Update "undo".

1 files changed, 24 insertions, 21 deletions

diff --git a/rules.js b/rules.js
index 019a7dc..c2e2d25 100644
--- a/rules.js
+++ b/rules.js
@@ -2854,8 +2854,6 @@ function observer_hand() {
 	return hand
 }
 
-exports.is_checkpoint = (a, b) => a.turn !== b.turn
-
 exports.view = function(state, current) {
 	game = state
 
@@ -3012,30 +3010,35 @@ function object_copy(original) {
 }
 
 function clear_undo() {
-	if (game.undo.length > 0)
-		game.undo = []
+	if (game.undo) {
+		game.undo.length = 0
+	}
 }
 
 function push_undo() {
-	let copy = {}
-	for (let k in game) {
-		let v = game[k]
-		if (k === "undo")
-			continue
-		else if (k === "log")
-			v = v.length
-		else if (typeof v === "object" && v !== null)
-			v = object_copy(v)
-		copy[k] = v
+	if (game.undo) {
+		let copy = {}
+		for (let k in game) {
+			let v = game[k]
+			if (k === "undo")
+				continue
+			else if (k === "log")
+				v = v.length
+			else if (typeof v === "object" && v !== null)
+				v = object_copy(v)
+			copy[k] = v
+		}
+		game.undo.push(copy)
 	}
-	game.undo.push(copy)
 }
 
 function pop_undo() {
-	let save_log = game.log
-	let save_undo = game.undo
-	game = save_undo.pop()
-	save_log.length = game.log
-	game.log = save_log
-	game.undo = save_undo
+	if (game.undo) {
+		let save_log = game.log
+		let save_undo = game.undo
+		game = save_undo.pop()
+		save_log.length = game.log
+		game.log = save_log
+		game.undo = save_undo
+	}
 }