/**
 * @license
 * Copyright 2025 Qwen Team
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * Reusable helpers for `qwen serve` daemon tests:
 *
 *   - `spawnDaemon` lifts the inline `beforeAll` boot pattern from
 *     `qwen-serve-routes.test.ts` / `qwen-serve-streaming.test.ts` into one
 *     place so test files don't reimplement port-0 wait + token + workspace
 *     pinning + SIGTERM teardown.
 *   - `getRssMB` / `startRssPolling` sample the daemon process's RSS via
 *     `ps -o rss=`. POSIX-only (no Windows). Used to capture the RSS curve
 *     across session counts.
 *   - `countDescendants` walks the daemon's process tree via `pgrep -P`
 *     (matches the existing inline pattern at
 *     `qwen-serve-streaming.test.ts:144`, with optional filtered subtree
 *     matching). Used to surface the P1 "MCP child × session"
 *     amplification before the M2 shared-pool fix.
 *   - `percentiles` is a dependency-free p50/p90/p99 calculator for the
 *     prompt-latency suite.
 *   - `consumeSseEvents` drives the daemon's SSE stream at a configurable
 *     rate so the SSE backpressure tests can observe `client_evicted`.
 *
 * Skip-on-Windows is the caller's responsibility: at the top of every test
 * file that imports this harness, gate with
 * `if (process.platform === 'win32') describe.skip(...)`. The harness
 * functions assume `ps` and `pgrep` are present.
 */

import {
  spawn,
  type ChildProcess,
  execFileSync,
  type ExecFileSyncOptionsWithStringEncoding,
} from 'node:child_process';
import * as fs from 'node:fs';
import * as os from 'node:os';
import * as path from 'node:path';
import { fileURLToPath } from 'node:url';
import { DaemonClient, type SubscribeOptions } from '@qwen-code/sdk';
import {
  hashMcpServerConfig,
  type MCPServerConfig,
} from '@qwen-code/qwen-code-core';

const __dirname = path.dirname(fileURLToPath(import.meta.url));

/**
 * Default workspace and CLI binary resolution mirrors the existing
 * `qwen-serve-routes.test.ts` constants so callers that copy/paste between
 * test files don't see drift.
 */
export const DEFAULT_REPO_ROOT = path.resolve(__dirname, '../..');
export const DEFAULT_TOKEN = 'integration-test-token';
export const DEFAULT_CLI_BIN =
  process.env['TEST_CLI_PATH'] ??
  path.resolve(__dirname, '../../packages/cli/dist/index.js');

export interface SpawnDaemonOptions {
  /**
   * Workspace path the daemon binds to (`--workspace`). Defaults to repo
   * root. Tests measuring MCP amplification or wanting their own settings
   * file should pass a temp dir created via `prepareWorkspace`.
   */
  workspaceCwd?: string;
  /** Bearer token. Defaults to the same string the existing tests use. */
  token?: string;
  /** CLI binary path. Defaults to `TEST_CLI_PATH` env or `dist/cli.js`. */
  cliBin?: string;
  /** Boot deadline for the listening-on regex parse. Default 10s. */
  bootTimeoutMs?: number;
  /** Extra args appended after the standard ones. */
  extraArgs?: string[];
  /** Optional env additions for the spawned daemon. */
  env?: Record<string, string>;
}

export interface SpawnedDaemon {
  client: DaemonClient;
  daemon: ChildProcess;
  port: number;
  base: string;
  workspaceCwd: string;
  token: string;
  /** Drain stdout into this buffer for post-mortem if a test fails. */
  stdoutBuf: { value: string };
  /** Drain stderr similarly — surface on dispose if exit code != 0. */
  stderrBuf: { value: string };
  /** Idempotent. Sends SIGTERM, awaits exit (up to 5s). */
  dispose: () => Promise<void>;
}

export const LISTENING_LINE_RE =
  /^(?<line>.*listening on http:\/\/127\.0\.0\.1:(?<port>\d+).*)$/m;
const DISPOSE_GRACE_MS = 5_000;
const MATCHED_DESCENDANT_DEPTH = 4;

export async function spawnDaemon(
  opts: SpawnDaemonOptions = {},
): Promise<SpawnedDaemon> {
  const workspaceCwd = opts.workspaceCwd ?? DEFAULT_REPO_ROOT;
  const token = opts.token ?? DEFAULT_TOKEN;
  const cliBin = opts.cliBin ?? DEFAULT_CLI_BIN;
  const bootTimeoutMs = opts.bootTimeoutMs ?? 10_000;
  const extraArgs = opts.extraArgs ?? [];

  const args = [
    cliBin,
    'serve',
    '--port',
    '0',
    '--token',
    token,
    '--hostname',
    '127.0.0.1',
    '--workspace',
    workspaceCwd,
    ...extraArgs,
  ];

  const daemon = spawn(process.execPath, args, {
    stdio: ['ignore', 'pipe', 'pipe'],
    env: { ...process.env, ...opts.env },
  });

  const stdoutBuf = { value: '' };
  const stderrBuf = { value: '' };
  daemon.stdout?.on('data', (chunk: Buffer) => {
    stdoutBuf.value += chunk.toString();
  });
  daemon.stderr?.on('data', (chunk: Buffer) => {
    stderrBuf.value += chunk.toString();
  });

  // Parse the listening port from stdout. Mirrors the pattern in
  // qwen-serve-routes.test.ts: capture the timer handle so a successful
  // resolution clears it (an un-cleared 10s timer leaks past the spawn
  // promise and shows up as flaky test timeouts on slow CI).
  const port = await new Promise<number>((resolve, reject) => {
    let settled = false;
    const cleanup = () => {
      daemon.stdout?.off('data', onData);
      daemon.off('exit', onExit);
      clearTimeout(bootTimer);
    };
    const fail = (err: Error, kill = false) => {
      if (settled) return;
      settled = true;
      cleanup();
      if (kill && daemon.exitCode === null) {
        daemon.kill('SIGTERM');
      }
      reject(err);
    };
    const bootTimer = setTimeout(() => {
      fail(
        new Error(
          `daemon boot timeout after ${bootTimeoutMs}ms:\n` +
            `stdout=${stdoutBuf.value}\nstderr=${stderrBuf.value}`,
        ),
        true,
      );
    }, bootTimeoutMs);
    const onData = (_chunk: Buffer) => {
      const port = stdoutBuf.value.match(LISTENING_LINE_RE)?.groups?.['port'];
      if (!port || settled) return;
      settled = true;
      cleanup();
      resolve(Number(port));
    };
    const onExit = (code: number | null) => {
      fail(
        new Error(
          `daemon exited with ${code} before listening:\n` +
            `stdout=${stdoutBuf.value}\nstderr=${stderrBuf.value}`,
        ),
      );
    };
    daemon.stdout!.on('data', onData);
    daemon.once('exit', onExit);
  });

  const base = `http://127.0.0.1:${port}`;
  const client = new DaemonClient({ baseUrl: base, token });

  const dispose = async () => {
    if (daemon.exitCode !== null) return;
    daemon.kill('SIGTERM');
    await new Promise<void>((resolve) => {
      const t = setTimeout(() => {
        // Force kill if SIGTERM didn't take in time. We don't await
        // exit again — the OS will clean up either way and a 5s
        // hang here multiplies into 5s × N tests on flaky machines.
        try {
          daemon.kill('SIGKILL');
        } catch {
          /* already gone */
        }
        resolve();
      }, DISPOSE_GRACE_MS);
      daemon.once('exit', () => {
        clearTimeout(t);
        resolve();
      });
    });
  };

  return {
    client,
    daemon,
    port,
    base,
    workspaceCwd,
    token,
    stdoutBuf,
    stderrBuf,
    dispose,
  };
}

/**
 * Write a `.qwen/settings.json` into `workspaceCwd` so the daemon picks up
 * `mcpServers` (and any other settings) at boot. Caller is responsible for
 * cleaning up the temp dir if they created one. Returns the absolute
 * settings file path for visibility in test output.
 */
export function writeWorkspaceSettings(
  workspaceCwd: string,
  settings: Record<string, unknown>,
): string {
  const settingsDir = path.join(workspaceCwd, '.qwen');
  fs.mkdirSync(settingsDir, { recursive: true });
  const settingsPath = path.join(settingsDir, 'settings.json');
  fs.writeFileSync(settingsPath, JSON.stringify(settings, null, 2));
  return settingsPath;
}

/**
 * Pre-approve gated (workspace / project scope, #4615) MCP servers for
 * `workspaceCwd` so the daemon's `qwen --acp` child connects them instead of
 * skipping them as pending-approval. Servers declared in `.qwen/settings.json`
 * are workspace-scoped and therefore gated: absent a stored approval, discovery
 * skips them BEFORE any spawn, which makes the MCP-amplification suite time out
 * waiting for grandchildren that never appear.
 *
 * Writes a standalone approvals file (NOT the developer's global
 * `~/.qwen/mcpApprovals.json`) under the workspace and returns the env that
 * points the daemon — and, by inheritance, its acp child — at it. Pass the
 * returned env to `spawnDaemon({ env })`. The approval hash binds to the same
 * behavioral fields the child hashes (`scope` is provenance-only and excluded),
 * so the plain settings config is sufficient. Mirrors the pre-approval pattern
 * in `simple-mcp-server.test.ts`.
 */
export function approveWorkspaceMcpServers(
  workspaceCwd: string,
  servers: Record<string, MCPServerConfig>,
): Record<string, string> {
  const approvalsPath = path.join(workspaceCwd, '.qwen', 'mcpApprovals.json');
  const project: Record<string, { hash: string; status: 'approved' }> = {};
  for (const [name, config] of Object.entries(servers)) {
    project[name] = { hash: hashMcpServerConfig(config), status: 'approved' };
  }
  // Key by the canonical (realpath) workspace, NOT `path.resolve`: the daemon
  // canonicalizes `--workspace` (e.g. macOS `/var` → `/private/var`) and the
  // acp child looks approvals up under that resolved path. Keying by the
  // un-resolved temp path would miss, leaving the servers pending.
  const root = fs.realpathSync(workspaceCwd);
  fs.mkdirSync(path.dirname(approvalsPath), { recursive: true });
  fs.writeFileSync(approvalsPath, JSON.stringify({ [root]: project }, null, 2));
  return { QWEN_CODE_MCP_APPROVALS_PATH: approvalsPath };
}

/**
 * One-shot RSS read via `ps -o rss= -p <pid>`. Returns megabytes (rounded
 * to 1 decimal). Returns NaN if the process is gone or `ps` errored — call
 * sites should treat NaN as "skip this sample" rather than fail loudly.
 */
export function getRssMB(pid: number): number {
  const psOpts: ExecFileSyncOptionsWithStringEncoding = {
    encoding: 'utf8',
    timeout: 2_000,
    stdio: ['ignore', 'pipe', 'ignore'],
  };
  try {
    const out = execFileSync('ps', ['-o', 'rss=', '-p', String(pid)], psOpts);
    const kb = parseInt(out.trim(), 10);
    if (!Number.isFinite(kb) || kb <= 0) return NaN;
    return Math.round((kb / 1024) * 10) / 10;
  } catch {
    return NaN;
  }
}

export interface RssSample {
  tMs: number;
  rssMB: number;
}

export interface RssPoller {
  samples: RssSample[];
  droppedSamples: number;
  stop(): void;
}

export function startRssPolling(pid: number, intervalMs = 100): RssPoller {
  const startedAt = Date.now();
  const samples: RssSample[] = [];
  let droppedSamples = 0;
  const tick = () => {
    const rssMB = getRssMB(pid);
    if (!Number.isNaN(rssMB)) {
      samples.push({ tMs: Date.now() - startedAt, rssMB });
    } else {
      droppedSamples++;
    }
  };
  // Capture an immediate sample so a short window still has data.
  tick();
  const handle = setInterval(tick, intervalMs);
  // unref so the test process can exit without waiting for the timer.
  handle.unref?.();
  return {
    samples,
    get droppedSamples() {
      return droppedSamples;
    },
    stop: () => clearInterval(handle),
  };
}

/**
 * Walk daemon → ACP child → MCP descendants via `pgrep -P` calls.
 * Pattern starts with the existing inline approach at
 * `qwen-serve-streaming.test.ts:144`. When `pgrepOpts.mcpFilter` is
 * supplied, matching MCP processes are searched recursively within each
 * ACP child subtree because the ACP transport can introduce an extra
 * `qwen --acp` process between the daemon-facing ACP child and stdio MCP
 * servers.
 *
 * `pgrepOpts.acpFilter` defaults to `'qwen.*--acp'` (matches the spawned
 * `qwen --acp` child); pass an override only if a future bridge changes
 * the ACP child invocation shape.
 *
 * Returns explicit PID arrays so callers can cross-check (e.g., assert
 * the ACP child PID matches what the test setup observed). `total` is
 * the sum.
 */
export interface DescendantCount {
  acpChildren: number[];
  mcpGrandchildren: number[];
  total: number;
}

export function countDescendants(
  daemonPid: number,
  pgrepOpts: { acpFilter?: string; mcpFilter?: string } = {},
): DescendantCount {
  const acpFilter = pgrepOpts.acpFilter ?? 'qwen.*--acp';
  const acpChildren = pgrepChildren(daemonPid, acpFilter);
  const mcpGrandchildren: number[] = [];
  for (const acpPid of acpChildren) {
    if (pgrepOpts.mcpFilter) {
      mcpGrandchildren.push(
        ...pgrepMatchingDescendants(
          acpPid,
          pgrepOpts.mcpFilter,
          MATCHED_DESCENDANT_DEPTH,
        ),
      );
    } else {
      mcpGrandchildren.push(...pgrepChildren(acpPid));
    }
  }
  return {
    acpChildren,
    mcpGrandchildren,
    total: acpChildren.length + mcpGrandchildren.length,
  };
}

function pgrepChildren(parentPid: number, fullCmdFilter?: string): number[] {
  const args = ['-P', String(parentPid)];
  if (fullCmdFilter) {
    args.unshift('-f');
    args.push(fullCmdFilter);
  }
  try {
    const out = execFileSync('pgrep', args, {
      encoding: 'utf8',
      timeout: 2_000,
      stdio: ['ignore', 'pipe', 'ignore'],
    });
    return out
      .trim()
      .split('\n')
      .filter(Boolean)
      .map((line) => parseInt(line, 10))
      .filter((n) => Number.isFinite(n) && n > 0);
  } catch (err) {
    const error = err as NodeJS.ErrnoException & {
      status?: number;
      signal?: NodeJS.Signals | string | null;
    };
    // pgrep returns non-zero when no processes match; that's a normal
    // "0 children" outcome, not an error.
    if (error.status === 1) {
      return [];
    }
    if (error.code === 'ENOENT') {
      throw new Error('pgrep is required for daemon descendant counting');
    }
    if (error.signal === 'SIGTERM') {
      throw new Error(`pgrep timed out while listing children of ${parentPid}`);
    }
    const detail =
      error instanceof Error && error.message ? `: ${error.message}` : '';
    throw new Error(
      `pgrep failed while listing children of ${parentPid}${detail}`,
    );
  }
}

function pgrepMatchingDescendants(
  parentPid: number,
  fullCmdFilter: string,
  maxDepth: number,
): number[] {
  const matches = new Set<number>();
  const visit = (pid: number, depth: number) => {
    if (depth <= 0) return;
    for (const match of pgrepChildren(pid, fullCmdFilter)) {
      matches.add(match);
    }
    for (const child of pgrepChildren(pid)) {
      visit(child, depth - 1);
    }
  };
  visit(parentPid, maxDepth);
  return [...matches];
}

/**
 * Compute p50 / p90 / p99 / mean / min / max from a numeric array. Uses
 * nearest-rank percentile (no interpolation) to keep behavior predictable
 * across small sample sizes. Returns all-NaN for an empty input rather
 * than throwing — callers handle the "no samples" case downstream.
 */
export interface Percentiles {
  count: number;
  p50: number;
  p90: number;
  p99: number;
  mean: number;
  min: number;
  max: number;
}

export function percentiles(values: number[]): Percentiles {
  if (values.length === 0) {
    return {
      count: 0,
      p50: NaN,
      p90: NaN,
      p99: NaN,
      mean: NaN,
      min: NaN,
      max: NaN,
    };
  }
  const sorted = [...values].sort((a, b) => a - b);
  const n = sorted.length;
  const pick = (p: number) =>
    sorted[Math.min(n - 1, Math.ceil((p / 100) * n) - 1)];
  const sum = sorted.reduce((acc, v) => acc + v, 0);
  return {
    count: n,
    p50: pick(50),
    p90: pick(90),
    p99: pick(99),
    mean: sum / n,
    min: sorted[0],
    max: sorted[n - 1],
  };
}

/**
 * Drive an SSE subscription at a configurable consumption rate. Returns
 * total events received, whether `client_evicted` fired (and the event
 * id when it did), plus elapsed time. `consumerDelayMs` introduces a
 * sleep between each consumed event so the test can simulate a slow
 * client and observe ring-buffer / per-subscriber-queue eviction.
 *
 * Callers that only want the live event stream should pass
 * `consumerDelayMs: 0`. Callers that want a fixed-window probe (e.g. to
 * verify the heartbeat fires on idle) can set `timeoutMs` and a small
 * `maxEvents` cap.
 */
export interface ConsumeSseResult {
  received: number;
  /** The last non-undefined `ev.id` observed (for `Last-Event-ID` reconnect). */
  lastSeenId?: number;
  evictedAt?: number;
  evictionReason?: string;
  elapsedMs: number;
}

export async function consumeSseEvents(
  client: DaemonClient,
  sessionId: string,
  opts: {
    maxEvents?: number;
    consumerDelayMs?: number;
    timeoutMs?: number;
    subscribe?: SubscribeOptions;
  } = {},
): Promise<ConsumeSseResult> {
  const maxEvents = opts.maxEvents ?? Number.POSITIVE_INFINITY;
  const consumerDelayMs = opts.consumerDelayMs ?? 0;
  const timeoutMs = opts.timeoutMs ?? 30_000;
  const startedAt = Date.now();
  let received = 0;
  let lastSeenId: number | undefined;
  let evictedAt: number | undefined;
  let evictionReason: string | undefined;

  const ac = new AbortController();
  const timer = setTimeout(() => ac.abort(), timeoutMs);
  timer.unref?.();
  // Fold caller signal in if provided.
  const callerSignal = opts.subscribe?.signal;
  if (callerSignal) {
    callerSignal.addEventListener('abort', () => ac.abort(), { once: true });
  }

  try {
    for await (const ev of client.subscribeEvents(sessionId, {
      ...opts.subscribe,
      signal: ac.signal,
    })) {
      received++;
      if (ev.id !== undefined) lastSeenId = ev.id;
      if (ev.type === 'client_evicted') {
        evictedAt = ev.id;
        const data = ev.data as { reason?: string } | undefined;
        evictionReason = data?.reason;
        break;
      }
      if (received >= maxEvents) break;
      if (consumerDelayMs > 0) {
        await sleep(consumerDelayMs);
      }
    }
  } catch (err) {
    // Aborted on purpose (timeout or caller) — fall through and return
    // what we collected. Re-throw anything else.
    if (
      !(err instanceof Error) ||
      (err.name !== 'AbortError' && !/abort/i.test(err.message))
    ) {
      throw err;
    }
  } finally {
    clearTimeout(timer);
  }

  return {
    received,
    lastSeenId,
    evictedAt,
    evictionReason,
    elapsedMs: Date.now() - startedAt,
  };
}

export function sleep(ms: number): Promise<void> {
  return new Promise((r) => setTimeout(r, ms));
}

export function gitHead(timeoutMs = 5_000): string | null {
  try {
    return execFileSync('git', ['rev-parse', 'HEAD'], {
      encoding: 'utf8',
      timeout: timeoutMs,
      stdio: ['ignore', 'pipe', 'ignore'],
    }).trim();
  } catch {
    return null;
  }
}

export function makeTempWorkspace(label: string, prefix = 'qwen-test'): string {
  return fs.mkdtempSync(path.join(os.tmpdir(), `${prefix}-${label}-`));
}

export interface ScenarioResult {
  name: string;
  status: 'passed' | 'failed' | 'skipped';
  durationMs: number;
  error?: string;
  metrics?: Record<string, unknown>;
}