From 1d0d5c6cffd489d86e8c13576656122ab84635ec Mon Sep 17 00:00:00 2001
From: Kir_Antipov <kp.antipov@gmail.com>
Date: Fri, 20 Jan 2023 11:46:18 +0000
Subject: [PATCH] Made a function to retrieve enum keys

---
 src/utils/enum/enum-key.ts             | 39 ++++++++++++++++++++++++++
 tests/unit/utils/enum/enum-key.spec.ts | 38 +++++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 src/utils/enum/enum-key.ts
 create mode 100644 tests/unit/utils/enum/enum-key.spec.ts

diff --git a/src/utils/enum/enum-key.ts b/src/utils/enum/enum-key.ts
new file mode 100644
index 0000000..a277951
--- /dev/null
+++ b/src/utils/enum/enum-key.ts
@@ -0,0 +1,39 @@
+import { isReadOnlyMap } from "@/utils/collections";
+
+/**
+ * A type that represents the key of an enum type `T`.
+ *
+ * @template T - The enum type whose keys are being represented.
+ */
+export type EnumKey<T> = keyof T extends string ? keyof T : never;
+
+/**
+ * Retrieves an array of the string keys of the specified `enum` object.
+ *
+ * @template T - Type of the enum.
+ *
+ * @param e - The enum object to retrieve the keys for.
+ *
+ * @returns An array of the string keys of the specified `enum` object.
+ */
+export function enumKeys<T>(e: T): EnumKey<T>[] {
+    if (isReadOnlyMap<EnumKey<T>, unknown>(e)) {
+        return [...e.keys()];
+    }
+
+    return Object.getOwnPropertyNames(e).filter(key => isEnumKey(e, key)) as EnumKey<T>[];
+}
+
+/**
+ * Determines if the provided key is an enumeration key.
+ *
+ * @template T - Type of the enum.
+ *
+ * @param e - The enum object to check the key against.
+ * @param key - The key to be checked.
+ *
+ * @returns `true` if the key is an enumeration key; otherwise, `false`.
+ */
+function isEnumKey<T>(e: T, key: string): key is EnumKey<T> {
+    return typeof e[key] !== "function" && key !== String(+key);
+}
diff --git a/tests/unit/utils/enum/enum-key.spec.ts b/tests/unit/utils/enum/enum-key.spec.ts
new file mode 100644
index 0000000..e1d0465
--- /dev/null
+++ b/tests/unit/utils/enum/enum-key.spec.ts
@@ -0,0 +1,38 @@
+import { Enum } from "@/utils/enum/enum";
+import { enumKeys } from "@/utils/enum/enum-key";
+
+describe("enumKeys", () => {
+    test("returns the correct keys for number-based built-in enums", () => {
+        enum NumberEnum {
+            A = 1,
+            B = 2,
+            C = 3,
+        }
+
+        const keys = enumKeys(NumberEnum);
+
+        expect(keys).toEqual(["A", "B", "C"]);
+    });
+
+    test("returns the correct keys for string-based built-in enums", () => {
+        enum StringEnum {
+            A = "a",
+            B = "b",
+            C = "c",
+        }
+
+        const keys = enumKeys(StringEnum);
+        expect(keys).toEqual(["A", "B", "C"]);
+    });
+
+    test("returns the correct keys for custom enums created with Enum.create", () => {
+        const CustomEnum = Enum.create({
+            A: 1n,
+            B: 2n,
+            C: 3n,
+        });
+
+        const keys = enumKeys(CustomEnum);
+        expect(keys).toEqual(["A", "B", "C"]);
+    });
+});