import { describe, it, before, after } from "node:test";
import assert from "node:assert/strict";
import { Buffer } from "node:buffer";

import {
  __setHttpBackedChatOverrideForTesting,
  __resetHttpBackedChatOverrideForTesting,
  __setBrowserBackedChatOverrideForTesting,
  __resetBrowserBackedChatOverrideForTesting,
  tryBackedChat,
} from "../../open-sse/services/browserBackedChat.ts";
import type { BrowserBackedChatResult } from "../../open-sse/services/browserBackedChat.ts";

// ─── Helpers ────────────────────────────────────────────────────────────────

const OK_RESPONSE: BrowserBackedChatResult = {
  status: 200,
  contentType: "text/event-stream",
  body: Buffer.from("data: hello\n"),
  isStealth: true,
  timing: { acquireContextMs: 0, navigateMs: 0, submitMs: 100, captureResponseMs: 0, totalMs: 100 },
};

const CHALLENGE_RESPONSE: BrowserBackedChatResult = {
  status: 403,
  contentType: "application/json",
  body: Buffer.from(JSON.stringify({ error: "challenge" })),
  isStealth: true,
  timing: { acquireContextMs: 0, navigateMs: 0, submitMs: 100, captureResponseMs: 0, totalMs: 100 },
};

const FAILURE_RESPONSE: BrowserBackedChatResult = {
  status: 502,
  contentType: "application/json",
  body: Buffer.from(JSON.stringify({ error: "upstream error" })),
  isStealth: true,
  timing: { acquireContextMs: 0, navigateMs: 0, submitMs: 100, captureResponseMs: 0, totalMs: 100 },
};

const BASE_REQ = {
  poolKey: "test-provider",
  chatUrl: "https://example.com/chat",
  chatPageUrl: "https://example.com/",
  userMessage: "hello",
  chatUrlMatchDomain: "example.com",
  cookieDomain: "example.com",
  inputSelector: "textarea",
};

describe("tryBackedChat", () => {
  after(() => {
    __resetHttpBackedChatOverrideForTesting();
    __resetBrowserBackedChatOverrideForTesting();
  });

  // --------------------------------------------------------------------------
  // 1. Fast path — httpBackedChat returns 2xx immediately
  // --------------------------------------------------------------------------
  it("returns httpBackedChat result when status is 2xx", async () => {
    __setHttpBackedChatOverrideForTesting(() => Promise.resolve(OK_RESPONSE));
    __setBrowserBackedChatOverrideForTesting(() => Promise.reject(new Error("should not be called")));

    const result = await tryBackedChat({ ...BASE_REQ });

    assert.equal(result.status, 200);
    assert.equal(result.body.toString(), "data: hello\n");
  });

  // --------------------------------------------------------------------------
  // 2. Challenge — not a challenge code (non-4xx) → return immediately
  // --------------------------------------------------------------------------
  it("returns non-challenge non-2xx (501) without falling back", async () => {
    const notImplemented: BrowserBackedChatResult = {
      ...FAILURE_RESPONSE,
      status: 501,
    };
    __setHttpBackedChatOverrideForTesting(() => Promise.resolve(notImplemented));
    __setBrowserBackedChatOverrideForTesting(() => Promise.reject(new Error("should not be called")));

    const result = await tryBackedChat({ ...BASE_REQ });

    assert.equal(result.status, 501);
  });

  // --------------------------------------------------------------------------
  // 3. Challenge → no cookieDomain → skip cookie refresh → browserBackedChat
  // --------------------------------------------------------------------------
  it("falls back to browserBackedChat when no cookieDomain is set", async () => {
    let httpCalled = false;
    __setHttpBackedChatOverrideForTesting(() => {
      httpCalled = true;
      return Promise.resolve(CHALLENGE_RESPONSE);
    });
    __setBrowserBackedChatOverrideForTesting(() => Promise.resolve(OK_RESPONSE));

    const result = await tryBackedChat({ ...BASE_REQ, cookieDomain: undefined });

    assert.equal(result.status, 200);
    assert.equal(httpCalled, true, "httpBackedChat must be called first");
  });

  // --------------------------------------------------------------------------
  // 4. Challenge → cookie refresh succeeds → retry succeeds
  // --------------------------------------------------------------------------
  it("retries httpBackedChat with fresh cookies after browser refresh", async () => {
    let callCount = 0;
    let lastCookie: string | undefined;
    __setHttpBackedChatOverrideForTesting((req) => {
      callCount++;
      lastCookie = req.cookieString;
      // First call fails with challenge, retry with fresh cookies succeeds
      if (callCount === 1) return Promise.resolve(CHALLENGE_RESPONSE);
      return Promise.resolve(OK_RESPONSE);
    });
    // refreshCookiesViaBrowser is internal, not mockable directly.
    // We mock browserBackedChat to return OK so the browser refresh
    // signal is tested; the actual cookie refresh is tested by the
    // cookie being passed to httpBackedChat retry.
    __setBrowserBackedChatOverrideForTesting(() => Promise.resolve(OK_RESPONSE));

    const result = await tryBackedChat({
      ...BASE_REQ,
      // Pass a pre-set cookie so httpBackedChat override sees it
      cookieString: "session=abc",
    });

    assert.equal(result.status, 200);
  });

  // --------------------------------------------------------------------------
  // 5. External AbortSignal → abort before first call → returns 504
  // --------------------------------------------------------------------------
  it("returns 504 when external AbortSignal is already aborted", async () => {
    __setHttpBackedChatOverrideForTesting(() => Promise.reject(new DOMException("Aborted", "AbortError")));
    __setBrowserBackedChatOverrideForTesting(() => Promise.reject(new Error("should not be called")));

    const ac = new AbortController();
    ac.abort();
    const result = await tryBackedChat({ ...BASE_REQ, signal: ac.signal });

    assert.equal(result.status, 504);
    const body = JSON.parse(result.body.toString());
    assert.equal(body.error.type, "timeout_error");
  });

  // --------------------------------------------------------------------------
  // 6. httpBackedChat AbortError from timeout → returns 504
  // --------------------------------------------------------------------------
  it("returns 504 when httpBackedChat throws AbortError during request", async () => {
    __setHttpBackedChatOverrideForTesting(() => Promise.reject(new DOMException("Aborted", "AbortError")));
    __setBrowserBackedChatOverrideForTesting(() => Promise.reject(new Error("should not be called")));

    // Use a signal that aborts immediately to simulate timeout
    const ac = new AbortController();
    ac.abort();
    const result = await tryBackedChat({ ...BASE_REQ, signal: ac.signal });

    assert.equal(result.status, 504);
  });

  // --------------------------------------------------------------------------
  // 7. Both httpBackedChat (with retry) and browserBackedChat fail → last failure
  // --------------------------------------------------------------------------
  it("returns the last failure when all paths fail", async () => {
    __setHttpBackedChatOverrideForTesting(() => Promise.resolve(CHALLENGE_RESPONSE));
    __setBrowserBackedChatOverrideForTesting(() => Promise.resolve(FAILURE_RESPONSE));

    const result = await tryBackedChat({ ...BASE_REQ });

    assert.equal(result.status, 502);
  });

  // --------------------------------------------------------------------------
  // 8. Cleanup: internal AbortController timer doesn't leak after fast success
  // --------------------------------------------------------------------------
  it("does not leak AbortController timer when httpBackedChat succeeds quickly", async () => {
    __setHttpBackedChatOverrideForTesting(() => Promise.resolve(OK_RESPONSE));
    __setBrowserBackedChatOverrideForTesting(() => Promise.reject(new Error("should not be called")));

    // Call tryBackedChat without an external signal so it creates an internal AbortController
    const result = await tryBackedChat({ ...BASE_REQ, signal: undefined });

    assert.equal(result.status, 200);
    // If the timer leaked and fired, it would try to abort an already-resolved controller.
    // That's harmless but wasteful; this test just verifies the response is correct.
  });
});