EPICFHIR Library

The EPICFHIR Library is an importable library containing functions to connect, authenticate, and interact with the Epic FHIR API. This library is used in the Epic FHIR Adapter.

When imported into projects, typically only the EPICFHIRclient module needs to be required in order to create the client and access the API methods.

require "EPICFHIR.EPICFHIRclient"

How it works:

Use the Translator’s built in help to review how to use each function:

Sets up the EPIC FHIR adapter framework, adding the various method modules to a metatable and storing the configurations added to the custom fields.

EPICcustom takes in any API requests and parameters to make the API call and return the response.

First, the function checks if the token key exists or is still valid (based on the key_expiry). If not, it calls EPICFHIRauth to perform the OAuth2.0 authentication workflow to obtain the token to be used in subsequent requests.
Uses the passed configurations API request parameters - the method (ex. post), API (ex. Patient) and parameters for the call (ex. the patient resource to be created) - to build and carry out the appropriate HTTP request.

The EPICFHIRauth function builds and makes the HTTP POST token request to obtain the access token required for any resource requests against the FHIR Server.

A separate EPICFHIRcreateJWT function creates the JSON Header and Payload components of the JWT and calls EPICFHIRjwt to sign and return the JWT required for the token request.

If the token requests is successful (HTTP 200 response), the token and token expiry returned are stored in the adapter object (key and key_expiry) and saved in an encrypted file via EPICFHIRencrypt.

EPICFHIRencrypt provides localized https://interfaceware.atlassian.net/wiki/x/EQCeqg functionality via save and load functions that encrypt and decrypt the provided API token and expiry time in an external file. This allows the token to be reused for subsequent API calls.

EPICFHIRjwt provides localized OAUTH Library functionality. It takes the provided JWT header, JWT payload, signing algorithm, and private key to generate and sign the JWT token.

EPICFHIRcreate prepares the arguments and calls EPICFHIRcustom for an FHIR Resource Create HTTP POST request.

EPICFHIRsearch prepares the arguments and calls EPICFHIRcustom for an FHIR Resource Search HTTP GET request.

EPICFHIRreadResource prepares the API endpoint and arguments to call EPICFHIRcustom for an FHIR Resource Read HTTP GET request.

EPICFHIRoperation prepares the arguments and calls EPICFHIRcustom for an FHIR Resource Create HTTP GET or POST request.

A FHIR operation is extended functionality unique across FHIR Servers. Extended operations on a resource use a $ in front of the operation. For example, when calling EPICFHIRcustom, the passed api argument may be “Patient/$match“ to perform a more detailed patient matching search.