chore: add utility stringUnionSelector

Author: trivikr

packages/middleware-flexible-checksums/src/stringUnionSelector.spec.ts

@@ -0,0 +1,40 @@
+import { SelectorType, stringUnionSelector } from "./stringUnionSelector";
+
+describe(stringUnionSelector.name, () => {
+  const key = "key";
+  const value = "VALUE";
+  const obj: { [key]: any } = {} as any;
+  const union = { [key]: value };
+
+  describe.each(Object.entries(SelectorType))(`Selector %s`, (selectorKey, selectorValue) => {
+    beforeEach(() => {
+      delete obj[key];
+    });
+
+    it(`should return undefined if ${key} is not defined`, () => {
+      // @ts-expect-error Element implicitly has an 'any' type
+      expect(stringUnionSelector(obj, key, union, SelectorType[selectorKey])).toBeUndefined();
+    });
+
+    it.each([
+      [value, value],
+      [value, value.toLowerCase()],
+      [value, [...value].map((c, i) => (i % 2 === 0 ? c.toLowerCase() : c.toUpperCase())).join("")],
+    ])(`should return number %s if ${key}="%s"`, (output, input) => {
+      obj[key] = input;
+      // @ts-expect-error Element implicitly has an 'any' type
+      expect(stringUnionSelector(obj, key, union, SelectorType[selectorKey])).toBe(output);
+    });
+
+    // Thows if the value is something other than different case.
+    it.each(["value1", "1value", [...value].reverse().join("")])(`should throw if ${key}=%s`, (input) => {
+      obj[key] = input;
+      // @ts-expect-error Element implicitly has an 'any' type
+      expect(() => stringUnionSelector(obj, key, union, SelectorType[selectorKey])).toThrow(
+        new TypeError(
+          `Cannot load ${selectorValue} '${key}'. Expected one of ${Object.values(union)}, got '${obj[key]}'.`
+        )
+      );
+    });
+  });
+});

packages/middleware-flexible-checksums/src/stringUnionSelector.ts

@@ -0,0 +1,27 @@
+export enum SelectorType {
+  ENV = "env",
+  CONFIG = "shared config entry",
+}
+
+/**
+ * Returns undefined, if obj[key] is not defined.
+ * Returns string value, if the string is defined in obj[key] and it's uppercase matches union value.
+ * Throws error for all other cases.
+ *
+ * @internal
+ */
+export const stringUnionSelector = (
+  obj: Record<string, string | undefined>,
+  key: string,
+  union: Record<string, string>,
+  type: SelectorType
+) => {
+  if (!(key in obj)) return undefined;
+
+  const value = obj[key]!.toUpperCase();
+  if (!Object.values(union).includes(value)) {
+    throw new TypeError(`Cannot load ${type} '${key}'. Expected one of ${Object.values(union)}, got '${obj[key]}'.`);
+  }
+
+  return value;
+};