| 1 | /**
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| 2 | * @typedef {import('unist').Node} Node
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| 3 | * @typedef {import('unist').Parent} Parent
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| 4 | * @typedef {import('unist-util-is').Test} Test
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| 5 | *
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| 6 | * @typedef Options
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| 7 | * Configuration.
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| 8 | * @property {boolean | null | undefined} [cascade=true]
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| 9 | * Whether to drop parent nodes if they had children, but all their children
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| 10 | * were filtered out.
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| 11 | */
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| 12 |
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| 13 | import {convert} from 'unist-util-is'
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| 14 |
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| 15 | /** @type {Array<unknown>} */
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| 16 | const empty = []
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| 17 |
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| 18 | /**
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| 19 | * Change the given `tree` by removing all nodes that pass `test`.
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| 20 | *
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| 21 | * The tree is walked in preorder (NLR), visiting the node itself, then its
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| 22 | * head, etc.
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| 23 | *
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| 24 | * @param tree
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| 25 | * Tree to change.
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| 26 | * @param options
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| 27 | * Configuration (optional).
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| 28 | * @param test
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| 29 | * `unist-util-is` compatible test.
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| 30 | * @returns
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| 31 | * The given `tree` without nodes that pass `test`.
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| 32 | *
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| 33 | * `null` is returned if `tree` itself didn’t pass the test or is cascaded
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| 34 | * away.
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| 35 | */
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| 36 | // To do: next major: don’t return `tree`.
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| 37 | export const remove =
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| 38 | /**
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| 39 | * @type {(
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| 40 | * (<Tree extends Node>(node: Tree, options: Options, test: Test) => Tree | null) &
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| 41 | * (<Tree extends Node>(node: Tree, test: Test) => Tree | null)
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| 42 | * )}
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| 43 | */
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| 44 | (
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| 45 | /**
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| 46 | * @param {Node} tree
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| 47 | * @param {Options | null | undefined} [options]
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| 48 | * @param {Test | null | undefined} [test]
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| 49 | * @returns {Node | null}
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| 50 | */
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| 51 | function (tree, options, test) {
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| 52 | const is = convert(test || options)
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| 53 | const cascade =
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| 54 | !options || options.cascade === undefined || options.cascade === null
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| 55 | ? true
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| 56 | : options.cascade
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| 57 |
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| 58 | return preorder(tree)
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| 59 |
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| 60 | /**
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| 61 | * Check and remove nodes recursively in preorder.
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| 62 | * For each composite node, modify its children array in-place.
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| 63 | *
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| 64 | * @param {Node} node
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| 65 | * @param {number | null | undefined} [index]
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| 66 | * @param {Parent | null | undefined} [parent]
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| 67 | * @returns {Node | null}
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| 68 | */
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| 69 | function preorder(node, index, parent) {
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| 70 | /** @type {Array<Node>} */
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| 71 | // @ts-expect-error looks like a parent.
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| 72 | const children = node.children || empty
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| 73 | let childIndex = -1
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| 74 | let position = 0
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| 75 |
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| 76 | if (is(node, index, parent)) {
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| 77 | return null
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| 78 | }
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| 79 |
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| 80 | if (children.length > 0) {
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| 81 | // Move all living children to the beginning of the children array.
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| 82 | while (++childIndex < children.length) {
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| 83 | // @ts-expect-error looks like a parent.
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| 84 | if (preorder(children[childIndex], childIndex, node)) {
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| 85 | children[position++] = children[childIndex]
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| 86 | }
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| 87 | }
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| 88 |
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| 89 | // Cascade delete.
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| 90 | if (cascade && !position) {
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| 91 | return null
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| 92 | }
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| 93 |
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| 94 | // Drop other nodes.
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| 95 | children.length = position
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| 96 | }
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| 97 |
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| 98 | return node
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| 99 | }
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| 100 | }
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| 101 | )
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