From c4483f073e8357106c43f481c3f1aefb82c637a4 Mon Sep 17 00:00:00 2001
From: Pablo Baleztena <pablo@ultharsoftware.com>
Date: Wed, 4 Sep 2024 20:08:34 -0300
Subject: [PATCH] [fabric-core] Add basic array-element utility types

---
 .../fabric/core/src/array/array-element.spec.ts | 12 ++++++++++++
 packages/fabric/core/src/array/array-element.ts | 17 +++++++++++++++++
 packages/fabric/core/src/array/index.ts         |  1 +
 packages/fabric/core/src/index.ts               |  1 +
 4 files changed, 31 insertions(+)
 create mode 100644 packages/fabric/core/src/array/array-element.spec.ts
 create mode 100644 packages/fabric/core/src/array/array-element.ts
 create mode 100644 packages/fabric/core/src/array/index.ts

diff --git a/packages/fabric/core/src/array/array-element.spec.ts b/packages/fabric/core/src/array/array-element.spec.ts
new file mode 100644
index 0000000..d345bd4
--- /dev/null
+++ b/packages/fabric/core/src/array/array-element.spec.ts
@@ -0,0 +1,12 @@
+import { describe, expectTypeOf, test } from "vitest";
+
+describe("ArrayElement utils", () => {
+  test("Given an array, it should return the element type of the array", () => {
+    type ArrayElement<T extends readonly unknown[]> =
+      T extends readonly (infer U)[] ? U : never;
+
+    type result = ArrayElement<["a", "b", "c"]>;
+
+    expectTypeOf<result>().toEqualTypeOf<"a" | "b" | "c">();
+  });
+});
diff --git a/packages/fabric/core/src/array/array-element.ts b/packages/fabric/core/src/array/array-element.ts
new file mode 100644
index 0000000..cb1c634
--- /dev/null
+++ b/packages/fabric/core/src/array/array-element.ts
@@ -0,0 +1,17 @@
+/**
+ * Get the element type of an array.
+ */
+export type ArrayElement<T extends readonly unknown[]> =
+  T extends readonly (infer U)[] ? U : never;
+
+/**
+ * Get the first element type of a tuple.
+ */
+export type TupleFirstElement<T extends readonly unknown[]> =
+  T extends readonly [infer U, ...unknown[]] ? U : never;
+
+/**
+ * Get the LAST element type of a tuple.
+ */
+export type TupleLastElement<T extends readonly unknown[]> =
+  T extends readonly [...unknown[], infer U] ? U : never;
diff --git a/packages/fabric/core/src/array/index.ts b/packages/fabric/core/src/array/index.ts
new file mode 100644
index 0000000..9062f34
--- /dev/null
+++ b/packages/fabric/core/src/array/index.ts
@@ -0,0 +1 @@
+export * from "./array-element.js";
diff --git a/packages/fabric/core/src/index.ts b/packages/fabric/core/src/index.ts
index ffac2ee..1a38f60 100644
--- a/packages/fabric/core/src/index.ts
+++ b/packages/fabric/core/src/index.ts
@@ -1,3 +1,4 @@
+export * from "./array/index.js";
 export * from "./domain/index.js";
 export * from "./error/index.js";
 export * from "./record/index.js";