VIA-630 MD/DB: calculate age based on birthdate

Author: marie-dedikova-nhs

package-lock.json

@@ -77,6 +77,7 @@
     "@types/aws-lambda": "^8.10.159",
     "axios": "^1.13.2",
     "cheerio": "^1.1.2",
+    "date-fns": "^4.1.0",
     "dotenv": "^17.2.3",
     "es-toolkit": "^1.42.0",
     "isomorphic-dompurify": "^2.33.0",

package.json

@@ -0,0 +1,47 @@
+import { calculateAge } from "./age";
+
+describe("calculateAge", () => {
+  beforeEach(() => {
+    jest.useFakeTimers().setSystemTime(new Date("2025-01-15T00:00:00.000Z").getTime());
+  });
+
+  it("should return age based on birthdate", () => {
+    const birthdate = "2011-11-01";
+
+    const result = calculateAge(birthdate);
+
+    expect(result).toEqual(13);
+  });
+
+  it("should return age of previous year if upcoming birthday is this month", () => {
+    const birthdate = "1987-01-17";
+
+    const result = calculateAge(birthdate);
+
+    expect(result).toEqual(37);
+  });
+
+  it("should return updated age if today is their birthday", () => {
+    const birthdate = "1987-01-15";
+
+    const result = calculateAge(birthdate);
+
+    expect(result).toEqual(38);
+  });
+
+  it("should return age of this year if birthday was yesterday", () => {
+    const birthdate = "1987-01-14";
+
+    const result = calculateAge(birthdate);
+
+    expect(result).toEqual(38);
+  });
+
+  it("should throw if birthdate is invalid", () => {
+    const birthdate = "1987-13-17";
+
+    expect(() => {
+      calculateAge(birthdate);
+    }).toThrow();
+  });
+});

src/utils/age.test.ts

@@ -0,0 +1,9 @@
+import { UtcDateFromStringSchema } from "@src/utils/date";
+import { differenceInYears } from "date-fns";
+
+export const calculateAge = (date: string): number => {
+  const today: Date = new Date();
+  const birthDate: Date = UtcDateFromStringSchema.parse(date);
+
+  return differenceInYears(today, birthDate);
+};