From f72838ebf2ced1db4d3b3c1b06787180df6ae10f Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Wed, 16 Nov 2016 18:38:51 +0100
Subject: [PATCH] Fix various off-by-ones, especially in the sparkline.

---
 www/js/remoteglot.js | 54 ++++++++++++++++++++++++++++----------------
 1 file changed, 34 insertions(+), 20 deletions(-)

diff --git a/www/js/remoteglot.js b/www/js/remoteglot.js
index b049c32..0748dce 100644
--- a/www/js/remoteglot.js
+++ b/www/js/remoteglot.js
@@ -1053,15 +1053,17 @@ var update_board = function() {
 	if (displayed_analysis_data) {
 		// Displaying some non-current position, pick out the last move
 		// from the history. This will work even if the fetch failed.
-		last_move = format_halfmove_with_number(
-			current_display_line.pv[current_display_move],
-			current_display_move + 1);
-		headline += ' after ' + last_move;
+		if (current_display_move !== -1) {
+			last_move = format_halfmove_with_number(
+				current_display_line.pv[current_display_move],
+				current_display_move);
+			headline += ' after ' + last_move;
+		}
 	} else if (data['position']['last_move'] !== 'none') {
 		last_move = format_move_with_number(
 			data['position']['last_move'],
 			data['position']['move_num'],
-			data['position']['toplay'] == 'W');
+			data['position']['toplay'] == 'B');
 		headline += ' after ' + last_move;
 	} else {
 		last_move = null;
@@ -1298,7 +1300,9 @@ var update_sparkline = function(data) {
 				chartRangeMin: min_score,
 				chartRangeMax: max_score,
 				tooltipFormatter: function(sparkline, options, fields) {
-					return format_tooltip(data, fields[0].offset + first_move_num);
+					// score_history contains the Nth _position_, but format_tooltip
+					// wants to format the Nth _move_; thus the -1.
+					return format_tooltip(data, fields[0].offset + first_move_num - 1);
 				}
 			});
 		} else {
@@ -1452,15 +1456,15 @@ var format_2d = function(x) {
 
 /**
  * @param {string} move
- * @param {Number} move_num
- * @param {boolean} white_to_play
+ * @param {Number} move_num Move number of this move.
+ * @param {boolean} white_to_play Whether white is to play this move.
  */
 var format_move_with_number = function(move, move_num, white_to_play) {
 	var ret;
 	if (white_to_play) {
-		ret = (move_num - 1) + '… ';
-	} else {
 		ret = move_num + '. ';
+	} else {
+		ret = move_num + '… ';
 	}
 	ret += move;
 	return ret;
@@ -1468,7 +1472,8 @@ var format_move_with_number = function(move, move_num, white_to_play) {
 
 /**
  * @param {string} move
- * @param {Number} halfmove_num
+ * @param {Number} halfmove_num Half-move number that is to be played,
+ *   starting from 0.
  */
 var format_halfmove_with_number = function(move, halfmove_num) {
 	return format_move_with_number(
@@ -1482,25 +1487,34 @@ var format_halfmove_with_number = function(move, halfmove_num) {
  * @param {Number} halfmove_num
  */
 var format_tooltip = function(data, halfmove_num) {
-	if (data['score_history'][halfmove_num] ||
-	    halfmove_num === data['position']['history'].length) {
+	if (data['score_history'][halfmove_num + 1] ||
+	    (halfmove_num + 1) === data['position']['history'].length) {
+		// Position is in the history, or it is the current position
+		// (which is implicitly tacked onto the history).
 		var move;
 		var short_score;
-		if (halfmove_num === data['position']['history'].length) {
+		if ((halfmove_num + 1) === data['position']['history'].length) {
 			move = data['position']['last_move'];
 			short_score = format_short_score(data['score']);
 		} else {
 			move = data['position']['history'][halfmove_num];
-			short_score = format_short_score(data['score_history'][halfmove_num]);
+			short_score = format_short_score(data['score_history'][halfmove_num + 1]);
+		}
+		if (halfmove_num === -1) {
+			return "Start position: " + short_score;
+		} else {
+			var move_with_number = format_halfmove_with_number(move, halfmove_num);
+			return "After " + move_with_number + ": " + short_score;
 		}
-		var move_with_number = format_halfmove_with_number(move, halfmove_num);
-
-		return "After " + move_with_number + ": " + short_score;
 	} else {
-		for (var i = halfmove_num; i --> 0; ) {
+		for (var i = halfmove_num; i --> -1; ) {
 			if (data['score_history'][i]) {
 				var move = data['position']['history'][i];
-				return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
+				if (i === -1) {
+					return "[Analysis kept from start position]";
+				} else {
+					return "[Analysis kept from " + format_halfmove_with_number(move, i) + "]";
+				}
 			}
 		}
 	}
-- 
2.39.2