mastodon/app/assets/javascripts/components/selectors/index.jsx

import { createSelector } from 'reselect'
import Immutable from 'immutable';

const getStatuses = state => state.get('statuses');
const getAccounts = state => state.get('accounts');

const getAccountBase         = (state, id) => state.getIn(['accounts', id], null);
const getAccountRelationship = (state, id) => state.getIn(['relationships', id]);

export const makeGetAccount = () => {
  return createSelector([getAccountBase, getAccountRelationship], (base, relationship) => {
    if (base === null) {
      return null;
    }

    return base.set('relationship', relationship);
  });
};

const getStatusBase = (state, id) => state.getIn(['statuses', id], null);

export const makeGetStatus = () => {
  return createSelector([getStatusBase, getStatuses, getAccounts], (base, statuses, accounts) => {
    if (base === null) {
      return null;
    }

    return assembleStatus(base.get('id'), statuses, accounts);
  });
};

const assembleStatus = (id, statuses, accounts) => {
  let status = statuses.get(id, null);
  let reblog = null;

  if (status === null) {
    return null;
  }

  if (status.get('reblog', null) !== null) {
    reblog = statuses.get(status.get('reblog'), null);

    if (reblog !== null) {
      reblog = reblog.set('account', accounts.get(reblog.get('account')));
    } else {
      return null;
    }
  }

  return status.set('reblog', reblog).set('account', accounts.get(status.get('account')));
};

const getAlertsBase = state => state.get('alerts');

export const getAlerts = createSelector([getAlertsBase], (base) => {
  let arr = [];

  base.forEach(item => {
    arr.push({
      message: item.get('message'),
      title: item.get('title'),
      key: item.get('key'),
      dismissAfter: 5000
    });
  });

  return arr;
});

export const makeGetNotification = () => {
  return createSelector([
    (_, base)             => base,
    (state, _, accountId) => state.getIn(['accounts', accountId])
  ], (base, account) => {
    return base.set('account', account);
  });
};