| 1 | import { lazy, memo, startTransition, Suspense, useEffect, useLayoutEffect, useMemo, useRef, useState } from "react"; |
| 2 | |
| 3 | const MarkdownRenderer = lazy(() => import("./MarkdownRenderer")); |
| 4 | const STREAMING_TAIL_THRESHOLD = 8_000; |
| 5 | const FINALIZE_SETTLE_MS = 50; |
| 6 | const FINALIZE_IDLE_TIMEOUT_MS = 1_000; |
| 7 | const MARKDOWN_SECTION_TARGET_CHARS = 12_000; |
| 8 | const CROSS_SECTION_REFERENCE_RE = /(?:^ {0,3}\[[^\]\n]+\]:|\[\^[^\]\n]+\])/m; |
| 9 | const CROSS_SECTION_CONTAINER_RE = /^ {0,3}(?:>|(?:[-+*]|\d{1,9}[.)])(?:[ \t]+|$)|<)/; |
| 10 | |
| 11 | function scanMarkdownSections(text: string): { boundaries: number[]; hasCrossSectionContainer: boolean } { |
| 12 | const boundaries = [0]; |
| 13 | let lineStart = 0; |
| 14 | let fence: { marker: string; length: number } | null = null; |
| 15 | let displayMath = false; |
| 16 | let boundaryAfterFence = false; |
| 17 | let hasCrossSectionContainer = false; |
| 18 | |
| 19 | const addBoundary = (offset: number) => { |
| 20 | if (offset > 0 && boundaries[boundaries.length - 1] !== offset) boundaries.push(offset); |
| 21 | }; |
| 22 | |
| 23 | while (lineStart < text.length) { |
| 24 | const newline = text.indexOf("\n", lineStart); |
| 25 | const lineEnd = newline === -1 ? text.length : newline + 1; |
| 26 | const line = text.slice(lineStart, newline === -1 ? text.length : newline).replace(/\r$/, ""); |
| 27 | const trimmed = line.trim(); |
| 28 | |
| 29 | if (fence) { |
| 30 | const close = new RegExp(`^ {0,3}${fence.marker}{${fence.length},}[ \\t]*$`); |
| 31 | if (close.test(line)) { |
| 32 | fence = null; |
| 33 | boundaryAfterFence = true; |
| 34 | } |
| 35 | lineStart = lineEnd; |
| 36 | continue; |
| 37 | } |
| 38 | |
| 39 | if (displayMath) { |
| 40 | if (trimmed === "$$") { |
| 41 | displayMath = false; |
| 42 | boundaryAfterFence = true; |
| 43 | } |
| 44 | lineStart = lineEnd; |
| 45 | continue; |
| 46 | } |
| 47 | |
| 48 | if (boundaryAfterFence && trimmed !== "") { |
| 49 | addBoundary(lineStart); |
| 50 | boundaryAfterFence = false; |
| 51 | } |
| 52 | |
| 53 | if (CROSS_SECTION_CONTAINER_RE.test(line)) { |
| 54 | hasCrossSectionContainer = true; |
| 55 | } |
| 56 | const fenceMatch = /^ {0,3}(`{3,}|~{3,})/.exec(line); |
| 57 | if (fenceMatch) { |
| 58 | addBoundary(lineStart); |
| 59 | fence = { marker: fenceMatch[1][0], length: fenceMatch[1].length }; |
| 60 | } else if (trimmed === "$$") { |
| 61 | addBoundary(lineStart); |
| 62 | displayMath = true; |
| 63 | } else if (/^ {0,3}#{1,6}(?:[ \t]+|$)/.test(line)) { |
| 64 | addBoundary(lineStart); |
| 65 | } |
| 66 | lineStart = lineEnd; |
| 67 | } |
| 68 | |
| 69 | return { boundaries, hasCrossSectionContainer }; |
| 70 | } |
| 71 | |
| 72 | // Stable top-level sections let React.memo retain completed Markdown while the |
| 73 | // streaming tail changes. Cross-section references intentionally stay in one |
| 74 | // renderer because their definitions can affect nodes anywhere in the document. |
| 75 | export function splitStableMarkdownSections(text: string): string[] { |
| 76 | if (text.length < MARKDOWN_SECTION_TARGET_CHARS || CROSS_SECTION_REFERENCE_RE.test(text)) return [text]; |
| 77 | const { boundaries, hasCrossSectionContainer } = scanMarkdownSections(text); |
| 78 | if (hasCrossSectionContainer) return [text]; |
| 79 | if (boundaries.length === 1) return [text]; |
| 80 | |
| 81 | const sections = boundaries.map((start, index) => text.slice(start, boundaries[index + 1] ?? text.length)); |
| 82 | const chunks: string[] = []; |
| 83 | let current = ""; |
| 84 | for (const section of sections) { |
| 85 | if (current && current.length + section.length > MARKDOWN_SECTION_TARGET_CHARS) { |
| 86 | chunks.push(current); |
| 87 | current = section; |
| 88 | } else { |
| 89 | current += section; |
| 90 | } |
| 91 | } |
| 92 | if (current) chunks.push(current); |
| 93 | return chunks.length > 1 ? chunks : [text]; |
| 94 | } |
| 95 | |
| 96 | type IdleWindow = Window & { |
| 97 | requestIdleCallback?: (callback: () => void, options?: { timeout: number }) => number; |
| 98 | cancelIdleCallback?: (handle: number) => void; |
| 99 | }; |
| 100 | |
| 101 | function scheduleMarkdownFinalization(callback: () => void): () => void { |
| 102 | const idleWindow = window as IdleWindow; |
| 103 | let cancelled = false; |
| 104 | let idleHandle: number | null = null; |
| 105 | let frameHandle: number | null = null; |
| 106 | const timeoutHandle = window.setTimeout(() => { |
| 107 | if (cancelled) return; |
| 108 | const run = () => { |
| 109 | if (cancelled) return; |
| 110 | startTransition(callback); |
| 111 | }; |
| 112 | if (idleWindow.requestIdleCallback) { |
| 113 | idleHandle = idleWindow.requestIdleCallback(run, { timeout: FINALIZE_IDLE_TIMEOUT_MS }); |
| 114 | } else { |
| 115 | frameHandle = requestAnimationFrame(run); |
| 116 | } |
| 117 | }, FINALIZE_SETTLE_MS); |
| 118 | |
| 119 | return () => { |
| 120 | cancelled = true; |
| 121 | window.clearTimeout(timeoutHandle); |
| 122 | if (idleHandle !== null) idleWindow.cancelIdleCallback?.(idleHandle); |
| 123 | if (frameHandle !== null) cancelAnimationFrame(frameHandle); |
| 124 | }; |
| 125 | } |
| 126 | |
| 127 | export function streamingMarkdownCommitInterval(textLength: number): number { |
| 128 | if (textLength >= 32_000) return 300; |
| 129 | if (textLength >= 8_000) return 150; |
| 130 | return 50; |
| 131 | } |
| 132 | |
| 133 | export function useRenderedMarkdownText(text: string, streaming: boolean): string { |
| 134 | const [renderedText, setRenderedText] = useState(text); |
| 135 | const latestTextRef = useRef(text); |
| 136 | const frameRef = useRef<number | null>(null); |
| 137 | const timeoutRef = useRef<number | null>(null); |
| 138 | const lastCommitAtRef = useRef(0); |
| 139 | const wasStreamingRef = useRef(streaming); |
| 140 | const finalizingTextRef = useRef<string | null>(null); |
| 141 | const cancelFinalizationRef = useRef<(() => void) | null>(null); |
| 142 | const finalizationStartedAtRef = useRef(0); |
| 143 | const finalizationLengthRef = useRef(0); |
| 144 | |
| 145 | latestTextRef.current = text; |
| 146 | |
| 147 | useLayoutEffect(() => { |
| 148 | const endedStreaming = wasStreamingRef.current && !streaming; |
| 149 | wasStreamingRef.current = streaming; |
| 150 | if (streaming) { |
| 151 | cancelFinalizationRef.current?.(); |
| 152 | cancelFinalizationRef.current = null; |
| 153 | finalizingTextRef.current = null; |
| 154 | return; |
| 155 | } |
| 156 | lastCommitAtRef.current = 0; |
| 157 | if (frameRef.current !== null) { |
| 158 | cancelAnimationFrame(frameRef.current); |
| 159 | frameRef.current = null; |
| 160 | } |
| 161 | if (timeoutRef.current !== null) { |
| 162 | window.clearTimeout(timeoutRef.current); |
| 163 | timeoutRef.current = null; |
| 164 | } |
| 165 | if (renderedText === text) { |
| 166 | cancelFinalizationRef.current?.(); |
| 167 | cancelFinalizationRef.current = null; |
| 168 | finalizingTextRef.current = null; |
| 169 | if (finalizationStartedAtRef.current > 0) { |
| 170 | performance.measure("reasonix:markdown-finalize", { |
| 171 | start: finalizationStartedAtRef.current, |
| 172 | end: performance.now(), |
| 173 | detail: { textLength: finalizationLengthRef.current }, |
| 174 | }); |
| 175 | finalizationStartedAtRef.current = 0; |
| 176 | finalizationLengthRef.current = 0; |
| 177 | } |
| 178 | return; |
| 179 | } |
| 180 | |
| 181 | const canFinalizeWhenIdle = |
| 182 | (endedStreaming || finalizingTextRef.current !== null) && |
| 183 | text.length >= STREAMING_TAIL_THRESHOLD && |
| 184 | text.startsWith(renderedText); |
| 185 | if (canFinalizeWhenIdle) { |
| 186 | if (finalizingTextRef.current === text) return; |
| 187 | cancelFinalizationRef.current?.(); |
| 188 | finalizingTextRef.current = text; |
| 189 | cancelFinalizationRef.current = scheduleMarkdownFinalization(() => { |
| 190 | cancelFinalizationRef.current = null; |
| 191 | finalizationStartedAtRef.current = performance.now(); |
| 192 | finalizationLengthRef.current = latestTextRef.current.length; |
| 193 | setRenderedText(latestTextRef.current); |
| 194 | }); |
| 195 | return; |
| 196 | } |
| 197 | |
| 198 | cancelFinalizationRef.current?.(); |
| 199 | cancelFinalizationRef.current = null; |
| 200 | finalizingTextRef.current = null; |
| 201 | setRenderedText(text); |
| 202 | }, [renderedText, streaming, text]); |
| 203 | |
| 204 | useLayoutEffect(() => { |
| 205 | if (streaming) lastCommitAtRef.current = performance.now(); |
| 206 | }, [renderedText, streaming]); |
| 207 | |
| 208 | useEffect(() => { |
| 209 | if (!streaming || renderedText === text || frameRef.current !== null || timeoutRef.current !== null) return; |
| 210 | const commit = () => { |
| 211 | timeoutRef.current = null; |
| 212 | frameRef.current = requestAnimationFrame(() => { |
| 213 | frameRef.current = null; |
| 214 | setRenderedText(latestTextRef.current); |
| 215 | }); |
| 216 | }; |
| 217 | const now = performance.now(); |
| 218 | const elapsed = lastCommitAtRef.current === 0 ? Number.POSITIVE_INFINITY : now - lastCommitAtRef.current; |
| 219 | const delay = streamingMarkdownCommitInterval(text.length) - elapsed; |
| 220 | if (delay <= 0) commit(); |
| 221 | else timeoutRef.current = window.setTimeout(commit, delay); |
| 222 | }, [renderedText, streaming, text]); |
| 223 | |
| 224 | useEffect(() => () => { |
| 225 | if (frameRef.current !== null) cancelAnimationFrame(frameRef.current); |
| 226 | if (timeoutRef.current !== null) window.clearTimeout(timeoutRef.current); |
| 227 | cancelFinalizationRef.current?.(); |
| 228 | }, []); |
| 229 | |
| 230 | return renderedText; |
| 231 | } |
| 232 | |
| 233 | const StreamingMarkdownTail = memo(function StreamingMarkdownTail({ text }: { text: string }) { |
| 234 | const elementRef = useRef<HTMLDivElement>(null); |
| 235 | const previousTextRef = useRef(""); |
| 236 | |
| 237 | useLayoutEffect(() => { |
| 238 | const element = elementRef.current; |
| 239 | if (!element) return; |
| 240 | const previousText = previousTextRef.current; |
| 241 | const textNode = element.firstChild; |
| 242 | if (text.startsWith(previousText) && textNode?.nodeType === Node.TEXT_NODE) { |
| 243 | (textNode as Text).appendData(text.slice(previousText.length)); |
| 244 | } else { |
| 245 | element.textContent = text; |
| 246 | } |
| 247 | previousTextRef.current = text; |
| 248 | }, [text]); |
| 249 | |
| 250 | return <div ref={elementRef} className="md md--stream-tail" />; |
| 251 | }); |
| 252 | |
| 253 | export const Markdown = memo(function Markdown({ |
| 254 | text, |
| 255 | plainStatusBlocks = false, |
| 256 | streaming = false, |
| 257 | }: { |
| 258 | text: string; |
| 259 | plainStatusBlocks?: boolean; |
| 260 | streaming?: boolean; |
| 261 | }) { |
| 262 | const renderedText = useRenderedMarkdownText(text, streaming); |
| 263 | const sections = useMemo(() => splitStableMarkdownSections(renderedText), [renderedText]); |
| 264 | const pendingText = text.length >= STREAMING_TAIL_THRESHOLD && text.startsWith(renderedText) |
| 265 | ? text.slice(renderedText.length) |
| 266 | : ""; |
| 267 | return ( |
| 268 | <> |
| 269 | <Suspense fallback={<div className="md">{renderedText}</div>}> |
| 270 | {sections.length === 1 ? ( |
| 271 | <MarkdownRenderer text={renderedText} plainStatusBlocks={plainStatusBlocks} /> |
| 272 | ) : ( |
| 273 | <div className="md" data-markdown-sections={sections.length}> |
| 274 | {sections.map((section, index) => ( |
| 275 | <MarkdownRenderer key={index} text={section} plainStatusBlocks={plainStatusBlocks} bare /> |
| 276 | ))} |
| 277 | </div> |
| 278 | )} |
| 279 | </Suspense> |
| 280 | {pendingText && <StreamingMarkdownTail text={pendingText} />} |
| 281 | </> |
| 282 | ); |
| 283 | }); |
| 284 |