Index: ps/trunk/binaries/data/mods/public/simulation/components/Barter.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/Barter.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/Barter.js
@@ -4,23 +4,37 @@
 	"<a:component type='system'/><empty/>";
 
 /**
- * The "true price" is a base price of 100 units of resource (for the case of some resources being of more worth than others).
+ * The "true price" is a base price of Barter.prototype.DEAL_AMOUNT units of resource (for the case of some resources being of more worth than others).
  * With current bartering system only relative values makes sense so if for example stone is two times more expensive than wood,
  * there will 2:1 exchange rate.
  *
+ * Keep gui/session/trade/BarterButton.js in sync with this value.
+ */
+Barter.prototype.DEAL_AMOUNT = 100;
+
+/**
+ * Deals per mass barter.
+ * Keep gui/session/trade/BarterButton.js in sync with this value.
+ */
+Barter.prototype.BATCH_SIZE = 5;
+
+/**
  * Constant part of price percentage difference between true price and buy/sell price.
  * Buy price equal to true price plus constant difference.
  * Sell price equal to true price minus constant difference.
  */
 Barter.prototype.CONSTANT_DIFFERENCE = 10;
+
 /**
  * Additional difference of prices in percents, added after each deal to specified resource price.
  */
 Barter.prototype.DIFFERENCE_PER_DEAL = 2;
+
 /**
  * Price difference percentage which restored each restore timer tick
  */
 Barter.prototype.DIFFERENCE_RESTORE = 0.5;
+
 /**
  * Interval of timer which slowly restore prices after deals
  */
@@ -29,20 +43,19 @@
 Barter.prototype.Init = function()
 {
 	this.priceDifferences = {};
-	for (let resource of Resources.GetBarterableCodes())
+	for (const resource of Resources.GetBarterableCodes())
 		this.priceDifferences[resource] = 0;
-	this.restoreTimer = undefined;
 };
 
 Barter.prototype.GetPrices = function(cmpPlayer)
 {
-	let prices = { "buy": {}, "sell": {} };
-	let multiplier = cmpPlayer.GetBarterMultiplier();
-	for (let resource of Resources.GetBarterableCodes())
-	{
-		let truePrice = Resources.GetResource(resource).truePrice;
-		prices.buy[resource] = truePrice * (100 + this.CONSTANT_DIFFERENCE + this.priceDifferences[resource]) * multiplier.buy[resource] / 100;
-		prices.sell[resource] = truePrice * (100 - this.CONSTANT_DIFFERENCE + this.priceDifferences[resource]) * multiplier.sell[resource] / 100;
+	const prices = { "buy": {}, "sell": {} };
+	const multiplier = cmpPlayer.GetBarterMultiplier();
+	for (const resource in this.priceDifferences)
+	{
+		const truePrice = Resources.GetResource(resource).truePrice;
+		prices.buy[resource] = truePrice * (this.DEAL_AMOUNT + this.CONSTANT_DIFFERENCE + this.priceDifferences[resource]) * multiplier.buy[resource] / this.DEAL_AMOUNT;
+		prices.sell[resource] = truePrice * (this.DEAL_AMOUNT - this.CONSTANT_DIFFERENCE + this.priceDifferences[resource]) * multiplier.sell[resource] / this.DEAL_AMOUNT;
 	}
 	return prices;
 };
@@ -55,85 +68,81 @@
 		return;
 	}
 
-	let availResources = Resources.GetBarterableCodes();
-	if (availResources.indexOf(resourceToSell) == -1)
+	if (!(resourceToSell in this.priceDifferences))
 	{
 		warn("ExchangeResources: incorrect resource to sell: " + uneval(resourceToSell));
 		return;
 	}
 
-	if (availResources.indexOf(resourceToBuy) == -1)
+	if (!(resourceToBuy in this.priceDifferences))
 	{
 		warn("ExchangeResources: incorrect resource to buy: " + uneval(resourceToBuy));
 		return;
 	}
 
-	if (amount != 100 && amount != 500)
+	if (amount !== this.DEAL_AMOUNT && amount !== (this.BATCH_SIZE * this.DEAL_AMOUNT))
 		return;
 
-	let cmpPlayer = QueryPlayerIDInterface(playerID);
-	if (!cmpPlayer || !cmpPlayer.CanBarter())
+	const cmpPlayer = QueryPlayerIDInterface(playerID);
+	if (!cmpPlayer?.CanBarter())
 		return;
 
-	let prices = this.GetPrices(cmpPlayer);
-	let amountsToSubtract = {};
-	amountsToSubtract[resourceToSell] = amount;
-	if (cmpPlayer.TrySubtractResources(amountsToSubtract))
-	{
-		let amountToAdd = Math.round(prices.sell[resourceToSell] / prices.buy[resourceToBuy] * amount);
-		cmpPlayer.AddResource(resourceToBuy, amountToAdd);
-
-		// Display chat message to observers.
-		let cmpGUIInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
-		if (cmpGUIInterface)
-			cmpGUIInterface.PushNotification({
-				"type": "barter",
-				"players": [playerID],
-				"amountGiven": amount,
-				"amountGained": amountToAdd,
-				"resourceGiven": resourceToSell,
-				"resourceGained": resourceToBuy
-			});
-
-		let cmpStatisticsTracker = QueryPlayerIDInterface(playerID, IID_StatisticsTracker);
-		if (cmpStatisticsTracker)
-		{
-			cmpStatisticsTracker.IncreaseResourcesSoldCounter(resourceToSell, amount);
-			cmpStatisticsTracker.IncreaseResourcesBoughtCounter(resourceToBuy, amountToAdd);
-		}
-
-		let difference = this.DIFFERENCE_PER_DEAL * amount / 100;
-		// Increase price difference for both exchange resources.
-		// Overall price difference (dynamic +/- constant) can't exceed +-99%.
-		this.priceDifferences[resourceToSell] -= difference;
-		this.priceDifferences[resourceToSell] = Math.min(99 - this.CONSTANT_DIFFERENCE, Math.max(this.CONSTANT_DIFFERENCE - 99, this.priceDifferences[resourceToSell]));
-		this.priceDifferences[resourceToBuy] += difference;
-		this.priceDifferences[resourceToBuy] = Math.min(99 - this.CONSTANT_DIFFERENCE, Math.max(this.CONSTANT_DIFFERENCE - 99, this.priceDifferences[resourceToBuy]));
-	}
+	const amountsToSubtract = {
+		[resourceToSell]: amount
+	};
+	if (!cmpPlayer.TrySubtractResources(amountsToSubtract))
+		return;
+
+	const prices = this.GetPrices(cmpPlayer);
+	const amountToAdd = Math.round(prices.sell[resourceToSell] / prices.buy[resourceToBuy] * amount);
+	cmpPlayer.AddResource(resourceToBuy, amountToAdd);
+
+	Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface)?.PushNotification({
+		"type": "barter",
+		"players": [playerID],
+		"amountGiven": amount,
+		"amountGained": amountToAdd,
+		"resourceGiven": resourceToSell,
+		"resourceGained": resourceToBuy
+	});
+
+	const cmpStatisticsTracker = QueryPlayerIDInterface(playerID, IID_StatisticsTracker);
+	if (cmpStatisticsTracker)
+	{
+		cmpStatisticsTracker.IncreaseResourcesSoldCounter(resourceToSell, amount);
+		cmpStatisticsTracker.IncreaseResourcesBoughtCounter(resourceToBuy, amountToAdd);
+	}
+
+	const difference = this.DIFFERENCE_PER_DEAL * amount / this.DEAL_AMOUNT;
+	// Overall price difference (dynamic +/- constant) can't exceed +-99%.
+	const maxDifference = this.DEAL_AMOUNT * 0.99;
+
+	// Increase price difference for both exchanged resources.
+	this.priceDifferences[resourceToSell] -= difference;
+	this.priceDifferences[resourceToSell] = Math.min(maxDifference - this.CONSTANT_DIFFERENCE, Math.max(this.CONSTANT_DIFFERENCE - maxDifference, this.priceDifferences[resourceToSell]));
+	this.priceDifferences[resourceToBuy] += difference;
+	this.priceDifferences[resourceToBuy] = Math.min(maxDifference - this.CONSTANT_DIFFERENCE, Math.max(this.CONSTANT_DIFFERENCE - maxDifference, this.priceDifferences[resourceToBuy]));
 
-	if (this.restoreTimer === undefined)
-		this.restoreTimer = Engine.QueryInterface(SYSTEM_ENTITY, IID_Timer).SetInterval(this.entity, IID_Barter, "ProgressTimeout", this.RESTORE_TIMER_INTERVAL, this.RESTORE_TIMER_INTERVAL, {});
+	if (!this.restoreTimer)
+		this.restoreTimer = Engine.QueryInterface(SYSTEM_ENTITY, IID_Timer).SetInterval(this.entity, IID_Barter, "ProgressTimeout", this.RESTORE_TIMER_INTERVAL, this.RESTORE_TIMER_INTERVAL, null);
 };
 
 Barter.prototype.ProgressTimeout = function(data)
 {
 	let needRestore = false;
-	for (let resource of Resources.GetBarterableCodes())
+	for (const resource in this.priceDifferences)
 	{
 		// Calculate value to restore, it should be limited to [-DIFFERENCE_RESTORE; DIFFERENCE_RESTORE] interval
-		let differenceRestore = Math.min(this.DIFFERENCE_RESTORE, Math.max(-this.DIFFERENCE_RESTORE, this.priceDifferences[resource]));
-		differenceRestore = -differenceRestore;
-		this.priceDifferences[resource] += differenceRestore;
-		// If price difference still exists then set flag to run timer again
-		if (this.priceDifferences[resource] != 0)
+		this.priceDifferences[resource] -= Math.min(this.DIFFERENCE_RESTORE, Math.max(-this.DIFFERENCE_RESTORE, this.priceDifferences[resource]));
+		// If price difference still exists then set flag to keep the timer running.
+		if (this.priceDifferences[resource] !== 0)
 			needRestore = true;
 	}
 
 	if (!needRestore)
 	{
-		let cmpTimer = Engine.QueryInterface(SYSTEM_ENTITY, IID_Timer);
-		cmpTimer.CancelTimer(this.restoreTimer);
-		this.restoreTimer = undefined;
+		Engine.QueryInterface(SYSTEM_ENTITY, IID_Timer).CancelTimer(this.restoreTimer);
+		delete this.restoreTimer;
 	}
 };
 
Index: ps/trunk/binaries/data/mods/public/simulation/components/tests/test_Barter.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/tests/test_Barter.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/tests/test_Barter.js
@@ -144,10 +144,6 @@
 });
 cmpBarter.ExchangeResources(playerID, "wood", "stone", 100);
 
-// It seems useless to try to activate the timer if we don't barter any resources.
-TS_ASSERT_EQUALS(cmpBarter.restoreTimer, 7);
-TS_ASSERT(timerActivated);
-
 TS_ASSERT_UNEVAL_EQUALS(cmpBarter.priceDifferences, { "wood": 0, "stone": 0, "metal": 0 });
 
 DeleteMock(playerEnt, IID_Player);