Add "animaltrap-reuse" tweak

docs/changelog.txt

@@ -54,6 +54,7 @@ Template for new versions:
 ## New Tools
 
 ## New Features
+- `tweak`: ``animaltrap-reuse``: make it so built animal traps automatically unload the vermin they catch into stockpiled animal traps, so that they can be automatically re-baited and reused
 
 ## Fixes
 

docs/plugins/tweak.rst

@@ -38,6 +38,9 @@ Commands
 ``adamantine-cloth-wear``
     Prevents adamantine clothing from wearing out while being worn
     (:bug:`6481`).
+``animaltrap-reuse``
+    Makes built animal traps unload caught vermin into stockpiled animal traps
+    so that they can be automatically re-baited and reused.
 ``craft-age-wear``
     Fixes crafted items not wearing out over time (:bug:`6003`). With this
     tweak, items made from cloth and leather will gain a level of wear every 20

plugins/tweak/tweak.cpp

@@ -14,6 +14,7 @@ using std::string;
 using namespace DFHack;
 
 #include "tweaks/adamantine-cloth-wear.h"
+#include "tweaks/animaltrap-reuse.h"
 #include "tweaks/craft-age-wear.h"
 #include "tweaks/eggs-fertile.h"
 #include "tweaks/fast-heat.h"
@@ -53,6 +54,8 @@ DFhackCExport command_result plugin_init(color_ostream &out, vector<PluginComman
     TWEAK_HOOK("adamantine-cloth-wear", adamantine_cloth_wear_shoes_hook, incWearTimer);
     TWEAK_HOOK("adamantine-cloth-wear", adamantine_cloth_wear_pants_hook, incWearTimer);
 
+    TWEAK_HOOK("animaltrap-reuse", animaltrap_reuse_hook, updateAction);
+
     TWEAK_HOOK("craft-age-wear", craft_age_wear_hook, ageItem);
 
     TWEAK_HOOK("eggs-fertile", eggs_fertile_hook, getItemDescription);

plugins/tweak/tweaks/animaltrap-reuse.h

@@ -0,0 +1,84 @@
+#include "modules/Job.h"
+#include "modules/Items.h"
+
+#include "df/building_animaltrapst.h"
+#include "df/buildingitemst.h"
+#include "df/general_ref_building_holderst.h"
+#include "df/general_ref_contained_in_itemst.h"
+#include "df/general_ref_contains_itemst.h"
+#include "df/job.h"
+
+using namespace df::enums;
+
+struct animaltrap_reuse_hook : df::building_animaltrapst {
+    typedef df::building_animaltrapst interpose_base;
+    DEFINE_VMETHOD_INTERPOSE(void, updateAction, ())
+    {
+        // Skip processing if the trap isn't fully built
+        if (getBuildStage() != getMaxBuildStage()) return;
+
+        // The first item is always the trap itself, and the second item (if any) is always either the Bait or the caught Vermin
+        if ((contained_items.size() > 1) && (contained_items[1]->item->getType() == df::item_type::VERMIN))
+        {
+            auto trap = contained_items[0]->item;
+            auto vermin = contained_items[1]->item;
+
+            // Make sure we don't already have a "Release Small Creature" job
+            for (size_t j = 0; j < jobs.size(); j++)
+            {
+                if (jobs[j]->job_type == df::job_type::ReleaseSmallCreature)
+                    return;
+                // Also bail out if the player marked the building for destruction
+                if (jobs[j]->job_type == df::job_type::DestroyBuilding)
+                    return;
+            }
+
+            // Create the job
+            auto job = new df::job();
+            Job::linkIntoWorld(job, true);
+
+            job->job_type = df::job_type::ReleaseSmallCreature;
+            job->pos.x = centerx;
+            job->pos.y = centery;
+            job->pos.z = z;
+
+            // Attach the vermin to the job
+            Job::attachJobItem(job, vermin, df::job_role_type::Hauled, -1, -1);
+
+            // Link the job to the building
+            df::general_ref *ref = df::allocate<df::general_ref_building_holderst>();
+            ref->setID(id);
+            job->general_refs.push_back(ref);
+
+            jobs.push_back(job);
+
+            // Hack: put the vermin inside the trap ITEM right away, otherwise the job will cancel.
+            // Normally, this doesn't happen until after the trap is deconstructed, but the game still
+            // seems to handle everything correctly and doesn't leave any bad references afterwards.
+            if (!Items::getContainer(vermin))
+            {
+                // We can't use Items::moveToContainer, because that would remove it from the Building
+                // (and cause the game to no longer recognize the trap as being "full").
+                // Instead, manually add the references and set the necessary bits.
+
+                ref = df::allocate<df::general_ref_contained_in_itemst>();
+                ref->setID(trap->id);
+                vermin->general_refs.push_back(ref);
+
+                ref = df::allocate<df::general_ref_contains_itemst>();
+                ref->setID(vermin->id);
+                trap->general_refs.push_back(ref);
+
+                vermin->flags.bits.in_inventory = true;
+                trap->flags.bits.weight_computed = false;
+                // Don't set this flag here (even though it would normally get set),
+                // since the game doesn't clear it after the vermin gets taken out
+                // trap->flags.bits.container = true;
+            }
+            return;
+        }
+        INTERPOSE_NEXT(updateAction)();
+    }
+};
+
+IMPLEMENT_VMETHOD_INTERPOSE(animaltrap_reuse_hook, updateAction);