import { useCallback, useEffect, useRef } from 'react';
import { useSetAtom } from 'jotai';
import { CallMembership } from 'matrix-js-sdk/lib/matrixrtc/CallMembership';
import { CallEmbed, useCallControlState } from '../plugins/call';
import { useCallMembersChange, useCallSession } from './useCall';
import { useMatrixClient } from './useMatrixClient';
import { getMemberName } from '../utils/room';
import { callAnnouncementAtom } from '../state/callAnnouncement';

const BURST_MS = 1500;

const listNames = (names: string[], verb: string): string => {
  if (names.length === 0) return '';
  if (names.length === 1) return `${names[0]} ${verb}`;
  if (names.length === 2) return `${names[0]} and ${names[1]} ${verb}`;
  return `${names.length} people ${verb}`;
};

/**
 * [Gitea #168] Screen-reader announcements for call events, via the
 * aria-live region CallEmbedProvider renders. Nothing visible, nothing
 * audible for anyone else. Joins/leaves within 1.5 s are batched ("3 people
 * joined"); your own mute / deafen / screenshare changes are announced as
 * they happen; "Call ended" fires when the embed goes away.
 */
export function useCallAnnouncements(embed: CallEmbed, joined: boolean): void {
  const mx = useMatrixClient();
  const setAnnouncement = useSetAtom(callAnnouncementAtom);
  const session = useCallSession(embed.room);
  const { microphone, sound, screenshare } = useCallControlState(embed.control);

  const announce = useCallback(
    (text: string) => {
      // Re-announce identical text by nudging it: aria-live only speaks changes.
      setAnnouncement((prev) => (prev === text ? `${text} ` : text));
    },
    [setAnnouncement],
  );

  // --- joins / leaves, batched per user
  const prevUsersRef = useRef<Set<string> | null>(null);
  const pending = useRef<{ joined: Set<string>; left: Set<string>; timer?: number }>({
    joined: new Set(),
    left: new Set(),
  });
  useEffect(() => {
    prevUsersRef.current = new Set(session.memberships.map((m) => m.sender ?? ''));
  }, [session]);

  const flush = useCallback(() => {
    const { joined: j, left: l } = pending.current;
    const room = embed.room;
    const parts = [
      listNames(
        Array.from(j, (u) => getMemberName(room, u)),
        'joined',
      ),
      listNames(
        Array.from(l, (u) => getMemberName(room, u)),
        'left',
      ),
    ].filter(Boolean);
    j.clear();
    l.clear();
    pending.current.timer = undefined;
    if (parts.length) announce(parts.join('. '));
  }, [announce, embed.room]);

  useCallMembersChange(
    session,
    useCallback(
      (members: CallMembership[]) => {
        const next = new Set(members.map((m) => m.sender ?? ''));
        const prev = prevUsersRef.current ?? next;
        prevUsersRef.current = next;
        if (!joined) return;
        const me = mx.getSafeUserId();
        next.forEach((u) => {
          if (!prev.has(u) && u !== me) {
            pending.current.left.delete(u);
            pending.current.joined.add(u);
          }
        });
        prev.forEach((u) => {
          if (!next.has(u) && u !== me) {
            pending.current.joined.delete(u);
            pending.current.left.add(u);
          }
        });
        if (pending.current.timer === undefined) {
          pending.current.timer = window.setTimeout(flush, BURST_MS);
        }
      },
      [joined, mx, flush],
    ),
  );

  // --- own state
  const first = useRef(true);
  const prevOwn = useRef({ microphone, sound, screenshare });
  useEffect(() => {
    const was = prevOwn.current;
    prevOwn.current = { microphone, sound, screenshare };
    if (!joined) return;
    if (first.current) {
      first.current = false;
      return;
    }
    if (was.microphone !== microphone) announce(microphone ? 'You are unmuted' : 'You are muted');
    if (was.sound !== sound) announce(sound ? 'You are undeafened' : 'You are deafened');
    if (was.screenshare !== screenshare) {
      announce(screenshare ? 'You started sharing your screen' : 'You stopped sharing your screen');
    }
  }, [microphone, sound, screenshare, joined, announce]);

  // --- call ended
  const wasJoined = useRef(false);
  useEffect(() => {
    if (joined) wasJoined.current = true;
  }, [joined]);
  useEffect(
    () => () => {
      if (pending.current.timer !== undefined) window.clearTimeout(pending.current.timer);
      if (wasJoined.current) announce('Call ended');
    },
    [announce],
  );
}