Monsters will now fire at moving vehicles

[Maleclypse]

Summary

Features "Monsters with guntypes will now fire at moving vehicles."

Purpose of change

Implementation in the port lacks a number of key features for this to go into DDA as it is unfairly punishing on the player in nonsensical ways. I however am unable to make the changes personally that would bring this into a mergeable state.
Ports the c++ from Cataclysm-TISH-team#4 which is a port of cataclysmbnteam/Cataclysm-BN#2165 by Night_Pryanik and joveeater respectively. Adds significantly more monster types to the monsters that will now shoot at a moving vehicle. Also adds documentation of this so that new contributors won't have to search the c++. Thus the two separate commits.

Describe the solution

C++ makes guntypes able to shoot at moving vehicles. Json defines what monsters will now target moving vehicles. Documentation explains the json object. Added it to gun toting monsters in Xedra Evolved and Dinomod.

Describe alternatives you've considered

Waiting on others

Testing

It works really well. I'm super happy with it.

Additional context

[Maleclypse]

@irwiss will this do what you were suggesting or get me closer to it?

std::vector<tripoint> valid_targets;
            for (const tripoint& p : veh->get_points()) {
                if (veh->part_with_feature(p, VPFLAG_CONTROLS, true) >= 0 &&
                    veh->part_with_feature(p, VPFLAG_ENGINE, true) >= 0 &&
                    veh->part_with_feature(p, VPFLAG_WHEEL, true) >= 0) {
                    valid_targets.push_back(p);
                }
            }

[Maleclypse]

(~[slow] ~[.],starting_items)=>   REQUIRE( attack->call( test_monster ) == true )
(~[slow] ~[.],starting_items)=> with expansion:
Error: (~[slow] ~[.],starting_items)=>   false == true```
Hmm I wonder if I borked this test?

[irwiss]

The test borked because aim_at is not initialized around line 880 when target != nullptr

I suggest the attached refactor below (applied on top of your changes);
Fixes the mentioned aim_at bug
Moves both parts of find-me-a-part into map, cutting the 2 extra includes
Iterates the parts once per vehicle; the current code will make points*part_count iterations, and each iteration will then iterate another vector of parts-in-this-square)
Filters based on vehicle part positions rather than vehicles; current code assumes if vehicle center is out of range then all parts are out of range, which is ok for long range turrets but looks bad for short range enemies

Cataclysm-DDA-5ef3600-Refactor.patch

For convenience putting the diff folded here

From bcb1ace95a522cad1ddb3d72b9b2361101aeb89e Mon Sep 17 00:00:00 2001
From: Alexey <irwiss@users.noreply.github.com>
Date: Thu, 6 Apr 2023 01:00:31 +0300
Subject: [PATCH] Refactor

---
 src/map.cpp            | 35 ++++++++++++++++++++++++
 src/map.h              |  4 +++
 src/mattack_actors.cpp | 62 +++++-------------------------------------
 3 files changed, 46 insertions(+), 55 deletions(-)

diff --git a/src/map.cpp b/src/map.cpp
index 726839e0eb..64d75795fc 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -1122,6 +1122,41 @@ bool map::deregister_vehicle_zone( zone_data &zone ) const
     return false;
 }
 
+std::set<tripoint_bub_ms> map::get_moving_vehicle_targets( const Creature &z, int max_range )
+{
+    const tripoint_bub_ms zpos( z.pos() );
+    std::set<tripoint_bub_ms> priority;
+    std::set<tripoint_bub_ms> visible;
+    for( wrapped_vehicle &v : get_vehicles() ) {
+        if( !v.v->is_moving() ) {
+            continue;
+        }
+        if( !fov_3d && v.pos.z != zpos.z() ) {
+            continue;
+        }
+        if( rl_dist( zpos, tripoint_bub_ms( v.pos ) ) > max_range + 40 ) {
+            continue; // coarse distance filter, 40 = ~24 * sqrt(2) - rough max diameter of a vehicle
+        }
+        for( const vpart_reference &vpr : v.v->get_all_parts() ) {
+            const tripoint_bub_ms vppos = static_cast<tripoint_bub_ms>( vpr.pos() );
+            if( rl_dist( zpos, vppos ) > max_range ) {
+                continue;
+            }
+            if( !z.sees( vppos ) ) {
+                continue;
+            }
+            if( vpr.has_feature( VPFLAG_CONTROLS ) ||
+                vpr.has_feature( VPFLAG_ENGINE ) ||
+                vpr.has_feature( VPFLAG_WHEEL ) ) {
+                priority.emplace( vppos );
+            } else {
+                visible.emplace( vppos );
+            }
+        }
+    }
+    return !priority.empty() ? priority : visible;
+}
+
 // 3D vehicle functions
 
 VehicleList map::get_vehicles( const tripoint &start, const tripoint &end )
diff --git a/src/map.h b/src/map.h
index 959d02196b..e98630af5c 100644
--- a/src/map.h
+++ b/src/map.h
@@ -675,6 +675,10 @@ class map
         std::vector<zone_data *> get_vehicle_zones( int zlev );
         void register_vehicle_zone( vehicle *, int zlev );
         bool deregister_vehicle_zone( zone_data &zone ) const;
+        // returns a list of tripoints which contain parts from moving vehicles within \p max_range
+        // distance from \p source position, if any parts are CONTROLS, ENGINE or WHEELS returns a
+        // list of tripoints with exclusively such parts instead. Used for monster gun actor targeting.
+        std::set<tripoint_bub_ms> get_moving_vehicle_targets( const Creature &source, int max_range );
 
         // Removes vehicle from map and returns it in unique_ptr
         std::unique_ptr<vehicle> detach_vehicle( vehicle *veh );
diff --git a/src/mattack_actors.cpp b/src/mattack_actors.cpp
index 95949cee50..025aef2691 100644
--- a/src/mattack_actors.cpp
+++ b/src/mattack_actors.cpp
@@ -32,9 +32,7 @@
 #include "rng.h"
 #include "sounds.h"
 #include "translations.h"
-#include "vehicle.h"
 #include "viewer.h"
-#include "veh_type.h"
 
 
 static const efftype_id effect_badpoison( "badpoison" );
@@ -833,27 +831,6 @@ int gun_actor::get_max_range()  const
     return max_range;
 }
 
-static vehicle *find_target_vehicle( monster &z, int range )
-{
-    map &here = get_map();
-    vehicle *chosen = nullptr;
-    for( wrapped_vehicle &v : here.get_vehicles() ) {
-        if( !z.sees( v.pos ) ) {
-            continue;
-        }
-        if( !fov_3d && v.pos.z != z.pos().z ) {
-            continue;
-        }
-        int new_dist = rl_dist( z.pos(), v.pos );
-        if( v.v->velocity != 0 && new_dist < range ) {
-            chosen = v.v;
-            range = new_dist;
-        }
-    }
-    return chosen;
-}
-
-
 bool gun_actor::call( monster &z ) const
 {
     Creature *target;
@@ -878,47 +855,22 @@ bool gun_actor::call( monster &z ) const
         aim_at = target->pos();
     } else {
         target = z.attack_target();
+        aim_at = target ? target->pos() : tripoint_zero;
         if( !target || !z.sees( *target ) || ( !target->is_monster() && !z.aggro_character ) ) {
-            //return false;
             if( !target_moving_vehicles ) {
                 return false;
             }
-            //No living targets, try to find a moving car
-            untargeted = true;
-            vehicle *veh = find_target_vehicle( z, get_max_range() );
-            if( !veh ) {
-                return false;
-            }
-            std::vector<tripoint> valid_targets;
-            std::vector<tripoint> visible_points;
-            for( const tripoint &p : veh->get_points() ) {
-                if( !z.sees( p ) ) {
-                    continue;
-                }
-                visible_points.push_back( p );
-                for( const vpart_reference &vp : veh->get_all_parts() ) {
-                    if( vp.pos() != p ) {
-                        continue;
-                    }
-                    if( veh->part_with_feature( vp.part_index(), VPFLAG_CONTROLS, true ) >= 0 &&
-                        veh->part_with_feature( vp.part_index(), VPFLAG_ENGINE, true ) >= 0 &&
-                        veh->part_with_feature( vp.part_index(), VPFLAG_WHEEL, true ) >= 0 ) {
-                        valid_targets.push_back( p );
-                        break;
-                    }
-                }
-            }
-            if( !valid_targets.empty() ) {
-                aim_at = random_entry( valid_targets, tripoint_zero );
-            } else if( !visible_points.empty() ) {
-                aim_at = random_entry( visible_points, tripoint_zero );
-            } else {
+            untargeted = true; // no living targets, try to find moving car parts
+            const std::set<tripoint_bub_ms> moving_veh_parts = get_map()
+                    .get_moving_vehicle_targets( z, get_max_range() );
+            if( moving_veh_parts.empty() ) {
                 return false;
             }
+            aim_at = random_entry( moving_veh_parts, tripoint_bub_ms() ).raw();
         }
     }
 
-    int dist = rl_dist( z.pos(), aim_at );
+    const int dist = rl_dist( z.pos(), aim_at );
     if( target ) {
         add_msg_debug( debugmode::DF_MATTACK, "Target %s at range %d", target->disp_name(), dist );
     } else {
-- 
2.39.1.windows.1

[Maleclypse]