Add deconstruction queue

src/lib/sim/BuildingSystem.h

@@ -77,10 +77,22 @@ public:
     // Defaults to world.regions.asteroid_width_tiles at construction.
     void setAsteroidWidth_tiles(int widthTiles) { m_asteroidWidth_tiles = widthTiles; }
 
-    // Remove a building or construction site by id.  Returns the refund in
-    // building blocks (floor(cost * refundPercentage / 100)).  Returns 0 for
-    // unknown ids.
-    int demolish(BuildingId id);
+    // Mark a building or construction site for demolition (REQ-BLD-DEMOLISH).
+    // A construction site is removed instantly and the full cost is returned.
+    // A fully-built building is instead appended to the deconstruction queue
+    // (REQ-BLD-DECON-QUEUE) and stops operating at once; its (partial) refund is
+    // credited later, on completion in tickDeconstruction, so this returns 0 for
+    // it. Returns 0 for unknown ids and for a building already queued.
+    int demolish(BuildingId id, Tick currentTick);
+
+    // Take a building back out of the deconstruction queue before it is removed
+    // (REQ-BLD-DECON-QUEUE). Clears its queued flag and resumes operation
+    // (re-registering belt/tunnel/splitter tiles); discards deconstruction
+    // progress and credits no refund. No-op if the id is not queued.
+    void cancelDeconstruction(BuildingId id);
+
+    // True if the building is currently in the deconstruction queue.
+    bool isQueuedForDeconstruction(BuildingId id) const;
 
     // Set the recipe (or schematic id for shipyard) on a building or queued
     // construction site.  Clears both buffers on an operational building.
@@ -104,6 +116,10 @@ public:
 
     // -- Tick hooks (called from Simulation::tick in the documented order) ---
     void tickConstruction(Tick currentTick);
+    // Advances the deconstruction queue (REQ-BLD-DECON-QUEUE): one building at a
+    // time, in parallel with tickConstruction. Removes the front building and
+    // credits its refund when its timer elapses.
+    void tickDeconstruction(Tick currentTick);
     void tickBeltPull();
     void tickProduction(Tick currentTick);
     void tickShipyardProduction(Tick currentTick);
@@ -205,6 +221,17 @@ public:
     void appendChecksum(Hasher& hasher) const;
 
 private:
+    // Starts the front deconstruction-queue entry's timer if not yet started
+    // (mirrors how tickConstruction starts a queued construction site).
+    void                 startFrontDeconstruction(Tick currentTick);
+
+    // 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);
+
     Building*            findBuildingMutable(BuildingId id);
     // 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
@@ -273,6 +300,19 @@ private:
     std::vector<Building>           m_buildings;
     std::deque<ConstructionSite>    m_constructionQueue;
 
+    // One pending demolition of a fully-built building (REQ-BLD-DECON-QUEUE).
+    // completesAt == 0 means "queued but its timer has not started yet"
+    // (mirrors ConstructionSite). For a Splitter, the filters it had are captured
+    // here so cancelDeconstruction can restore them on re-registration.
+    struct DeconstructionEntry
+    {
+        BuildingId            id          = kInvalidBuildingId;
+        Tick                  completesAt = 0;
+        std::vector<ItemType> splitterFilterA;
+        std::vector<ItemType> splitterFilterB;
+    };
+    std::deque<DeconstructionEntry> m_deconstructionQueue;
+
     // Maps every occupied body-cell coordinate to the entity that owns it.
     std::map<std::pair<int, int>, BuildingId> m_tileOccupancy;
 };