import { eq, and, lt } from "drizzle-orm";
import { rm } from "node:fs/promises";
import { join } from "node:path";
import { whatsappAccounts } from "@cmbot/db";
import { db } from "../db.js";
import { env } from "../env.js";
import { logger } from "../logger.js";
import { sessionManager } from "../whatsapp/session-manager.js";
import { renderQrPng } from "../whatsapp/qr-renderer.js";
import { syncGroupsForAccount } from "../whatsapp/group-sync.js";
import { writeAuditLog } from "../audit.js";
import { pgNotifyWeb } from "./notify.js";
import { decidePairListenerOnClose } from "./pair-state.js";

const PAIR_TIMEOUT_MS = 5 * 60 * 1000;
const offByAccount = new Map<string, () => void>();
const lastQrPayload = new Map<string, string>();
const pairTimeouts = new Map<string, NodeJS.Timeout>();
// "Warming" set: while present, the just-attached listener will ignore
// close events. Cleared the moment a qr/open arrives. This prevents the
// old session's close (broadcast asynchronously by sessionManager after
// our await sessionManager.stop() returns) from being mis-read as the
// NEW session timing out — which manifested as: get QR → go back →
// click Pair again → instantly see "Pairing timed out".
const pairingWarmingUp = new Set<string>();

async function abandonPair(accountId: string): Promise<{ existed: boolean; label: string | null }> {
  const account = await db.query.whatsappAccounts.findFirst({
    where: (a, { eq }) => eq(a.id, accountId),
  });
  if (!account || account.status !== "pending") {
    return { existed: false, label: account?.label ?? null };
  }
  const off = offByAccount.get(accountId);
  if (off) {
    off();
    offByAccount.delete(accountId);
  }
  const t = pairTimeouts.get(accountId);
  if (t) {
    clearTimeout(t);
    pairTimeouts.delete(accountId);
  }
  lastQrPayload.delete(accountId);
  pairingWarmingUp.delete(accountId);
  if (sessionManager.hasSession(accountId)) {
    await sessionManager.stop(accountId);
  }
  // Throw away the partial Baileys session files so the next pair
  // attempt starts clean — but KEEP the account row so the operator
  // sees it on the list with a "Re-pair" affordance.
  await rm(join(env.SESSIONS_DIR, accountId), { recursive: true, force: true });
  await db
    .update(whatsappAccounts)
    .set({ status: "unpaired", lastQrPng: null })
    .where(eq(whatsappAccounts.id, accountId));
  return { existed: true, label: account.label };
}

export async function handleStartPairing(accountId: string): Promise<void> {
  const account = await db.query.whatsappAccounts.findFirst({
    where: (a, { eq }) => eq(a.id, accountId),
  });
  if (!account) {
    logger.warn({ accountId }, "pair: account row missing");
    return;
  }

  // Detach any listener still subscribed from a prior pairing attempt for
  // this account. Without this, repeated Re-pair clicks accumulate
  // listeners and each one writes a fresh QR to the DB on every Baileys
  // event — the UI then flashes through new QRs constantly.
  const prevOff = offByAccount.get(accountId);
  if (prevOff) {
    prevOff();
    offByAccount.delete(accountId);
  }

  // For Re-pair, an old session may still be alive. Stop it so
  // sessionManager.start() actually opens a fresh socket and Baileys emits
  // a new QR. (start() is a no-op when a session is already registered.)
  if (sessionManager.hasSession(accountId)) {
    await sessionManager.stop(accountId);
  }
  // Clear any stale QR lingering from a prior attempt.
  lastQrPayload.delete(accountId);
  await db
    .update(whatsappAccounts)
    .set({ lastQrPng: null })
    .where(eq(whatsappAccounts.id, accountId));

  // Mark the new attempt as warming up. Cleared by the first qr/open we
  // observe; while set, any close event is treated as the leaked tail of
  // the previous session being torn down (see comment near
  // `pairingWarmingUp` declaration).
  pairingWarmingUp.add(accountId);

  const off = sessionManager.on(async (id, _state, event) => {
    if (id !== accountId) return;
    try {
      if (event.type === "qr") {
        pairingWarmingUp.delete(id);
        // Dedupe by payload — Baileys can re-emit the same QR string in a
        // burst. Different strings (a fresh QR) always pass through, so
        // the user gets a new QR as soon as Baileys generates one.
        if (lastQrPayload.get(id) === event.payload) return;
        lastQrPayload.set(id, event.payload);
        const png = await renderQrPng(event.payload);
        // PNG is too large (~5-10KB) for pg_notify (8000 byte limit).
        // Persist on the account row; web fetches via /api/qr/[id].
        await db
          .update(whatsappAccounts)
          .set({ lastQrPng: png.toString("base64"), lastQrAt: new Date() })
          .where(eq(whatsappAccounts.id, id));
        await pgNotifyWeb({
          type: "session.qr",
          accountId: id,
          ts: Date.now(),
        });
      } else if (event.type === "open") {
        pairingWarmingUp.delete(id);
        const t = pairTimeouts.get(id);
        if (t) {
          clearTimeout(t);
          pairTimeouts.delete(id);
        }
        lastQrPayload.delete(id);
        offByAccount.delete(id);
        const session = sessionManager.getSession(id);
        let synced = 0;
        if (session) {
          const r = await syncGroupsForAccount(id, session.socket);
          synced = r.synced;
        }
        await writeAuditLog(db, {
          operatorId: account.operatorId,
          source: "web",
          action: "account.paired",
          targetType: "whatsapp_account",
          targetId: id,
          payload: { label: account.label },
        });
        await pgNotifyWeb({
          type: "session.connected",
          accountId: id,
          phoneNumber: event.phoneNumber ?? null,
        });
        await pgNotifyWeb({
          type: "groups.synced",
          accountId: id,
          count: synced,
        });
        off();
      } else if (event.type === "close") {
        const decision = decidePairListenerOnClose({
          warmingUp: pairingWarmingUp.has(id),
          restartRequired: event.restartRequired,
        });
        if (decision === "ignore-leaked-close") {
          logger.info(
            { accountId: id },
            "pair: ignoring close from previous attempt while warming up",
          );
          return;
        }
        if (decision === "post-pair-restart") {
          // After the user scans, WhatsApp tells Baileys to "restart"
          // the connection. The socket closes with status 515 and the
          // session-manager will reopen it with the new credentials —
          // the next `open` event finishes the pairing. Keep the
          // listener attached and don't surface a timeout to the UI.
          logger.info(
            { accountId: id },
            "pair: restart-required close (post-pair reconnect) — keeping listener alive",
          );
          return;
        }
        // decision === "treat-as-timeout": ephemeral close on a live
        // attempt. Park the row as `unpaired` and push session.timeout
        // so the operator sees the "Re-pair" affordance.
        const t = pairTimeouts.get(id);
        if (t) {
          clearTimeout(t);
          pairTimeouts.delete(id);
        }
        lastQrPayload.delete(id);
        offByAccount.delete(id);
        await db
          .update(whatsappAccounts)
          .set({ status: "unpaired", lastQrPng: null })
          .where(eq(whatsappAccounts.id, id));
        await pgNotifyWeb({ type: "session.timeout", accountId: id });
        off();
      }
    } catch (err) {
      logger.error({ err, accountId: id }, "pair: handler error");
    }
  });
  offByAccount.set(accountId, off);

  try {
    await sessionManager.start(accountId);
  } catch (err) {
    logger.error({ err, accountId }, "pair: start failed");
    off();
    offByAccount.delete(accountId);
    await pgNotifyWeb({ type: "session.timeout", accountId });
    return;
  }

  const timeoutId = setTimeout(() => {
    void (async () => {
      try {
        const r = await abandonPair(accountId);
        if (r.existed) {
          await pgNotifyWeb({ type: "session.timeout", accountId });
        }
      } catch (err) {
        logger.error({ err, accountId }, "pair: timeout cleanup failed");
      }
    })();
  }, PAIR_TIMEOUT_MS);
  pairTimeouts.set(accountId, timeoutId);
}

/**
 * Sweep stale `pending` accounts on bot startup. The bot was probably
 * restarted mid-pair (or the operator never finished scanning) — the
 * row is parked as `unpaired` so the operator sees it on the list and
 * can hit Re-pair, instead of silently disappearing.
 */
export async function sweepStalePendingAccounts(): Promise<void> {
  const cutoff = new Date(Date.now() - 60 * 60 * 1000);
  const stale = await db
    .select({ id: whatsappAccounts.id, label: whatsappAccounts.label })
    .from(whatsappAccounts)
    .where(and(eq(whatsappAccounts.status, "pending"), lt(whatsappAccounts.createdAt, cutoff)));
  for (const row of stale) {
    await rm(join(env.SESSIONS_DIR, row.id), { recursive: true, force: true });
    await db
      .update(whatsappAccounts)
      .set({ status: "unpaired", lastQrPng: null })
      .where(eq(whatsappAccounts.id, row.id));
    logger.info({ accountId: row.id, label: row.label }, "sweep: parked stale pending account as unpaired");
  }
}