/**
 * browserPool.ts — Shared stealth browser pool for web-cookie providers.
 *
 * The DuckDuckGo VQD challenge and Claude web's Cloudflare Turnstile both
 * validate values that only a real browser can produce (DOM layout
 * measurements like offsetWidth/Height, getBoundingClientRect,
 * getComputedStyle, iframe contentWindow probes). Plain Node fetch + a
 * VM-stubs solver structurally runs the JS but cannot match those values,
 * so the server rejects the request.
 *
 * This pool keeps one Chromium instance warm and serves "browser contexts"
 * (one per provider) on demand. Each context owns one or more pages; the
 * caller is expected to be polite (one page per request, close on done).
 *
 * The pool prefers `cloakbrowser` (npm) when available — its binary-level
 * fingerprint patches (--fingerprint-timezone, --fingerprint-locale, and
 * dozens more) are the only thing that gets past DuckDuckGo's anti-bot
 * in this environment. Falls back to plain `playwright` if cloakbrowser
 * is not installed; the fallback works for Claude web (which only needs
 * valid cookies) but not for DDG's VQD challenge.
 *
 * Opt-in: pool only launches Chromium when an executor explicitly asks
 * for a context, so users who never use the browser-backed path pay zero
 * startup cost. Set OMNIROUTE_BROWSER_POOL=off to fully disable.
 */

import { Buffer } from "node:buffer";

type Browser = import("playwright").Browser;
type BrowserContext = import("playwright").BrowserContext;
type Page = import("playwright").Page;

export interface BrowserPoolContextOptions {
  cookieDomain: string;
  cookieString?: string | null;
  warmupUrl?: string | null;
  userAgent?: string;
  locale?: string;
  timezone?: string;
  preferCloakbrowser?: boolean;
}

export interface PooledContext {
  id: string;
  context: BrowserContext;
  warmupPage: Page | null;
  lastUsed: number;
  isStealth: boolean;
}

// #3368 PR7 — lightweight, cumulative browser-pool telemetry. Counters are
// incremented at lifecycle points and surfaced via getBrowserPoolMetrics()
// (and the omniroute_browser_pool_status MCP tool), giving the previously
// caller-less getBrowserPoolStatus() an observability home.
export interface BrowserPoolMetrics {
  browserLaunches: number;
  browserLaunchFailures: number;
  contextsCreated: number;
  contextsReused: number;
  contextsEvicted: number;
  contextsReleased: number;
  contextCreateFailures: number;
  shutdowns: number;
  lastShutdownReason: string | null;
}

function createBrowserPoolMetrics(): BrowserPoolMetrics {
  return {
    browserLaunches: 0,
    browserLaunchFailures: 0,
    contextsCreated: 0,
    contextsReused: 0,
    contextsEvicted: 0,
    contextsReleased: 0,
    contextCreateFailures: 0,
    shutdowns: 0,
    lastShutdownReason: null,
  };
}

interface PoolState {
  browser: Browser | null;
  contexts: Map<string, PooledContext>;
  pendingContexts: Map<string, Promise<PooledContext>>;
  launching: Promise<Browser> | null;
  lastActivity: number;
  idleTimer: NodeJS.Timeout | null;
  evictTimer: NodeJS.Timeout | null;
  cloakLaunch: ((opts: unknown) => Promise<Browser>) | null;
  cloakLaunchResolved: boolean;
  metrics: BrowserPoolMetrics;
}

const POOL_IDLE_TIMEOUT_MS = 5 * 60 * 1000;
const CONTEXT_TTL_MS = 10 * 60 * 1000; // 10 min — evict stale contexts
const EVICT_INTERVAL_MS = 60 * 1000; // check every 60s
const DEFAULT_USER_AGENT =
  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36";

const state: PoolState = {
  browser: null,
  contexts: new Map(),
  pendingContexts: new Map(),
  launching: null,
  lastActivity: 0,
  idleTimer: null,
  evictTimer: null,
  cloakLaunch: null,
  cloakLaunchResolved: false,
  metrics: createBrowserPoolMetrics(),
};

function getCloakbrowserModuleId(): string {
  // Keep this computed: cloakbrowser is an optional runtime enhancer, and a literal
  // dynamic import with the package name makes Turbopack resolve it during route compilation.
  return ["cloak", "browser"].join("");
}

async function resolveCloakLaunch(): Promise<((opts: unknown) => Promise<Browser>) | null> {
  if (state.cloakLaunchResolved) return state.cloakLaunch;
  state.cloakLaunchResolved = true;
  try {
    const mod = (await import(getCloakbrowserModuleId())) as unknown as {
      launch?: (opts: unknown) => Promise<Browser>;
    };
    state.cloakLaunch = mod.launch ?? null;
  } catch {
    state.cloakLaunch = null;
  }
  return state.cloakLaunch;
}

function isPoolEnabled(): boolean {
  const flag = process.env.OMNIROUTE_BROWSER_POOL;
  if (flag === undefined) return true;
  return flag !== "off" && flag !== "0" && flag !== "false";
}

function resetIdleTimer(): void {
  if (state.idleTimer) clearTimeout(state.idleTimer);
  state.idleTimer = setTimeout(() => {
    void shutdownPool("idle-timeout");
  }, POOL_IDLE_TIMEOUT_MS);
  state.idleTimer.unref?.();
}

function evictStaleContexts(): void {
  const now = Date.now();
  for (const [key, pooled] of state.contexts) {
    if (now - pooled.lastUsed > CONTEXT_TTL_MS) {
      console.log(
        "[BrowserPool] Evicted stale context:",
        key,
        "(idle",
        ((now - pooled.lastUsed) / 1000).toFixed(0) + "s)"
      );
      state.contexts.delete(key);
      state.metrics.contextsEvicted++;
      pooled.context.close().catch(() => {});
    }
  }
  if (state.contexts.size === 0 && !state.launching) {
    void shutdownPool("all-contexts-evicted");
  }
}

function startEvictTimer(): void {
  if (state.evictTimer) clearInterval(state.evictTimer);
  state.evictTimer = setInterval(() => evictStaleContexts(), EVICT_INTERVAL_MS);
  state.evictTimer.unref?.();
}

interface ProxyRecord {
  type?: string;
  host: string;
  port: number;
  username?: string | null;
  password?: string | null;
}

interface ResolvePlaywrightProxyDeps {
  resolveProxy?: (providerId: string) => Promise<ProxyRecord | null | undefined>;
}

// Exported for tests (deps injection avoids mock.module()).
export async function resolvePlaywrightProxy(
  providerKey: string,
  deps?: ResolvePlaywrightProxyDeps
): Promise<import("playwright").LaunchOptions["proxy"] | undefined> {
  try {
    const resolver =
      deps?.resolveProxy ??
      (async (id: string) => {
        const { resolveProxyForProvider } = await import("../../src/lib/db/proxies");
        return resolveProxyForProvider(id);
      });
    const p = await resolver(providerKey);
    if (!p?.host) return undefined;
    const scheme = p.type === "socks5" ? "socks5" : "http";
    // Build explicitly instead of a conditional object spread: the spread form
    // widens username/password to `{}` under the LaunchOptions["proxy"] type,
    // tripping typecheck once browserPool.ts is pulled into typecheck-core scope.
    const proxy: NonNullable<import("playwright").LaunchOptions["proxy"]> = {
      server: `${scheme}://${p.host}:${p.port}`,
    };
    if (p.username) {
      proxy.username = String(p.username);
      proxy.password = p.password == null ? "" : String(p.password);
    }
    return proxy;
  } catch (err) {
    console.warn("[BrowserPool] Failed to resolve proxy from DB:", err);
    return undefined;
  }
}

async function launchBrowser(): Promise<Browser> {
  if (state.browser) return state.browser;
  if (state.launching) return state.launching;
  state.launching = (async () => {
    const cloakLaunch = await resolveCloakLaunch();
    let browser: Browser;
    if (cloakLaunch) {
      browser = await cloakLaunch({
        headless: true,
        args: ["--no-sandbox", "--disable-dev-shm-usage"],
      });
    } else {
      // Fallback: plain Playwright. Works for Claude web (cookie-only
      // auth) but DDG's VQD challenge will detect this Chromium build.
      const { chromium } = await import("playwright");
      browser = await chromium.launch({
        headless: true,
        args: [
          "--no-sandbox",
          "--disable-dev-shm-usage",
          "--disable-blink-features=AutomationControlled",
        ],
      });
    }
    state.browser = browser;
    state.launching = null;
    state.metrics.browserLaunches++;
    return browser;
  })();
  try {
    return await state.launching;
  } catch (err) {
    state.launching = null;
    state.metrics.browserLaunchFailures++;
    throw err;
  }
}

function parseCookieString(
  raw: string,
  domain: string
): Array<{
  name: string;
  value: string;
  domain: string;
  path: string;
  expires: number;
  httpOnly: boolean;
  secure: boolean;
  sameSite: "Lax" | "Strict" | "None";
}> {
  return raw
    .split(";")
    .map((p) => p.trim())
    .filter(Boolean)
    .map((pair) => {
      const eq = pair.indexOf("=");
      if (eq < 0) return null;
      const name = pair.slice(0, eq).trim();
      const value = pair.slice(eq + 1).trim();
      if (!name || !value) return null;
      return {
        name,
        value,
        domain: domain.startsWith(".") ? domain : `.${domain}`,
        path: "/",
        expires: -1,
        httpOnly: false,
        secure: true,
        sameSite: "Lax" as const,
      };
    })
    .filter(Boolean) as Array<{
    name: string;
    value: string;
    domain: string;
    path: string;
    expires: number;
    httpOnly: boolean;
    secure: boolean;
    sameSite: "Lax" | "Strict" | "None";
  }>;
}

// Clear a key from the pending-creation map once its promise settles, counting
// failures. Kept as a leaf helper so acquireBrowserContext stays under the
// function-length ceiling (#3368 PR7 metrics).
function settlePendingContext(key: string, failed: boolean): void {
  if (failed) state.metrics.contextCreateFailures++;
  state.pendingContexts.delete(key);
}

export async function acquireBrowserContext(
  key: string,
  options: BrowserPoolContextOptions
): Promise<PooledContext> {
  if (!isPoolEnabled()) {
    throw new Error(
      "browserPool: OMNIROUTE_BROWSER_POOL=off — context requested but pool is disabled"
    );
  }
  const existing = state.contexts.get(key);
  if (existing) {
    existing.lastUsed = Date.now();
    state.lastActivity = Date.now();
    state.metrics.contextsReused++;
    resetIdleTimer();
    return existing;
  }

  // Dedup concurrent creations for the same key
  const pending = state.pendingContexts.get(key);
  if (pending) return pending;

  const createPromise = (async (): Promise<PooledContext> => {
    const [browser, proxy] = await Promise.all([launchBrowser(), resolvePlaywrightProxy(key)]);
    const isStealth = state.cloakLaunch !== null;
    const context = await browser.newContext({
      userAgent: options.userAgent || DEFAULT_USER_AGENT,
      locale: options.locale || "en-US",
      timezoneId: options.timezone || "America/New_York",
      viewport: { width: 1280, height: 800 },
      ...(proxy ? { proxy } : {}),
    });

    if (options.cookieString) {
      const cookies = parseCookieString(options.cookieString, options.cookieDomain);
      if (cookies.length > 0) {
        await context.addCookies(cookies);
      }
    }

    let warmupPage: Page | null = null;
    if (options.warmupUrl) {
      try {
        warmupPage = await context.newPage();
        await warmupPage.goto(options.warmupUrl, {
          waitUntil: "domcontentloaded",
          timeout: 30000,
        });
        // Give the warmup a moment for the upstream's status/auth/country
        // JSON endpoints to fire. Without this, the first chat request would
        // pay the warmup cost on the hot path.
        await new Promise((r) => setTimeout(r, 1500));
      } catch (err) {
        try {
          await warmupPage?.close();
        } catch {
          /* ignore */
        }
        warmupPage = null;
        void err;
      }
    }

    // Guard: if shutdownPool() ran while we were creating this context,
    // the browser we obtained is now closed. Close our temp context and
    // throw so the caller knows to retry.
    if (state.browser !== browser) {
      await context.close().catch(() => {});
      if (warmupPage) {
        await warmupPage.close().catch(() => {});
      }
      throw new Error("Pool shut down during context creation");
    }

    const pooled: PooledContext = {
      id: key,
      context,
      warmupPage,
      lastUsed: Date.now(),
      isStealth,
    };
    state.contexts.set(key, pooled);
    state.metrics.contextsCreated++;
    state.lastActivity = Date.now();
    resetIdleTimer();
    startEvictTimer();
    return pooled;
  })();

  state.pendingContexts.set(key, createPromise);
  createPromise
    .then(() => settlePendingContext(key, false))
    .catch(() => settlePendingContext(key, true));

  return createPromise;
}

export async function openPage(pooled: PooledContext): Promise<Page> {
  return pooled.context.newPage();
}

export async function releaseBrowserContext(key: string): Promise<void> {
  const pooled = state.contexts.get(key);
  if (!pooled) return;
  state.contexts.delete(key);
  state.metrics.contextsReleased++;
  try {
    await pooled.context.close();
  } catch {
    /* ignore */
  }
  if (state.contexts.size === 0) {
    await shutdownPool("last-context-closed");
  }
}

export async function shutdownPool(reason: string): Promise<void> {
  state.metrics.shutdowns++;
  state.metrics.lastShutdownReason = reason;
  if (state.idleTimer) {
    clearTimeout(state.idleTimer);
    state.idleTimer = null;
  }
  if (state.evictTimer) {
    clearInterval(state.evictTimer);
    state.evictTimer = null;
  }
  state.pendingContexts.clear();
  for (const [key, pooled] of state.contexts) {
    try {
      await pooled.context.close();
    } catch {
      /* ignore */
    }
    state.contexts.delete(key);
  }
  if (state.browser) {
    try {
      await state.browser.close();
    } catch {
      /* ignore */
    }
    state.browser = null;
  }
  state.lastActivity = Date.now();
  // Avoid unused-parameter lint: log reason via debug if anyone hooks
  // process.on('exit') and prints state.
  void reason;
}

export function getBrowserPoolStatus(): {
  enabled: boolean;
  contexts: number;
  browserRunning: boolean;
  stealthAvailable: boolean;
  lastActivityAgoMs: number;
} {
  return {
    enabled: isPoolEnabled(),
    contexts: state.contexts.size,
    browserRunning: state.browser !== null,
    stealthAvailable: state.cloakLaunch !== null,
    lastActivityAgoMs: state.lastActivity === 0 ? -1 : Date.now() - state.lastActivity,
  };
}

/**
 * #3368 PR7 — browser-pool observability. Returns live status plus cumulative
 * lifecycle telemetry (launches, context create/reuse/evict/release counts,
 * failures, shutdowns). Surfaced via the omniroute_browser_pool_status MCP tool.
 */
export function getBrowserPoolMetrics(): {
  status: ReturnType<typeof getBrowserPoolStatus>;
  metrics: BrowserPoolMetrics;
} {
  return { status: getBrowserPoolStatus(), metrics: { ...state.metrics } };
}

/** Test-only: reset cumulative metrics so assertions start from a clean slate. */
export function __resetBrowserPoolMetricsForTest(): void {
  state.metrics = createBrowserPoolMetrics();
}

export async function readPageResponseBody(
  response: import("playwright").Response
): Promise<{ status: number; headers: Record<string, string>; body: Buffer }> {
  const headers: Record<string, string> = {};
  for (const [name, value] of Object.entries(response.headers())) {
    headers[name] = value;
  }
  const body = await response.body();
  return { status: response.status(), headers, body: Buffer.from(body) };
}