index.js

import process from 'node:process';
import ansiEscapes from 'ansi-escapes';
import cliCursor from 'cli-cursor';
import wrapAnsi from 'wrap-ansi';
import sliceAnsi from 'slice-ansi';

const defaultTerminalHeight = 24;

const getWidth = stream => {
	const {columns} = stream;

	if (!columns) {
		return 80;
	}

	return columns;
};

const fitToTerminalHeight = (stream, text) => {
	const terminalHeight = stream.rows || defaultTerminalHeight;
	const lines = text.split('\n');

	const toRemove = lines.length - terminalHeight;
	if (toRemove <= 0) {
		return text;
	}

	return sliceAnsi(
		text,
		lines.slice(0, toRemove).join('\n').length + 1,
		text.length);
};

export function createLogUpdate(stream, {showCursor = false} = {}) {
	let previousLineCount = 0;
	let previousWidth = getWidth(stream);
	let previousOutput = '';

	const render = (...arguments_) => {
		if (!showCursor) {
			cliCursor.hide();
		}

		let output = arguments_.join(' ') + '\n';
		output = fitToTerminalHeight(stream, output);
		const width = getWidth(stream);
		if (output === previousOutput && previousWidth === width) {
			return;
		}

		previousOutput = output;
		previousWidth = width;
		output = wrapAnsi(output, width, {
			trim: false,
			hard: true,
			wordWrap: false,
		});
		stream.write(ansiEscapes.eraseLines(previousLineCount) + output);
		previousLineCount = output.split('\n').length;
	};

	render.clear = () => {
		stream.write(ansiEscapes.eraseLines(previousLineCount));
		previousOutput = '';
		previousWidth = getWidth(stream);
		previousLineCount = 0;
	};

	render.done = () => {
		previousOutput = '';
		previousWidth = getWidth(stream);
		previousLineCount = 0;

		if (!showCursor) {
			cliCursor.show();
		}
	};

	return render;
}

const logUpdate = createLogUpdate(process.stdout);
export default logUpdate;

export const logUpdateStderr = createLogUpdate(process.stderr);