Expose and test makeRecencyFilter so cgm-remote-monitor can use it

filter.js

@@ -0,0 +1,24 @@
+/* jshint node: true */
+"use strict";
+
+// Returns a stateful filter which remembers the time of the last-seen entry to
+// prevent uploading duplicates.
+function makeRecencyFilter(timeFn) {
+  var lastTime = 0;
+
+  return function(items) {
+    var out = [];
+    items.forEach(function(item) {
+      if (timeFn(item) > lastTime) {
+        out.push(item);
+      }
+    });
+    out.forEach(function(item) {
+      lastTime = Math.max(lastTime, timeFn(item));
+    });
+
+    return out;
+  };
+}
+
+module.exports.makeRecencyFilter = makeRecencyFilter;

index.js

@@ -1,5 +1,6 @@
 module.exports = {
   carelink: require('./carelink'),
+  filter: require('./filter'),
   logger: require('./logger'),
   nightscout: require('./nightscout'),
   transform: require('./transform')

run.js

@@ -2,6 +2,7 @@
 "use strict";
 
 var carelink = require('./carelink'),
+  filter = require('./filter'),
   logger = require('./logger'),
   nightscout = require('./nightscout'),
   transform = require('./transform');
@@ -43,29 +44,11 @@ var devicestatusUrl = (config.nsBaseUrl ? config.nsBaseUrl : 'https://' + config
 
 logger.setVerbose(config.verbose);
 
-function makeRecencyFilter(timeFn) {
-  var lastTime = 0;
-
-  return function(items) {
-    var out = [];
-    items.forEach(function(item) {
-      if (timeFn(item) > lastTime) {
-        out.push(item);
-      }
-    });
-    out.forEach(function(item) {
-      lastTime = Math.max(lastTime, timeFn(item));
-    });
-
-    return out;
-  };
-}
-
-var filterSgvs = makeRecencyFilter(function(item) {
+var filterSgvs = filter.makeRecencyFilter(function(item) {
   return item['date'];
 });
 
-var filterDeviceStatus = makeRecencyFilter(function(item) {
+var filterDeviceStatus = filter.makeRecencyFilter(function(item) {
   return new Date(item['created_at']).getTime();
 });
 

test/filter.js

@@ -0,0 +1,30 @@
+/* jshint node: true */
+/* globals describe, it */
+"use strict";
+
+var _ = require('lodash'),
+  expect = require('expect.js');
+
+var makeRecencyFilter = require('../filter.js').makeRecencyFilter;
+
+describe('makeRecencyFilter()', function() {
+  it('should return a stateful filter which discards items older than the most recent one seen', function() {
+    function sgv(date) {
+      return {type: 'sgv', someDateKey: date};
+    }
+
+    var filter = makeRecencyFilter(function(item) {
+      return item['someDateKey'];
+    });
+
+    expect(filter([2, 3, 4].map(sgv))).to.have.length(3);
+
+    expect(filter([2, 3, 4].map(sgv))).to.have.length(0);
+
+    var filtered = filter([2, 3, 4, 8, 6, 7, 5].map(sgv));
+    expect(filtered).to.have.length(4);
+    [5, 6, 7, 8].forEach(function(val) {
+      expect(_.pluck(filtered, 'someDateKey')).to.contain(val);
+    });
+  });
+});