@lobehub/ui/es/Highlighter/SyntaxHighlighter/tokenFade.mjs

Lobe UI is an open-source UI component library for building AIGC web apps

import { STREAM_FADE_DURATION } from "@lobehub/streamdown";
//#region src/Highlighter/SyntaxHighlighter/tokenFade.ts
const MIN_GAP_MS = 16;
const MAX_GAP_MS = 160;
const MIN_CHAR_PACE_MS = 2;
const MAX_CHAR_PACE_MS = 18;
const createTokenFadeStore = () => ({
	births: [],
	lastCommitTs: 0,
	styles: /* @__PURE__ */ new Map()
});
const clamp = (value, min, max) => Math.min(max, Math.max(min, value));
const RETOKENIZED_LINES = 2;
const markTokenBirths = (store, lines, now) => {
	const lineStarts = [];
	const tokens = [];
	let offset = 0;
	for (const [lineIndex, line] of lines.entries()) {
		if (lineIndex > 0) offset += 1;
		lineStarts.push(offset);
		if (lineIndex >= lines.length - RETOKENIZED_LINES) for (const token of line) {
			tokens.push({
				length: token.content.length,
				offset
			});
			offset += token.content.length;
		}
		else for (const token of line) offset += token.content.length;
	}
	const { births } = store;
	const newChars = offset - births.length;
	if (newChars > 0) {
		const gapMs = store.lastCommitTs === 0 ? MIN_GAP_MS : clamp(now - store.lastCommitTs, MIN_GAP_MS, MAX_GAP_MS);
		const pace = clamp(gapMs / newChars, MIN_CHAR_PACE_MS, MAX_CHAR_PACE_MS);
		const cap = now + gapMs + STREAM_FADE_DURATION;
		for (let i = births.length; i < offset; i++) {
			const chained = i > 0 ? births[i - 1] + pace : now;
			births.push(Math.min(cap, Math.max(chained, now)));
		}
		store.lastCommitTs = now;
	}
	for (const token of tokens) {
		let birth = births[token.offset];
		for (let i = token.offset + 1; i < token.offset + token.length; i++) if (births[i] < birth) birth = births[i];
		for (let i = token.offset; i < token.offset + token.length; i++) births[i] = birth;
	}
	return lineStarts;
};
const resolveTokenFadeStyle = (store, offset, now) => {
	const birth = store.births[offset];
	const cached = store.styles.get(offset);
	if (cached && cached.birth === birth) return cached.style;
	const elapsed = now - birth;
	const style = elapsed >= STREAM_FADE_DURATION ? null : { animationDelay: `${-elapsed}ms` };
	store.styles.set(offset, {
		birth,
		style
	});
	return style;
};
//#endregion
export { createTokenFadeStore, markTokenBirths, resolveTokenFadeStyle };

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