"use client";

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useMemo,
  useState,
  type ReactNode,
} from "react";
import { ApiError, getAccessToken, isAbortError, migrateTokensToSharedCookies } from "@/lib/meshkee-api";
import {
  getAdminDashboardOrigin,
  getCustomerDashboardOrigin,
  hostAppFor,
  type HostApp,
} from "@/lib/host";
import {
  clearManagedBusinessId,
  getManagedBusinessId,
  setManagedBusinessId,
} from "@/lib/managed-business";
import {
  fetchCurrentUser,
  login as loginRequest,
  logout as logoutRequest,
  register as registerRequest,
  type RegisterPayload,
} from "@/services/auth";
import type { AuthUser, DashboardType } from "@/types/auth";

interface AuthContextValue {
  user: AuthUser | null;
  isLoading: boolean;
  activeBusinessId: string | null;
  isBusinessOwner: boolean;
  isSuperAdmin: boolean;
  login: (cellNumber: string, password: string) => Promise<DashboardType>;
  register: (payload: RegisterPayload) => Promise<DashboardType>;
  logout: () => void;
}

const AuthContext = createContext<AuthContextValue | null>(null);

export function pickActiveBusinessId(user: AuthUser): string | null {
  const owned = user.businesses.find((item) => item.isOwner);
  const first = owned ?? user.businesses[0];
  return first ? String(first.id) : null;
}

export function userCanAccessApp(user: AuthUser, app: HostApp): boolean {
  if (app === "admin") return user.dashboard === "super_admin";
  if (app === "customer") {
    // Shared entry: customer, business owners, and superadmins all land here first.
    return (
      user.dashboard === "customer" ||
      user.dashboard === "business" ||
      user.dashboard === "super_admin"
    );
  }
  // Business dashboard: owners/staff, or superadmin (via managed business id).
  if (user.dashboard === "super_admin") return true;
  return Boolean(pickActiveBusinessId(user));
}

function currentHost(): string {
  if (typeof window === "undefined") return "";
  return window.location.host;
}

/** Prefer ?businessId= on the URL, then stored managed id. */
function syncManagedBusinessFromUrl() {
  if (typeof window === "undefined") return getManagedBusinessId();
  const fromUrl = new URLSearchParams(window.location.search)
    .get("businessId")
    ?.trim();
  if (fromUrl) {
    setManagedBusinessId(fromUrl);
    return fromUrl;
  }
  return getManagedBusinessId();
}

export function AuthProvider({ children }: { children: ReactNode }) {
  const [user, setUser] = useState<AuthUser | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [managedBusinessId, setManagedBusinessIdState] = useState<string | null>(
    null,
  );

  const logout = useCallback(() => {
    logoutRequest();
    clearManagedBusinessId();
    setManagedBusinessIdState(null);
    setUser(null);
  }, []);

  useEffect(() => {
    const controller = new AbortController();

    async function init() {
      // Handoff installs tokens via inline script and redirects — don't race it.
      if (
        typeof window !== "undefined" &&
        window.location.pathname === "/auth/handoff"
      ) {
        if (!controller.signal.aborted) setIsLoading(false);
        return;
      }

      migrateTokensToSharedCookies();
      setManagedBusinessIdState(syncManagedBusinessFromUrl());

      if (!getAccessToken()) {
        if (!controller.signal.aborted) setIsLoading(false);
        return;
      }

      try {
        const { user: currentUser } = await fetchCurrentUser(controller.signal);
        if (controller.signal.aborted) return;

        const app = hostAppFor(currentHost());
        if (!userCanAccessApp(currentUser, app)) {
          logout();
          return;
        }

        const managed = syncManagedBusinessFromUrl();
        setManagedBusinessIdState(managed);
        setUser(currentUser);
      } catch (err) {
        if (isAbortError(err) || controller.signal.aborted) return;
        // On business host, keep tokens so a transient /me failure doesn't
        // bounce manage-business back to admin.
        if (hostAppFor(currentHost()) === "business") {
          if (!controller.signal.aborted) setIsLoading(false);
          return;
        }
        logout();
      } finally {
        if (!controller.signal.aborted) setIsLoading(false);
      }
    }

    void init();
    return () => controller.abort();
  }, [logout]);

  const login = useCallback(async (cellNumber: string, password: string) => {
    const data = await loginRequest(cellNumber, password);
    const app = hostAppFor(currentHost());

    if (!userCanAccessApp(data.user, app)) {
      logoutRequest();
      const message =
        app === "admin"
          ? "This account does not have super admin access."
          : app === "business"
            ? "No business is linked to this account."
            : "This account cannot use the customer dashboard.";
      throw new ApiError(message, 403);
    }

    if (app === "business" && data.user.dashboard === "super_admin") {
      const managed = syncManagedBusinessFromUrl();
      setManagedBusinessIdState(managed);
      if (!managed && !pickActiveBusinessId(data.user)) {
        logoutRequest();
        throw new ApiError(
          "Open a business from the admin dashboard and use Manage business.",
          403,
        );
      }
    }

    setManagedBusinessIdState(syncManagedBusinessFromUrl());
    setUser(data.user);
    return data.user.dashboard;
  }, []);

  const register = useCallback(async (payload: RegisterPayload) => {
    const data = await registerRequest(payload);

    if (!data.accessToken || !data.refreshToken || !data.user) {
      throw new ApiError(
        data.message ||
          "Registration needs phone verification before you can continue.",
        403,
      );
    }

    const app = hostAppFor(currentHost());
    if (!userCanAccessApp(data.user, app)) {
      logoutRequest();
      throw new ApiError(
        "This account cannot use the customer dashboard.",
        403,
      );
    }

    setManagedBusinessIdState(syncManagedBusinessFromUrl());
    setUser(data.user);
    return data.user.dashboard;
  }, []);

  const isSuperAdmin = user?.dashboard === "super_admin";

  /**
   * Shared business.* host — which Meshkee business?
   * - Superadmin: managed id from “Manage business” handoff (required for other businesses)
   * - Everyone else: first owned / linked business on the user
   */
  const activeBusinessId = useMemo(() => {
    if (!user) return null;
    if (user.dashboard === "super_admin") {
      return managedBusinessId || pickActiveBusinessId(user);
    }
    return pickActiveBusinessId(user);
  }, [user, managedBusinessId]);

  const isBusinessOwner = useMemo(
    () => Boolean(user?.businesses.some((item) => item.isOwner)),
    [user],
  );

  const value = useMemo(
    () => ({
      user,
      isLoading,
      activeBusinessId,
      isBusinessOwner,
      isSuperAdmin: Boolean(isSuperAdmin),
      login,
      register,
      logout,
    }),
    [
      user,
      isLoading,
      activeBusinessId,
      isBusinessOwner,
      isSuperAdmin,
      login,
      register,
      logout,
    ],
  );

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

export function useAuth() {
  const context = useContext(AuthContext);
  if (!context) {
    throw new Error("useAuth must be used within AuthProvider");
  }
  return context;
}

/**
 * After login: stay on the host you signed into.
 * Superadmin can open the admin dashboard from customer home when needed.
 */
export function postLoginHref(dashboard: DashboardType): string {
  const app = hostAppFor(currentHost());

  if (app === "admin") {
    return dashboard === "super_admin" ? "/" : `${getCustomerDashboardOrigin()}/`;
  }

  if (app === "business") return "/profile";
  if (app === "customer") return "/";

  if (dashboard === "super_admin") return `${getAdminDashboardOrigin()}/`;
  return `${getCustomerDashboardOrigin()}/`;
}