free the buffer setup and belt registration from BuildingSystem

Prerequisite for ConstructionSystem completing a building itself rather than
handing a finished site back: materialisation needs the buffer initialisers and
the BeltSystem registration, and both were BuildingSystem members.

initBuffers turned out to need nothing at all — it works purely on the Building
and RecipeDef it is given. The other three need only the config.
reregisterBeltTile takes BeltSystem and the config; it stays shared rather than
moving, because cancelDeconstruction and rotateInPlace use it too and are staying
on BuildingSystem.

Verified with a golden-checksum capture before and after — all four sample ticks
identical.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/sim/BuildingBuffers.cpp

@@ -0,0 +1,173 @@
+#include "BuildingBuffers.h"
+
+#include <algorithm>
+#include <cassert>
+
+#include "BuildingType.h"
+#include "ItemType.h"
+#include "ModulesConfig.h"
+#include "ShipsConfig.h"
+
+void initBuffers(Building& b, const RecipeDef& recipe)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+    for (const RecipeIngredient& ing : recipe.inputs)
+    {
+        const ItemType type{ing.item};
+        b.inputBuffer.counts[type] = 0;
+        b.inputBuffer.caps[type]   = 2 * ing.amount;
+    }
+
+    b.outputBuffer.items.clear();
+    if (b.type == BuildingType::ReprocessingPlant)
+    {
+        // 1× max-per-roll (REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
+        int maxAmount = 0;
+        for (const RecipeOutput& out : recipe.outputs)
+        {
+            if (out.amount > maxAmount)
+            {
+                maxAmount = out.amount;
+            }
+        }
+        b.outputBuffer.capacity = maxAmount;
+    }
+    else
+    {
+        // 2× per-cycle output.
+        int totalAmount = 0;
+        for (const RecipeOutput& out : recipe.outputs)
+        {
+            totalAmount += out.amount;
+        }
+        b.outputBuffer.capacity = 2 * totalAmount;
+    }
+}
+
+void initAutoBuffers(const GameConfig& config, Building& b)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+
+    // Union the inputs of every recipe of this building type; the cap for each
+    // item is twice the largest per-cycle requirement across those recipes.
+    // Output capacity follows the same rules as initBuffers: the Reprocessing
+    // Plant holds one cycle's max output (REQ-MAT-OUTPUT-BUFFER-REPROCESSING),
+    // other auto buildings hold twice the largest per-cycle output.
+    int outputCapacity = 0;
+    for (const RecipeDef& recipe : config.recipes.recipes)
+    {
+        if (recipe.building != b.type)
+        {
+            continue;
+        }
+
+        for (const RecipeIngredient& ing : recipe.inputs)
+        {
+            const ItemType type{ing.item};
+            b.inputBuffer.counts[type] = 0;
+            b.inputBuffer.caps[type] =
+                std::max(b.inputBuffer.caps[type], 2 * ing.amount);
+        }
+
+        if (b.type == BuildingType::ReprocessingPlant)
+        {
+            int maxAmount = 0;
+            for (const RecipeOutput& out : recipe.outputs)
+            {
+                maxAmount = std::max(maxAmount, out.amount);
+            }
+            outputCapacity = std::max(outputCapacity, maxAmount);
+        }
+        else
+        {
+            int totalAmount = 0;
+            for (const RecipeOutput& out : recipe.outputs)
+            {
+                totalAmount += out.amount;
+            }
+            outputCapacity = std::max(outputCapacity, 2 * totalAmount);
+        }
+    }
+
+    b.outputBuffer.items.clear();
+    b.outputBuffer.capacity = outputCapacity;
+}
+
+void initShipyardBuffers(const GameConfig& config, Building& b)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+    b.outputBuffer.items.clear();
+    b.outputBuffer.capacity = 0;
+    const ShipDef* def = config.ships.findShipDef(b.recipeId);
+    if (!def)
+    {
+        return;
+    }
+    for (const RecipeIngredient& ing : def->schematic.materials)
+    {
+        const ItemType type{ing.item};
+        b.inputBuffer.counts[type] = 0;
+        b.inputBuffer.caps[type]   = 2 * ing.amount;
+    }
+    if (b.shipLayout.has_value())
+    {
+        for (const PlacedModule& pm : b.shipLayout->placedModules)
+        {
+            const ModuleDef* modDef = config.modules.findModuleDef(pm.moduleId);
+            if (!modDef)
+            {
+                continue;
+            }
+            for (const RecipeIngredient& ing : modDef->materials)
+            {
+                const ItemType type{ing.item};
+                b.inputBuffer.counts.try_emplace(type, 0);
+                b.inputBuffer.caps[type] += 2 * ing.amount;
+            }
+        }
+    }
+}
+
+void initSalvageBayBuffer(const GameConfig& config, Building& b)
+{
+    // Salvage Bay has no recipe-driven buffer; its output-buffer holding size for
+    // ship drop-off is config-defined (REQ-BLD-SALVAGE-BAY).
+    b.outputBuffer.items.clear();
+    const BuildingDef* def = config.buildings.findBuildingDef(BuildingType::SalvageBay);
+    b.outputBuffer.capacity =
+        (def && def->outputBufferCapacity) ? *def->outputBufferCapacity : 0;
+}
+
+
+void reregisterBeltTile(BeltSystem& belts, const GameConfig& config,
+                        const Building& building,
+                                        const std::vector<ItemType>& splitterFilterA,
+                                        const std::vector<ItemType>& splitterFilterB)
+{
+    switch (building.type)
+    {
+        case BuildingType::Belt:
+            belts.placeBelt(building.anchor, building.rotation);
+            break;
+        case BuildingType::Splitter:
+            assert(building.outputPorts.size() >= 2);
+            belts.placeSplitter(building.anchor,
+                                  building.outputPorts[0].direction,
+                                  building.outputPorts[1].direction);
+            belts.setSplitterFilters(building.anchor, splitterFilterA, splitterFilterB);
+            break;
+        case BuildingType::TunnelEntry:
+            belts.placeTunnelEntry(building.anchor, building.rotation,
+                                     config.world.tunnelMaxDistance_tiles);
+            break;
+        case BuildingType::TunnelExit:
+            belts.placeTunnelExit(building.anchor, building.rotation);
+            break;
+        default:
+            break;
+    }
+}
+

src/lib/sim/BuildingBuffers.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <vector>
+
+#include "BeltSystem.h"
+#include "Building.h"
+#include "GameConfig.h"
+#include "ItemType.h"
+#include "RecipesConfig.h"
+
+// Setting a building up when it starts existing or is reconfigured: sizing its
+// input/output buffers from what it will produce, and handing belt-like types back
+// to BeltSystem. Free functions over the config and the building — they read no
+// factory state, so both BuildingSystem and ConstructionSystem can use them.
+
+// Buffers for a building running one known recipe: inputs capped at twice each
+// ingredient's per-cycle amount, output at twice the per-cycle total (one cycle's
+// max for a Reprocessing Plant, REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
+void initBuffers(Building& b, const RecipeDef& recipe);
+
+// Buffers for an auto-recipe building (Smelter, Reprocessing Plant), unioned over
+// every recipe of its type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
+void initAutoBuffers(const GameConfig& config, Building& b);
+
+// Buffers for a shipyard: its schematic's materials plus those of every placed
+// module (REQ-BLD-SHIPYARD).
+void initShipyardBuffers(const GameConfig& config, Building& b);
+
+// The Salvage Bay holds no recipe inputs; its output capacity is config-defined
+// (REQ-BLD-SALVAGE-BAY).
+void initSalvageBayBuffer(const GameConfig& config, Building& b);
+
+// Registers a belt, splitter or tunnel end with BeltSystem. A splitter's filters
+// live in BeltSystem and are lost by removeTile, so they are passed back in
+// (REQ-BLD-SPLITTER). No-op for every other building type.
+void reregisterBeltTile(BeltSystem& belts, const GameConfig& config,
+                        const Building& building,
+                        const std::vector<ItemType>& splitterFilterA,
+                        const std::vector<ItemType>& splitterFilterB);

src/lib/sim/BuildingSystem.cpp

@@ -47,139 +47,6 @@ BuildingSystem::BuildingSystem(const GameConfig& config,
 // Private helpers
 // ---------------------------------------------------------------------------
 
-void BuildingSystem::initBuffers(Building& b, const RecipeDef& recipe) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-    for (const RecipeIngredient& ing : recipe.inputs)
-    {
-        const ItemType type{ing.item};
-        b.inputBuffer.counts[type] = 0;
-        b.inputBuffer.caps[type]   = 2 * ing.amount;
-    }
-
-    b.outputBuffer.items.clear();
-    if (b.type == BuildingType::ReprocessingPlant)
-    {
-        // 1× max-per-roll (REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
-        int maxAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            if (out.amount > maxAmount)
-            {
-                maxAmount = out.amount;
-            }
-        }
-        b.outputBuffer.capacity = maxAmount;
-    }
-    else
-    {
-        // 2× per-cycle output.
-        int totalAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            totalAmount += out.amount;
-        }
-        b.outputBuffer.capacity = 2 * totalAmount;
-    }
-}
-
-void BuildingSystem::initAutoBuffers(Building& b) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-
-    // Union the inputs of every recipe of this building type; the cap for each
-    // item is twice the largest per-cycle requirement across those recipes.
-    // Output capacity follows the same rules as initBuffers: the Reprocessing
-    // Plant holds one cycle's max output (REQ-MAT-OUTPUT-BUFFER-REPROCESSING),
-    // other auto buildings hold twice the largest per-cycle output.
-    int outputCapacity = 0;
-    for (const RecipeDef& recipe : m_config.recipes.recipes)
-    {
-        if (recipe.building != b.type)
-        {
-            continue;
-        }
-
-        for (const RecipeIngredient& ing : recipe.inputs)
-        {
-            const ItemType type{ing.item};
-            b.inputBuffer.counts[type] = 0;
-            b.inputBuffer.caps[type] =
-                std::max(b.inputBuffer.caps[type], 2 * ing.amount);
-        }
-
-        if (b.type == BuildingType::ReprocessingPlant)
-        {
-            int maxAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                maxAmount = std::max(maxAmount, out.amount);
-            }
-            outputCapacity = std::max(outputCapacity, maxAmount);
-        }
-        else
-        {
-            int totalAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                totalAmount += out.amount;
-            }
-            outputCapacity = std::max(outputCapacity, 2 * totalAmount);
-        }
-    }
-
-    b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = outputCapacity;
-}
-
-void BuildingSystem::initShipyardBuffers(Building& b) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-    b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = 0;
-    const ShipDef* def = m_config.ships.findShipDef(b.recipeId);
-    if (!def)
-    {
-        return;
-    }
-    for (const RecipeIngredient& ing : def->schematic.materials)
-    {
-        const ItemType type{ing.item};
-        b.inputBuffer.counts[type] = 0;
-        b.inputBuffer.caps[type]   = 2 * ing.amount;
-    }
-    if (b.shipLayout.has_value())
-    {
-        for (const PlacedModule& pm : b.shipLayout->placedModules)
-        {
-            const ModuleDef* modDef = m_config.modules.findModuleDef(pm.moduleId);
-            if (!modDef)
-            {
-                continue;
-            }
-            for (const RecipeIngredient& ing : modDef->materials)
-            {
-                const ItemType type{ing.item};
-                b.inputBuffer.counts.try_emplace(type, 0);
-                b.inputBuffer.caps[type] += 2 * ing.amount;
-            }
-        }
-    }
-}
-
-void BuildingSystem::initSalvageBayBuffer(Building& b) const
-{
-    // Salvage Bay has no recipe-driven buffer; its output-buffer holding size for
-    // ship drop-off is config-defined (REQ-BLD-SALVAGE-BAY).
-    b.outputBuffer.items.clear();
-    const BuildingDef* def = m_config.buildings.findBuildingDef(BuildingType::SalvageBay);
-    b.outputBuffer.capacity =
-        (def && def->outputBufferCapacity) ? *def->outputBufferCapacity : 0;
-}
-
 
 std::vector<Item> BuildingSystem::rollReprocessingOutput(const RecipeDef& recipe)
 {
@@ -397,7 +264,7 @@ void BuildingSystem::setRecipe(FactoryState& state, BuildingId id, const std::st
             {
                 if (building.type == BuildingType::Shipyard)
                 {
-                    initShipyardBuffers(building);
+                    initShipyardBuffers(m_config, building);
                 }
                 else
                 {
@@ -441,7 +308,7 @@ void BuildingSystem::setShipLayout(FactoryState& state, BuildingId id, const Shi
             for (std::vector<BeltItemSlot>& lane : building.incomingItems) { lane.clear(); }
             if (!building.recipeId.empty() && building.type == BuildingType::Shipyard)
             {
-                initShipyardBuffers(building);
+                initShipyardBuffers(m_config, building);
             }
             return;
         }
@@ -525,19 +392,19 @@ void BuildingSystem::tickConstruction(FactoryState& state, Tick currentTick)
 
     if (building.type == BuildingType::SalvageBay)
     {
-        initSalvageBayBuffer(building);
+        initSalvageBayBuffer(m_config, building);
     }
     else if (isAutoRecipeBuildingType(building.type))
     {
         // Smelter/Reprocessing Plant need no recipe selection; buffers are set
         // up from all recipes of the type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-        initAutoBuffers(building);
+        initAutoBuffers(m_config, building);
     }
     else if (!building.recipeId.empty())
     {
         if (building.type == BuildingType::Shipyard)
         {
-            initShipyardBuffers(building);
+            initShipyardBuffers(m_config, building);
         }
         else
         {
@@ -551,7 +418,7 @@ void BuildingSystem::tickConstruction(FactoryState& state, Tick currentTick)
 
     // Register with BeltSystem before the move (mask/building stays valid). Any
     // filters configured while under construction carry over (REQ-BLD-SITE-CONFIG).
-    reregisterBeltTile(building, front.splitterFilterA, front.splitterFilterB);
+    reregisterBeltTile(m_belts, m_config, building, front.splitterFilterA, front.splitterFilterB);
 
     state.buildings.push_back(std::move(building));
 
@@ -570,34 +437,6 @@ void BuildingSystem::tickConstruction(FactoryState& state, Tick currentTick)
     }
 }
 
-void BuildingSystem::reregisterBeltTile(const Building& building,
-                                        const std::vector<ItemType>& splitterFilterA,
-                                        const std::vector<ItemType>& splitterFilterB)
-{
-    switch (building.type)
-    {
-        case BuildingType::Belt:
-            m_belts.placeBelt(building.anchor, building.rotation);
-            break;
-        case BuildingType::Splitter:
-            assert(building.outputPorts.size() >= 2);
-            m_belts.placeSplitter(building.anchor,
-                                  building.outputPorts[0].direction,
-                                  building.outputPorts[1].direction);
-            m_belts.setSplitterFilters(building.anchor, splitterFilterA, splitterFilterB);
-            break;
-        case BuildingType::TunnelEntry:
-            m_belts.placeTunnelEntry(building.anchor, building.rotation,
-                                     m_config.world.tunnelMaxDistance_tiles);
-            break;
-        case BuildingType::TunnelExit:
-            m_belts.placeTunnelExit(building.anchor, building.rotation);
-            break;
-        default:
-            break;
-    }
-}
-
 void BuildingSystem::tickDeconstruction(FactoryState& state, Tick currentTick)
 {
     TRACE();
@@ -659,7 +498,7 @@ void BuildingSystem::cancelDeconstruction(FactoryState& state, BuildingId id)
         if (Building* building = findBuilding(state, id))
         {
             building->queuedForDeconstruction = false;
-            reregisterBeltTile(*building, it->splitterFilterA, it->splitterFilterB);
+            reregisterBeltTile(m_belts, m_config, *building, it->splitterFilterA, it->splitterFilterB);
         }
 
         state.deconstructionQueue.erase(it);
@@ -1151,7 +990,7 @@ void BuildingSystem::rotateInPlace(FactoryState& state, BuildingId id, Rotation
             }
 
             m_belts.removeTile(b.anchor);
-            reregisterBeltTile(b, splitterFilterA, splitterFilterB);
+            reregisterBeltTile(m_belts, m_config, b, splitterFilterA, splitterFilterB);
         }
 
         return;
@@ -1191,7 +1030,7 @@ BuildingId BuildingSystem::placeImmediate(FactoryState& state, BuildingType type
 
     if (type == BuildingType::SalvageBay)
     {
-        initSalvageBayBuffer(building);
+        initSalvageBayBuffer(m_config, building);
     }
 
     state.buildings.push_back(std::move(building));

src/lib/sim/BuildingSystem.h

@@ -16,6 +16,7 @@
 #include "BeltSystem.h"
 #include "Building.h"
 #include "FactoryState.h"
+#include "BuildingBuffers.h"
 #include "PlacementRules.h"
 #include "ProductionRules.h"
 #include "BuildingType.h"
@@ -188,9 +189,6 @@ private:
     // Registers a belt/splitter/tunnel building's tile with the belt subsystem
     // (on construction completion, or when un-queuing a deconstruction). No-op for
     // non-belt-subsystem types. Splitter filters are (re)applied after placement.
-    void                 reregisterBeltTile(const Building& building,
-                                            const std::vector<ItemType>& splitterFilterA,
-                                            const std::vector<ItemType>& splitterFilterB);
 
     // True if the consumer would accept `type` at the given input port right now:
     // it is a required input (or a building block for the HQ), the reservation-aware
@@ -221,13 +219,9 @@ private:
     // (ignoring output-buffer space); drives the Starved/Blocked distinction of
     // the status light (REQ-UI-STATUS-LIGHT).
 
-    void                initBuffers(Building& b, const RecipeDef& recipe) const;
     // Buffers for an auto-recipe building (Smelter, Reprocessing Plant): input
     // caps span the union of every recipe of the building's type; no player
     // recipe is selected (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-    void                initAutoBuffers(Building& b) const;
-    void                initShipyardBuffers(Building& b) const;
-    void                initSalvageBayBuffer(Building& b) const;
     // Core input-edge scan shared by operational buildings and construction sites.
     std::vector<Item>   rollReprocessingOutput(const RecipeDef& recipe);
 

src/lib/sim/CMakeLists.txt

@@ -13,6 +13,7 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/Building.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingConfig.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingGrid.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingBuffers.h
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryState.h
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryQueries.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionRules.h
@@ -42,6 +43,7 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/BeltSystem.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingConfig.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingGrid.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingBuffers.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryQueries.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionRules.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/PlacementRules.cpp