yomichan/ext/js/general/object-property-accessor.js

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/*
* Copyright (C) 2016-2022 Yomichan Authors
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*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/**
* Class used to get and mutate generic properties of an object by using path strings.
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*/
class ObjectPropertyAccessor {
/**
* Create a new accessor for a specific object.
* @param target The object which the getter and mutation methods are applied to.
* @returns A new ObjectPropertyAccessor instance.
*/
constructor(target) {
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this._target = target;
}
/**
* Gets the value at the specified path.
* @param pathArray The path to the property on the target object.
* @param pathLength How many parts of the pathArray to use.
* This parameter is optional and defaults to the length of pathArray.
* @returns The value found at the path.
* @throws An error is thrown if pathArray is not valid for the target object.
*/
get(pathArray, pathLength) {
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let target = this._target;
const ii = typeof pathLength === 'number' ? Math.min(pathArray.length, pathLength) : pathArray.length;
for (let i = 0; i < ii; ++i) {
const key = pathArray[i];
if (!ObjectPropertyAccessor.hasProperty(target, key)) {
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throw new Error(`Invalid path: ${ObjectPropertyAccessor.getPathString(pathArray.slice(0, i + 1))}`);
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}
target = target[key];
}
return target;
}
/**
* Sets the value at the specified path.
* @param pathArray The path to the property on the target object.
* @param value The value to assign to the property.
* @throws An error is thrown if pathArray is not valid for the target object.
*/
set(pathArray, value) {
const ii = pathArray.length - 1;
if (ii < 0) { throw new Error('Invalid path'); }
const target = this.get(pathArray, ii);
const key = pathArray[ii];
if (!ObjectPropertyAccessor.isValidPropertyType(target, key)) {
throw new Error(`Invalid path: ${ObjectPropertyAccessor.getPathString(pathArray)}`);
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}
target[key] = value;
}
/**
* Deletes the property of the target object at the specified path.
* @param pathArray The path to the property on the target object.
* @throws An error is thrown if pathArray is not valid for the target object.
*/
delete(pathArray) {
const ii = pathArray.length - 1;
if (ii < 0) { throw new Error('Invalid path'); }
const target = this.get(pathArray, ii);
const key = pathArray[ii];
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if (!ObjectPropertyAccessor.isValidPropertyType(target, key)) {
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throw new Error(`Invalid path: ${ObjectPropertyAccessor.getPathString(pathArray)}`);
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}
if (Array.isArray(target)) {
throw new Error('Invalid type');
}
delete target[key];
}
/**
* Swaps two properties of an object or array.
* @param pathArray1 The path to the first property on the target object.
* @param pathArray2 The path to the second property on the target object.
* @throws An error is thrown if pathArray1 or pathArray2 is not valid for the target object,
* or if the swap cannot be performed.
*/
swap(pathArray1, pathArray2) {
const ii1 = pathArray1.length - 1;
if (ii1 < 0) { throw new Error('Invalid path 1'); }
const target1 = this.get(pathArray1, ii1);
const key1 = pathArray1[ii1];
if (!ObjectPropertyAccessor.isValidPropertyType(target1, key1)) { throw new Error(`Invalid path 1: ${ObjectPropertyAccessor.getPathString(pathArray1)}`); }
const ii2 = pathArray2.length - 1;
if (ii2 < 0) { throw new Error('Invalid path 2'); }
const target2 = this.get(pathArray2, ii2);
const key2 = pathArray2[ii2];
if (!ObjectPropertyAccessor.isValidPropertyType(target2, key2)) { throw new Error(`Invalid path 2: ${ObjectPropertyAccessor.getPathString(pathArray2)}`); }
const value1 = target1[key1];
const value2 = target2[key2];
target1[key1] = value2;
try {
target2[key2] = value1;
} catch (e) {
// Revert
try {
target1[key1] = value1;
} catch (e2) {
// NOP
}
throw e;
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}
}
/**
* Converts a path string to a path array.
* @param pathArray The path array to convert.
* @returns A string representation of pathArray.
*/
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static getPathString(pathArray) {
const regexShort = /^[a-zA-Z_][a-zA-Z0-9_]*$/;
let pathString = '';
let first = true;
for (let part of pathArray) {
switch (typeof part) {
case 'number':
if (Math.floor(part) !== part || part < 0) {
throw new Error('Invalid index');
}
part = `[${part}]`;
break;
case 'string':
if (!regexShort.test(part)) {
const escapedPart = part.replace(/["\\]/g, '\\$&');
part = `["${escapedPart}"]`;
} else {
if (!first) {
part = `.${part}`;
}
}
break;
default:
throw new Error(`Invalid type: ${typeof part}`);
}
pathString += part;
first = false;
}
return pathString;
}
/**
* Converts a path array to a path string. For the most part, the format of this string
* matches Javascript's notation for property access.
* @param pathString The path string to convert.
* @returns An array representation of pathString.
*/
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static getPathArray(pathString) {
const pathArray = [];
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let state = 'empty';
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let quote = 0;
let value = '';
let escaped = false;
for (const c of pathString) {
const v = c.codePointAt(0);
switch (state) {
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case 'empty': // Empty
case 'id-start': // Expecting identifier start
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if (v === 0x5b) { // '['
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if (state === 'id-start') {
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throw new Error(`Unexpected character: ${c}`);
}
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state = 'open-bracket';
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} else if (
(v >= 0x41 && v <= 0x5a) || // ['A', 'Z']
(v >= 0x61 && v <= 0x7a) || // ['a', 'z']
v === 0x5f // '_'
) {
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state = 'id';
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value += c;
} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
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case 'id': // Identifier
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if (
(v >= 0x41 && v <= 0x5a) || // ['A', 'Z']
(v >= 0x61 && v <= 0x7a) || // ['a', 'z']
(v >= 0x30 && v <= 0x39) || // ['0', '9']
v === 0x5f // '_'
) {
value += c;
} else if (v === 0x5b) { // '['
pathArray.push(value);
value = '';
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state = 'open-bracket';
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} else if (v === 0x2e) { // '.'
pathArray.push(value);
value = '';
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state = 'id-start';
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} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
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case 'open-bracket': // Open bracket
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if (v === 0x22 || v === 0x27) { // '"' or '\''
quote = v;
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state = 'string';
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} else if (v >= 0x30 && v <= 0x39) { // ['0', '9']
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state = 'number';
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value += c;
} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
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case 'string': // Quoted string
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if (escaped) {
value += c;
escaped = false;
} else if (v === 0x5c) { // '\\'
escaped = true;
} else if (v !== quote) {
value += c;
} else {
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state = 'close-bracket';
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}
break;
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case 'number': // Number
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if (v >= 0x30 && v <= 0x39) { // ['0', '9']
value += c;
} else if (v === 0x5d) { // ']'
pathArray.push(Number.parseInt(value, 10));
value = '';
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state = 'next';
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} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
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case 'close-bracket': // Expecting closing bracket after quoted string
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if (v === 0x5d) { // ']'
pathArray.push(value);
value = '';
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state = 'next';
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} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
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case 'next': // Expecting . or [
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if (v === 0x5b) { // '['
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state = 'open-bracket';
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} else if (v === 0x2e) { // '.'
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state = 'id-start';
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} else {
throw new Error(`Unexpected character: ${c}`);
}
break;
}
}
switch (state) {
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case 'empty':
case 'next':
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break;
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case 'id':
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pathArray.push(value);
value = '';
break;
default:
throw new Error('Path not terminated correctly');
}
return pathArray;
}
/**
* Checks whether an object or array has the specified property.
* @param object The object to test.
* @param property The property to check for existence.
* This value should be a string if the object is a non-array object.
* For arrays, it should be an integer.
* @returns true if the property exists, otherwise false.
*/
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static hasProperty(object, property) {
switch (typeof property) {
case 'string':
return (
typeof object === 'object' &&
object !== null &&
!Array.isArray(object) &&
Object.prototype.hasOwnProperty.call(object, property)
);
case 'number':
return (
Array.isArray(object) &&
property >= 0 &&
property < object.length &&
property === Math.floor(property)
);
default:
return false;
}
}
/**
* Checks whether a property is valid for the given object
* @param object The object to test.
* @param property The property to check for existence.
* @returns true if the property is correct for the given object type, otherwise false.
* For arrays, this means that the property should be a positive integer.
* For non-array objects, the property should be a string.
*/
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static isValidPropertyType(object, property) {
switch (typeof property) {
case 'string':
return (
typeof object === 'object' &&
object !== null &&
!Array.isArray(object)
);
case 'number':
return (
Array.isArray(object) &&
property >= 0 &&
property === Math.floor(property)
);
default:
return false;
}
}
}