import { test, expect } from "vitest";
import { buildApp } from "../src/app.js";
import { loadConfig } from "../src/config.js";
import { SseHub } from "../src/sse/sse-hub.js";

const seqOf = (id: string) => Number(id.split(":")[1]);

async function readUntil(
  reader: ReadableStreamDefaultReader<Uint8Array>,
  predicate: (text: string) => boolean,
): Promise<string> {
  const decoder = new TextDecoder();
  let text = "";
  const deadline = Date.now() + 1_000;
  while (Date.now() < deadline) {
    const result = await Promise.race([
      reader.read(),
      new Promise<{ timeout: true }>((resolve) =>
        setTimeout(() => resolve({ timeout: true }), Math.max(0, deadline - Date.now())),
      ),
    ]);
    if ("timeout" in result || result.done) break;
    text += decoder.decode(result.value);
    if (predicate(text)) break;
  }
  return text;
}

async function captureReplay(
  options: { query?: (ids: string[]) => string; lastEventId?: (ids: string[]) => string },
): Promise<{ body: string; ids: string[] }> {
  const hub = new SseHub();
  const ids = [
    hub.publish("s1", "info", { type: "info", text: "one" }),
    hub.publish("s1", "info", { type: "info", text: "two" }),
    hub.publish("s1", "info", { type: "info", text: "three" }),
  ];
  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "/tmp/h" }), {
    hub,
    thtRunner: {} as any,
  });
  await app.listen({ port: 0, host: "127.0.0.1" });
  const port = (app.server.address() as { port: number }).port;
  const controller = new AbortController();

  try {
    const lastEventId = options.lastEventId?.(ids);
    const query = options.query ? `?lastEventId=${encodeURIComponent(options.query(ids))}` : "";
    const response = await fetch(
      `http://127.0.0.1:${port}/sessions/s1/events${query}`,
      {
        headers: lastEventId ? { "Last-Event-ID": lastEventId } : undefined,
        signal: controller.signal,
      },
    );
    const reader = response.body!.getReader();
    const body = await readUntil(reader, (text) => text.includes('"three"'));
    await reader.cancel();
    return { body, ids };
  } finally {
    controller.abort();
    await app.close();
  }
}

async function expectStreamEnd(reader: ReadableStreamDefaultReader<Uint8Array>): Promise<void> {
  const result = await Promise.race([
    reader.read(),
    new Promise<{ timeout: true }>((resolve) =>
      setTimeout(() => resolve({ timeout: true }), 1_000),
    ),
  ]);
  expect(result).not.toEqual({ timeout: true });
  expect("done" in result && result.done).toBe(true);
}

test("SSE emits ids and honors the native Last-Event-ID replay cursor", async () => {
  const { body, ids } = await captureReplay({ lastEventId: (published) => published[0] });

  expect(body).not.toContain('"one"');
  expect(body).toContain(`id: ${ids[1]}\nevent: info\n`);
  expect(body).toContain('data: {"type":"info","text":"two"}');
  expect(body).toContain(`id: ${ids[2]}\nevent: info\n`);
  expect(body).toContain('data: {"type":"info","text":"three"}');
});

test("SSE honors the manual lastEventId query cursor", async () => {
  const { body, ids } = await captureReplay({ query: (published) => published[1] });

  expect(body).not.toContain('"one"');
  expect(body).not.toContain('"two"');
  expect(body).toContain(`id: ${ids[2]}\nevent: info\n`);
  expect(body).toContain('data: {"type":"info","text":"three"}');
});

test("SSE uses the newer valid cursor when header and query are both present", async () => {
  const { body } = await captureReplay({
    query: (published) => published[1],
    lastEventId: (published) => published[0],
  });

  expect(body).not.toContain('"two"');
  expect(body).toContain('"three"');
});

test("SSE resets a cursor from an older backend generation and emits a buffered pending gate once", async () => {
  // The cursor comes from a PREVIOUS process: same session, ids restarted. It must be
  // treated as stale (replay from the beginning), not honored against the new ids.
  const oldGeneration = new SseHub();
  oldGeneration.publish("s1", "info", { type: "info", text: "old" });
  const staleCursor = oldGeneration.publish("s1", "info", { type: "info", text: "older" });

  const hub = new SseHub();
  const descriptor = { id: "gate-fresh", widget: "select", title: "Choose" };
  const infoId = hub.publish("s1", "info", { type: "info", text: "fresh generation" });
  const gateId = hub.publish("s1", "ui_request", { type: "ui_request", ui_request: descriptor });
  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "/tmp/h" }), {
    hub,
    thtRunner: {} as any,
    mgr: {
      get: () => ({ bridge: { pendingWidget: () => ({ ...descriptor }) } }),
    } as any,
  });
  await app.listen({ port: 0, host: "127.0.0.1" });
  const port = (app.server.address() as { port: number }).port;
  const controller = new AbortController();

  try {
    const response = await fetch(`http://127.0.0.1:${port}/sessions/s1/events`, {
      headers: { "Last-Event-ID": staleCursor },
      signal: controller.signal,
    });
    const reader = response.body!.getReader();
    const body = await readUntil(reader, (text) => text.includes('"gate-fresh"'));
    await reader.cancel();

    expect(body).toContain(`id: ${infoId}\nevent: info\n`);
    expect(body).toContain('data: {"type":"info","text":"fresh generation"}');
    expect(body.match(/event: ui_request/g)).toHaveLength(1);
    expect(body).toContain(`id: ${gateId}\nevent: ui_request\n`);
    expect(body).toContain('"ui_request":{"id":"gate-fresh","widget":"select","title":"Choose"}');
  } finally {
    controller.abort();
    await app.close();
  }
});

test("clear ends every live SSE response and a cursor reconnect replays post-clear events", async () => {
  const hub = new SseHub();
  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "/tmp/h" }), {
    hub,
    thtRunner: {} as any,
  });
  await app.listen({ port: 0, host: "127.0.0.1" });
  const port = (app.server.address() as { port: number }).port;
  const controllers = [new AbortController(), new AbortController(), new AbortController()];

  try {
    const responses = await Promise.all(controllers.slice(0, 2).map((controller) => fetch(
      `http://127.0.0.1:${port}/sessions/s1/events`,
      { signal: controller.signal },
    )));
    const readers = responses.map((response) => response.body!.getReader());

    const beforeId = hub.publish("s1", "info", { type: "info", text: "before" });
    expect(seqOf(beforeId)).toBe(1);
    const initial = await Promise.all(readers.map((reader) =>
      readUntil(reader, (text) => text.includes('"before"'))));
    expect(initial.every((body) => body.includes(`id: ${beforeId}\nevent: info\n`))).toBe(true);

    hub.clear("s1");
    await Promise.all(readers.map(expectStreamEnd));

    const afterId = hub.publish("s1", "info", { type: "info", text: "after" });
    expect(seqOf(afterId)).toBe(2);
    const gateId = hub.publish("s1", "ui_request", {
      type: "ui_request",
      ui_request: { id: "gate-1", widget: "select" },
    });
    expect(seqOf(gateId)).toBe(3);

    const reconnected = await fetch(
      `http://127.0.0.1:${port}/sessions/s1/events`,
      {
        headers: { "Last-Event-ID": beforeId },
        signal: controllers[2].signal,
      },
    );
    const reconnectReader = reconnected.body!.getReader();
    const replay = await readUntil(reconnectReader, (text) => text.includes('"gate-1"'));
    expect(replay).toContain(`id: ${afterId}\nevent: info\n`);
    expect(replay).toContain('data: {"type":"info","text":"after"}');
    expect(replay).toContain(`id: ${gateId}\nevent: ui_request\n`);
    expect(replay).toContain('"ui_request":{"id":"gate-1","widget":"select"}');
    await reconnectReader.cancel();
  } finally {
    for (const controller of controllers) controller.abort();
    await app.close();
  }
});