readline.js

// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// Inspiration for this code comes from Salvatore Sanfilippo's linenoise.
// https://github.com/antirez/linenoise
// Reference:
// * http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
// * http://www.3waylabs.com/nw/WWW/products/wizcon/vt220.html

'use strict';

const {
    ERR_INVALID_ARG_TYPE,
    ERR_INVALID_CURSOR_POS,
    ERR_INVALID_OPT_VALUE
} = require('internal/errors').codes;
const { debug, inherits } = require('util');
const { Buffer } = require('buffer');
const EventEmitter = require('events');
const {
    CSI,
    emitKeys,
    getStringWidth,
    isFullWidthCodePoint,
    stripVTControlCharacters
} = require('internal/readline');

const {
    kEscape,
    kClearToBeginning,
    kClearToEnd,
    kClearLine,
    kClearScreenDown
} = CSI;

// Lazy load StringDecoder for startup performance.
let StringDecoder;

const kHistorySize = 30;
const kMincrlfDelay = 100;
// \r\n, \n, or \r followed by something other than \n
const lineEnding = /\r?\n|\r(?!\n)/;

const KEYPRESS_DECODER = Symbol('keypress-decoder');
const ESCAPE_DECODER = Symbol('escape-decoder');

// GNU readline library - keyseq-timeout is 500ms (default)
const ESCAPE_CODE_TIMEOUT = 500;

function createInterface(input, output, completer, terminal) {
    return new Interface(input, output, completer, terminal);
}


function Interface(input, output, completer, terminal) {
    if (!(this instanceof Interface)) {
        return new Interface(input, output, completer, terminal);
    }

    if (StringDecoder === undefined)
        StringDecoder = require('string_decoder').StringDecoder;

    this._sawReturnAt = 0;
    this.isCompletionEnabled = true;
    this._sawKeyPress = false;
    this._previousKey = null;

    EventEmitter.call(this);
    var historySize;
    var removeHistoryDuplicates = false;
    let crlfDelay;
    let prompt = '> ';

    if (input && input.input) {
        // an options object was given
        output = input.output;
        completer = input.completer;
        terminal = input.terminal;
        historySize = input.historySize;
        removeHistoryDuplicates = input.removeHistoryDuplicates;
        if (input.prompt !== undefined) {
            prompt = input.prompt;
        }
        crlfDelay = input.crlfDelay;
        input = input.input;
    }

    if (completer && typeof completer !== 'function') {
        throw new ERR_INVALID_OPT_VALUE('completer', completer);
    }

    if (historySize === undefined) {
        historySize = kHistorySize;
    }

    if (typeof historySize !== 'number' ||
        Number.isNaN(historySize) ||
        historySize < 0) {
        throw new ERR_INVALID_OPT_VALUE.RangeError('historySize', historySize);
    }

    // backwards compat; check the isTTY prop of the output stream
    //  when `terminal` was not specified
    if (terminal === undefined && !(output === null || output === undefined)) {
        terminal = !!output.isTTY;
    }

    var self = this;

    this.output = output;
    this.input = input;
    this.historySize = historySize;
    this.removeHistoryDuplicates = !!removeHistoryDuplicates;
    this.crlfDelay = crlfDelay ?
        Math.max(kMincrlfDelay, crlfDelay) : kMincrlfDelay;

    // Check arity, 2 - for async, 1 for sync
    if (typeof completer === 'function') {
        this.completer = completer.length === 2 ?
            completer :
            function completerWrapper(v, cb) {
                cb(null, completer(v));
            };
    }

    this.setPrompt(prompt);

    this.terminal = !!terminal;

    function ondata(data) {
        self._normalWrite(data);
    }

    function onend() {
        if (typeof self._line_buffer === 'string' &&
            self._line_buffer.length > 0) {
            self.emit('line', self._line_buffer);
        }
        self.close();
    }

    function ontermend() {
        if (typeof self.line === 'string' && self.line.length > 0) {
            self.emit('line', self.line);
        }
        self.close();
    }

    function onkeypress(s, key) {
        self._ttyWrite(s, key);
        if (key && key.sequence) {
            // if the key.sequence is half of a surrogate pair
            // (>= 0xd800 and <= 0xdfff), refresh the line so
            // the character is displayed appropriately.
            const ch = key.sequence.codePointAt(0);
            if (ch >= 0xd800 && ch <= 0xdfff)
                self._refreshLine();
        }
    }

    function onresize() {
        self._refreshLine();
    }

    function onSelfCloseWithoutTerminal() {
        input.removeListener('data', ondata);
        input.removeListener('end', onend);
    }
    function onSelfCloseWithTerminal() {
        input.removeListener('keypress', onkeypress);
        input.removeListener('end', ontermend);
        if (output !== null && output !== undefined) {
            output.removeListener('resize', onresize);
        }
    }

    if (!this.terminal) {
        input.on('data', ondata);
        input.on('end', onend);
        self.once('close', onSelfCloseWithoutTerminal);
        this._decoder = new StringDecoder('utf8');
    } else {
        emitKeypressEvents(input, this);

        // input usually refers to stdin
        input.on('keypress', onkeypress);
        input.on('end', ontermend);

        // Current line
        this.line = '';

        this._setRawMode(true);
        this.terminal = true;

        // Cursor position on the line.
        this.cursor = 0;

        this.history = [];
        this.historyIndex = -1;

        if (output !== null && output !== undefined)
            output.on('resize', onresize);

        self.once('close', onSelfCloseWithTerminal);
    }

    input.resume();
}

inherits(Interface, EventEmitter);

Object.defineProperty(Interface.prototype, 'columns', {
    configurable: true,
    enumerable: true,
    get: function () {
        var columns = Infinity;
        if (this.output && this.output.columns)
            columns = this.output.columns;
        return columns;
    }
});

Interface.prototype.setPrompt = function (prompt) {
    this._prompt = prompt;
};


Interface.prototype._setRawMode = function (mode) {
    const wasInRawMode = this.input.isRaw;

    if (typeof this.input.setRawMode === 'function') {
        this.input.setRawMode(mode);
    }

    return wasInRawMode;
};


Interface.prototype.prompt = function (preserveCursor) {
    if (this.paused) this.resume();
    if (this.terminal) {
        if (!preserveCursor) this.cursor = 0;
        this._refreshLine();
    } else {
        this._writeToOutput(this._prompt);
    }
};


Interface.prototype.question = function (query, cb) {
    if (typeof cb === 'function') {
        if (this._questionCallback) {
            this.prompt();
        } else {
            this._oldPrompt = this._prompt;
            this.setPrompt(query);
            this._questionCallback = cb;
            this.prompt();
        }
    }
};


Interface.prototype._onLine = function (line) {
    if (this._questionCallback) {
        var cb = this._questionCallback;
        this._questionCallback = null;
        this.setPrompt(this._oldPrompt);
        cb(line);
    } else {
        this.emit('line', line);
    }
};

Interface.prototype._writeToOutput = function _writeToOutput(stringToWrite) {
    if (typeof stringToWrite !== 'string') {
        throw new ERR_INVALID_ARG_TYPE('stringToWrite', 'string', stringToWrite);
    }

    if (this.output !== null && this.output !== undefined) {
        this.output.write(stringToWrite);
    }
};

Interface.prototype._addHistory = function () {
    if (this.line.length === 0) return '';

    // if the history is disabled then return the line
    if (this.historySize === 0) return this.line;

    // if the trimmed line is empty then return the line
    if (this.line.trim().length === 0) return this.line;

    if (this.history.length === 0 || this.history[0] !== this.line) {
        if (this.removeHistoryDuplicates) {
            // Remove older history line if identical to new one
            const dupIndex = this.history.indexOf(this.line);
            if (dupIndex !== -1) this.history.splice(dupIndex, 1);
        }

        this.history.unshift(this.line);

        // Only store so many
        if (this.history.length > this.historySize) this.history.pop();
    }

    this.historyIndex = -1;
    return this.history[0];
};


Interface.prototype._refreshLine = function () {
    // line length
    var line = this._prompt + this.line;
    var dispPos = this._getDisplayPos(line);
    var lineCols = dispPos.cols;
    var lineRows = dispPos.rows;

    // cursor position
    var cursorPos = this._getCursorPos();

    // first move to the bottom of the current line, based on cursor pos
    var prevRows = this.prevRows || 0;
    if (prevRows > 0) {
        moveCursor(this.output, 0, -prevRows);
    }

    // Cursor to left edge.
    cursorTo(this.output, 0);
    // erase data
    clearScreenDown(this.output);

    // Write the prompt and the current buffer content.
    this._writeToOutput(line);

    // Force terminal to allocate a new line
    if (lineCols === 0) {
        this._writeToOutput(' ');
    }

    // Move cursor to original position.
    cursorTo(this.output, cursorPos.cols);

    var diff = lineRows - cursorPos.rows;
    if (diff > 0) {
        moveCursor(this.output, 0, -diff);
    }

    this.prevRows = cursorPos.rows;
};


Interface.prototype.close = function () {
    if (this.closed) return;
    this.pause();
    if (this.terminal) {
        this._setRawMode(false);
    }
    this.closed = true;
    this.emit('close');
};


Interface.prototype.pause = function () {
    if (this.paused) return;
    this.input.pause();
    this.paused = true;
    this.emit('pause');
    return this;
};


Interface.prototype.resume = function () {
    if (!this.paused) return;
    this.input.resume();
    this.paused = false;
    this.emit('resume');
    return this;
};


Interface.prototype.write = function (d, key) {
    if (this.paused) this.resume();
    this.terminal ? this._ttyWrite(d, key) : this._normalWrite(d);
};

Interface.prototype._normalWrite = function (b) {
    if (b === undefined) {
        return;
    }
    var string = this._decoder.write(b);
    if (this._sawReturnAt &&
        Date.now() - this._sawReturnAt <= this.crlfDelay) {
        string = string.replace(/^\n/, '');
        this._sawReturnAt = 0;
    }

    // Run test() on the new string chunk, not on the entire line buffer.
    var newPartContainsEnding = lineEnding.test(string);

    if (this._line_buffer) {
        string = this._line_buffer + string;
        this._line_buffer = null;
    }
    if (newPartContainsEnding) {
        this._sawReturnAt = string.endsWith('\r') ? Date.now() : 0;

        // got one or more newlines; process into "line" events
        var lines = string.split(lineEnding);
        // either '' or (conceivably) the unfinished portion of the next line
        string = lines.pop();
        this._line_buffer = string;
        for (var n = 0; n < lines.length; n++)
            this._onLine(lines[n]);
    } else if (string) {
        // no newlines this time, save what we have for next time
        this._line_buffer = string;
    }
};

Interface.prototype._insertString = function (c) {
    if (this.cursor < this.line.length) {
        var beg = this.line.slice(0, this.cursor);
        var end = this.line.slice(this.cursor, this.line.length);
        this.line = beg + c + end;
        this.cursor += c.length;
        this._refreshLine();
    } else {
        this.line += c;
        this.cursor += c.length;

        if (this._getCursorPos().cols === 0) {
            this._refreshLine();
        } else {
            this._writeToOutput(c);
        }

        // a hack to get the line refreshed if it's needed
        this._moveCursor(0);
    }
};

Interface.prototype._tabComplete = function (lastKeypressWasTab) {
    var self = this;

    self.pause();
    self.completer(self.line.slice(0, self.cursor), function onComplete(err, rv) {
        self.resume();

        if (err) {
            debug('tab completion error %j', err);
            return;
        }

        const completions = rv[0];
        const completeOn = rv[1];  // the text that was completed
        if (completions && completions.length) {
            // Apply/show completions.
            if (lastKeypressWasTab) {
                self._writeToOutput('\r\n');
                var width = completions.reduce(function completionReducer(a, b) {
                    return a.length > b.length ? a : b;
                }).length + 2;  // 2 space padding
                var maxColumns = Math.floor(self.columns / width);
                if (!maxColumns || maxColumns === Infinity) {
                    maxColumns = 1;
                }
                var group = [];
                for (var i = 0; i < completions.length; i++) {
                    var c = completions[i];
                    if (c === '') {
                        handleGroup(self, group, width, maxColumns);
                        group = [];
                    } else {
                        group.push(c);
                    }
                }
                handleGroup(self, group, width, maxColumns);
            }

            // If there is a common prefix to all matches, then apply that portion.
            var f = completions.filter((e) => e);
            var prefix = commonPrefix(f);
            if (prefix.length > completeOn.length) {
                self._insertString(prefix.slice(completeOn.length));
            }

            self._refreshLine();
        }
    });
};

// this = Interface instance
function handleGroup(self, group, width, maxColumns) {
    if (group.length === 0) {
        return;
    }
    var minRows = Math.ceil(group.length / maxColumns);
    for (var row = 0; row < minRows; row++) {
        for (var col = 0; col < maxColumns; col++) {
            var idx = row * maxColumns + col;
            if (idx >= group.length) {
                break;
            }
            var item = group[idx];
            self._writeToOutput(item);
            if (col < maxColumns - 1) {
                for (var s = 0; s < width - item.length; s++) {
                    self._writeToOutput(' ');
                }
            }
        }
        self._writeToOutput('\r\n');
    }
    self._writeToOutput('\r\n');
}

function commonPrefix(strings) {
    if (!strings || strings.length === 0) {
        return '';
    }
    if (strings.length === 1) return strings[0];
    var sorted = strings.slice().sort();
    var min = sorted[0];
    var max = sorted[sorted.length - 1];
    for (var i = 0, len = min.length; i < len; i++) {
        if (min[i] !== max[i]) {
            return min.slice(0, i);
        }
    }
    return min;
}


Interface.prototype._wordLeft = function () {
    if (this.cursor > 0) {
        var leading = this.line.slice(0, this.cursor);
        var match = leading.match(/(?:[^\w\s]+|\w+|)\s*$/);
        this._moveCursor(-match[0].length);
    }
};


Interface.prototype._wordRight = function () {
    if (this.cursor < this.line.length) {
        var trailing = this.line.slice(this.cursor);
        var match = trailing.match(/^(?:\s+|\W+|\w+)\s*/);
        this._moveCursor(match[0].length);
    }
};


Interface.prototype._deleteLeft = function () {
    if (this.cursor > 0 && this.line.length > 0) {
        this.line = this.line.slice(0, this.cursor - 1) +
            this.line.slice(this.cursor, this.line.length);

        this.cursor--;
        this._refreshLine();
    }
};


Interface.prototype._deleteRight = function () {
    this.line = this.line.slice(0, this.cursor) +
        this.line.slice(this.cursor + 1, this.line.length);
    this._refreshLine();
};


Interface.prototype._deleteWordLeft = function () {
    if (this.cursor > 0) {
        var leading = this.line.slice(0, this.cursor);
        var match = leading.match(/(?:[^\w\s]+|\w+|)\s*$/);
        leading = leading.slice(0, leading.length - match[0].length);
        this.line = leading + this.line.slice(this.cursor, this.line.length);
        this.cursor = leading.length;
        this._refreshLine();
    }
};


Interface.prototype._deleteWordRight = function () {
    if (this.cursor < this.line.length) {
        var trailing = this.line.slice(this.cursor);
        var match = trailing.match(/^(?:\s+|\W+|\w+)\s*/);
        this.line = this.line.slice(0, this.cursor) +
            trailing.slice(match[0].length);
        this._refreshLine();
    }
};


Interface.prototype._deleteLineLeft = function () {
    this.line = this.line.slice(this.cursor);
    this.cursor = 0;
    this._refreshLine();
};


Interface.prototype._deleteLineRight = function () {
    this.line = this.line.slice(0, this.cursor);
    this._refreshLine();
};


Interface.prototype.clearLine = function () {
    this._moveCursor(+Infinity);
    this._writeToOutput('\r\n');
    this.line = '';
    this.cursor = 0;
    this.prevRows = 0;
};


Interface.prototype._line = function () {
    var line = this._addHistory();
    this.clearLine();
    this._onLine(line);
};


Interface.prototype._historyNext = function () {
    if (this.historyIndex > 0) {
        this.historyIndex--;
        this.line = this.history[this.historyIndex];
        this.cursor = this.line.length; // set cursor to end of line.
        this._refreshLine();

    } else if (this.historyIndex === 0) {
        this.historyIndex = -1;
        this.cursor = 0;
        this.line = '';
        this._refreshLine();
    }
};


Interface.prototype._historyPrev = function () {
    if (this.historyIndex + 1 < this.history.length) {
        this.historyIndex++;
        this.line = this.history[this.historyIndex];
        this.cursor = this.line.length; // set cursor to end of line.

        this._refreshLine();
    }
};


// Returns the last character's display position of the given string
Interface.prototype._getDisplayPos = function (str) {
    var offset = 0;
    var col = this.columns;
    var row = 0;
    var code;
    str = stripVTControlCharacters(str);
    for (var i = 0, len = str.length; i < len; i++) {
        code = str.codePointAt(i);
        if (code >= 0x10000) { // surrogates
            i++;
        }
        if (code === 0x0a) { // new line \n
            offset = 0;
            row += 1;
            continue;
        }
        const width = getStringWidth(code);
        if (width === 0 || width === 1) {
            offset += width;
        } else { // width === 2
            if ((offset + 1) % col === 0) {
                offset++;
            }
            offset += 2;
        }
    }
    var cols = offset % col;
    var rows = row + (offset - cols) / col;
    return { cols: cols, rows: rows };
};


// Returns current cursor's position and line
Interface.prototype._getCursorPos = function () {
    var columns = this.columns;
    var strBeforeCursor = this._prompt + this.line.substring(0, this.cursor);
    var dispPos = this._getDisplayPos(stripVTControlCharacters(strBeforeCursor));
    var cols = dispPos.cols;
    var rows = dispPos.rows;
    // If the cursor is on a full-width character which steps over the line,
    // move the cursor to the beginning of the next line.
    if (cols + 1 === columns &&
        this.cursor < this.line.length &&
        isFullWidthCodePoint(this.line.codePointAt(this.cursor))) {
        rows++;
        cols = 0;
    }
    return { cols: cols, rows: rows };
};


// This function moves cursor dx places to the right
// (-dx for left) and refreshes the line if it is needed
Interface.prototype._moveCursor = function (dx) {
    var oldcursor = this.cursor;
    var oldPos = this._getCursorPos();
    this.cursor += dx;

    // bounds check
    if (this.cursor < 0) this.cursor = 0;
    else if (this.cursor > this.line.length) this.cursor = this.line.length;

    var newPos = this._getCursorPos();

    // check if cursors are in the same line
    if (oldPos.rows === newPos.rows) {
        var diffCursor = this.cursor - oldcursor;
        var diffWidth;
        if (diffCursor < 0) {
            diffWidth = -getStringWidth(
                this.line.substring(this.cursor, oldcursor)
            );
        } else if (diffCursor > 0) {
            diffWidth = getStringWidth(
                this.line.substring(this.cursor, oldcursor)
            );
        }
        moveCursor(this.output, diffWidth, 0);
        this.prevRows = newPos.rows;
    } else {
        this._refreshLine();
    }
};


// handle a write from the tty
Interface.prototype._ttyWrite = function (s, key) {
    const previousKey = this._previousKey;
    key = key || {};
    this._previousKey = key;

    // Ignore escape key, fixes
    // https://github.com/nodejs/node-v0.x-archive/issues/2876.
    if (key.name === 'escape') return;

    if (key.ctrl && key.shift) {
        /* Control and shift pressed */
        switch (key.name) {
            case 'backspace':
                this._deleteLineLeft();
                break;

            case 'delete':
                this._deleteLineRight();
                break;
        }

    } else if (key.ctrl) {
        /* Control key pressed */

        switch (key.name) {
            case 'c':
                if (this.listenerCount('SIGINT') > 0) {
                    this.emit('SIGINT');
                } else {
                    // This readline instance is finished
                    this.close();
                }
                break;

            case 'h': // delete left
                this._deleteLeft();
                break;

            case 'd': // delete right or EOF
                if (this.cursor === 0 && this.line.length === 0) {
                    // This readline instance is finished
                    this.close();
                } else if (this.cursor < this.line.length) {
                    this._deleteRight();
                }
                break;

            case 'u': // delete from current to start of line
                this._deleteLineLeft();
                break;

            case 'k': // delete from current to end of line
                this._deleteLineRight();
                break;

            case 'a': // go to the start of the line
                this._moveCursor(-Infinity);
                break;

            case 'e': // go to the end of the line
                this._moveCursor(+Infinity);
                break;

            case 'b': // back one character
                this._moveCursor(-1);
                break;

            case 'f': // forward one character
                this._moveCursor(+1);
                break;

            case 'l': // clear the whole screen
                cursorTo(this.output, 0, 0);
                clearScreenDown(this.output);
                this._refreshLine();
                break;

            case 'n': // next history item
                this._historyNext();
                break;

            case 'p': // previous history item
                this._historyPrev();
                break;

            case 'z':
                if (process.platform === 'win32') break;
                if (this.listenerCount('SIGTSTP') > 0) {
                    this.emit('SIGTSTP');
                } else {
                    process.once('SIGCONT', (function (self) {
                        return function () {
                            // Don't raise events if stream has already been abandoned.
                            if (!self.paused) {
                                // Stream must be paused and resumed after SIGCONT to catch
                                // SIGINT, SIGTSTP, and EOF.
                                self.pause();
                                self.emit('SIGCONT');
                            }
                            // explicitly re-enable "raw mode" and move the cursor to
                            // the correct position.
                            // See https://github.com/joyent/node/issues/3295.
                            self._setRawMode(true);
                            self._refreshLine();
                        };
                    })(this));
                    this._setRawMode(false);
                    process.kill(process.pid, 'SIGTSTP');
                }
                break;

            case 'w': // delete backwards to a word boundary
            case 'backspace':
                this._deleteWordLeft();
                break;

            case 'delete': // delete forward to a word boundary
                this._deleteWordRight();
                break;

            case 'left':
                this._wordLeft();
                break;

            case 'right':
                this._wordRight();
                break;
        }

    } else if (key.meta) {
        /* Meta key pressed */

        switch (key.name) {
            case 'b': // backward word
                this._wordLeft();
                break;

            case 'f': // forward word
                this._wordRight();
                break;

            case 'd': // delete forward word
            case 'delete':
                this._deleteWordRight();
                break;

            case 'backspace': // delete backwards to a word boundary
                this._deleteWordLeft();
                break;
        }

    } else {
        /* No modifier keys used */

        // \r bookkeeping is only relevant if a \n comes right after.
        if (this._sawReturnAt && key.name !== 'enter')
            this._sawReturnAt = 0;

        switch (key.name) {
            case 'return':  // carriage return, i.e. \r
                this._sawReturnAt = Date.now();
                this._line();
                break;

            case 'enter':
                // When key interval > crlfDelay
                if (this._sawReturnAt === 0 ||
                    Date.now() - this._sawReturnAt > this.crlfDelay) {
                    this._line();
                }
                this._sawReturnAt = 0;
                break;

            case 'backspace':
                this._deleteLeft();
                break;

            case 'delete':
                this._deleteRight();
                break;

            case 'left':
                this._moveCursor(-1);
                break;

            case 'right':
                this._moveCursor(+1);
                break;

            case 'home':
                this._moveCursor(-Infinity);
                break;

            case 'end':
                this._moveCursor(+Infinity);
                break;

            case 'up':
                this._historyPrev();
                break;

            case 'down':
                this._historyNext();
                break;

            case 'tab':
                // If tab completion enabled, do that...
                if (typeof this.completer === 'function' && this.isCompletionEnabled) {
                    const lastKeypressWasTab = previousKey && previousKey.name === 'tab';
                    this._tabComplete(lastKeypressWasTab);
                    break;
                }
            // falls through

            default:
                if (s instanceof Buffer)
                    s = s.toString('utf-8');

                if (s) {
                    var lines = s.split(/\r\n|\n|\r/);
                    for (var i = 0, len = lines.length; i < len; i++) {
                        if (i > 0) {
                            this._line();
                        }
                        this._insertString(lines[i]);
                    }
                }
        }
    }
};

/**
 * accepts a readable Stream instance and makes it emit "keypress" events
 */

function emitKeypressEvents(stream, iface) {
    if (stream[KEYPRESS_DECODER]) return;

    if (StringDecoder === undefined)
        StringDecoder = require('string_decoder').StringDecoder;
    stream[KEYPRESS_DECODER] = new StringDecoder('utf8');

    stream[ESCAPE_DECODER] = emitKeys(stream);
    stream[ESCAPE_DECODER].next();

    const escapeCodeTimeout = () => stream[ESCAPE_DECODER].next('');
    let timeoutId;

    function onData(b) {
        if (stream.listenerCount('keypress') > 0) {
            var r = stream[KEYPRESS_DECODER].write(b);
            if (r) {
                clearTimeout(timeoutId);

                if (iface) {
                    iface._sawKeyPress = r.length === 1;
                }

                for (var i = 0; i < r.length; i++) {
                    if (r[i] === '\t' && typeof r[i + 1] === 'string' && iface) {
                        iface.isCompletionEnabled = false;
                    }

                    try {
                        stream[ESCAPE_DECODER].next(r[i]);
                        // Escape letter at the tail position
                        if (r[i] === kEscape && i + 1 === r.length) {
                            timeoutId = setTimeout(escapeCodeTimeout, ESCAPE_CODE_TIMEOUT);
                        }
                    } catch (err) {
                        // if the generator throws (it could happen in the `keypress`
                        // event), we need to restart it.
                        stream[ESCAPE_DECODER] = emitKeys(stream);
                        stream[ESCAPE_DECODER].next();
                        throw err;
                    } finally {
                        if (iface) {
                            iface.isCompletionEnabled = true;
                        }
                    }
                }
            }
        } else {
            // Nobody's watching anyway
            stream.removeListener('data', onData);
            stream.on('newListener', onNewListener);
        }
    }

    function onNewListener(event) {
        if (event === 'keypress') {
            stream.on('data', onData);
            stream.removeListener('newListener', onNewListener);
        }
    }

    if (stream.listenerCount('keypress') > 0) {
        stream.on('data', onData);
    } else {
        stream.on('newListener', onNewListener);
    }
}

/**
 * moves the cursor to the x and y coordinate on the given stream
 */

function cursorTo(stream, x, y) {
    if (stream === null || stream === undefined)
        return;

    if (typeof x !== 'number' && typeof y !== 'number')
        return;

    if (typeof x !== 'number')
        throw new ERR_INVALID_CURSOR_POS();

    if (typeof y !== 'number') {
        stream.write(CSI`${x + 1}G`);
    } else {
        stream.write(CSI`${y + 1};${x + 1}H`);
    }
}

/**
 * moves the cursor relative to its current location
 */

function moveCursor(stream, dx, dy) {
    if (stream === null || stream === undefined)
        return;

    if (dx < 0) {
        stream.write(CSI`${-dx}D`);
    } else if (dx > 0) {
        stream.write(CSI`${dx}C`);
    }

    if (dy < 0) {
        stream.write(CSI`${-dy}A`);
    } else if (dy > 0) {
        stream.write(CSI`${dy}B`);
    }
}

/**
 * clears the current line the cursor is on:
 *   -1 for left of the cursor
 *   +1 for right of the cursor
 *    0 for the entire line
 */

function clearLine(stream, dir) {
    if (stream === null || stream === undefined)
        return;

    if (dir < 0) {
        // to the beginning
        stream.write(kClearToBeginning);
    } else if (dir > 0) {
        // to the end
        stream.write(kClearToEnd);
    } else {
        // entire line
        stream.write(kClearLine);
    }
}

/**
 * clears the screen from the current position of the cursor down
 */

function clearScreenDown(stream) {
    if (stream === null || stream === undefined)
        return;

    stream.write(kClearScreenDown);
}

module.exports = {
    Interface,
    clearLine,
    clearScreenDown,
    createInterface,
    cursorTo,
    emitKeypressEvents,
    moveCursor
};