share BuildingSystem's free functions instead of copying them

src/lib/core/BuildingType.cpp

@@ -38,3 +38,17 @@ std::string buildingTypeId(BuildingType type)
     }
     return "";
 }
+
+bool isAutoRecipeBuildingType(BuildingType type)
+{
+    return type == BuildingType::Smelter
+        || type == BuildingType::ReprocessingPlant;
+}
+
+bool isBeltSubsystemType(BuildingType type)
+{
+    return type == BuildingType::Belt
+        || type == BuildingType::Splitter
+        || type == BuildingType::TunnelEntry
+        || type == BuildingType::TunnelExit;
+}

src/lib/core/BuildingType.h

@@ -29,3 +29,13 @@ std::optional<BuildingType> parseBuildingType(const std::string& id);
 
 // Canonical id string for a BuildingType. The inverse of parseBuildingType.
 std::string buildingTypeId(BuildingType type);
+
+// Smelter and Reprocessing Plant have no player-selected recipe
+// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). They auto-process whatever inputs
+// they receive, matching against every recipe of their building type.
+bool isAutoRecipeBuildingType(BuildingType type);
+
+// Belts, splitters, and tunnel ends keep their runtime data in the belt subsystem
+// rather than in the Building instance, so placing/removing them must register or
+// unregister a tile with BeltSystem.
+bool isBeltSubsystemType(BuildingType type);

src/lib/core/CMakeLists.txt

@@ -9,6 +9,7 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemType.h
     ${CMAKE_CURRENT_SOURCE_DIR}/Item.h
     ${CMAKE_CURRENT_SOURCE_DIR}/Port.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/PortGeometry.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoiceOption.h
     ${CMAKE_CURRENT_SOURCE_DIR}/DisplayName.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BeltDragPath.h

src/lib/core/PortGeometry.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <QPoint>
+
+#include "Rotation.h"
+
+// Geometry of a building's input/output ports. A Port names the tile *outside* the
+// building together with the direction items flow across it; these helpers give the
+// building body tile on the other side of that edge, which is where the virtual
+// input/output belt lives.
+//
+// Shared by the simulation (which moves items across the edge) and the renderer
+// (which draws the virtual belt), so the two cannot disagree about which tile a
+// port belongs to.
+
+// The building body tile that owns an output port, given the port's outside tile
+// (port.tile) and its facing direction. The virtual output belt occupies this tile
+// and flows toward port.tile (REQ-MAT-OUTPUT-EMERGE).
+inline QPoint outputBodyTile(QPoint portTile, Rotation direction)
+{
+    switch (direction)
+    {
+        case Rotation::East:  return portTile + QPoint(-1,  0);
+        case Rotation::West:  return portTile + QPoint( 1,  0);
+        case Rotation::North: return portTile + QPoint( 0,  1);
+        case Rotation::South: return portTile + QPoint( 0, -1);
+    }
+    return portTile;
+}
+
+// The building body tile an input port feeds into, given the port's outside belt
+// tile (port.tile) and its inward flow direction. The virtual input belt occupies
+// this tile and flows from the outer edge (progress 0.0) to the centre (0.5)
+// (REQ-MAT-INPUT-INTAKE).
+inline QPoint inputBodyTile(QPoint portTile, Rotation inwardDirection)
+{
+    switch (inwardDirection)
+    {
+        case Rotation::East:  return portTile + QPoint( 1,  0);
+        case Rotation::West:  return portTile + QPoint(-1,  0);
+        case Rotation::North: return portTile + QPoint( 0, -1);
+        case Rotation::South: return portTile + QPoint( 0,  1);
+    }
+    return portTile;
+}