import { mkdir } from "node:fs/promises";
import { join } from "node:path";
import {
  makeWASocket,
  useMultiFileAuthState,
  fetchLatestBaileysVersion,
  type WASocket,
  type ConnectionState,
  DisconnectReason,
  Browsers,
} from "@whiskeysockets/baileys";
import { logger } from "../logger.js";
import { env } from "../env.js";
import { syncGroupsForAccount } from "./group-sync.js";

export type SessionEvent =
  | { type: "qr"; payload: string }
  | { type: "open"; phoneNumber: string | undefined }
  // `restartRequired` is set when Baileys closes the socket with status
  // 515 — the normal post-pair handshake reconnect, NOT a failure. Both
  // pair-handler and session-manager use it to skip the "pairing failed"
  // path and re-open the socket so the account finishes linking.
  | { type: "close"; reason: number; loggedOut: boolean; restartRequired: boolean };

export type SessionEventHandler = (event: SessionEvent) => void | Promise<void>;

export type Session = {
  accountId: string;
  socket: WASocket;
  close: () => Promise<void>;
};

export async function startSession(params: {
  accountId: string;
  onEvent: SessionEventHandler;
}): Promise<Session> {
  const { accountId, onEvent } = params;
  const sessionDir = join(env.SESSIONS_DIR, accountId);
  await mkdir(sessionDir, { recursive: true });

  const { state, saveCreds } = await useMultiFileAuthState(sessionDir);

  // Fetch the WhatsApp Web version Baileys should announce. Without this,
  // the noise handshake fails because WA's server-side rejects stale versions.
  const { version, isLatest } = await fetchLatestBaileysVersion();
  logger.info({ accountId, version, isLatest }, "session: using WA Web version");

  const socket = makeWASocket({
    version,
    auth: state,
    browser: Browsers.macOS("Safari"),
    syncFullHistory: false,
    // Use Baileys' default QR cadence (60 s for the first ref, ~20 s for
    // each subsequent ref) — that's the native WhatsApp Web cadence and
    // each rotation just refreshes the displayed QR. The earlier "QR
    // refresh every 5 s" bug was the session-manager reconnect loop,
    // not the cadence.
    logger: logger.child({ accountId, component: "baileys" }) as never,
  });

  socket.ev.on("creds.update", () => void saveCreds());

  // Keep `whatsapp_groups` in sync as Baileys discovers new groups or updates.
  // Debounced so a flurry of upsert events from the initial sync collapses
  // into a single DB write.
  let groupsSyncTimer: NodeJS.Timeout | null = null;
  const scheduleGroupsSync = (): void => {
    if (groupsSyncTimer) return;
    groupsSyncTimer = setTimeout(() => {
      groupsSyncTimer = null;
      void syncGroupsForAccount(accountId, socket).catch((err) =>
        logger.warn({ err, accountId }, "auto group sync failed"),
      );
    }, 1500);
  };
  socket.ev.on("groups.upsert", scheduleGroupsSync);
  socket.ev.on("groups.update", scheduleGroupsSync);

  socket.ev.on("connection.update", (update: Partial<ConnectionState>) => {
    if (update.qr) {
      void onEvent({ type: "qr", payload: update.qr });
    }
    if (update.connection === "open") {
      const phoneNumber = socket.user?.id?.split(":")[0];
      void onEvent({ type: "open", phoneNumber });
    }
    if (update.connection === "close") {
      const reason =
        (update.lastDisconnect?.error as { output?: { statusCode?: number } } | undefined)?.output?.statusCode ?? 0;
      const loggedOut = reason === DisconnectReason.loggedOut;
      const restartRequired = reason === DisconnectReason.restartRequired;
      void onEvent({ type: "close", reason, loggedOut, restartRequired });
    }
  });

  return {
    accountId,
    socket,
    close: async () => {
      try {
        socket.end(undefined);
      } catch (err) {
        logger.warn({ err, accountId }, "session.close: error closing socket");
      }
    },
  };
}