From e46338a2f1905c132c785040eb718bf10a8f1f8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=CE=B6eh=20Matt?= <5415177+ZehMatt@users.noreply.github.com>
Date: Wed, 16 Feb 2022 19:41:59 +0200
Subject: [PATCH] Fix scripting API returning 0 instead of null.

---
 distribution/openrct2.d.ts                    |  8 +--
 src/openrct2/scripting/Duktape.hpp            |  6 ++
 .../scripting/bindings/entity/ScVehicle.cpp   | 59 ++++++++++++++-----
 .../scripting/bindings/entity/ScVehicle.hpp   | 10 ++--
 4 files changed, 61 insertions(+), 22 deletions(-)

diff --git a/distribution/openrct2.d.ts b/distribution/openrct2.d.ts
index 416ff265fa..6823cf158a 100644
--- a/distribution/openrct2.d.ts
+++ b/distribution/openrct2.d.ts
@@ -1161,15 +1161,15 @@ declare global {
 
         /**
          * The previous car on the ride. This may be the on the same train or the previous
-         * train. This will point to the last car if this is the first car on the ride.
+         * train. This will return null if there is no previous car.
          */
-        previousCarOnRide: number;
+        previousCarOnRide: number | null;
 
         /**
          * The next car on the ride. This may be the on the same train or the next
-         * train. This will point to the first car if this is the last car on the ride.
+         * train. This will return null if there is no next car.
          */
-        nextCarOnRide: number;
+        nextCarOnRide: number | null;
 
         /**
          * The current station the train is in or departing.
diff --git a/src/openrct2/scripting/Duktape.hpp b/src/openrct2/scripting/Duktape.hpp
index abf01f670f..afe96f18e2 100644
--- a/src/openrct2/scripting/Duktape.hpp
+++ b/src/openrct2/scripting/Duktape.hpp
@@ -286,6 +286,12 @@ namespace OpenRCT2::Scripting
         return DukValue::take_from_stack(ctx);
     }
 
+    template<> inline DukValue ToDuk(duk_context* ctx, const uint16_t& value)
+    {
+        duk_push_int(ctx, value);
+        return DukValue::take_from_stack(ctx);
+    }
+
     template<> inline DukValue ToDuk(duk_context* ctx, const int32_t& value)
     {
         duk_push_int(ctx, value);
diff --git a/src/openrct2/scripting/bindings/entity/ScVehicle.cpp b/src/openrct2/scripting/bindings/entity/ScVehicle.cpp
index bf564ab0d2..05b0cf4922 100644
--- a/src/openrct2/scripting/bindings/entity/ScVehicle.cpp
+++ b/src/openrct2/scripting/bindings/entity/ScVehicle.cpp
@@ -196,34 +196,65 @@ namespace OpenRCT2::Scripting
         }
     }
 
-    uint16_t ScVehicle::previousCarOnRide_get() const
+    DukValue ScVehicle::previousCarOnRide_get() const
     {
-        auto vehicle = GetVehicle();
-        return vehicle != nullptr ? vehicle->prev_vehicle_on_ride.ToUnderlying() : EntityId::GetNull().ToUnderlying();
+        auto ctx = GetContext()->GetScriptEngine().GetContext();
+
+        const auto* vehicle = GetVehicle();
+        if (vehicle == nullptr)
+            return ToDuk(ctx, nullptr);
+
+        if (vehicle->prev_vehicle_on_ride.IsNull())
+            return ToDuk(ctx, nullptr);
+
+        return ToDuk(ctx, vehicle->prev_vehicle_on_ride.ToUnderlying());
     }
-    void ScVehicle::previousCarOnRide_set(uint16_t value)
+    void ScVehicle::previousCarOnRide_set(DukValue value)
     {
         ThrowIfGameStateNotMutable();
-        auto vehicle = GetVehicle();
-        if (vehicle != nullptr)
+        auto* vehicle = GetVehicle();
+        if (vehicle == nullptr)
+            return;
+
+        if (value.type() == DukValue::Type::NUMBER)
         {
-            vehicle->prev_vehicle_on_ride = EntityId::FromUnderlying(value);
+            vehicle->prev_vehicle_on_ride = EntityId::FromUnderlying(value.as_uint());
+        }
+        else
+        {
+            vehicle->prev_vehicle_on_ride = EntityId::GetNull();
         }
     }
 
-    uint16_t ScVehicle::nextCarOnRide_get() const
+    DukValue ScVehicle::nextCarOnRide_get() const
     {
-        auto vehicle = GetVehicle();
-        return vehicle != nullptr ? vehicle->next_vehicle_on_ride.ToUnderlying() : EntityId::GetNull().ToUnderlying();
+        auto ctx = GetContext()->GetScriptEngine().GetContext();
+
+        const auto* vehicle = GetVehicle();
+        if (vehicle == nullptr)
+            return ToDuk(ctx, nullptr);
+
+        if (vehicle->next_vehicle_on_ride.IsNull())
+            return ToDuk(ctx, nullptr);
+
+        return ToDuk(ctx, vehicle->next_vehicle_on_ride.ToUnderlying());
     }
-    void ScVehicle::nextCarOnRide_set(uint16_t value)
+    void ScVehicle::nextCarOnRide_set(DukValue value)
     {
         ThrowIfGameStateNotMutable();
-        auto vehicle = GetVehicle();
-        if (vehicle != nullptr)
+        auto* vehicle = GetVehicle();
+        if (vehicle == nullptr)
+            return;
+
+        if (value.type() == DukValue::Type::NUMBER)
         {
-            vehicle->next_vehicle_on_ride = EntityId::FromUnderlying(value);
+            vehicle->next_vehicle_on_ride = EntityId::FromUnderlying(value.as_uint());
         }
+        else
+        {
+            vehicle->next_vehicle_on_ride = EntityId::GetNull();
+        }
+
     }
 
     StationIndex ScVehicle::currentStation_get() const
diff --git a/src/openrct2/scripting/bindings/entity/ScVehicle.hpp b/src/openrct2/scripting/bindings/entity/ScVehicle.hpp
index 743887f1c3..cf8b0d96be 100644
--- a/src/openrct2/scripting/bindings/entity/ScVehicle.hpp
+++ b/src/openrct2/scripting/bindings/entity/ScVehicle.hpp
@@ -14,6 +14,8 @@
 #    include "../../../ride/Ride.h"
 #    include "ScEntity.hpp"
 
+#    include <optional>
+
 namespace OpenRCT2::Scripting
 {
     class ScVehicle : public ScEntity
@@ -44,11 +46,11 @@ namespace OpenRCT2::Scripting
         DukValue nextCarOnTrain_get() const;
         void nextCarOnTrain_set(DukValue value);
 
-        uint16_t previousCarOnRide_get() const;
-        void previousCarOnRide_set(uint16_t value);
+        DukValue previousCarOnRide_get() const;
+        void previousCarOnRide_set(DukValue value);
 
-        uint16_t nextCarOnRide_get() const;
-        void nextCarOnRide_set(uint16_t value);
+        DukValue nextCarOnRide_get() const;
+        void nextCarOnRide_set(DukValue value);
 
         StationIndex currentStation_get() const;
         void currentStation_set(StationIndex value);