import { Readable } from "node:stream";
import { afterEach, describe, expect, it, vi } from "vitest";
const fsMocks = vi.hoisted(() => ({
createReadStream: vi.fn(),
}));
vi.mock("node:fs", async (importOriginal) => {
const actual = await importOriginal<typeof import("node:fs")>();
return {
...actual,
createReadStream: fsMocks.createReadStream,
};
});
const { readLinesAsBuffers } = await import("../src/utils/file-lines.js");
afterEach(() => {
fsMocks.createReadStream.mockReset();
vi.restoreAllMocks();
});
describe("readLinesAsBuffers", () => {
it("releases pending chunks before yielding a newline-terminated multi-chunk record", async () => {
const chunkSize = 64 * 1024;
const firstPart = Buffer.alloc(chunkSize, 0x61);
const secondPart = Buffer.concat([Buffer.alloc(chunkSize, 0x62), Buffer.from("\ntail\n")]);
fsMocks.createReadStream.mockReturnValue(Readable.from([firstPart, secondPart]));
const concatSpy = vi.spyOn(Buffer, "concat");
const lines = readLinesAsBuffers("/unused");
const first = await lines.next();
expect(first.done).toBe(false);
expect(first.value?.toString("utf8")).toBe("a".repeat(chunkSize) + "b".repeat(chunkSize));
expect(concatSpy).toHaveBeenCalledOnce();
expect(concatSpy.mock.calls[0]?.[0]).toHaveLength(0);
const second = await lines.next();
expect(second.done).toBe(false);
expect(second.value?.toString("utf8")).toBe("tail");
expect((await lines.next()).done).toBe(true);
});
it("releases pending chunks before yielding an EOF-terminated multi-chunk record", async () => {
const chunkSize = 64 * 1024;
const firstPart = Buffer.alloc(chunkSize, 0x61);
const secondPart = Buffer.alloc(chunkSize, 0x62);
fsMocks.createReadStream.mockReturnValue(Readable.from([firstPart, secondPart]));
const concatSpy = vi.spyOn(Buffer, "concat");
const lines = readLinesAsBuffers("/unused");
const line = await lines.next();
expect(line.done).toBe(false);
expect(line.value?.toString("utf8")).toBe("a".repeat(chunkSize) + "b".repeat(chunkSize));
expect(concatSpy).toHaveBeenCalledOnce();
expect(concatSpy.mock.calls[0]?.[0]).toHaveLength(0);
expect((await lines.next()).done).toBe(true);
});
});