import { useCallback, useEffect, useRef, useState } from 'react';
import { MatrixClient, SyncState } from 'matrix-js-sdk';
import { MatrixRTCSessionEvent } from 'matrix-js-sdk/lib/matrixrtc';
import { useAtomValue, useSetAtom } from 'jotai';
import { Icons } from 'folds';
import { ElementWidgetActions } from '../plugins/call/types';
import { CallEmbed, useCallControlState, useClientWidgetApiEvent } from '../plugins/call';
import { useMatrixClient } from './useMatrixClient';
import { useSyncState } from './useSyncState';
import { useCallStart } from './useCallEmbed';
import { useSetting } from '../state/hooks/settings';
import { settingsAtom } from '../state/settings';
import { useCallPreferences } from '../state/hooks/callPreferences';
import { toastQueueAtom, dismissToastAtom } from '../state/toast';
import { mDirectAtom } from '../state/mDirectList';
import {
  CALL_SESSION_HEARTBEAT_MS,
  clearCallSession,
  decideRejoin,
  readCallSession,
  writeCallSession,
} from '../utils/callRejoin';

const TOAST_ID = 'call-rejoin';
/** How long after the first sync to wait for the RTC session to report members. */
const MEMBERSHIP_WAIT_MS = 10_000;

const isSynced = (mx: MatrixClient): boolean => {
  const state = mx.getSyncState();
  return state === SyncState.Prepared || state === SyncState.Syncing;
};

/**
 * [Gitea #118] Keep a heartbeat record of the voice room you are in, clear
 * it on a deliberate hangup, and on the next start put you back (or ask)
 * when the call is still going and the record is fresh.
 */
export function useCallRejoin(embed: CallEmbed | undefined, joined: boolean): void {
  const mx = useMatrixClient();
  const [mode] = useSetting(settingsAtom, 'callRejoinAfterRestart');
  const { microphone, video } = useCallControlState(embed?.control);
  const setToast = useSetAtom(toastQueueAtom);
  const dismissToast = useSetAtom(dismissToastAtom);
  const directs = useAtomValue(mDirectAtom);
  const { microphone: prefMic, sound } = useCallPreferences();
  const [cameraOnJoin] = useSetting(settingsAtom, 'cameraOnJoin');
  const startRoomCall = useCallStart(false);
  const startDmCall = useCallStart(true);

  // --- record while joined
  useEffect(() => {
    if (!embed || !joined) return undefined;
    const deviceId = mx.getDeviceId() ?? '';
    const write = () =>
      writeCallSession({
        roomId: embed.roomId,
        deviceId,
        joinedAt: embed.joinedAt ?? Date.now(),
        lastSeen: Date.now(),
        microphone,
        video,
      });
    write();
    const timer = window.setInterval(write, CALL_SESSION_HEARTBEAT_MS);
    return () => window.clearInterval(timer);
  }, [embed, joined, mx, microphone, video]);

  // --- deliberate hangup clears it
  useClientWidgetApiEvent(embed?.call, ElementWidgetActions.HangupCall, clearCallSession);
  useClientWidgetApiEvent(embed?.call, ElementWidgetActions.Close, clearCallSession);

  // --- startup: offer / perform a rejoin once
  // The startup effect must run exactly once and outlive re-renders (its
  // membership wait spans several seconds), so it reads these through a ref.
  const latest = useRef({
    mode,
    prefMic,
    sound,
    cameraOnJoin,
    directs,
    startRoomCall,
    startDmCall,
  });
  latest.current = { mode, prefMic, sound, cameraOnJoin, directs, startRoomCall, startDmCall };
  const checkedRef = useRef(false);
  const [synced, setSynced] = useState(() => isSynced(mx));
  useSyncState(
    mx,
    useCallback(() => {
      if (isSynced(mx)) setSynced(true);
    }, [mx]),
  );
  useEffect(() => {
    // Wait for the first sync so the room and its call memberships are known;
    // deciding earlier would read an empty session and wrongly drop the record.
    if (checkedRef.current || embed || !synced) return undefined;
    checkedRef.current = true;
    const record = readCallSession();
    if (!record) return undefined;
    const room = mx.getRoom(record.roomId);
    if (!room) {
      clearCallSession();
      return undefined;
    }
    const session = mx.matrixRTC.getRoomSession(room);
    const rejoin = () => {
      const l = latest.current;
      const pref = {
        microphone: record.microphone ?? l.prefMic,
        video: l.cameraOnJoin && record.video,
        sound: l.sound,
      };
      dismissToast(TOAST_ID);
      clearCallSession();
      try {
        (l.directs.has(room.roomId) ? l.startDmCall : l.startRoomCall)(room, pref);
      } catch {
        /* no embed container yet — the user can join from the room */
      }
    };
    let done = false;
    let timer: number | undefined;
    const evaluate = (final: boolean) => {
      if (done) return;
      const memberships = session.memberships;
      const decision = decideRejoin({
        record,
        mode: latest.current.mode,
        now: Date.now(),
        myDeviceId: mx.getDeviceId() ?? '',
        roomJoined: room.getMyMembership() === 'join',
        ownMemberDevices: memberships
          .filter((m) => m.userId === mx.getUserId())
          .map((m) => m.deviceId),
        memberCount: memberships.length,
      });
      // The RTC session fills in a moment after sync; keep waiting while it is
      // empty unless this is the final (timed-out) look.
      if (decision.action === 'none' && memberships.length === 0 && !final) return;
      done = true;
      if (timer !== undefined) window.clearTimeout(timer);
      session.off(MatrixRTCSessionEvent.MembershipsChanged, onChange);
      if (decision.action === 'none') {
        clearCallSession();
        return;
      }
      if (decision.action === 'auto') {
        rejoin();
        return;
      }
      setToast({
        id: TOAST_ID,
        iconSrc: Icons.Phone,
        displayName: 'Rejoin voice?',
        body: `You were in the call in ${room.name ?? 'a room'} before the restart. Tap to rejoin.`,
        roomName: room.name ?? '',
        roomId: room.roomId,
        sticky: true,
        onClick: rejoin,
        onDismiss: clearCallSession,
      });
    };
    const onChange = () => evaluate(false);
    session.on(MatrixRTCSessionEvent.MembershipsChanged, onChange);
    timer = window.setTimeout(() => evaluate(true), MEMBERSHIP_WAIT_MS);
    evaluate(false);
    return () => {
      session.off(MatrixRTCSessionEvent.MembershipsChanged, onChange);
      if (timer !== undefined) window.clearTimeout(timer);
    };
  }, [embed, synced, mx, setToast, dismissToast]);
}