feat(primitives): implement date type

packages/primitives/src/date.ts

@@ -0,0 +1,22 @@
+/**
+ * Date FHIR Primitive Runtime Type
+ */
+
+import { Type, success, failure, identity } from "io-ts";
+
+// TODO: This regex seems too permissive
+const DATE_REGEX = /([0-9]([0-9]([0-9][1-9]|[1-9]0)|[1-9]00)|[1-9]000)(-(0[1-9]|1[0-2])(-(0[1-9]|[1-2][0-9]|3[0-1]))?)?/;
+
+export class DateType extends Type<string> {
+  readonly _tag: "DateType" = "DateType";
+  constructor() {
+    super(
+      "date",
+      (m): m is string => typeof m === "string" && DATE_REGEX.test(m),
+      (m, c) => (this.is(m) ? success(m) : failure(m, c)),
+      identity
+    );
+  }
+}
+
+export const date = new DateType();

packages/primitives/src/index.ts

@@ -5,6 +5,7 @@
 import { Base64BinaryType, base64binary } from "./base64binary";
 import { BooleanType, boolean } from "./boolean";
 import { CanonicalType, canonical } from "./canonical";
+import { DateType, date } from "./date";
 import { DecimalType, decimal } from "./decimal";
 import { InstantType, instant } from "./instant";
 import { IntegerType, integer } from "./integer";
@@ -19,6 +20,8 @@ export {
   BooleanType,
   canonical,
   CanonicalType,
+  date,
+  DateType,
   decimal,
   DecimalType,
   instant,

packages/primitives/test/date.test.ts

@@ -0,0 +1,38 @@
+/**
+ * Tests for Date Runtime Type
+ */
+
+import { date } from "../src";
+import { assertSuccess, assertFailure, assertStrictEqual } from "./helpers";
+
+describe("DateType", () => {
+  it("should succeed validating a valid value", () => {
+    const T = date;
+    assertSuccess(T.decode("1905-08-23"));
+  });
+
+  it("should return the same reference if validation succeeded and nothing changed", () => {
+    const T = date;
+    const value = "1905-08-23";
+    assertStrictEqual(T.decode(value), value);
+  });
+
+  it("should fail validating an invalid value", () => {
+    const T = date;
+    assertFailure(T.decode(2), ["Invalid value 2 supplied to : date"]);
+  });
+
+  it("should fail validating non YYYY, YYYY-MM, or YYYY-MM-DD formatted date", () => {
+    const T = date;
+    assertFailure(T.decode("08/23"), [
+      'Invalid value "08/23" supplied to : date'
+    ]);
+  });
+
+  it("should type guard", () => {
+    const T = date;
+    expect(T.is("1905-08-23")).toEqual(true);
+    expect(T.is(true)).toEqual(false);
+    expect(T.is(undefined)).toEqual(false);
+  });
+});