| 1 | import rehypeKatex from "rehype-katex"; |
| 2 | |
| 3 | type HastNode = { |
| 4 | type: string; |
| 5 | tagName?: string; |
| 6 | value?: string; |
| 7 | properties?: Record<string, unknown>; |
| 8 | children?: HastNode[]; |
| 9 | }; |
| 10 | |
| 11 | const SOURCE_MARKER = "reasonix-latex-source:"; |
| 12 | |
| 13 | function markLatexSources(node: HastNode, sources: string[]): void { |
| 14 | const children = node.children; |
| 15 | if (!children) return; |
| 16 | |
| 17 | for (let index = 0; index < children.length; index += 1) { |
| 18 | const child = children[index]; |
| 19 | const source = child.properties?.dataLatexSource; |
| 20 | if (child.type === "element" && typeof source === "string") { |
| 21 | const marker = `${SOURCE_MARKER}${sources.push(source) - 1}`; |
| 22 | children.splice(index, 0, { type: "comment", value: marker }); |
| 23 | index += 1; |
| 24 | continue; |
| 25 | } |
| 26 | markLatexSources(child, sources); |
| 27 | } |
| 28 | } |
| 29 | |
| 30 | function classNames(node: HastNode): string[] { |
| 31 | const value = node.properties?.className; |
| 32 | return Array.isArray(value) ? value.filter((item): item is string => typeof item === "string") : []; |
| 33 | } |
| 34 | |
| 35 | function findKatexRoot(node: HastNode): HastNode | null { |
| 36 | if ( |
| 37 | node.type === "element" |
| 38 | && (classNames(node).includes("katex-display") || classNames(node).includes("katex")) |
| 39 | ) { |
| 40 | return node; |
| 41 | } |
| 42 | for (const child of node.children ?? []) { |
| 43 | const root = findKatexRoot(child); |
| 44 | if (root) return root; |
| 45 | } |
| 46 | return null; |
| 47 | } |
| 48 | |
| 49 | function findTexAnnotation(node: HastNode): HastNode | null { |
| 50 | if ( |
| 51 | node.type === "element" |
| 52 | && node.tagName === "annotation" |
| 53 | && node.properties?.encoding === "application/x-tex" |
| 54 | ) { |
| 55 | return node; |
| 56 | } |
| 57 | for (const child of node.children ?? []) { |
| 58 | const annotation = findTexAnnotation(child); |
| 59 | if (annotation) return annotation; |
| 60 | } |
| 61 | return null; |
| 62 | } |
| 63 | |
| 64 | function restoreLatexSources(node: HastNode, sources: string[]): void { |
| 65 | const children = node.children; |
| 66 | if (!children) return; |
| 67 | |
| 68 | for (let index = 0; index < children.length;) { |
| 69 | const child = children[index]; |
| 70 | const markerIndex = child.type === "comment" && child.value?.startsWith(SOURCE_MARKER) |
| 71 | ? Number(child.value.slice(SOURCE_MARKER.length)) |
| 72 | : Number.NaN; |
| 73 | if (Number.isInteger(markerIndex)) { |
| 74 | const source = sources[markerIndex]; |
| 75 | const rendered = children[index + 1]; |
| 76 | const root = rendered ? findKatexRoot(rendered) : null; |
| 77 | const annotation = root ? findTexAnnotation(root) : null; |
| 78 | if (root && source !== undefined) { |
| 79 | root.properties ??= {}; |
| 80 | root.properties.dataLatexSource = source; |
| 81 | } |
| 82 | if (annotation && source !== undefined) { |
| 83 | annotation.children = [{ type: "text", value: source }]; |
| 84 | } |
| 85 | children.splice(index, 1); |
| 86 | continue; |
| 87 | } |
| 88 | restoreLatexSources(child, sources); |
| 89 | index += 1; |
| 90 | } |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Render the normalised TeX with KaTeX, then restore the original source into |
| 95 | * the generated MathML annotation so selection-copy can round-trip user input. |
| 96 | */ |
| 97 | export function rehypeReasonixKatex() { |
| 98 | const renderKatex = rehypeKatex(); |
| 99 | return ( |
| 100 | tree: Parameters<typeof renderKatex>[0], |
| 101 | file: Parameters<typeof renderKatex>[1], |
| 102 | ): undefined => { |
| 103 | const sources: string[] = []; |
| 104 | markLatexSources(tree as HastNode, sources); |
| 105 | renderKatex(tree, file); |
| 106 | restoreLatexSources(tree as HastNode, sources); |
| 107 | }; |
| 108 | } |
| 109 | |
| 110 | export const reasonixRehypePlugins = [rehypeReasonixKatex]; |
| 111 |