@wordpress/components/build-module/input-control/reducer/reducer.js

UI components for WordPress.

/**
 * External dependencies
 */

/**
 * WordPress dependencies
 */
import { useReducer, useLayoutEffect, useRef } from '@wordpress/element';

/**
 * Internal dependencies
 */

import { initialInputControlState, initialStateReducer } from './state';
import * as actions from './actions';
/**
 * Prepares initialState for the reducer.
 *
 * @param initialState The initial state.
 * @return Prepared initialState for the reducer
 */
function mergeInitialState(initialState = initialInputControlState) {
  const {
    value
  } = initialState;
  return {
    ...initialInputControlState,
    ...initialState,
    initialValue: value
  };
}

/**
 * Creates the base reducer which may be coupled to a specializing reducer.
 * As its final step, for all actions other than CONTROL, the base reducer
 * passes the state and action on through the specializing reducer. The
 * exception for CONTROL actions is because they represent controlled updates
 * from props and no case has yet presented for their specialization.
 *
 * @param composedStateReducers A reducer to specialize state changes.
 * @return The reducer.
 */
function inputControlStateReducer(composedStateReducers) {
  return (state, action) => {
    const nextState = {
      ...state
    };
    switch (action.type) {
      /*
       * Controlled updates
       */
      case actions.CONTROL:
        nextState.value = action.payload.value;
        nextState.isDirty = false;
        nextState._event = undefined;
        // Returns immediately to avoid invoking additional reducers.
        return nextState;

      /**
       * Keyboard events
       */
      case actions.PRESS_UP:
        nextState.isDirty = false;
        break;
      case actions.PRESS_DOWN:
        nextState.isDirty = false;
        break;

      /**
       * Drag events
       */
      case actions.DRAG_START:
        nextState.isDragging = true;
        break;
      case actions.DRAG_END:
        nextState.isDragging = false;
        break;

      /**
       * Input events
       */
      case actions.CHANGE:
        nextState.error = null;
        nextState.value = action.payload.value;
        if (state.isPressEnterToChange) {
          nextState.isDirty = true;
        }
        break;
      case actions.COMMIT:
        nextState.value = action.payload.value;
        nextState.isDirty = false;
        break;
      case actions.RESET:
        nextState.error = null;
        nextState.isDirty = false;
        nextState.value = action.payload.value || state.initialValue;
        break;

      /**
       * Validation
       */
      case actions.INVALIDATE:
        nextState.error = action.payload.error;
        break;
    }
    nextState._event = action.payload.event;

    /**
     * Send the nextState + action to the composedReducers via
     * this "bridge" mechanism. This allows external stateReducers
     * to hook into actions, and modify state if needed.
     */
    return composedStateReducers(nextState, action);
  };
}

/**
 * A custom hook that connects and external stateReducer with an internal
 * reducer. This hook manages the internal state of InputControl.
 * However, by connecting an external stateReducer function, other
 * components can react to actions as well as modify state before it is
 * applied.
 *
 * This technique uses the "stateReducer" design pattern:
 * https://kentcdodds.com/blog/the-state-reducer-pattern/
 *
 * @param stateReducer    An external state reducer.
 * @param initialState    The initial state for the reducer.
 * @param onChangeHandler A handler for the onChange event.
 * @return State, dispatch, and a collection of actions.
 */
export function useInputControlStateReducer(stateReducer = initialStateReducer, initialState = initialInputControlState, onChangeHandler) {
  const [state, dispatch] = useReducer(inputControlStateReducer(stateReducer), mergeInitialState(initialState));
  const createChangeEvent = type => (nextValue, event) => {
    dispatch({
      type,
      payload: {
        value: nextValue,
        event
      }
    });
  };
  const createKeyEvent = type => event => {
    dispatch({
      type,
      payload: {
        event
      }
    });
  };
  const createDragEvent = type => payload => {
    dispatch({
      type,
      payload
    });
  };

  /**
   * Actions for the reducer
   */
  const change = createChangeEvent(actions.CHANGE);
  const invalidate = (error, event) => dispatch({
    type: actions.INVALIDATE,
    payload: {
      error,
      event
    }
  });
  const reset = createChangeEvent(actions.RESET);
  const commit = createChangeEvent(actions.COMMIT);
  const dragStart = createDragEvent(actions.DRAG_START);
  const drag = createDragEvent(actions.DRAG);
  const dragEnd = createDragEvent(actions.DRAG_END);
  const pressUp = createKeyEvent(actions.PRESS_UP);
  const pressDown = createKeyEvent(actions.PRESS_DOWN);
  const pressEnter = createKeyEvent(actions.PRESS_ENTER);
  const currentStateRef = useRef(state);
  const refPropsRef = useRef({
    value: initialState.value,
    onChangeHandler
  });

  // Freshens refs to props and state so that subsequent effects have access
  // to their latest values without their changes causing effect runs.
  useLayoutEffect(() => {
    currentStateRef.current = state;
    refPropsRef.current = {
      value: initialState.value,
      onChangeHandler
    };
  });

  // Propagates the latest state through onChange.
  useLayoutEffect(() => {
    if (currentStateRef.current._event !== undefined && state.value !== refPropsRef.current.value && !state.isDirty) {
      var _state$value;
      refPropsRef.current.onChangeHandler((_state$value = state.value) !== null && _state$value !== void 0 ? _state$value : '', {
        event: currentStateRef.current._event
      });
    }
  }, [state.value, state.isDirty]);

  // Updates the state from props.
  useLayoutEffect(() => {
    if (initialState.value !== currentStateRef.current.value && !currentStateRef.current.isDirty) {
      var _initialState$value;
      dispatch({
        type: actions.CONTROL,
        payload: {
          value: (_initialState$value = initialState.value) !== null && _initialState$value !== void 0 ? _initialState$value : ''
        }
      });
    }
  }, [initialState.value]);
  return {
    change,
    commit,
    dispatch,
    drag,
    dragEnd,
    dragStart,
    invalidate,
    pressDown,
    pressEnter,
    pressUp,
    reset,
    state
  };
}
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