fluidstate/extras/reactive-plugin-array.js

Library for fine-grained reactivity state management

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.getArraySetChanges = exports.getArrayDeleteChanges = void 0;
var _reactivePlugin = require("./reactive-plugin");
/**
 * Generates a list of change descriptions for an array set operation.
 * This function is intended to be called before the actual mutation occurs,
 * so `array` reflects the state *before* the change.
 *
 * @param array The reactive array proxy, reflecting state *before* the change.
 * @param inertArr The underlying inert array.
 * @param property The property being set (either a numeric index or the string 'length').
 * @param previousValue For numeric `property`, the current value at that index. For 'length' `property`, the current length of the array.
 * @param nextValue For numeric `property`, the new value to be set at the index. For 'length' `property`, the new length to be set.
 * @param currentLength The length of `array` *before* the operation.
 * @returns An array of ReactiveChange objects, or null if no reportable changes occurred.
 */
const getArraySetChanges = (array, inertArr, property, previousValue, nextValue, currentLength) => {
  const changes = [];
  if (property === "length") {
    const newLength = Number(nextValue);
    if (!Number.isInteger(newLength) || newLength >= 2 ** 32 || newLength < 0) {
      return null;
    }
    if (newLength < currentLength) {
      for (let i = currentLength - 1; i >= newLength; i--) {
        changes.push({
          type: _reactivePlugin.ArrayChangeType.PopValue,
          index: i,
          previousValue: inertArr[i]
        });
      }
    } else if (newLength > currentLength) {
      for (let i = currentLength; i < newLength; i++) {
        changes.push({
          type: _reactivePlugin.ArrayChangeType.PushValue,
          index: i,
          nextValue: undefined
        });
      }
    }
  } else {
    const index = Number(property);
    if (!Number.isInteger(index) || index >= 2 ** 32 - 1 || index < 0) {
      return null;
    }
    if (index < currentLength) {
      // Standard set within existing bounds
      changes.push({
        type: _reactivePlugin.ArrayChangeType.SetValue,
        index,
        previousValue,
        nextValue
      });
    } else {
      for (let i = currentLength; i < index; i++) {
        changes.push({
          type: _reactivePlugin.ArrayChangeType.PushValue,
          index: i,
          nextValue: undefined
        });
      }
      changes.push({
        type: _reactivePlugin.ArrayChangeType.PushValue,
        index,
        nextValue
      });
    }
  }
  if (changes.length === 0) {
    return null;
  }
  return changes.map(arrayChange => ({
    type: _reactivePlugin.ReactiveChangeType.Array,
    array,
    arrayChange
  }));
};

/**
 * Generates a list of change descriptions for an array delete operation.
 * `delete array[index]` makes the property at `index` a "hole", and accessing it yields `undefined`.
 * The array length does not change. This is treated as setting the value at `index` to `undefined`.
 *
 * @param array The reactive array proxy, reflecting state *before* the change.
 * @param property The property being set (either a numeric index or the string 'length').
 * @param previousValue The value at the `property` index *before* deletion.
 * @returns An array of ReactiveChange objects, or null if no reportable changes occurred.
 */
exports.getArraySetChanges = getArraySetChanges;
const getArrayDeleteChanges = (array, property, previousValue) => {
  if (property === "length") {
    return null;
  }
  const index = Number(property);
  if (!Number.isInteger(index) || index >= 2 ** 32 - 1 || index < 0) {
    return null;
  }
  const arrayChange = {
    type: _reactivePlugin.ArrayChangeType.SetValue,
    index,
    previousValue,
    nextValue: undefined
  };
  return [{
    type: _reactivePlugin.ReactiveChangeType.Array,
    array,
    arrayChange
  }];
};
exports.getArrayDeleteChanges = getArrayDeleteChanges;
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