tech-log-frontend/tests/unit/bounded-body-reader.test.ts

import { describe, expect, it, vi } from "vitest";

import {
  declaredContentLength,
  decodeJsonBytes,
  isEffectivelyEmpty,
  isJsonMediaType,
  probeForbiddenBody,
  readBoundedBytes,
} from "../../src/adapters/http/bounded-body-reader.ts";

function responseWithBody(
  body: ReadableStream<Uint8Array> | null,
  contentLength?: string,
): Response {
  return new Response(body, {
    headers:
      contentLength === undefined ? undefined : { "content-length": contentLength },
  });
}

describe("bounded body reader", () => {
  it.each([
    [null, false],
    ["", false],
    [" application/json ; charset=utf-8 ", true],
    ["APPLICATION/PROBLEM+JSON", true],
    ["text/json", false],
    ["application/jsonp", false],
  ] as const)("classifies JSON media type %j", (header, expected) => {
    expect(isJsonMediaType(header)).toBe(expected);
  });

  it.each([
    [undefined, null],
    ["0", 0],
    ["12", 12],
    ["-1", null],
    ["NaN", null],
    ["Infinity", null],
  ] as const)("parses declared content length %s", (header, expected) => {
    expect(declaredContentLength(responseWithBody(null, header))).toBe(expected);
  });

  it("rejects an oversized declared body and tolerates cancellation failure", async () => {
    const cancel = vi.fn(async () => {
      throw new Error("already settled");
    });
    const response = {
      headers: new Headers({ "content-length": "9" }),
      body: { cancel },
    } as unknown as Response;

    await expect(readBoundedBytes(response, 8)).resolves.toEqual({
      ok: false,
      code: "RESPONSE_TOO_LARGE",
    });
    expect(cancel).toHaveBeenCalledOnce();
  });

  it("returns empty bytes when a successful response has no body", async () => {
    const result = await readBoundedBytes(responseWithBody(null), 8);
    expect(result).toEqual({ ok: true, bytes: new Uint8Array(0) });
  });

  it("joins chunks without retaining empty chunks", async () => {
    const body = new ReadableStream<Uint8Array>({
      start(controller) {
        controller.enqueue(new Uint8Array(0));
        controller.enqueue(Uint8Array.of(1, 2));
        controller.enqueue(Uint8Array.of(3));
        controller.close();
      },
    });

    await expect(readBoundedBytes(responseWithBody(body), 3)).resolves.toEqual({
      ok: true,
      bytes: Uint8Array.of(1, 2, 3),
    });
  });

  it("cancels streaming input as soon as the accumulated limit is exceeded", async () => {
    const cancel = vi.fn().mockRejectedValue(new Error("cancel failed"));
    const reader = {
      read: vi
        .fn()
        .mockResolvedValueOnce({ done: false, value: Uint8Array.of(1, 2) })
        .mockResolvedValueOnce({ done: false, value: Uint8Array.of(3, 4) }),
      cancel,
      releaseLock: vi.fn(),
    };
    const response = {
      headers: new Headers(),
      body: { getReader: () => reader },
    } as unknown as Response;

    await expect(readBoundedBytes(response, 3)).resolves.toEqual({
      ok: false,
      code: "RESPONSE_TOO_LARGE",
    });
    expect(cancel).toHaveBeenCalledOnce();
    expect(reader.releaseLock).toHaveBeenCalledOnce();
  });

  it("maps reader failure and cancellation failure to a stream failure", async () => {
    const reader = {
      read: vi.fn().mockRejectedValue(new Error("stream failed")),
      cancel: vi.fn().mockRejectedValue(new Error("cancel failed")),
      releaseLock: vi.fn(() => {
        throw new Error("already released");
      }),
    };
    const response = {
      headers: new Headers(),
      body: { getReader: () => reader },
    } as unknown as Response;

    await expect(readBoundedBytes(response, 3)).resolves.toEqual({
      ok: false,
      code: "RESPONSE_STREAM_FAILURE",
    });
  });

  it("detects a forbidden body from declared length without reading it", async () => {
    const cancel = vi.fn();
    const response = {
      headers: new Headers({ "content-length": "1" }),
      body: { cancel },
    } as unknown as Response;

    await expect(probeForbiddenBody(response)).resolves.toEqual({
      ok: true,
      present: true,
    });
    expect(cancel).toHaveBeenCalledOnce();
  });

  it("accepts an absent, completed, or zero-byte forbidden body", async () => {
    await expect(probeForbiddenBody(responseWithBody(null))).resolves.toEqual({
      ok: true,
      present: false,
    });

    for (const next of [
      { done: true, value: undefined },
      { done: false, value: new Uint8Array(0) },
    ]) {
      const reader = {
        read: vi.fn().mockResolvedValue(next),
        cancel: vi.fn(),
        releaseLock: vi.fn(),
      };
      const response = {
        headers: new Headers(),
        body: { getReader: () => reader },
      } as unknown as Response;
      await expect(probeForbiddenBody(response)).resolves.toEqual({
        ok: true,
        present: false,
      });
      expect(reader.cancel).not.toHaveBeenCalled();
    }
  });

  it("probes only one present byte and cancels the remaining body", async () => {
    const reader = {
      read: vi.fn().mockResolvedValue({ done: false, value: Uint8Array.of(1) }),
      cancel: vi.fn().mockRejectedValue(new Error("cancel failed")),
      releaseLock: vi.fn(),
    };
    const response = {
      headers: new Headers(),
      body: { getReader: () => reader },
    } as unknown as Response;

    await expect(probeForbiddenBody(response)).resolves.toEqual({
      ok: true,
      present: true,
    });
    expect(reader.read).toHaveBeenCalledOnce();
    expect(reader.cancel).toHaveBeenCalledOnce();
  });

  it("maps a forbidden-body probe error even when cleanup also fails", async () => {
    const reader = {
      read: vi.fn().mockRejectedValue(new Error("probe failed")),
      cancel: vi.fn().mockRejectedValue(new Error("cancel failed")),
      releaseLock: vi.fn(() => {
        throw new Error("released");
      }),
    };
    const response = {
      headers: new Headers(),
      body: { getReader: () => reader },
    } as unknown as Response;

    await expect(probeForbiddenBody(response)).resolves.toEqual({
      ok: false,
      code: "RESPONSE_STREAM_FAILURE",
    });
  });

  it("decodes valid JSON and distinguishes UTF-8 from JSON failures", () => {
    expect(decodeJsonBytes(new TextEncoder().encode('{"ok":true}'))).toEqual({
      ok: true,
      value: { ok: true },
    });
    expect(decodeJsonBytes(Uint8Array.of(0xc3, 0x28))).toEqual({
      ok: false,
      code: "UTF8_INVALID",
    });
    expect(decodeJsonBytes(new TextEncoder().encode("{"))).toEqual({
      ok: false,
      code: "JSON_INVALID",
    });
  });

  it.each([
    [new Uint8Array(0), true],
    [Uint8Array.of(0x20, 0x09, 0x0a, 0x0d), true],
    [Uint8Array.of(0x20, 0x00), false],
  ])("classifies effective emptiness %#", (bytes, expected) => {
    expect(isEffectivelyEmpty(bytes)).toBe(expected);
  });
});