chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/coding-agent/src/utils/syntax-highlight.ts

@@ -0,0 +1,212 @@
+import hljs from "highlight.js/lib/core.js";
+import bash from "highlight.js/lib/languages/bash.js";
+import c from "highlight.js/lib/languages/c.js";
+import cpp from "highlight.js/lib/languages/cpp.js";
+import csharp from "highlight.js/lib/languages/csharp.js";
+import dart from "highlight.js/lib/languages/dart.js";
+import go from "highlight.js/lib/languages/go.js";
+import groovy from "highlight.js/lib/languages/groovy.js";
+import java from "highlight.js/lib/languages/java.js";
+import javascript from "highlight.js/lib/languages/javascript.js";
+import kotlin from "highlight.js/lib/languages/kotlin.js";
+import lua from "highlight.js/lib/languages/lua.js";
+import nix from "highlight.js/lib/languages/nix.js";
+import perl from "highlight.js/lib/languages/perl.js";
+import php from "highlight.js/lib/languages/php.js";
+import python from "highlight.js/lib/languages/python.js";
+import ruby from "highlight.js/lib/languages/ruby.js";
+import rust from "highlight.js/lib/languages/rust.js";
+import scala from "highlight.js/lib/languages/scala.js";
+import swift from "highlight.js/lib/languages/swift.js";
+import typescript from "highlight.js/lib/languages/typescript.js";
+import { decodeHtmlEntityAt } from "./html.ts";
+
+const eagerLanguages = {
+	python,
+	java,
+	go,
+	javascript,
+	cpp,
+	typescript,
+	php,
+	ruby,
+	c,
+	csharp,
+	nix,
+	bash,
+	rust,
+	scala,
+	kotlin,
+	swift,
+	dart,
+	groovy,
+	perl,
+	lua,
+};
+
+for (const [name, language] of Object.entries(eagerLanguages)) {
+	hljs.registerLanguage(name, language);
+}
+
+let allLanguagesPromise: Promise<void> | undefined;
+
+export function loadAllHighlightLanguages(): Promise<void> {
+	if (!allLanguagesPromise) {
+		allLanguagesPromise = new Promise((resolve) => {
+			setImmediate(() => {
+				void import("highlight.js/lib/index.js").then(
+					() => resolve(),
+					() => {
+						// Eager languages and plaintext fallback remain available.
+						resolve();
+					},
+				);
+			});
+		});
+	}
+	return allLanguagesPromise;
+}
+
+export type HighlightFormatter = (text: string) => string;
+export type HighlightTheme = Partial<Record<string, HighlightFormatter>>;
+
+export interface HighlightOptions {
+	language?: string;
+	ignoreIllegals?: boolean;
+	languageSubset?: string[];
+	theme?: HighlightTheme;
+}
+
+const SPAN_CLOSE = "</span>";
+const HIGHLIGHT_CLASS_PREFIX = "hljs-";
+
+function getScopeFromSpanTag(tag: string): string | undefined {
+	const match = /\sclass\s*=\s*(?:"([^"]*)"|'([^']*)')/.exec(tag);
+	const classValue = match?.[1] ?? match?.[2];
+	if (!classValue) {
+		return undefined;
+	}
+
+	for (const className of classValue.split(/\s+/)) {
+		if (className.startsWith(HIGHLIGHT_CLASS_PREFIX)) {
+			return className.slice(HIGHLIGHT_CLASS_PREFIX.length);
+		}
+	}
+
+	return undefined;
+}
+
+function getScopeFormatter(scope: string, theme: HighlightTheme): HighlightFormatter | undefined {
+	const exact = theme[scope];
+	if (exact) {
+		return exact;
+	}
+
+	const dotIndex = scope.indexOf(".");
+	if (dotIndex !== -1) {
+		const prefixFormatter = theme[scope.slice(0, dotIndex)];
+		if (prefixFormatter) {
+			return prefixFormatter;
+		}
+	}
+
+	const dashIndex = scope.indexOf("-");
+	if (dashIndex !== -1) {
+		const prefixFormatter = theme[scope.slice(0, dashIndex)];
+		if (prefixFormatter) {
+			return prefixFormatter;
+		}
+	}
+
+	return undefined;
+}
+
+function getActiveFormatter(scopes: Array<string | undefined>, theme: HighlightTheme): HighlightFormatter | undefined {
+	for (let i = scopes.length - 1; i >= 0; i--) {
+		const scope = scopes[i];
+		if (!scope) {
+			continue;
+		}
+		const formatter = getScopeFormatter(scope, theme);
+		if (formatter) {
+			return formatter;
+		}
+	}
+	return theme.default;
+}
+
+function isSpanOpenTagStart(html: string, index: number): boolean {
+	if (!html.startsWith("<span", index)) {
+		return false;
+	}
+	const nextChar = html[index + "<span".length];
+	return nextChar === ">" || nextChar === " " || nextChar === "\t" || nextChar === "\n" || nextChar === "\r";
+}
+
+export function renderHighlightedHtml(html: string, theme: HighlightTheme = {}): string {
+	let output = "";
+	let textBuffer = "";
+	const scopes: Array<string | undefined> = [];
+
+	const flushText = () => {
+		if (!textBuffer) {
+			return;
+		}
+		const formatter = getActiveFormatter(scopes, theme);
+		output += formatter ? formatter(textBuffer) : textBuffer;
+		textBuffer = "";
+	};
+
+	let index = 0;
+	while (index < html.length) {
+		if (isSpanOpenTagStart(html, index)) {
+			const tagEndIndex = html.indexOf(">", index + 5);
+			if (tagEndIndex !== -1) {
+				flushText();
+				const tag = html.slice(index, tagEndIndex + 1);
+				const scope = getScopeFromSpanTag(tag);
+				scopes.push(scope);
+				index = tagEndIndex + 1;
+				continue;
+			}
+		}
+
+		if (html.startsWith(SPAN_CLOSE, index)) {
+			flushText();
+			if (scopes.length > 0) {
+				scopes.pop();
+			}
+			index += SPAN_CLOSE.length;
+			continue;
+		}
+
+		if (html[index] === "&") {
+			const decoded = decodeHtmlEntityAt(html, index);
+			if (decoded) {
+				textBuffer += decoded.text;
+				index += decoded.length;
+				continue;
+			}
+		}
+
+		textBuffer += html[index];
+		index++;
+	}
+
+	flushText();
+	return output;
+}
+
+export function highlight(code: string, options: HighlightOptions = {}): string {
+	const html = options.language
+		? hljs.highlight(code, {
+				language: options.language,
+				ignoreIllegals: options.ignoreIllegals,
+			}).value
+		: hljs.highlightAuto(code, options.languageSubset).value;
+	return renderHighlightedHtml(html, options.theme);
+}
+
+export function supportsLanguage(name: string): boolean {
+	return hljs.getLanguage(name) !== undefined;
+}