move two placement queries out of the view into PlacementRules

src/lib/sim/PlacementRules.cpp

@@ -119,3 +119,82 @@ std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state, con
     return std::nullopt;
 }
 
+
+bool canPlaceBuilding(const FactoryState& state, const GameConfig& config,
+                      BuildingType type, QPoint anchor, Rotation rotation)
+{
+    // Terrain and world-bounds validity first (REQ-BLD-PLACE-VALID); occupancy is
+    // the extra rule this adds.
+    if (!isPlacementValid(state, config, type, anchor, rotation))
+    {
+        return false;
+    }
+
+    const BuildingDef* def = config.buildings.findBuildingDef(type);
+    if (!def) { return false; }
+    const ParsedSurfaceMask parsed = parseSurfaceMask(def->surfaceMask, rotation);
+
+    bool anyOccupied = false;
+    for (const QPoint& relativeCell : parsed.bodyCells)
+    {
+        if (isTileOccupied(state, anchor + relativeCell))
+        {
+            anyOccupied = true;
+            break;
+        }
+    }
+
+    if (anyOccupied)
+    {
+        // Occupied is still placeable when what is there is the same building being
+        // re-oriented (REQ-BLD-ROTATE-IN-PLACE).
+        return findRotateInPlaceTarget(state, config, type, anchor, rotation).has_value();
+    }
+    return true;
+}
+
+std::vector<BeltDragResolved> resolveBeltDragPath(const std::vector<BeltPathTile>& path,
+                                                  const FactoryState& state,
+                                                  const GameConfig& config,
+                                                  int buildingBlocksStock)
+{
+    std::vector<BeltDragResolved> resolved;
+    resolved.reserve(path.size());
+
+    const BuildingDef* def = config.buildings.findBuildingDef(BuildingType::Belt);
+    const int beltCost = (def != nullptr) ? def->cost : 0;
+    int       spent    = 0;
+
+    for (const BeltPathTile& entry : path)
+    {
+        BeltDragResolved item;
+        const std::optional<BuildingId> rotateTarget =
+            findRotateInPlaceTarget(state, config, BuildingType::Belt,
+                                    entry.tile, entry.rotation);
+        if (rotateTarget.has_value())
+        {
+            // A tile holding only a belt (or belt site) is re-oriented, no cost.
+            item.action     = BeltTileAction::RotateInPlace;
+            item.affordable = true;
+            item.rotateId   = rotateTarget;
+        }
+        else if (canPlaceBuilding(state, config, BuildingType::Belt,
+                                  entry.tile, entry.rotation))
+        {
+            // Empty, valid cell: a new belt, subject to cumulative affordability.
+            item.action     = BeltTileAction::PlaceNew;
+            item.affordable = (spent + beltCost <= buildingBlocksStock);
+            item.rotateId   = std::nullopt;
+            if (item.affordable) { spent += beltCost; }
+        }
+        else
+        {
+            // Occupied by a non-belt building/site, or otherwise invalid terrain.
+            item.action     = BeltTileAction::Invalid;
+            item.affordable = false;
+            item.rotateId   = std::nullopt;
+        }
+        resolved.push_back(item);
+    }
+    return resolved;
+}

src/lib/sim/PlacementRules.h

@@ -5,6 +5,7 @@
 
 #include <QPoint>
 
+#include "BeltDragPath.h"
 #include "BuildingId.h"
 #include "BuildingType.h"
 #include "FactoryState.h"
@@ -36,3 +37,35 @@ std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state,
                                                   const GameConfig& config,
                                                   BuildingType type, QPoint anchor,
                                                   Rotation rot);
+
+// True if placing here would actually do something: the terrain and bounds rules of
+// isPlacementValid hold, and the body cells are either all free or occupied only by
+// a building this placement would rotate in place. This is the question the ghost
+// asks to colour itself and the click path asks before enqueuing a command
+// (REQ-BLD-GHOST, REQ-BLD-PLACE-VALID, REQ-BLD-ROTATE-IN-PLACE).
+bool canPlaceBuilding(const FactoryState& state, const GameConfig& config,
+                      BuildingType type, QPoint anchor, Rotation rotation);
+
+// What a belt drag would do to one tile of its path (REQ-BLD-BELT-DRAG).
+enum class BeltTileAction
+{
+    PlaceNew,       // empty, valid cell: a new belt, subject to affordability
+    RotateInPlace,  // already a belt (or belt site): re-oriented, free
+    Invalid         // occupied by something else, or invalid terrain
+};
+
+struct BeltDragResolved
+{
+    BeltTileAction            action;
+    bool                      affordable;  // meaningful only for PlaceNew
+    std::optional<BuildingId> rotateId;    // set only for RotateInPlace
+};
+
+// Classifies every tile of a belt drag path against the current factory state,
+// spending `buildingBlocksStock` cumulatively across the PlaceNew tiles so a path
+// longer than the player can afford is only partly buildable (REQ-BLD-BELT-DRAG).
+// Shared so the previewed ghosts and the placement on release cannot disagree.
+std::vector<BeltDragResolved> resolveBeltDragPath(const std::vector<BeltPathTile>& path,
+                                                  const FactoryState& state,
+                                                  const GameConfig& config,
+                                                  int buildingBlocksStock);

src/ui/GameWorldView.cpp

@@ -563,36 +563,11 @@ ScrollBounds GameWorldView::getScrollBounds() const
 // Placement helpers
 // ---------------------------------------------------------------------------
 
-bool GameWorldView::isValidPlacement(BuildingType type, QPoint anchor,
+bool GameWorldView::canPlaceBuildingHere(BuildingType type, QPoint anchor,
-                                     Rotation rot) const
+                                         Rotation rot) const
 {
-    // Terrain and world-bounds validity are owned by the simulation
+    return canPlaceBuilding(m_sim->getFactoryState(), m_sim->getConfig(),
-    // (REQ-BLD-PLACE-VALID); the presentation layer only adds the occupancy /
+                            type, anchor, rot);
-    // rotate-in-place check.
-    if (!isPlacementValid(m_sim->getFactoryState(), m_sim->getConfig(), type, anchor, rot))
-    {
-        return false;
-    }
-
-    const BuildingDef* def = m_config->buildings.findBuildingDef(type);
-    if (!def) { return false; }
-    const ParsedSurfaceMask parsed = parseSurfaceMask(def->surfaceMask, rot);
-
-    bool anyOccupied = false;
-    for (const QPoint& relCell : parsed.bodyCells)
-    {
-        if (isTileOccupied(m_sim->getFactoryState(), anchor + relCell))
-        {
-            anyOccupied = true;
-            break;
-        }
-    }
-
-    if (anyOccupied)
-    {
-        return findRotateInPlaceTarget(m_sim->getFactoryState(), m_sim->getConfig(), type, anchor, rot).has_value();
-    }
-    return true;
 }
 
 std::optional<BuildingId> GameWorldView::buildingAtTile(QPoint tile) const
@@ -736,7 +711,7 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
         // Locked building types are excluded from this placement entirely
         // (REQ-LOCK-BUILDING, REQ-LOCK-UI-BLUEPRINT): not validity-checked here.
         if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
-        if (!isValidPlacement(bb.type, center + bb.offset, bb.rotation)) { return; }
+        if (!canPlaceBuildingHere(bb.type, center + bb.offset, bb.rotation)) { return; }
     }
 
     // Cost only applies to buildings that are genuinely new (not rotate-in-place),
@@ -878,7 +853,7 @@ void GameWorldView::placeAtTile(QPoint tile)
     const BuildingType type     = m_buildMode.getEffectiveBuilderType();
     const Rotation     rotation = m_buildMode.getGhostRotation();
 
-    if (!isValidPlacement(type, tile, rotation))
+    if (!canPlaceBuildingHere(type, tile, rotation))
 	{
 		return;
 	}
@@ -980,46 +955,11 @@ void GameWorldView::recomputeBeltDragPath(QPoint cursorTile)
     m_buildMode.setBeltDragPath(std::move(path));
 }
 
-std::vector<GameWorldView::BeltDragResolved> GameWorldView::resolveBeltDragPath() const
+std::vector<BeltDragResolved> GameWorldView::resolveBeltDragPath() const
 {
-    std::vector<BeltDragResolved> resolved;
+    return ::resolveBeltDragPath(m_buildMode.getBeltDragPath(),
-    resolved.reserve(m_buildMode.getBeltDragPath().size());
+                                 m_sim->getFactoryState(), m_sim->getConfig(),
-
+                                 m_sim->getBuildingBlocksStock());
-    const BuildingDef* def = m_config->buildings.findBuildingDef(BuildingType::Belt);
-    const int beltCost      = (def != nullptr) ? def->cost : 0;
-    const int stock         = m_sim->getBuildingBlocksStock();
-    int       spent         = 0;
-
-    for (const BeltPathTile& entry : m_buildMode.getBeltDragPath())
-    {
-        BeltDragResolved item;
-        const std::optional<BuildingId> rotateTarget =
-            findRotateInPlaceTarget(m_sim->getFactoryState(), m_sim->getConfig(), BuildingType::Belt, entry.tile, entry.rotation);
-        if (rotateTarget.has_value())
-        {
-            // A tile holding only a belt (or belt site) is re-oriented, no cost.
-            item.action     = BeltTileAction::RotateInPlace;
-            item.affordable = true;
-            item.rotateId   = rotateTarget;
-        }
-        else if (isValidPlacement(BuildingType::Belt, entry.tile, entry.rotation))
-        {
-            // Empty, valid cell: a new belt, subject to cumulative affordability.
-            item.action     = BeltTileAction::PlaceNew;
-            item.affordable = (spent + beltCost <= stock);
-            item.rotateId   = std::nullopt;
-            if (item.affordable) { spent += beltCost; }
-        }
-        else
-        {
-            // Occupied by a non-belt building/site, or otherwise invalid terrain.
-            item.action     = BeltTileAction::Invalid;
-            item.affordable = false;
-            item.rotateId   = std::nullopt;
-        }
-        resolved.push_back(item);
-    }
-    return resolved;
 }
 
 void GameWorldView::applyBeltDragPath()
@@ -1947,7 +1887,7 @@ void GameWorldView::drawOverlays(QPainter& painter, const WorldCoordinates& coor
             // REQ-LOCK-UI-BLUEPRINT), so they are not ghosted either.
             if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
             const QPoint anchor = m_buildMode.getBlueprintGhostTile() + bb.offset;
-            const bool   valid  = isValidPlacement(bb.type, anchor, bb.rotation);
+            const bool   valid  = canPlaceBuildingHere(bb.type, anchor, bb.rotation);
             drawBuildingGhost(painter, coordinates, bb.type, anchor, bb.rotation,
                               valid, /*showPortTargetGlyphs*/ false);
         }
@@ -2442,7 +2382,7 @@ void GameWorldView::mouseMoveEvent(QMouseEvent* event)
     {
         m_buildMode.setGhostTile(tile);
         m_buildMode.setGhostValidity(
-            isValidPlacement(m_buildMode.getBuilderType(), tile,
+            canPlaceBuildingHere(m_buildMode.getBuilderType(), tile,
                              m_buildMode.getGhostRotation()));
 
         if (m_buildMode.isTunnelMode())
@@ -2569,7 +2509,7 @@ void GameWorldView::rotateGhost(bool clockwise)
     {
         m_buildMode.rotateGhost(clockwise);
         m_buildMode.setGhostValidity(
-            isValidPlacement(m_buildMode.getBuilderType(), m_buildMode.getGhostTile(),
+            canPlaceBuildingHere(m_buildMode.getBuilderType(), m_buildMode.getGhostTile(),
                              m_buildMode.getGhostRotation()));
         // A new facing changes which tunnels the ghost could complete (REQ-BLD-TUNNEL-MODE).
         if (m_buildMode.isTunnelMode()) { updateTunnelGhost(); }

src/ui/GameWorldView.h

@@ -52,6 +52,7 @@
 #include "CommandManager.h"
 #include "EntitySelectionChangedEvent.h"
 #include "GameConfig.h"
+#include "PlacementRules.h"
 #include "Rotation.h"
 #include "SelectionController.h"
 #include "Tick.h"
@@ -213,7 +214,8 @@ private:
     // both edges move with asteroid expansion and with pushes (REQ-GW-SCROLL-LIMIT).
     ScrollBounds getScrollBounds() const;
 
-    bool     isValidPlacement(BuildingType type, QPoint anchor, Rotation rot) const;
+    // canPlaceBuilding (PlacementRules) against this view's simulation.
+    bool     canPlaceBuildingHere(BuildingType type, QPoint anchor, Rotation rot) const;
     std::optional<BuildingId> buildingAtTile(QPoint tile) const;
     std::optional<BuildingId> siteAtTile(QPoint tile) const;
     // Ids of all buildings and construction sites whose footprint intersects
@@ -277,19 +279,10 @@ private:
                                                const WorldCoordinates& coordinates);
 
     // Belt drag placement (REQ-BLD-BELT-DRAG).
-    // Per-path-tile decision, shared by ghost drawing and release-time placement.
-    enum class BeltTileAction { PlaceNew, RotateInPlace, Invalid };
-    struct BeltDragResolved
-    {
-        BeltTileAction            action;
-        bool                      affordable;   // meaningful only for PlaceNew
-        std::optional<BuildingId> rotateId;     // set only for RotateInPlace
-    };
     // Recomputes the drag path from its anchor to cursorTile using the current ghost
     // orientation, and stores it on the build mode controller.
     void                          recomputeBeltDragPath(QPoint cursorTile);
-    // Classifies each path tile against the current sim state, applying cumulative
+    // resolveBeltDragPath (PlacementRules) against this view's simulation.
-    // affordability to the PlaceNew tiles.
     std::vector<BeltDragResolved> resolveBeltDragPath() const;
     // Enqueues placements and rotate-in-place commands for the resolved path.
     void                          applyBeltDragPath();