typedux/src/reducers/LeafReducer.ts

Slightly adjusted Redux (awesome by default) for TS

import type { ActionMessage } from "../actions"
import type { State } from "./State"

/**
 * Check object shape to see if
 * its a valid ILeafReducer
 *
 * @param o
 * @returns {boolean}
 */
export function isLeafReducer(o: any): o is ILeafReducer<any, any> {
  return o.leaf && o.defaultState
}

/**
 * S - type of State
 * T - type of actions/enum
 * M - type of message
 */
export interface ILeafReducer<
  S extends State,
  A extends ActionMessage<S> = ActionMessage<S>
> {
  /**
   * The path to the leaf it handles
   */
  leaf(): string

  /**
   * Get the default state
   */
  defaultState(o?: any): S

  /**
   * Optional init function coverage
   *
   * @param state
   */
  init?: (state: S) => S

  /**
   * Handle an incoming action
   * @param state
   * @param action
   */
  handle?: (state: S, action: A) => S

  /**
   * Handle an error occurence
   *
   * @param state
   * @param action
   * @param error
   */
  handleError?: (state: S, action: A, error: Error) => S
}