mutative/src/current.ts

A JavaScript library for efficient immutable updates

import { type Draft, DraftType, type ProxyDraft } from './interface';
import {
  forEach,
  get,
  getProxyDraft,
  getType,
  isBaseMapInstance,
  isBaseSetInstance,
  isDraft,
  isDraftable,
  isEqual,
  set,
  shallowCopy,
} from './utils';

export function handleReturnValue<T extends object>(options: {
  rootDraft: ProxyDraft<any> | undefined;
  value: T;
  useRawReturn?: boolean;
  isContainDraft?: boolean;
  isRoot?: boolean;
}) {
  const { rootDraft, value, useRawReturn = false, isRoot = true } = options;
  forEach(value, (key, item, source) => {
    const proxyDraft = getProxyDraft(item);
    // just handle the draft which is created by the same rootDraft
    if (
      proxyDraft &&
      rootDraft &&
      proxyDraft.finalities === rootDraft.finalities
    ) {
      options.isContainDraft = true;
      const currentValue = proxyDraft.original;
      // final update value, but just handle return value
      if (source instanceof Set) {
        const arr = Array.from(source);
        source.clear();
        arr.forEach((_item) =>
          source.add(key === _item ? currentValue : _item)
        );
      } else {
        set(source, key, currentValue);
      }
    } else if (typeof item === 'object' && item !== null) {
      options.value = item;
      options.isRoot = false;
      handleReturnValue(options);
    }
  });
  if (__DEV__ && isRoot) {
    if (!options.isContainDraft)
      console.warn(
        `The return value does not contain any draft, please use 'rawReturn()' to wrap the return value to improve performance.`
      );

    if (useRawReturn) {
      console.warn(
        `The return value contains drafts, please don't use 'rawReturn()' to wrap the return value.`
      );
    }
  }
}

function getCurrent(target: any) {
  const proxyDraft = getProxyDraft(target);
  if (!isDraftable(target, proxyDraft?.options)) return target;
  const type = getType(target);
  if (proxyDraft && !proxyDraft.operated) return proxyDraft.original;
  let currentValue: any;
  function ensureShallowCopy() {
    currentValue =
      type === DraftType.Map
        ? !isBaseMapInstance(target)
          ? new (Object.getPrototypeOf(target).constructor)(target)
          : new Map(target)
        : type === DraftType.Set
          ? Array.from(proxyDraft!.setMap!.values()!)
          : shallowCopy(target, proxyDraft?.options);
  }

  if (proxyDraft) {
    // It's a proxy draft, let's create a shallow copy eagerly
    proxyDraft.finalized = true;
    try {
      ensureShallowCopy();
    } finally {
      proxyDraft.finalized = false;
    }
  } else {
    // It's not a proxy draft, let's use the target directly and let's see
    // lazily if we need to create a shallow copy
    currentValue = target;
  }

  forEach(currentValue, (key, value) => {
    if (proxyDraft && isEqual(get(proxyDraft.original, key), value)) return;
    const newValue = getCurrent(value);
    if (newValue !== value) {
      if (currentValue === target) ensureShallowCopy();
      set(currentValue, key, newValue);
    }
  });
  if (type === DraftType.Set) {
    const value = proxyDraft?.original ?? currentValue;
    return !isBaseSetInstance(value)
      ? new (Object.getPrototypeOf(value).constructor)(currentValue)
      : new Set(currentValue);
  }
  return currentValue;
}

/**
 * `current(draft)` to get current state in the draft mutation function.
 *
 * ## Example
 *
 * ```ts
 * import { create, current } from '../index';
 *
 * const baseState = { foo: { bar: 'str' }, arr: [] };
 * const state = create(
 *   baseState,
 *   (draft) => {
 *     draft.foo.bar = 'str2';
 *     expect(current(draft.foo)).toEqual({ bar: 'str2' });
 *   },
 * );
 * ```
 */
export function current<T extends object>(target: Draft<T>): T;
/** @deprecated You should call current only on `Draft<T>` types. */
export function current<T extends object>(target: T): T;
export function current<T extends object>(target: T | Draft<T>): T {
  if (!isDraft(target)) {
    throw new Error(`current() is only used for Draft, parameter: ${target}`);
  }
  return getCurrent(target);
}