From 29946e95b2bdb2cfd8499d139941dc9c40a79381 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Wed, 17 Jul 2024 18:02:26 +0100
Subject: [PATCH] Fix refit in station when using articulated vehicles and
 simultaneous unload

---
 src/economy.cpp | 39 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/economy.cpp b/src/economy.cpp
index 3aff51a1e5..41e54be13d 100644
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -1658,6 +1658,22 @@ struct IsEmptyAction
 	}
 };
 
+/**
+ * Action to check if a vehicle is unloading cargo.
+ */
+struct IsUnloadingAction
+{
+	/**
+	 * Checks if the vehicle is unloading cargo.
+	 * @param v Vehicle to be checked.
+	 * @return true if v is unloading, false otherwise.
+	 */
+	bool operator()(const Vehicle *v)
+	{
+		return HasBit(v->vehicle_flags, VF_CARGO_UNLOADING);
+	}
+};
+
 /**
  * Action to check whether a vehicle is wholly in the platform.
  */
@@ -1774,14 +1790,14 @@ struct FinalizeRefitAction
 /**
  * Refit a vehicle in a station.
  * @param v Vehicle to be refitted.
+ * @param v_start v->GetFirstEnginePart().
  * @param consist_capleft Added cargo capacities in the consist.
  * @param st Station the vehicle is loading at.
  * @param next_station Possible next stations the vehicle can travel to.
  * @param new_cid Target cargo for refit.
  */
-static void HandleStationRefit(Vehicle *v, CargoArray &consist_capleft, Station *st, CargoStationIDStackSet next_station, CargoID new_cid)
+static void HandleStationRefit(Vehicle *v, Vehicle *v_start, CargoArray &consist_capleft, Station *st, CargoStationIDStackSet next_station, CargoID new_cid)
 {
-	Vehicle *v_start = v->GetFirstEnginePart();
 	if (!IterateVehicleParts(v_start, IsEmptyAction())) return;
 	if (v->type == VEH_TRAIN && !IterateVehicleParts(v_start, ThroughLoadTrainInPlatformAction())) return;
 
@@ -2039,6 +2055,7 @@ static void LoadUnloadVehicle(Vehicle *front)
 	CargoPayment *payment = front->cargo_payment;
 
 	uint artic_part = 0; // Articulated part we are currently trying to load. (not counting parts without capacity)
+	bool suppress_artic_load = false;
 	for (Vehicle *v = front; v != nullptr; v = v->Next()) {
 		if (pull_through_mode && HasBit(Train::From(v)->flags, VRF_BEYOND_PLATFORM_END)) {
 			if (v->cargo_cap != 0) {
@@ -2076,7 +2093,10 @@ static void LoadUnloadVehicle(Vehicle *front)
 			}
 			platform_length_left -= length;
 		}
-		if (v == front || !v->Previous()->HasArticulatedPart()) artic_part = 0;
+		if (v == front || !v->IsArticulatedPart()) {
+			artic_part = 0;
+			suppress_artic_load = false;
+		}
 		if (v->cargo_cap == 0) continue;
 		artic_part++;
 
@@ -2151,7 +2171,9 @@ static void LoadUnloadVehicle(Vehicle *front)
 				/* We have finished unloading (cargo count == 0) */
 				ClrBit(v->vehicle_flags, VF_CARGO_UNLOADING);
 			}
-
+			if (front->current_order.IsRefit() && front->current_order.GetRefitCargo() != v->cargo_type) {
+				suppress_artic_load = true;
+			}
 			continue;
 		}
 
@@ -2161,11 +2183,18 @@ static void LoadUnloadVehicle(Vehicle *front)
 
 		/* This order has a refit, if this is the first vehicle part carrying cargo and the whole vehicle is empty, try refitting. */
 		if (front->current_order.IsRefit() && artic_part == 1) {
-			HandleStationRefit(v, consist_capleft, st, next_station, front->current_order.GetRefitCargo());
+			Vehicle *v_start = v->GetFirstEnginePart();
+			if (front->current_order.GetRefitCargo() != v->cargo_type && IterateVehicleParts(v_start, IsUnloadingAction())) {
+				suppress_artic_load = true;
+				continue;
+			}
+			HandleStationRefit(v, v_start, consist_capleft, st, next_station, front->current_order.GetRefitCargo());
 			ge = &st->goods[v->cargo_type];
 			ged = &ge->CreateData();
 		}
 
+		if (suppress_artic_load) continue;
+
 		/* Do not pick up goods when we have no-load set. */
 		if (GetLoadType(v) & OLFB_NO_LOAD) continue;