/**
 * Graceful shutdown sequence (#2193).
 *
 * The reported symptom was a container that exited 137 exactly ten seconds
 * after every `docker stop`. The cause was that nothing in the shutdown path
 * could release a WebSocket: `http.Server.close()` waits for open connections
 * and an upgraded socket never ends on its own, so the close callback — which
 * is where `closeDb()` and `process.exit(0)` lived — never ran, and the only
 * remaining exit was a fallback timer set to the very second Docker sends
 * SIGKILL.
 *
 * These tests pin the three things that fix required: the sockets are actively
 * released, the database is closed on BOTH exit paths, and the fallback timer
 * fires inside Docker's 10s grace rather than on top of it.
 */
import { runShutdown, createFatalHandler, SOCKET_DRAIN_MS, FORCED_EXIT_MS } from '../../src/shutdown';

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';

type Deps = Parameters<typeof runShutdown>[1];

function makeSocket() {
  return { close: vi.fn(), terminate: vi.fn() };
}

/**
 * A server whose close callback only fires once told to — the whole point is
 * that the real one does not fire while a socket is still attached.
 */
function makeServer() {
  let done: (() => void) | undefined;
  return {
    close: vi.fn((cb: () => void) => {
      done = cb;
    }),
    closeIdleConnections: vi.fn(),
    closeAllConnections: vi.fn(),
    /** Stand-in for the last connection going away. */
    finishClose: () => done?.(),
  };
}

function makeDeps(
  over: Partial<Deps> = {},
): Deps & { exit: ReturnType<typeof vi.fn>; closeDb: ReturnType<typeof vi.fn> } {
  const server = makeServer();
  return {
    server: server as unknown as Deps['server'],
    closeNestApp: vi.fn(async () => {}),
    getWsClients: () => null,
    closeMcpSessions: vi.fn(),
    closeDb: vi.fn(),
    logInfo: vi.fn(),
    logError: vi.fn(),
    exit: vi.fn(),
    ...over,
  } as never;
}

beforeEach(() => {
  vi.useFakeTimers();
});
afterEach(() => {
  vi.useRealTimers();
});

describe('runShutdown', () => {
  it('SHUTDOWN-001 asks every ws client to go away before Nest tears the adapter down', async () => {
    const a = makeSocket();
    const b = makeSocket();
    const order: string[] = [];
    const deps = makeDeps({
      getWsClients: () => {
        order.push('ws');
        return [a, b];
      },
      closeNestApp: vi.fn(async () => {
        order.push('nest');
      }),
    });

    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;

    expect(a.close).toHaveBeenCalledWith(1001, 'Server shutting down');
    expect(b.close).toHaveBeenCalledWith(1001, 'Server shutting down');
    // The adapter's own close() drops the server reference, so the clients have
    // to be collected before Nest gets a chance to run.
    expect(order).toEqual(['ws', 'nest']);
  });

  it('SHUTDOWN-002 drops idle keep-alive sockets immediately', async () => {
    const deps = makeDeps();
    const server = deps.server as unknown as ReturnType<typeof makeServer>;

    const run = runShutdown('SIGTERM', deps);
    expect(server.closeIdleConnections).toHaveBeenCalled();
    // Nothing is destroyed yet — an in-flight request still has its drain window.
    expect(server.closeAllConnections).not.toHaveBeenCalled();

    server.finishClose();
    await run;
  });

  it('SHUTDOWN-003 destroys whatever is still attached after the drain window', async () => {
    const socket = makeSocket();
    const deps = makeDeps({ getWsClients: () => [socket] });
    const server = deps.server as unknown as ReturnType<typeof makeServer>;

    // Never resolves on its own: this is the hang #2193 died on. Deliberately
    // not awaited, so the rejection path is logged rather than left unobserved.
    void runShutdown('SIGTERM', deps).catch((err: unknown) => console.error(err));
    await vi.advanceTimersByTimeAsync(SOCKET_DRAIN_MS);

    expect(socket.terminate).toHaveBeenCalled();
    expect(server.closeAllConnections).toHaveBeenCalled();
  });

  it('SHUTDOWN-004 closes the database and exits 0 once the server is down', async () => {
    const deps = makeDeps();
    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;

    expect(deps.closeDb).toHaveBeenCalledTimes(1);
    expect(deps.exit).toHaveBeenCalledWith(0);
  });

  it('SHUTDOWN-005 still closes the database when it has to force the exit', async () => {
    // The close callback never fires — exactly the case that used to leave the
    // WAL behind for boot-time recovery on every restart.
    const deps = makeDeps({ closeNestApp: vi.fn(() => new Promise<void>(() => {})) });

    // Deliberately not awaited: the close callback never fires, so this promise
    // only settles through the forced exit below.
    void runShutdown('SIGTERM', deps).catch((err: unknown) => console.error(err));
    await vi.advanceTimersByTimeAsync(FORCED_EXIT_MS);

    expect(deps.closeDb).toHaveBeenCalledTimes(1);
    expect(deps.exit).toHaveBeenCalledWith(1);
  });

  it('SHUTDOWN-006 forces the exit inside Docker default 10s stop grace', () => {
    // The old value was exactly 10_000 — the same moment Docker sends SIGKILL,
    // and since Docker starts counting first that timer could never win.
    expect(FORCED_EXIT_MS).toBeLessThan(10_000);
    expect(SOCKET_DRAIN_MS).toBeLessThan(FORCED_EXIT_MS);
  });

  it('SHUTDOWN-007 exits once even if the forced timer and the clean path race', async () => {
    const deps = makeDeps();
    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;
    await vi.advanceTimersByTimeAsync(FORCED_EXIT_MS * 2);

    expect(deps.exit).toHaveBeenCalledTimes(1);
    expect(deps.closeDb).toHaveBeenCalledTimes(1);
  });

  it('SHUTDOWN-010 says so when Nest teardown fails, and still exits cleanly', async () => {
    // allSettled absorbs the rejection; without an explicit report the operator
    // would read "Shutdown complete" and exit 0 while the crons and the plugin
    // children were never torn down.
    const deps = makeDeps({
      closeNestApp: vi.fn(async () => {
        throw new Error('hook boom');
      }),
    });

    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;

    expect(deps.logError).toHaveBeenCalledWith(expect.stringContaining('hook boom'));
    expect(deps.exit).toHaveBeenCalledWith(0);
  });

  it('SHUTDOWN-009 still exits when the signal beats the bootstrap', async () => {
    // An orchestrator stopping a container mid-boot: there is no http server yet.
    // The old path called server.close() on undefined, and the fire-and-forget
    // promise turned that into an unhandled rejection instead of an exit.
    const deps = makeDeps({ server: undefined as never });

    await runShutdown('SIGTERM', deps);

    expect(deps.closeDb).toHaveBeenCalledTimes(1);
    expect(deps.exit).toHaveBeenCalledWith(0);
  });

  it('SHUTDOWN-008 carries on when a teardown step throws', async () => {
    const deps = makeDeps({
      closeMcpSessions: vi.fn(() => {
        throw new Error('mcp boom');
      }),
      getWsClients: () => {
        throw new Error('ws boom');
      },
    });

    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;

    // A failing step is logged, never a reason to strand the process.
    expect(deps.logError).toHaveBeenCalled();
    expect(deps.exit).toHaveBeenCalledWith(0);
  });
});

describe('runShutdown: readiness and the exit code', () => {
  it('SHUTDOWN-020 marks the process as draining before anything else happens', async () => {
    const order: string[] = [];
    const deps = makeDeps({
      markDraining: vi.fn(() => {
        order.push('draining');
      }),
      closeMcpSessions: vi.fn(() => {
        order.push('mcp');
      }),
      getWsClients: () => {
        order.push('ws');
        return null;
      },
    });
    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;
    expect(order[0]).toBe('draining');
    expect(order).toEqual(['draining', 'mcp', 'ws']);
  });

  it('SHUTDOWN-021 a readiness flag that cannot be set is logged and the shutdown goes on', async () => {
    const deps = makeDeps({
      markDraining: () => {
        throw new Error('no app yet');
      },
    });
    const run = runShutdown('SIGTERM', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;
    expect(deps.logError).toHaveBeenCalledWith('markDraining failed during shutdown: no app yet');
    expect(deps.exit).toHaveBeenCalledWith(0);
  });

  it('SHUTDOWN-022 a shutdown started by a fatal error exits with its code', async () => {
    const deps = makeDeps({ exitCode: 1 });
    const run = runShutdown('Uncaught exception', deps);
    (deps.server as unknown as ReturnType<typeof makeServer>).finishClose();
    await run;
    expect(deps.closeDb).toHaveBeenCalledTimes(1);
    expect(deps.exit).toHaveBeenCalledWith(1);
  });
});

describe('createFatalHandler', () => {
  function fatalDeps() {
    return { logError: vi.fn(), shutdown: vi.fn(), exit: vi.fn() };
  }

  it('FATAL-001 logs the stack and starts the orderly shutdown with exit code 1', () => {
    const deps = fatalDeps();
    const onFatal = createFatalHandler(deps);
    const error = new Error('boom');
    onFatal('Uncaught exception', error);
    expect(deps.logError).toHaveBeenCalledWith(`Uncaught exception: ${error.stack}`);
    expect(deps.shutdown).toHaveBeenCalledWith('Uncaught exception', 1);
    expect(deps.exit).not.toHaveBeenCalled();
  });

  it('FATAL-002 a rejection with a non-error reason is logged as text', () => {
    const deps = fatalDeps();
    createFatalHandler(deps)('Unhandled promise rejection', 'plain reason');
    expect(deps.logError).toHaveBeenCalledWith('Unhandled promise rejection: plain reason');
  });

  it('FATAL-003 a second fatal error during the shutdown exits at once', () => {
    const deps = fatalDeps();
    const onFatal = createFatalHandler(deps);
    onFatal('Uncaught exception', new Error('first'));
    onFatal('Unhandled promise rejection', new Error('second'));
    expect(deps.shutdown).toHaveBeenCalledTimes(1);
    expect(deps.exit).toHaveBeenCalledWith(1);
    expect(deps.logError).toHaveBeenCalledTimes(2);
  });

  it('FATAL-004 a logger that throws does not stop the shutdown', () => {
    const deps = fatalDeps();
    deps.logError.mockImplementation(() => {
      throw new Error('disk gone');
    });
    createFatalHandler(deps)('Uncaught exception', new Error('boom'));
    expect(deps.shutdown).toHaveBeenCalledWith('Uncaught exception', 1);
  });
});