import { useCallback, useEffect, useMemo, useRef, useState, type ReactNode } from "react";
import { ApiError, errorCode, onApiError } from "../api/client";
import { authApi, departmentsApi } from "./api";
import { AuthCtx, type AuthState, type AuthStatus } from "./context";
import { roleLabel as labelFor } from "./roles";
import type { Department, Factor, Me } from "./types";
import { useEvents } from "./useEvents";

/** The old build's screen lock. The server locks at SESSION_LOCK_MINUTES too; it is the authority. */
export const IDLE_LOCK_MS = 3 * 60_000;
/** A tab hidden for longer than this comes back locked (the old build's rule). */
export const HIDDEN_LOCK_MS = 60_000;
const IDLE_CHECK_MS = 15_000;
const ACTIVITY_EVENTS = ["pointerdown", "keydown", "wheel", "touchstart"] as const;

/** 401 codes that mean this browser's session is gone. Other 401s (a wrong unlock PIN) are not. */
const SESSION_GONE = new Set(["no_session", "session_expired", "session_ended"]);

function goneNotice(err: ApiError): string {
  const code = errorCode(err);
  if (code === "no_session") return "Your session ended. Sign in again.";
  return err.message || "Your session ended. Sign in again.";
}

interface AuthProviderProps {
  children: ReactNode;
  /** Idle time before the local lock. Tests pass a small value. */
  idleLockMs?: number;
  /** How often the idle timer checks. */
  idleCheckMs?: number;
  /** Hidden time after which the tab comes back locked. Tests pass a small value. */
  hiddenLockMs?: number;
}

export function AuthProvider({ children, idleLockMs = IDLE_LOCK_MS, idleCheckMs = IDLE_CHECK_MS, hiddenLockMs = HIDDEN_LOCK_MS }: AuthProviderProps) {
  const [status, setStatusState] = useState<AuthStatus>("loading");
  const [me, setMeState] = useState<Me | null>(null);
  const [departments, setDepartments] = useState<Department[]>([]);
  const [notice, setNotice] = useState<string | null>(null);
  const statusRef = useRef<AuthStatus>("loading");
  const lastActivity = useRef(Date.now());
  const deptsFor = useRef<string | null>(null);

  const setStatus = useCallback((s: AuthStatus) => {
    statusRef.current = s;
    setStatusState(s);
  }, []);

  const accept = useCallback(
    (m: Me) => {
      setMeState(m);
      setNotice(null);
      lastActivity.current = Date.now();
      setStatus(m.session.locked ? "locked" : "ready");
    },
    [setStatus],
  );

  const endSession = useCallback(
    (msg: string | null) => {
      setMeState(null);
      setDepartments([]);
      deptsFor.current = null;
      setNotice(msg);
      setStatus("anonymous");
    },
    [setStatus],
  );

  const refresh = useCallback(async () => {
    try {
      accept(await authApi.me());
    } catch (err) {
      if (err instanceof ApiError && err.status === 423) setStatus("locked");
      else if (err instanceof ApiError && err.status === 401) endSession(null);
      else endSession(err instanceof Error ? err.message : "Could not reach the server.");
    }
  }, [accept, endSession, setStatus]);

  useEffect(() => {
    void refresh();
  }, [refresh]);

  // 401 and 423 from any call, not only the auth calls.
  useEffect(
    () =>
      onApiError((err, path) => {
        if (path.startsWith("/api/auth/signin")) return;
        const st = statusRef.current;
        if (st === "loading" || st === "anonymous") return;
        if (err.status === 423) {
          setStatus("locked");
        } else if (err.status === 401 && SESSION_GONE.has(errorCode(err) ?? "")) {
          endSession(goneNotice(err));
        }
      }),
    [endSession, setStatus],
  );

  // Department names for the role labels, once per signed-in user.
  const userId = me?.user.id ?? null;
  useEffect(() => {
    if (status !== "ready" || !userId || deptsFor.current === userId) return;
    deptsFor.current = userId;
    departmentsApi
      .list()
      .then((d) => setDepartments(Array.isArray(d) ? d : []))
      .catch(() => {
        deptsFor.current = null;
      });
  }, [status, userId]);

  const signInPassword = useCallback(
    async (login: string, password: string) => {
      const m = await authApi.signInPassword(login, password);
      accept(m);
      return m;
    },
    [accept],
  );

  const signInPin = useCallback(
    async (empNo: string, pin: string) => {
      const m = await authApi.signInPin(empNo, pin);
      accept(m);
      return m;
    },
    [accept],
  );

  const signOut = useCallback(async () => {
    try {
      await authApi.signOut();
    } catch {
      // The cookie may already be gone. Signing out locally is what matters here.
    }
    endSession(null);
  }, [endSession]);

  const unlock = useCallback(
    async (factor: Factor, secret: string) => {
      const m = await authApi.unlock(factor, secret);
      accept({ ...m, session: { ...m.session, locked: false } });
      return m;
    },
    [accept],
  );

  const lock = useCallback(async () => {
    if (statusRef.current !== "ready") return;
    setStatus("locked");
    try {
      await authApi.lock();
    } catch {
      // A 401 here signs out through the listener. Otherwise the local lock stands.
    }
  }, [setStatus]);

  // Hidden is reported, never locked at once: a reload or navigation fires hidden on the old page.
  // Coming back is reported, then Me decides. Hidden longer than hiddenLockMs locks locally right away.
  const hiddenAt = useRef<number | null>(null);
  useEffect(() => {
    const onVisibility = () => {
      const st = statusRef.current;
      if (st !== "ready" && st !== "locked") return;
      if (document.hidden) {
        hiddenAt.current = Date.now();
        authApi.visibility(true).catch(() => undefined);
        return;
      }
      const since = hiddenAt.current;
      hiddenAt.current = null;
      if (since !== null && Date.now() - since > hiddenLockMs && st === "ready") setStatus("locked");
      authApi
        .visibility(false)
        .catch(() => undefined)
        .then(() => refresh());
    };
    document.addEventListener("visibilitychange", onVisibility);
    return () => document.removeEventListener("visibilitychange", onVisibility);
  }, [setStatus, refresh, hiddenLockMs]);

  // Local idle lock.
  useEffect(() => {
    const bump = () => {
      lastActivity.current = Date.now();
    };
    for (const ev of ACTIVITY_EVENTS) document.addEventListener(ev, bump, { capture: true, passive: true });
    return () => {
      for (const ev of ACTIVITY_EVENTS) document.removeEventListener(ev, bump, { capture: true });
    };
  }, []);

  useEffect(() => {
    if (status !== "ready") return;
    lastActivity.current = Date.now();
    const id = window.setInterval(() => {
      if (Date.now() - lastActivity.current >= idleLockMs) void lock();
    }, idleCheckMs);
    return () => window.clearInterval(id);
  }, [status, idleLockMs, idleCheckMs, lock]);

  const sessionId = status === "ready" || status === "locked" ? (me?.session.id ?? null) : null;
  const presence = useEvents(sessionId, {
    onRevoked: () => endSession("This session was signed out from another place."),
  });

  const roleLabel = useCallback((role: string) => labelFor(role, departments), [departments]);

  const value = useMemo<AuthState>(
    () => ({
      status,
      me,
      departments,
      notice,
      presence,
      refresh,
      signInPassword,
      signInPin,
      signOut,
      endSession,
      unlock,
      lock,
      setMe: setMeState,
      roleLabel,
    }),
    [status, me, departments, notice, presence, refresh, signInPassword, signInPin, signOut, endSession, unlock, lock, roleLabel],
  );

  return <AuthCtx.Provider value={value}>{children}</AuthCtx.Provider>;
}