139 lines
4.8 KiB
JavaScript
139 lines
4.8 KiB
JavaScript
/* @flow */
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import _ from 'lodash';
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/**
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* Sets specific properties of a specific state to specific values and prevents
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* unnecessary state changes.
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*
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* @param {Object} target - The state on which the specified properties are to
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* be set.
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* @param {Object} source - The map of properties to values which are to be set
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* on the specified target.
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* @returns {Object} The specified target if the values of the specified
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* properties equal the specified values; otherwise, a new state constructed
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* from the specified target by setting the specified properties to the
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* specified values.
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*/
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export function assign(target: Object, source: Object) {
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let t = target;
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for (const property in source) { // eslint-disable-line guard-for-in
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t = set(t, property, source[property], t === target);
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}
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return t;
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}
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/**
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* Determines whether {@code a} equals {@code b} according to deep comparison
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* (which makes sense for Redux and its state definition).
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*
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* @param {*} a - The value to compare to {@code b}.
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* @param {*} b - The value to compare to {@code a}.
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* @returns {boolean} True if {@code a} equals {@code b} (according to deep
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* comparison); false, otherwise.
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*/
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export function equals(a: any, b: any) {
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return _.isEqual(a, b);
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}
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/**
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* Sets a specific property of a specific state to a specific value. Prevents
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* unnecessary state changes (when the specified <tt>value</tt> is equal to the
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* value of the specified <tt>property</tt> of the specified <tt>state</tt>).
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*
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* @param {Object} state - The (Redux) state from which a new state is to be
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* constructed by setting the specified <tt>property</tt> to the specified
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* <tt>value</tt>.
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* @param {string} property - The property of <tt>state</tt> which is to be
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* assigned the specified <tt>value</tt> (in the new state).
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* @param {*} value - The value to assign to the specified <tt>property</tt>.
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* @returns {Object} The specified <tt>state</tt> if the value of the specified
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* <tt>property</tt> equals the specified <tt>value/tt>; otherwise, a new state
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* constructed from the specified <tt>state</tt> by setting the specified
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* <tt>property</tt> to the specified <tt>value</tt>.
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*/
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export function set(state: Object, property: string, value: any) {
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return _set(state, property, value, /* copyOnWrite */ true);
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}
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/* eslint-disable max-params */
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/**
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* Sets a specific property of a specific state to a specific value. Prevents
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* unnecessary state changes (when the specified <tt>value</tt> is equal to the
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* value of the specified <tt>property</tt> of the specified <tt>state</tt>).
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*
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* @param {Object} state - The (Redux) state from which a state is to be
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* constructed by setting the specified <tt>property</tt> to the specified
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* <tt>value</tt>.
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* @param {string} property - The property of <tt>state</tt> which is to be
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* assigned the specified <tt>value</tt>.
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* @param {*} value - The value to assign to the specified <tt>property</tt>.
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* @param {boolean} copyOnWrite - If the specified <tt>state</tt> is to not be
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* modified, <tt>true</tt>; otherwise, <tt>false</tt>.
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* @returns {Object} The specified <tt>state</tt> if the value of the specified
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* <tt>property</tt> equals the specified <tt>value/tt> or <tt>copyOnWrite</tt>
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* is truthy; otherwise, a new state constructed from the specified
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* <tt>state</tt> by setting the specified <tt>property</tt> to the specified
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* <tt>value</tt>.
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*/
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function _set(
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state: Object,
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property: string,
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value: any,
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copyOnWrite: boolean) {
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// Delete state properties that are to be set to undefined. (It is a matter
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// of personal preference, mostly.)
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if (typeof value === 'undefined'
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&& Object.prototype.hasOwnProperty.call(state, property)) {
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const newState = copyOnWrite ? { ...state } : state;
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if (delete newState[property]) {
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return newState;
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}
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}
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if (state[property] !== value) {
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if (copyOnWrite) {
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return {
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...state,
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[property]: value
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};
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}
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state[property] = value;
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}
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return state;
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}
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/* eslint-enable max-params */
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/**
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* Returns redux state from the specified <tt>stateful</tt> which is presumed to
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* be related to the redux state (e.g. the redux store, the redux
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* <tt>getState</tt> function).
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*
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* @param {Function|Object} stateful - The entity such as the redux store or the
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* redux <tt>getState</tt> function from which the redux state is to be
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* returned.
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* @returns {Object} The redux state.
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*/
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export function toState(stateful: Function | Object) {
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if (stateful) {
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if (typeof stateful === 'function') {
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return stateful();
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}
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const { getState } = stateful;
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if (typeof getState === 'function') {
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return getState();
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}
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}
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return stateful;
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}
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