GOV.UK Tariff API Documentation

This is a microsite for providing documentation for the GOV.UK Tariff API.

This documentation is built from source files in this repository and an OpenAPI specification file for the Tariff API.

The framework for this documentation is provided by the GOV.UK Tech Docs Template and through the use of a fork of widdershins to convert the openapi.yaml to Markdown.

These docs are deployed to the following URLs:

• Development - https://api.dev.trade-tariff.service.gov.uk
• Staging - https://api.staging.trade-tariff.service.gov.uk
• Production - https://api.trade-tariff.service.gov.uk

Updating content

To update content of this site, modify the files under source directory, i.e., source/v2/openapi.yaml.

HTML pages are in the /source of this repository and are authored using Markdown. You can make edits to these pages by making changes in a branch and then opening a pull request.

The /reference.html page is built using the source/v2/openapi.yaml file, which is an OAS 3.0 document that describes the Trade Tariff API and is used to build the HTML documentation website.

The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly defined, a consumer can understand and interact with the remote service with a minimal amount of implementation logic.

Updating the API Documentation

To update the Trade Tariff API documentation, you may follow this general workflow:

• If the changes involve the content of the HTML pages ( /index and /getting_started), edit the corresponding .md or .md.erb template under source/*.

  • edit source/index.html.md.erb or source/getting-started.html.md
  • open or view http://localhost:4567 in a browser, the browser should automatically reload the page after changes are saved

• If the changes involve the API specification itself, edit the source/v2/openapi.yaml file. This file is used to build the HTML file build/reference.html.

  • edit source/v2/openapi.yaml

  • make serve

  • manually (re)load http://localhost:4567 in a browser when the Middleman server (re)starts

• It is also useful to add an entry in the NEWS.yml file, this information will be published on the Latest News page for users viewing these docs. It will also be added to the /feed.xml atom feed for anyone subscribing for updates.

Support for multiple API versions

As we release new versions of the API, we will continue to support older versions (until they're deprecated). Therefore, we should continue to publish that version's API reference and the corresponding openapi.yaml file.

In order to do this, some modifications to the default Middleman templates and options are required:

1. create a new openapi.yaml file for the new API version and a directory in which to store it

mkdir v2
touch v2/openapi.yaml

2. edit config/tech-docs.yml - add new link in the header for old reference file, i.e.;

 Reference: /reference.html

3. edit Makefile

• add new task to generate old reference file

• rename previous reference file, add "-v1" (or whatever the old version number is) to the output filename

  ./generate.js source/v1/openapi.yaml source/reference-v1.html.md.erb
  

Editing the openapi.yaml file

An OpenAPI document that conforms to the OpenAPI Specification is itself a JSON object, which may be represented either in JSON or YAML format. For this project, we are using the YAML format.

Example from openapi.yaml

paths:
  /api/v2/sections:
    get:
      summary: Retrieves all sections
      description: |
        This resource represents _all sections_ in the Tariff.

        Each section has a `position`, which is its numerical order within the Tariff, and a `section_id`, which is a unique record identifier.

      tags:
        - Sections
      produces:
        - application/json
      responses:
        200:
          description: Sections were found
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Sections"
              example:
                $ref: "#/components/schemas/Sections/example"
        5XX:
          description: Unexpected error.
      x-code-samples:
        /api/api/v2/sections:
          lang: shell
          source: |-
            curl -X GET https://www.trade-tariff.service.gov.uk/api/v2/sections

The example above is rendered into HTML:

Use of $ref

The openapi.yaml file makes use of $ref to refer to connected parts of the specification. In the example above, $ref is used to refer to the schema and example response in another part of the document.

Information on $ref: https://swagger.io/specification/#documentStructure

Links

• OAS 3.0 Specification (https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#oasDocument)
• Swagger, upon which OAS is based (https://swagger.io/specification/)

Running documentation locally

Pre Requisite

Graphviz installed in your local environment

Manual Build and Deploy

Manual build and deploy is not necessary if automated deploy is used.

1. Build the documentation

bundle exec middleman build --clean

2. Push to prod

cf push tariff-api-production

Installing dependencies

Setting up the documentation requires Ruby and Node. Run the following to install the necessary dependencies:

make requirements

Note: You will also need to manually install Graphviz via your package manager

Preview changes

Whilst writing documentation we can run a middleman server to preview how the published version will look in the browser. After saving a change the preview in the browser will automatically refresh on HTML pages. However for changes to openapi.yaml you will need to restart the preview.

Type the following to start the server:

make serve

You should now be able to view a live preview at http://localhost:4567.

Publishing documentation

Development

Any changes pushed to GitHub on a branch (eg, a Pull Request) will be deployed automatically to the Development URL

Production

Any changes to main on GitHub will be deployed automatically to our published docs at api.trade-tariff.service.gov.uk

License

MIT License