From a793de784465220970af617db0660b7b778393fb Mon Sep 17 00:00:00 2001
From: Chad Kruse <314653+chadokruse@users.noreply.github.com>
Date: Mon, 25 Nov 2024 20:42:51 -0600
Subject: [PATCH] Inactive algorithm

---
 shared/algorithms/inactive.ts | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 shared/algorithms/inactive.ts

diff --git a/shared/algorithms/inactive.ts b/shared/algorithms/inactive.ts
new file mode 100644
index 0000000..ffcd703
--- /dev/null
+++ b/shared/algorithms/inactive.ts
@@ -0,0 +1,31 @@
+interface Config {
+  monthsThreshold: number;
+}
+
+const config: Config = {
+  monthsThreshold: 36,
+};
+
+const calculateMonthsBetween = (fyeDate: number, currentDate: Date): number => {
+  const fyeYear = Math.floor(fyeDate / 100);
+  const fyeMonth = fyeDate % 100;
+
+  if (fyeDate < 100000 || fyeDate > 999999 || fyeMonth < 1 || fyeMonth > 12) {
+    throw new Error('fyeDate is expected to be in IRS tax period format YYYYMM');
+  }
+
+  const currentYear = currentDate.getFullYear();
+  const currentMonth = currentDate.getMonth() + 1;
+
+  return (currentYear - fyeYear) * 12 + (currentMonth - fyeMonth);
+};
+
+export const isLikelyInactive = (eobmfStatus: boolean, taxPeriod: number): boolean => {
+  const monthsSinceFye = calculateMonthsBetween(taxPeriod, new Date());
+  if (eobmfStatus === false) {
+    if (monthsSinceFye >= config.monthsThreshold) {
+      return true;
+    }
+  }
+  return false;
+};