feat: allow cycling through multiline commands using up/down in the REPL

PR-URL: #2531
Closes: #2070 
Ref: #2069

---------

Signed-off-by: Snehil Shah <[email protected]>
Signed-off-by: Athan Reines <[email protected]>
Co-authored-by: Athan Reines <[email protected]>
Reviewed-by: Philipp Burckhardt <[email protected]> 
Reviewed-by: Athan Reines <[email protected]>

Author: Snehil-Shah

lib/node_modules/@stdlib/repl/lib/multiline_handler.js

@@ -27,6 +27,7 @@ var logger = require( 'debug' );
 var Parser = require( 'acorn' ).Parser;
 var parseLoose = require( 'acorn-loose' ).parse;
 var setNonEnumerableReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
+var startsWith = require( '@stdlib/string/starts-with' );
 var copy = require( '@stdlib/array/base/copy' );
 var min = require( '@stdlib/math/base/special/min' );
 var max = require( '@stdlib/math/base/special/max' );
@@ -83,6 +84,12 @@ function MultilineHandler( repl, ttyWrite ) {
 	// Cache a reference to the command queue:
 	this._queue = repl._queue;
 
+	// Initialize an internal object for command history:
+	this._history = {};
+	this._history.list = repl._history;
+	this._history.index = 0; // index points to the next "previous" command in history
+	this._history.prefix = '';
+
 	// Initialize an internal status object for multi-line mode:
 	this._multiline = {};
 	this._multiline.active = false;
@@ -155,6 +162,95 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, '_moveCursor', function mo
 	this._rli.cursor = x;
 });
 
+/**
+* Inserts a command in the input prompt.
+*
+* @private
+* @name _insertCommand
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @param {string} cmd - command
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, '_insertCommand', function insertCommand( cmd ) {
+	var i;
+
+	this.clearInput();
+
+	// For each newline, trigger a `return` keypress in paste-mode...
+	cmd = cmd.split( '\n' );
+	this._multiline.pasteMode = true;
+	for ( i = 0; i < cmd.length - 1; i++ ) {
+		this._rli.write( cmd[ i ] );
+		this._rli.write( null, {
+			'name': 'return'
+		});
+	}
+	this._rli.write( cmd[ cmd.length - 1 ] );
+	this._multiline.pasteMode = false;
+});
+
+/**
+* Inserts previous command matching the prefix from history.
+*
+* @private
+* @name _prevCommand
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, '_prevCommand', function prevCommand() {
+	var cmd;
+
+	// If we are starting from zero, save the prefix for this cycle...
+	if ( this._history.index === 0 ) {
+		this._history.prefix = this._rli.line.slice( 0, this._rli.cursor );
+	}
+	// Traverse the history until we find the command with a common prefix...
+	while ( this._history.index < this._history.list.length / 3 ) {
+		cmd = this._history.list[ this._history.list.length - ( 3 * this._history.index ) - 2 ]; // eslint-disable-line max-len
+		if ( startsWith( cmd, this._history.prefix ) ) {
+			this._insertCommand( cmd );
+			this._history.index += 1; // update index to point to the next "previous" command
+			break;
+		}
+		this._history.index += 1;
+	}
+});
+
+/**
+* Inserts next command matching the prefix from history.
+*
+* @private
+* @name _nextCommand
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, '_nextCommand', function nextCommand() {
+	var cmd;
+
+	if ( this._history.index === 0 ) {
+		return; // no more history to traverse
+	}
+	// Traverse the history until we find the command with a common prefix...
+	this._history.index -= 1; // updating index to point to the next "previous" command
+	while ( this._history.index > 0 ) {
+		cmd = this._history.list[ this._history.list.length - ( 3 * ( this._history.index - 1 ) ) - 2 ]; // eslint-disable-line max-len
+		if ( startsWith( cmd, this._history.prefix ) ) {
+			this._insertCommand( cmd );
+			break;
+		}
+		this._history.index -= 1;
+	}
+	// If we didn't find a match in history, bring up the original prefix and reset cycle...
+	if ( this._history.index === 0 ) {
+		this.clearInput();
+		this._rli.write( this._history.prefix );
+		this._resetHistoryBuffers();
+	}
+});
+
 /**
 * Moves cursor up to the previous line.
 *
@@ -167,8 +263,9 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, '_moveCursor', function mo
 setNonEnumerableReadOnly( MultilineHandler.prototype, '_moveUp', function moveUp() {
 	var cursor;
 
-	// If already at the first line, ignore...
+	// If already at the first line, try to insert previous command from history...
 	if ( this._lineIndex <= 0 ) {
+		this._prevCommand();
 		return;
 	}
 	this._cmd[ this._lineIndex ] = this._rli.line; // update current line in command
@@ -190,8 +287,9 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, '_moveUp', function moveUp
 setNonEnumerableReadOnly( MultilineHandler.prototype, '_moveDown', function moveDown() {
 	var cursor;
 
-	// If already at the last line, ignore...
+	// If already at the last line, try to insert next command from history...
 	if ( this._lineIndex >= this._lines.length - 1 ) {
+		this._nextCommand();
 		return;
 	}
 	this._cmd[ this._lineIndex ] = this._rli.line; // update current line in command
@@ -347,9 +445,37 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, '_isMultilineInput', funct
 });
 
 /**
-* Returns current line number in input.
+* Resets input buffers.
+*
+* @private
+* @name _resetInputBuffers
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, '_resetInputBuffers', function resetInputBuffers() {
+	this._cmd.length = 0;
+	this._lineIndex = 0;
+	this._lines.length = 0;
+});
+
+/**
+* Resets history buffers.
 *
 * @private
+* @name _resetHistoryBuffers
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, '_resetHistoryBuffers', function resetHistoryBuffers() {
+	this._history.index = 0;
+	this._history.prefix = '';
+});
+
+/**
+* Returns current line number in input.
+*
 * @name lineIndex
 * @memberof MultilineHandler.prototype
 * @type {Function}
@@ -362,7 +488,6 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'lineIndex', function line
 /**
 * Returns the number of rows occupied by current input.
 *
-* @private
 * @name inputHeight
 * @memberof MultilineHandler.prototype
 * @type {Function}
@@ -385,19 +510,39 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'updateLine', function upd
 	this._lines[ this._lineIndex ] = line;
 });
 
+/**
+* Clears current input.
+*
+* @name clearInput
+* @memberof MultilineHandler.prototype
+* @type {Function}
+* @returns {void}
+*/
+setNonEnumerableReadOnly( MultilineHandler.prototype, 'clearInput', function clearInput() {
+	if ( this._lineIndex !== 0 ) {
+		// Bring the cursor to the first line:
+		readline.moveCursor( this._ostream, 0, -1 * this._lineIndex );
+	}
+	// Clear lines and buffers:
+	this._resetInputBuffers();
+	readline.cursorTo( this._ostream, this._repl.promptLength() );
+	readline.clearLine( this._ostream, 1 );
+	readline.clearScreenDown( this._ostream );
+	this._rli.line = '';
+	this._rli.cursor = 0;
+});
+
 /**
 * Resets input and command buffers.
 *
-* @private
 * @name resetInput
 * @memberof MultilineHandler.prototype
 * @type {Function}
 * @returns {void}
 */
 setNonEnumerableReadOnly( MultilineHandler.prototype, 'resetInput', function resetInput() {
-	this._cmd.length = 0;
-	this._lineIndex = 0;
-	this._lines.length = 0;
+	this._resetHistoryBuffers();
+	this._resetInputBuffers();
 });
 
 /**
@@ -587,8 +732,9 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'beforeKeypress', function
 		this._ttyWrite.call( this._rli, data, key );
 		return;
 	}
+	switch ( key.name ) {
 	// Check whether to trigger multi-line mode or execute the command when `return` key is encountered...
-	if ( key.name === 'return' ) {
+	case 'return':
 		cmd = copy( this._cmd );
 		cmd[ this._lineIndex ] = this._rli.line;
 
@@ -598,53 +744,77 @@ setNonEnumerableReadOnly( MultilineHandler.prototype, 'beforeKeypress', function
 			return;
 		}
 		this._triggerMultiline();
-
+		if ( this._history.index !== 0 && !this._multiline.pasteMode ) {
+			// Reset current history cycle:
+			this._resetHistoryBuffers();
+		}
 		// Trigger `line` event:
 		this._ttyWrite.call( this._rli, data, key );
-		return;
-	}
-	if ( !this._multiline.active ) {
-		this._ttyWrite.call( this._rli, data, key );
-		return;
-	}
+		break;
+
 	// If multi-line mode is active, enable navigation...
-	switch ( key.name ) {
 	case 'up':
 		this._moveUp();
-		this._renderLines();
+		if ( this._multiline.active ) {
+			this._renderLines();
+		}
 		break;
 	case 'down':
 		this._moveDown();
-		this._renderLines();
+		if ( this._multiline.active ) {
+			this._renderLines();
+		}
 		break;
 	case 'left':
+		if ( this._history.index !== 0 ) {
+			// Reset current history cycle:
+			this._resetHistoryBuffers();
+		}
 		// If at the beginning of the line, move up to the previous line; otherwise, trigger default behavior...
 		if ( this._rli.cursor === 0 ) {
 			this._moveLeft();
-			this._renderLines();
+			if ( this._multiline.active ) {
+				this._renderLines();
+			}
 			return;
 		}
 		this._ttyWrite.call( this._rli, data, key );
 		break;
 	case 'right':
+		if ( this._history.index !== 0 ) {
+			// Reset current history cycle:
+			this._resetHistoryBuffers();
+		}
 		// If at the end of the line, move up to the next line; otherwise, trigger default behavior...
 		if ( this._rli.cursor === this._rli.line.length ) {
 			this._moveRight();
-			this._renderLines();
+			if ( this._multiline.active ) {
+				this._renderLines();
+			}
 			return;
 		}
 		this._ttyWrite.call( this._rli, data, key );
 		break;
 	case 'backspace':
+		if ( this._history.index !== 0 ) {
+			// Reset current history cycle:
+			this._resetHistoryBuffers();
+		}
 		// If at the beginning of the line, remove and move up to the previous line; otherwise, trigger default behavior...
 		if ( this._rli.cursor === 0 ) {
 			this._backspace();
-			this._renderLines();
+			if ( this._multiline.active ) {
+				this._renderLines();
+			}
 			return;
 		}
 		this._ttyWrite.call( this._rli, data, key );
 		break;
 	default:
+		if ( this._history.index !== 0 ) {
+			// Reset current history cycle:
+			this._resetHistoryBuffers();
+		}
 		this._ttyWrite.call( this._rli, data, key );
 		break;
 	}