masto-fe-archos/app/javascript/flavours/glitch/reducers/alerts.js

import { Map as ImmutableMap, List as ImmutableList } from "immutable";

import {
  ALERT_SHOW,
  ALERT_DISMISS,
  ALERT_CLEAR,
} from "flavours/glitch/actions/alerts";

const initialState = ImmutableList([]);

export default function alerts(state = initialState, action) {
  switch(action.type) {
    case ALERT_SHOW:
      return state.push(ImmutableMap({
        key: state.size > 0 ? state.last().get("key") + 1 : 0,
        title: action.title,
        message: action.message,
        message_values: action.message_values,
      }));
    case ALERT_DISMISS:
      return state.filterNot(item => item.get("key") === action.alert.key);
    case ALERT_CLEAR:
      return state.clear();
    default:
      return state;
  }
}