From 652025e5e5b191447bae787e351bb97c126ec7a5 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Mon, 22 Dec 2014 01:44:00 +0100
Subject: [PATCH] Support reverse-dragging, also with engine suggestions.

---
 www/js/book.js | 83 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 68 insertions(+), 15 deletions(-)

diff --git a/www/js/book.js b/www/js/book.js
index bc6adfc..dce293b 100644
--- a/www/js/book.js
+++ b/www/js/book.js
@@ -8,7 +8,8 @@ var includetransp = true;
 var stockfish = new Worker('/js/stockfish.js');
 var engine_running = false;
 var engine_replacement_callback = null;
-var recommended_dest = null;
+var recommended_move = null;
+var reverse_dragging_from = null;
 
 var entity_map = {
 	"&": "&amp;",
@@ -343,25 +344,74 @@ var onDragStart = function(source, piece, position, orientation) {
 		return false;
 	}
 
-	recommended_dest = null;
-	get_best_dest(pseudogame, source, function(dest) {
+	recommended_move = null;
+	get_best_dest(pseudogame, source, null, function(src, dest) {
 		$("#board").find('.square-55d63').removeClass('nonuglyhighlight');
 		if (dest !== null) {
 			var squareEl = $('#board .square-' + dest);
 			squareEl.addClass('highlight1-32417');
+			recommended_move = [src, dest];
 		}
-		recommended_dest = dest;
 	});
 }
 
-var get_best_dest = function(game, source, cb) {
-	var moves = game.moves({ square: source, verbose: true });
+var mousedownSquare = function(e) {
+	reverse_dragging_from = null;
+	var square = $(this).attr('data-square');
+
+	var pseudogame = new Chess(current_display_fen());
+	if (pseudogame.game_over() === true) {
+		return;
+	}
+
+	// If the square is empty, or has a piece of the side not to move,
+	// we handle it. If not, normal piece dragging will take it.
+	var position = board.position();
+	if (!position.hasOwnProperty(square) ||
+	    (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
+	    (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
+		reverse_dragging_from = square;
+		get_best_dest(pseudogame, null, square, function(src, dest) {
+			if (src !== null) {
+				var squareEl = $('#board .square-' + src);
+				squareEl.addClass('highlight1-32417');
+				squareEl = $('#board .square-' + dest);
+				squareEl.addClass('highlight1-32417');
+				recommended_move = [src, dest];
+			}
+		});
+	} else {
+		recommended_src = null;
+	}
+}
+
+var mouseupSquare = function(e) {
+	if (reverse_dragging_from === null) {
+		return;
+	}
+	var source = $(this).attr('data-square');
+	var target = reverse_dragging_from;
+	reverse_dragging_from = null;
+	if (onDrop(source, target) !== 'snapback') {
+		onSnapEnd(source, target);
+	}
+	$("#board").find('.square-55d63').removeClass('highlight1-32417');
+}
+
+var get_best_dest = function(game, source, target, cb) {
+	var moves = game.moves({ verbose: true });
+	if (source !== null) {
+		moves = moves.filter(function(move) { return move.from == source; });
+	}
+	if (target !== null) {
+		moves = moves.filter(function(move) { return move.to == target; });
+	}
 	if (moves.length == 0) {
-		cb(null);
+		cb(null, null);
 		return;
 	}
 	if (moves.length == 1) {
-		cb(moves[0].to);
+		cb(moves[0].from, moves[0].to);
 		return;
 	}
 
@@ -370,7 +420,7 @@ var get_best_dest = function(game, source, cb) {
 	var when_engine_is_ready = function() {
 		engine_running = true;
 		stockfish.onmessage = function(event) {
-			var res = event.data.match(/^bestmove \S\S(\S\S)/);
+			var res = event.data.match(/^bestmove (\S\S)(\S\S)/);
 			if (res !== null) {
 				engine_running = false;
 				if (engine_replacement_callback !== null) {
@@ -379,7 +429,7 @@ var get_best_dest = function(game, source, cb) {
 					engine_replacement_callback();
 					engine_replacement_callback = null;
 				} else {
-					cb(res[1]);
+					cb(res[1], res[2]);
 				}
 			}
 		};
@@ -400,7 +450,7 @@ var onDrop = function(source, target) {
 		engine_replacement_callback = function() {};
 	}
 	if (source == target) {
-		if (recommended_dest === null) {
+		if (recommended_move === null) {
 			return 'snapback';
 		} else {
 			// Accept the move. It will be changed in onSnapEnd.
@@ -408,7 +458,7 @@ var onDrop = function(source, target) {
 		}
 	} else {
 		// Suggestion not asked for.
-		recommended_dest = null;
+		recommended_move = null;
 	}
 
 	// see if the move is legal
@@ -424,10 +474,11 @@ var onDrop = function(source, target) {
 }
 
 var onSnapEnd = function(source, target) {
-	if (source == target && recommended_dest !== null) {
-		target = recommended_dest;
+	if (source == target && recommended_move !== null) {
+		source = recommended_move[0];
+		target = recommended_move[1];
 	}
-	recommended_dest = null;
+	recommended_move = null;
 	var pseudogame = new Chess(current_display_fen());
 	var move = pseudogame.move({
 		from: source,
@@ -470,6 +521,8 @@ var init = function() {
 		onDrop: onDrop,
 		onSnapEnd: onSnapEnd
 	});
+	$("#board").on('mousedown', '.square-55d63', mousedownSquare);
+	$("#board").on('mouseup', '.square-55d63', mouseupSquare);
 
 	window.onpopstate = onpopstate;
 	onpopstate();
-- 
2.39.2