Add shared library for APIs/chunking

lib/chunk.test.js

@@ -0,0 +1,27 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { chunkText } from "./chunk.js";
+
+describe("chunkText", () => {
+    it("returns empty array for blank input", () => {
+        assert.deepEqual(chunkText(""), []);
+        assert.deepEqual(chunkText("   "), []);
+    });
+
+    it("keeps short text as a single chunk", () => {
+        const text = "A short paragraph.";
+        assert.deepEqual(chunkText(text), [text]);
+    });
+
+    it("splits long text into overlapping chunks under 2000 chars", () => {
+        const word = "word ";
+        const text = word.repeat(900);
+        const chunks = chunkText(text);
+        assert.ok(chunks.length > 1);
+        for (const chunk of chunks) {
+            assert.ok(chunk.length <= 2000);
+        }
+        const overlap = chunks[0].slice(-50);
+        assert.ok(chunks[1].includes(overlap.trim().slice(0, 20)));
+    });
+});