psc.rb

psc.rb is a ruby client for Patient Study Calendar's RESTful HTTP API. It provides assistance with authentication to PSC's API and with executing common tasks. It also provides a lower-level interface (Psc::Connection) to allow for making HTTP requests against the configured PSC's API directly.

By design, the client provides a very thin abstraction over the API itself. Please be familiar with the API (whose documentation is available in your PSC instance at api/v1/docs or on the demo site) before using this library.

require 'psc'
require 'pp'

psc = Psc::Client.new(
  'https://demos.nubic.northwestern.edu/psc',
  :authenticator => { :basic => ['superuser', 'superuser'] }
)

pp psc.studies

(This code will run if you have the psc gem installed, so long as your ruby's openssl has a reasonable set of commercial CAs configured; try it and see. If you get a certificate validation error, check out {file:README-ssl.md} for some tips.)

Note that this overview uses the high-level Psc::Client interface. It does not provide a complete interface to PSC; for most of PSC's API, you'll need to use the lower-level Psc::Connection interface; see below.

psc.rb is available as a rubygem:

$ gem install psc

PSC supports two forms of authentication for API calls: HTTP Basic (i.e., username & password) and psc_token. (Which forms are supported in your PSC instance will depend on its authentication system configuration.)

A particular client instance will only use one authentication mechanism. There are three options.

PSC Client allows you to specify a username and password to use for all requests. Include the :authenticator key like so:

:authenticator => { :basic => %w(alice password) }

=> Authorization: Basic YWxpY2U6cGFzc3dvcmQ=

Alternatively, you can provide a token to use in all requests:

:authenticator => { :token => 'The raven flies at midnight' }

=> Authorization: psc_token The raven flies at midnight

Finally, you can provide a callable object which will be invoked for each request and whose return value will be used for the PSC token:

:authenticator => { :token => lambda { cas_client.get_proxy_ticket } }

=> Authorization: psc_token PT-133-236H522

The callable will be called with no arguments.

{Psc::Client} provides a high-level interface to some of PSC's API capabilities.

psc.rb is based on Faraday, a modular ruby HTTP client. {Psc::Connection} is a Faraday connection configured for access to a particular PSC instance. You can create a Psc::Connection directly:

conn = Psc::Connection.new(
  'https://demos.nubic.northwestern.edu/psc',
  :authenticator => { :basic => %w(superuser superuser) })

Or you can get an instance from the {Psc::Client} high-level interface:

client = Psc::Client.new(
  'https://demos.nubic.northwestern.edu/psc',
  :authenticator => { :basic => %w(superuser superuser) })
conn = client.connection

The connection is set up to automatically parse JSON reponses into appropriate ruby primitives and XML responses into Nokogiri documents.

studies_json = conn.get('studies.json')
first_study_name =
  studies_json.body['studies'].first['assigned_identifier']

sites_xml = conn.get('sites.xml')
first_site_name =
  sites_xml.body.xpath('//psc:site', Psc.xml_namespace).first.attr('site-name')

Similarly, for PUT and POST it will encode a Hash or Array entity as JSON and will assume that a String entity is XML.

PSC's API resources all start with api/v1. To help you DRY things up, PSC::Connection automatically adds this to the base URL on construction. You don't need to include it when constructing relative URLs.

Faraday connections are built up from middleware. Psc::Connection uses a combination of off-the-shelf and custom middleware classes. The custom classes are in the {Psc::Faraday} module.

• Source code
• API documentation
• Bug reports and feature requests
• Continuous integration
• Version policy: semantic versioning

psc.rb has an rspec suite for unit tests and a set of cucumber features for integration tests. Before you can run the cucumber features you will need to either

• Execute rake int-psc:war to download a copy of PSC to use
• Copy a PSC war into int-psc/bin

Patches with tests are happily considered. Please use a pull request.