import { MatrixClient } from 'matrix-js-sdk';
import { Unread } from '../../types/matrix/room';

export type SortFunc<T> = (a: T, b: T) => number;

export const factoryRoomIdByActivity =
  (mx: MatrixClient): SortFunc<string> =>
  (a, b) => {
    const room1 = mx.getRoom(a);
    const room2 = mx.getRoom(b);

    return (
      (room2?.getLastActiveTimestamp() ?? Number.MIN_SAFE_INTEGER) -
      (room1?.getLastActiveTimestamp() ?? Number.MIN_SAFE_INTEGER)
    );
  };

export const factoryRoomIdByAtoZ =
  (mx: MatrixClient): SortFunc<string> =>
  (a, b) => {
    let aName = mx.getRoom(a)?.name ?? '';
    let bName = mx.getRoom(b)?.name ?? '';

    // remove "#" from the room name
    // To ignore it in sorting
    aName = aName.replace(/#/g, '');
    bName = bName.replace(/#/g, '');

    if (aName.toLowerCase() < bName.toLowerCase()) {
      return -1;
    }
    if (aName.toLowerCase() > bName.toLowerCase()) {
      return 1;
    }
    return 0;
  };

export const factoryRoomIdByUnreadCount =
  (getUnreadCount: (roomId: string) => number): SortFunc<string> =>
  (a, b) => {
    const aT = getUnreadCount(a) ?? 0;
    const bT = getUnreadCount(b) ?? 0;
    return bT - aT;
  };

// "Unread First": rooms with unread sort before those without, then by unread
// count desc, then — crucially for the large all-read tail where counts tie —
// by recent activity, so it isn't left in arbitrary order.
export const factoryRoomIdByUnread = (
  roomToUnread: Map<string, Unread>,
  mx: MatrixClient,
): SortFunc<string> => {
  const byActivity = factoryRoomIdByActivity(mx);
  return (a, b) => {
    const aUnread = roomToUnread.get(a);
    const bUnread = roomToUnread.get(b);
    const aHas = (aUnread?.total ?? 0) > 0;
    const bHas = (bUnread?.total ?? 0) > 0;
    if (aHas !== bHas) return aHas ? -1 : 1;
    const byCount = (bUnread?.total ?? 0) - (aUnread?.total ?? 0);
    if (byCount !== 0) return byCount;
    return byActivity(a, b);
  };
};

export const byTsOldToNew: SortFunc<number> = (a, b) => a - b;

export const byOrderKey: SortFunc<string | undefined> = (a, b) => {
  if (!a && !b) {
    return 0;
  }

  if (!b) return -1;
  if (!a) return 1;

  if (a < b) {
    return -1;
  }
  return 1;
};