From ca1caa1aa572f60102b6bb2dbdd8bc55614dd171 Mon Sep 17 00:00:00 2001
From: zacc <zac.campbell@protonmail.com>
Date: Wed, 13 Mar 2024 12:22:45 +0900
Subject: [PATCH] Change: Calculate Drive Through RoadStop occupied level with
 regard to when a stopped vehicle is blocking access to tiles.

---
 src/roadstop.cpp    | 20 +++++++++++++++-----
 src/roadstop_base.h |  5 +++--
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/roadstop.cpp b/src/roadstop.cpp
index 2e4f441973..29674df483 100644
--- a/src/roadstop.cpp
+++ b/src/roadstop.cpp
@@ -221,7 +221,7 @@ void RoadStop::Leave(RoadVehicle *rv)
 		this->SetEntranceBusy(false);
 	} else {
 		/* Otherwise just leave the drive through's entry cache. */
-		this->GetEntry(DirToDiagDir(rv->direction))->Leave(rv);
+		this->GetEntry(DirToDiagDir(rv->direction))->Leave();
 	}
 }
 
@@ -275,11 +275,17 @@ bool RoadStop::Enter(RoadVehicle *rv)
 
 /**
  * Leave the road stop
- * @param rv the vehicle that leaves the stop
  */
-void RoadStop::Entry::Leave(const RoadVehicle *rv)
+void RoadStop::Entry::Leave()
 {
-	this->occupied -= rv->gcache.cached_total_length;
+	this->vehicles -= 1;
+
+	/* Only re-set occupied when the stop is fully clear of RVs.
+	 * occupied should match the last-entered vehicle so how many free spaces
+	 * at the entry to the stop can be calculated by pathfinders. */
+	if (this->vehicles == 0) this->occupied = 0;
+
+	assert(this->vehicles >= 0);
 	assert(this->occupied >= 0);
 }
 
@@ -292,7 +298,9 @@ void RoadStop::Entry::Enter(const RoadVehicle *rv)
 	/* we cannot assert on this->occupied < this->length because of the
 	 * remote possibility that RVs are running through each other when
 	 * trying to prevention an infinite jam. */
+	this->vehicles += 1;
 	this->occupied += rv->gcache.cached_total_length;
+	assert(this->vehicles >= 0);
 }
 
 /**
@@ -367,8 +375,10 @@ void RoadStop::Entry::Rebuild(const RoadStop *rs, int side)
 	}
 
 	this->occupied = 0;
+	this->vehicles = 0;
 	for (const auto &it : rserh.vehicles) {
 		this->occupied += it->gcache.cached_total_length;
+		this->vehicles += 1;
 	}
 }
 
@@ -386,5 +396,5 @@ void RoadStop::Entry::CheckIntegrity(const RoadStop *rs) const
 
 	Entry temp;
 	temp.Rebuild(rs, rs->east == this);
-	if (temp.length != this->length || temp.occupied != this->occupied) NOT_REACHED();
+	if (temp.length != this->length || temp.occupied != this->occupied || temp.vehicles != this->vehicles) NOT_REACHED();
 }
diff --git a/src/roadstop_base.h b/src/roadstop_base.h
index 768b54282d..c46d7356b5 100644
--- a/src/roadstop_base.h
+++ b/src/roadstop_base.h
@@ -33,12 +33,13 @@ struct RoadStop : RoadStopPool::PoolItem<&_roadstop_pool> {
 	private:
 		int length;      ///< The length of the stop in tile 'units'
 		int occupied;    ///< The amount of occupied stop in tile 'units'
+		int vehicles;    ///< The number of vehicles in the stop
 
 	public:
 		friend struct RoadStop; ///< Oh yeah, the road stop may play with me.
 
 		/** Create an entry */
-		Entry() : length(0), occupied(0) {}
+		Entry() : length(0), occupied(0), vehicles(0) {}
 
 		/**
 		 * Get the length of this drive through stop.
@@ -58,7 +59,7 @@ struct RoadStop : RoadStopPool::PoolItem<&_roadstop_pool> {
 			return this->occupied;
 		}
 
-		void Leave(const RoadVehicle *rv);
+		void Leave();
 		void Enter(const RoadVehicle *rv);
 		void CheckIntegrity(const RoadStop *rs) const;
 		void Rebuild(const RoadStop *rs, int side = -1);