Support for VSAC FHIR API (#28)

* Add support for using the FHIR VSAC endpoint (via a flag to the CodeService constructor)
* Refactor code to reduce duplication and minimize footprint of different APIs (FHIR vs SVS).
* Switch promise handling to use async / await where it makes sense
* Update dependencies

.mocharc.js

@@ -0,0 +1,5 @@
+'use strict';
+
+module.exports = {
+  file: ['./test/setup.js']
+};

README.md

@@ -29,10 +29,18 @@ valueset "Diabetes": 'https://cts.nlm.nih.gov/fhir/ValueSet/2.16.840.1.113883.3.
 The embedded version, however, is only supported for the canonical URL form of value sets.  It is not supported for URN
 or OID identifiers.
 
-## Credentials Required
+## UMLS API Key Required
 
-This library requires that the credentials of a valid UMLS account be provided to it.  If you do not have an UMLS
-account, you can request one here: https://uts.nlm.nih.gov/license.html
+This library requires a valid UMLS API key.  If you do not have an UMLS account, you can request one here:
+https://uts.nlm.nih.gov/license.html
+
+## SVS and FHIR APIs
+
+The CQL Execution Code Service supports the Value Set Authority Center's
+[SVS API](https://www.nlm.nih.gov/vsac/support/usingvsac/vsacsvsapiv2.html) and
+[FHIR API](https://www.nlm.nih.gov/vsac/support/usingvsac/vsacfhirapi.html). The SVS API is used by default, as our
+internal testing has shown it to be more performant than the FHIR API. The chosen API can be switched by passing
+in the `useFHIR` flag to the `CodeService` constructor.
 
 # Setting Up the Environment
 
@@ -65,8 +73,8 @@ provided via the `UMLS_API_KEY` environment variable.
 
 The `ensureValueSetsWithAPIKey` and `ensureValueSetsInLibraryWithAPIKey` functions are the only functions that attempt
 to download value sets from VSAC.  Before they make a request to VSAC, they will check the cache.  If the value set is
-already in the cache, they will not make a request to VSAC.  Otherwise, they will use VSAC's SVS2 API to download the
-expanded codes from the value set.
+already in the cache, they will not make a request to VSAC.  Otherwise, they will use VSAC's SVS2 API or FHIR API 
+to download the expanded codes from the value set.
 
 The `findValueSet` and `findValueSets` functions (including the legacy `findValueSetsByOid` function) do not reach out
 to VSAC, so implementations should call `ensureValueSetsInLibraryWithAPIKey` or `ensureValueSetsWithAPIKey` before

manual-test.js

@@ -7,32 +7,46 @@ const VALUESET = {
   name: 'HDL Cholesterol',
   id: '2.16.840.1.113883.3.464.1003.104.12.1013'
 };
+// Use this value set if you want something > 1000 codes
+// const VALUESET = {
+//   name: 'Diabetes mellitus',
+//   id: '2.16.840.1.113762.1.4.1078.405'
+// };
 
 async function main() {
   if (env['UMLS_API_KEY'] == null) {
     console.error('This test requires you to set the UMLS_API_KEY environment variable');
     process.exit(1);
   }
+  await run(false); // SVS
+  console.log();
+  await run(true); // FHIR
+}
 
-  const codeService = new CodeService('manual-test-vsac-cache', false);
-  console.log(`CALL: codeService.findValueSet(${VALUESET.id})`);
+async function run(useFHIR) {
+  const api = useFHIR ? 'FHIR' : 'SVS';
+  const start = new Date();
+  const codeService = new CodeService('manual-test-vsac-cache', false, useFHIR);
+  console.log(`${api} CALL: codeService.findValueSet(${VALUESET.id})`);
   console.log('EXPECT: undefined');
   let found = codeService.findValueSet(VALUESET.id);
   console.log(`RESULT: ${found}`);
   console.log();
   console.log(
-    `CALL: codeService.ensureValueSetsWithAPIKey(['${JSON.stringify(
+    `${api} CALL: codeService.ensureValueSetsWithAPIKey(['${JSON.stringify(
       VALUESET
     )}'], env['UMLS_API_KEY'], false);`
   );
   await codeService.ensureValueSetsWithAPIKey([VALUESET], env['UMLS_API_KEY'], false);
   console.log('EXPECT: <void>');
   console.log(`RESULT: <void>`);
   console.log();
-  console.log(`CALL: codeService.findValueSet(${VALUESET.id})`);
+  console.log(`${api} CALL: codeService.findValueSet(${VALUESET.id})`);
   found = codeService.findValueSet(VALUESET.id);
   console.log('EXPECT: <valueSet w/ two codes>');
-  console.log(`RESULT: ${JSON.stringify(found, null, 2)}`);
+  console.log(`RESULT: ${JSON.stringify(found, null, 2)}\n(${found.codes.length} codes)`);
+  console.log();
+  console.log(`${api} TOTAL TIME: ${new Date() - start} ms`);
 }
 
 main().catch(e => console.error(e));