//@flow
const { db } = require('shared/db');

export type DBDirectMessageThread = {
  createdAt: Date,
  id: string,
  name?: string,
  threadLastActive: Date,
};

// prettier-ignore
const checkForExistingDMThread = async (participants: Array<string>): Promise<?string> => {
  // return a list of all threadIds where both participants are active
  let idsToCheck = await db
    .table('usersDirectMessageThreads')
    .getAll(...participants, { index: 'userId' })
    .group('threadId')
    .map(row => row('userId'))
    .ungroup()
    .filter(row =>
      row('reduction')
        .count()
        .eq(participants.length)
    )
    .pluck('group')
    .run();

  if (!idsToCheck || idsToCheck.length === 0) return null;

  // return only the thread Ids
  idsToCheck = idsToCheck.map(row => row.group);

  // given a list of threads where both users are active (includes all groups)
  // return only threads where these exact participants are used
  return await db
    .table('usersDirectMessageThreads')
    .getAll(...idsToCheck, { index: 'threadId' })
    .group('threadId')
    .ungroup()
    .filter(row =>
      row('reduction')
        .count()
        .eq(participants.length)
    )
    .pluck('group')
    .map(row => row('group'))
    .run()
    .then(results => (results && results.length > 0 ? results[0] : null));
};

// prettier-ignore
const getDirectMessageThread = (directMessageThreadId: string): Promise<DBDirectMessageThread> => {
  return db
    .table('directMessageThreads')
    .get(directMessageThreadId)
    .run()
    .then(res => res && !res.deletedAt ? res : null);
};

// prettier-ignore
const getDirectMessageThreads = (ids: Array<string>): Promise<Array<DBDirectMessageThread>> => {
  return db
    .table('directMessageThreads')
    .getAll(...ids)
    .filter(row => row.hasFields('deletedAt').not())
    .run();
};

const getDirectMessageThreadsByUser = (
  userId: string,
  // $FlowFixMe
  { first, after }
): Promise<Array<DBDirectMessageThread>> => {
  return db
    .table('usersDirectMessageThreads')
    .getAll(userId, { index: 'userId' })
    .filter(row => row.hasFields('deletedAt').not())
    .eqJoin('threadId', db.table('directMessageThreads'))
    .without({
      left: ['id', 'createdAt', 'threadId', 'userId', 'lastActive', 'lastSeen'],
    })
    .zip()
    .orderBy(db.desc('threadLastActive'))
    .skip(after || 0)
    .limit(first)
    .run();
};

module.exports = {
  checkForExistingDMThread,
  getDirectMessageThread,
  getDirectMessageThreads,
  getDirectMessageThreadsByUser,
};