bnash/src/prompt.js

A command-line editor for bash or compatible shells, aiming to provide great UX and productivity

const env = require('./env')
const terminal = require('./terminal')


let cursor = null

// Default prompt function
let prompt = (pinfo) => 'nash> '


/**
 * Sets the function that will be invoked for building the prompt string
 * @param {function(object): string} promptFunction - The function that will be
 *  invoked whenever the prompt needs to be displayed. This function should
 *  return a string, which will be presented to the user when typing a command.
 *
 * The prompt function receives a single object parameter with relevant
 * information about the environment, which can be optionally used by the
 * prompt function in order to build the prompt string.
 * Those properties are the following:
 * 	- cwd: the current working directory
 *  - username: the current user name
 *  - hostname: the host name
 *  - fqdn: the fully qualified domain name of the host
 *  - retCode: the return code of the most recent command
 *  - isRemote: true if `nash` is acting on a remote connection
 */
function setPrompt(promptFunction) {
	prompt = promptFunction
}

function put(str) {
	process.stdout.write(str)
}

function hideCursor() {
	put(terminal.HIDE_CURSOR)
}

function showCursor() {
	put(terminal.SHOW_CURSOR)
}

let cursorCB = null
let captureBuf = ''

function promptOwnsInput() {
	return !!cursorCB
}

function captureCursorPosition() {
	process.stdin.on('data', buf => {
		if (!cursorCB) return
		captureBuf += buf.toString()
		if (captureBuf.length < 6) return
		let m = captureBuf.match(/\x1b\[([0-9]+);([0-9]+)R/)
		if (!m || m.length < 3) return
		cursor = {
			x: parseInt(m[2]) - 1,
			y: parseInt(m[1]) - 1
		}
		put(terminal.SHOW_TEXT + terminal.SHOW_CURSOR)
		cursorCB(cursor)
		cursorCB = null
		captureBuf = ''
	})
}

function getPromptPosition() {
	return cursor
}

function adjustPromptPosition(rows) {
	if (cursor.y + rows >= process.stdout.rows)
		cursor.y = process.stdout.rows - rows - 1
}

async function putPrompt() {
	let promptStr = await prompt(env.getUserStatus())
	put(promptStr)
	cursor = null
    put(terminal.HIDE_TEXT + terminal.HIDE_CURSOR + terminal.GET_CURSOR_POS)
	return new Promise(resolve => cursorCB = resolve)
}

function lineEndPosition(len) {
	let ll = cursor.x + len
	let cols = process.stdout.columns
	let x = ll % cols
	let h = Math.floor(ll / cols)
	return { x, h }
}

function putCursorAtPrompt(lineLen) {
	let { x, h } = lineEndPosition(lineLen)
	process.stdout.cursorTo(x, cursor.y + h)
}


captureCursorPosition()


module.exports = {
    setPrompt,
	putPrompt,
	hideCursor,
	showCursor,
	putCursorAtPrompt,
	lineEndPosition,
	promptOwnsInput,
	getPromptPosition,
	adjustPromptPosition
}