Improve internal API

src/utils.ts

@@ -1,3 +1,6 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
 export function left_pad(str: string, len: number) {
 	while (str.length < len) str = ` ${str}`;
 	return str;
@@ -7,4 +10,110 @@ export function repeat(str: string, i: number) {
 	let result = '';
 	while (i--) result += str;
 	return result;
-}
+}
+
+export function format_milliseconds(ms: number) {
+	if (ms < 1000) return `${ms}ms`;
+	if (ms < 60000) return `${(ms / 1000).toFixed(1)}s`;
+
+	const minutes = ~~(ms / 60000);
+	const seconds = Math.round((ms % 60000) / 1000);
+	return `${minutes}m${seconds < 10 ? '0' : ''}${seconds}s`;
+}
+
+export function elapsed(start: number) {
+	return format_milliseconds(Date.now() - start);
+}
+
+export function walk(cwd: string, dir = cwd, files: string[] = []) {
+	fs.readdirSync(dir).forEach(file => {
+		const resolved = path.resolve(dir, file);
+		if (fs.statSync(resolved).isDirectory()) {
+			walk(cwd, resolved, files);
+		} else {
+			files.push(posixify(path.relative(cwd, resolved)));
+		}
+	});
+
+	return files;
+}
+
+export function posixify(str: string) {
+	return str.replace(/\\/g, '/');
+}
+
+const previous_contents = new Map();
+
+export function write_if_changed(file: string, code: string) {
+	if (code !== previous_contents.get(file)) {
+		previous_contents.set(file, code);
+		fs.writeFileSync(file, code);
+		fudge_mtime(file);
+	}
+}
+
+export function stringify(string: string, includeQuotes: boolean = true) {
+	const quoted = JSON.stringify(string);
+	return includeQuotes ? quoted : quoted.slice(1, -1);
+}
+
+export function fudge_mtime(file: string) {
+	// need to fudge the mtime so that webpack doesn't go doolally
+	const { atime, mtime } = fs.statSync(file);
+	fs.utimesSync(
+		file,
+		new Date(atime.getTime() - 999999),
+		new Date(mtime.getTime() - 999999)
+	);
+}
+
+export const reserved_words = new Set([
+	'arguments',
+	'await',
+	'break',
+	'case',
+	'catch',
+	'class',
+	'const',
+	'continue',
+	'debugger',
+	'default',
+	'delete',
+	'do',
+	'else',
+	'enum',
+	'eval',
+	'export',
+	'extends',
+	'false',
+	'finally',
+	'for',
+	'function',
+	'if',
+	'implements',
+	'import',
+	'in',
+	'instanceof',
+	'interface',
+	'let',
+	'new',
+	'null',
+	'package',
+	'private',
+	'protected',
+	'public',
+	'return',
+	'static',
+	'super',
+	'switch',
+	'this',
+	'throw',
+	'true',
+	'try',
+	'typeof',
+	'var',
+	'void',
+	'while',
+	'with',
+	'yield',
+]);