import { describe, it } from "node:test";
import assert from "node:assert/strict";

import { chunkText } from "./chunking.js";

describe("chunkText", () => {
  it("returns no chunks for empty or whitespace-only text", () => {
    assert.deepEqual(chunkText(""), []);
    assert.deepEqual(chunkText("   \n\t "), []);
  });

  it("returns one chunk when text fits within the chunk size", () => {
    assert.deepEqual(chunkText("Hello world"), [
      { chunkIndex: 0, content: "Hello world" },
    ]);
  });

  it("splits text into chunks with the configured overlap", () => {
    const chunks = chunkText("abcdefghijkl", {
      chunkSize: 6,
      overlap: 2,
    });

    assert.deepEqual(chunks, [
      { chunkIndex: 0, content: "abcdef" },
      { chunkIndex: 1, content: "efghij" },
      { chunkIndex: 2, content: "ijkl" },
    ]);
  });

  it("assigns sequential chunk indices", () => {
    const chunks = chunkText("abcdefghijkl", {
      chunkSize: 4,
      overlap: 1,
    });

    assert.deepEqual(
      chunks.map((chunk) => chunk.chunkIndex),
      [0, 1, 2, 3],
    );
  });

  it("rejects invalid chunk sizes", () => {
    assert.throws(() => chunkText("text", { chunkSize: 0 }));
    assert.throws(() => chunkText("text", { chunkSize: -1 }));
    assert.throws(() => chunkText("text", { chunkSize: 1.5 }));
  });
});