daddy/client/src/store/reducers/flags.ts

import { Action } from "redux";

export interface FlagsState {
  actions: { [actionName: string]: ActionState }
}

export interface ActionState {
  isLoading: boolean
}

const defaultState = {
  actions: {}
};

export function flagsReducer(state = defaultState, action: Action): FlagsState {
  const matches = (/^(.*)_((SUCCESS)|(FAILURE)|(REQUEST))$/).exec(action.type);

  if(!matches) return state;

  const actionPrefix = matches[1];

  return {
    ...state,
    actions: {
      ...state.actions,
      [actionPrefix]: {
        isLoading: matches[2] === 'REQUEST'
      }
    }
  };

}