| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | * |
| 7 | * @flow |
| 8 | */ |
| 9 | |
| 10 | import {TEXT_NODE} from './HTMLNodeType'; |
| 11 | |
| 12 | /** |
| 13 | * Given any node return the first leaf node without children. |
| 14 | * |
| 15 | * @param {DOMElement|DOMTextNode} node |
| 16 | * @return {DOMElement|DOMTextNode} |
| 17 | */ |
| 18 | function getLeafNode(node: ?(Node | Element)) { |
| 19 | while (node && node.firstChild) { |
| 20 | node = node.firstChild; |
| 21 | } |
| 22 | return node; |
| 23 | } |
| 24 | |
| 25 | /** |
| 26 | * Get the next sibling within a container. This will walk up the |
| 27 | * DOM if a node's siblings have been exhausted. |
| 28 | * |
| 29 | * @param {DOMElement|DOMTextNode} node |
| 30 | * @return {?DOMElement|DOMTextNode} |
| 31 | */ |
| 32 | function getSiblingNode(node: ?(Node | Element)) { |
| 33 | while (node) { |
| 34 | if (node.nextSibling) { |
| 35 | return node.nextSibling; |
| 36 | } |
| 37 | node = node.parentNode; |
| 38 | } |
| 39 | } |
| 40 | |
| 41 | /** |
| 42 | * Get object describing the nodes which contain characters at offset. |
| 43 | * |
| 44 | * @param {DOMElement|DOMTextNode} root |
| 45 | * @param {number} offset |
| 46 | * @return {?object} |
| 47 | */ |
| 48 | function getNodeForCharacterOffset(root: Element, offset: number): ?Object { |
| 49 | let node = getLeafNode(root); |
| 50 | let nodeStart = 0; |
| 51 | let nodeEnd = 0; |
| 52 | |
| 53 | while (node) { |
| 54 | if (node.nodeType === TEXT_NODE) { |
| 55 | nodeEnd = nodeStart + node.textContent.length; |
| 56 | |
| 57 | if (nodeStart <= offset && nodeEnd >= offset) { |
| 58 | return { |
| 59 | node: node, |
| 60 | offset: offset - nodeStart, |
| 61 | }; |
| 62 | } |
| 63 | |
| 64 | nodeStart = nodeEnd; |
| 65 | } |
| 66 | |
| 67 | node = getLeafNode(getSiblingNode(node)); |
| 68 | } |
| 69 | } |
| 70 | |
| 71 | export default getNodeForCharacterOffset; |