"use client";

/**
 * NotificationsProvider — holds the live unread-notification count and a
 * WebSocket connection to our Soketi (Pusher-compatible) server so the
 * bell badge + a toast update in realtime.
 *
 * Transport: subscribes to the PUBLIC channel `notifications.{userId}` and
 * binds the `notification` event the BFF triggers on each follow-request /
 * follow-accept. The event is a lightweight nudge — we bump the unread
 * count locally and toast — while the authoritative list/count still come
 * from the REST endpoints. (Public channel for now; once Soketi App auth
 * is configured, switch to a `private-` channel + a /broadcasting/auth
 * endpoint — only the channel name and a Pusher `authEndpoint` change.)
 *
 * Config via NEXT_PUBLIC_SOKETI_* env vars; when the key/host are absent
 * realtime silently disables and the bell falls back to its fetched count.
 */

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useState,
} from "react";
import { toast } from "sonner";
import { useAuth } from "@/components/auth/auth-provider";
import { notifications } from "@/lib/social";

type NotificationsContextValue = {
  /** Live unread count for the header bell. */
  unread: number;
  /** Bumps on each realtime event; pages can depend on it to refetch. */
  lastEventAt: number;
  /** Re-fetch the authoritative unread count from the BFF. */
  refreshUnread: () => void;
  /** Zero the badge locally (after the page marks everything read). */
  clearUnread: () => void;
};

const NotificationsContext = createContext<NotificationsContextValue | null>(
  null,
);

type IncomingEvent = {
  kind?: string;
  actor_name?: string;
  actor_handle?: string;
  actor_avatar_url?: string | null;
};

function messageFor(e: IncomingEvent): string {
  const who =
    e.actor_name || (e.actor_handle ? `@${e.actor_handle}` : "Someone");
  switch (e.kind) {
    case "follow_request":
      return `${who} requested to follow you`;
    case "follow_accepted":
      return `${who} accepted your follow request`;
    default:
      return "You have a new notification";
  }
}

export function NotificationsProvider({
  children,
}: {
  children: React.ReactNode;
}) {
  const { user } = useAuth();
  const [unread, setUnread] = useState(0);
  const [lastEventAt, setLastEventAt] = useState(0);

  const refreshUnread = useCallback(() => {
    notifications
      .unreadCount()
      .then((r) => setUnread(r?.count ?? 0))
      .catch(() => {
        /* badge is non-critical */
      });
  }, []);

  const clearUnread = useCallback(() => setUnread(0), []);

  // Seed the count whenever the signed-in user changes (async — no
  // synchronous setState in the effect body).
  useEffect(() => {
    if (!user) return;
    refreshUnread();
  }, [user?.id, refreshUnread]);

  // Open the realtime connection while signed in.
  useEffect(() => {
    if (!user) return;
    const key = process.env.NEXT_PUBLIC_SOKETI_KEY;
    const host = process.env.NEXT_PUBLIC_SOKETI_HOST;
    if (!key || !host) return; // realtime not configured

    const port = Number(process.env.NEXT_PUBLIC_SOKETI_PORT || "443");
    const forceTLS =
      (process.env.NEXT_PUBLIC_SOKETI_FORCE_TLS ?? "true") !== "false";
    const channelName = `notifications.${user.id}`;

    let cancelled = false;
    // Dynamic import keeps pusher-js out of SSR (it touches window) and the
    // initial bundle.
    let cleanup: (() => void) | undefined;
    void import("pusher-js").then(({ default: Pusher }) => {
      if (cancelled) return;
      const pusher = new Pusher(key, {
        wsHost: host,
        wsPort: port,
        wssPort: port,
        forceTLS,
        enabledTransports: ["ws", "wss"],
        disableStats: true,
        // Ignored when wsHost is set, but required by the type.
        cluster: "",
      });
      const channel = pusher.subscribe(channelName);
      channel.bind("notification", (data: IncomingEvent) => {
        setUnread((u) => u + 1);
        setLastEventAt(Date.now());
        toast(messageFor(data ?? {}), { duration: 4000 });
      });
      cleanup = () => {
        channel.unbind_all();
        pusher.unsubscribe(channelName);
        pusher.disconnect();
      };
    });

    return () => {
      cancelled = true;
      cleanup?.();
    };
  }, [user?.id]);

  return (
    <NotificationsContext.Provider
      value={{ unread, lastEventAt, refreshUnread, clearUnread }}
    >
      {children}
    </NotificationsContext.Provider>
  );
}

export function useNotifications(): NotificationsContextValue {
  const ctx = useContext(NotificationsContext);
  if (!ctx) {
    throw new Error(
      "useNotifications must be used inside <NotificationsProvider>",
    );
  }
  return ctx;
}