifth failed attempt, with the status code 403 Forbidden.

Parameters

For GET requests, parameters SHOULD be passed as HTTP query string parameter, with the format https://api.uclcssa.cn/resource?{key1}={value1}&{key2}={value2}.

That is, query string parameters are suffixes to the URI of the resource, beginning with query operator ?, then followed by key-value pairs, with multiple pairs conjuncted with the & operator.

Additional data SHALL be sent as JSON body (i.e. Content).

Client Errors

If clients send requests with invalid JSON body, that is, if clients send:

  1. Invalid JSON: The server MUST return with 400 Bad Request response.
HTTP/1.1 400 Bad Request
Content-Length: 31

{"message":"Cannot parse JSON"}
  1. Incorrect JSON value types: The server MUST return with 400 Bad Request response.
HTTP/1.1 400 Bad Request
Content-Length: 40

{"message":"Incorrect JSON value types"}
  1. Invalid fields: The server MUST return with 422 Unprocessable Entity response.
HTTP/1.1 422 Unprocessable Entity
Content-Length: 149

{
  "message": "Validation Failed",
  "errors": [
    {
      "resource": "Library",
      "field": "title",
      "code": "missing-field"
    }
  ]
}

Each error object in errors SHOULD contain resource, field and code entries for diagnostics.

Possible validation error codes include:

Error Code Description
missing Resource does not exist.
missing-field Required field missing.
invalid Incorrect formatting.
duplicate Resource with identical value already exists.

Resources MAY also respond with custom error codes, which means they MUST then have a complementary message field for describing the problem.

For example,

HTTP/1.1 422 Unprocessable Entity
Content-Length: 191

{
  "message": "Validation Failed",
  "errors": [
    {
      "resource": "Library",
      "field": "title",
      "code": "custom",
      "message": "UCL API service unavailable"
    }
  ]
}

HTTP Redirects

Clients SHOULD assume that any requests to resources may cause a redirect response, which clients SHOULD follow.

Redirect responses MUST contain the Location header field which specifies the destination URI of the resource.

HTTP Status Code Description
301 Permanent redirection. Clients SHOULD migrate to new URI.
302, 307 Temporary redirection. Clients SHOULD use original URI.

HTTP Verbs

Suitable HTTP Verbs SHOULD be used to convey action semantics:

HTTP Verb Description
HEAD Get only header information.
GET Fetching resource.
POST Create resource.
PATCH Update resource.
PUT Replace resource.
DELETE Delete resource.

Pagination

Requests which return list containing multiple items SHOULD be paginated with 30 items be default. Clients SHOULD be able to specify custom pages via the ?page={PAGE_NUMBER} query parameter. Page numbers MUST begin at 1. Clients SHOULD be able to specify items per page via ?per_page={NUM_ITEMS}.

For feed pagination, the client SHOULD be responsible for storing the latest post id. The server SHOULD allow the client to access posts by offset, e.g.

/posts?offset={OFFSET_AMOUNT}&per_page={NUM_ITEMS}

User Agent

Clients MUST supply a valid User-Agent header in their requests.

For the WeChat app, the User-Agent should take the form

User-Agent: UCLCSSA-WeChat-App ("{PLATFORM}"; rv:"{VERSION}")

Where {PLATFORM} is the native platform information, e.g. iOS or Andriod, and {VERSION} is the client version.

For example, for UCLCSSA WeChat App on iOS with version 1.0.0-rc1, its User-Agent should be

User-Agent: UCLCSSA-WeChat-App ("ios"; rv:"1.0.0-rc1")

This allows for diagnostics and user-agent monitoring.