Fused monster transfers killing mission to fuser

src/map.cpp

@@ -7564,7 +7564,7 @@ void map::spawn_monsters_submap( const tripoint &gp, bool ignore_sight )
 
         for( int j = 0; j < i.count; j++ ) {
             monster tmp( i.type );
-            tmp.mission_id = i.mission_id;
+            tmp.mission_ids = { i.mission_id };
             if( i.name != "NONE" ) {
                 tmp.unique_name = i.name;
             }

src/mission.cpp

@@ -142,16 +142,18 @@ void mission::on_creature_death( Creature &poor_dead_dude )
     }
     monster *mon = dynamic_cast<monster *>( &poor_dead_dude );
     if( mon != nullptr ) {
-        if( mon->mission_id == -1 ) {
+        if( mon->mission_ids.empty() ) {
             return;
         }
-        mission *found_mission = mission::find( mon->mission_id );
-        const mission_type *type = found_mission->type;
-        if( type->goal == MGOAL_FIND_MONSTER ) {
-            found_mission->fail();
-        }
-        if( type->goal == MGOAL_KILL_MONSTER ) {
-            found_mission->step_complete( 1 );
+        for( const int mission_id : mon->mission_ids ) {
+            mission *found_mission = mission::find( mission_id );
+            const mission_type *type = found_mission->type;
+            if( type->goal == MGOAL_FIND_MONSTER ) {
+                found_mission->fail();
+            }
+            if( type->goal == MGOAL_KILL_MONSTER ) {
+                found_mission->step_complete( 1 );
+            }
         }
         return;
     }
@@ -188,6 +190,32 @@ void mission::on_creature_death( Creature &poor_dead_dude )
     }
 }
 
+void mission::on_creature_fusion( Creature &fuser, Creature &fused )
+{
+    if( fuser.is_hallucination() || fused.is_hallucination() ) {
+        return;
+    }
+    monster *mon_fuser = dynamic_cast<monster *>( &fuser );
+    if( mon_fuser == nullptr ) {
+        debugmsg( "Unimplemented: fuser is not a monster" );
+        return;
+    }
+    monster *mon_fused = dynamic_cast<monster *>( &fused );
+    if( mon_fused == nullptr ) {
+        debugmsg( "Unimplemented: fused it not a monster" );
+        return;
+    }
+    for( const int mission_id : mon_fused->mission_ids ) {
+        const mission *const found_mission = mission::find( mission_id );
+        const mission_type *const type = found_mission->type;
+        if( type->goal == MGOAL_KILL_MONSTER ) {
+            // the fuser has to be killed now!
+            mon_fuser->mission_ids.emplace( mission_id );
+            mon_fused->mission_ids.erase( mission_id );
+        }
+    }
+}
+
 void mission::on_talk_with_npc( const character_id &npc_id )
 {
     switch( type->goal ) {
@@ -468,7 +496,7 @@ bool mission::is_complete( const character_id &_npc_id ) const
             }
             return g->get_creature_if( [&]( const Creature & critter ) {
                 const monster *const mon_ptr = dynamic_cast<const monster *>( &critter );
-                return mon_ptr && mon_ptr->mission_id == uid;
+                return mon_ptr && mon_ptr->mission_ids.count( uid );
             } );
 
         case MGOAL_RECRUIT_NPC: {

src/mission.h

@@ -446,6 +446,7 @@ class mission
          */
         /*@{*/
         static void on_creature_death( Creature &poor_dead_dude );
+        static void on_creature_fusion( Creature &fuser, Creature &fused );
         /*@}*/
 
         // Serializes and unserializes all missions

src/monattack.cpp

@@ -53,6 +53,7 @@
 #include "material.h"
 #include "memorial_logger.h"
 #include "messages.h"
+#include "mission.h"
 #include "mondefense.h"
 #include "monfaction.h"
 #include "monster.h"
@@ -5750,6 +5751,10 @@ bool mattack::zombie_fuse( monster *z )
     z->add_effect( effect_grown_of_fuse, 10_days, true,
                    critter->get_hp_max() + z->get_effect( effect_grown_of_fuse ).get_intensity() );
     z->heal( critter->get_hp(), true );
+    z->mission_fused.emplace_back( critter->name() );
+    z->mission_fused.insert( z->mission_fused.end(),
+                             critter->mission_fused.begin(), critter->mission_fused.end() );
+    mission::on_creature_fusion( *z, *critter );
     critter->death_drops = false;
     critter->die( z );
     return true;

src/monster.cpp

@@ -207,7 +207,6 @@ monster::monster()
     anger = 0;
     morale = 2;
     faction = mfaction_id( 0 );
-    mission_id = -1;
     no_extra_death_drops = false;
     dead = false;
     death_drops = true;
@@ -673,6 +672,17 @@ int monster::print_info( const catacurses::window &w, int vStart, int vLines, in
         mvwprintz( w, point( column, ++vStart ), c_light_gray, lines[i] );
     }
 
+    if( !mission_fused.empty() ) {
+        // Mission monsters fused into this monster
+        const std::string fused_desc = string_format( _( "Parts of %s extrude from its body." ),
+                                       enumerate_as_string( mission_fused ) );
+        lines = foldstring( fused_desc, max_width );
+        numlines = lines.size();
+        for( int i = 0; i < numlines && vStart < vEnd; i++ ) {
+            mvwprintz( w, point( column, ++vStart ), c_light_gray, lines[i] );
+        }
+    }
+
     // Riding indicator on next line after description.
     if( has_effect( effect_ridden ) && mounted_player ) {
         mvwprintz( w, point( column, ++vStart ), c_white, _( "Rider: %s" ), mounted_player->disp_name() );
@@ -732,6 +742,13 @@ std::string monster::extended_description() const
     ss += "--\n";
     ss += string_format( "<dark>%s</dark>", type->get_description() ) + "\n";
     ss += "--\n";
+    if( !mission_fused.empty() ) {
+        // Mission monsters fused into this monster
+        const std::string fused_desc = string_format( _( "Parts of %s extrude from its body." ),
+                                       enumerate_as_string( mission_fused ) );
+        ss += string_format( "<dark>%s</dark>", fused_desc ) + "\n";
+        ss += "--\n";
+    }
 
     ss += string_format( _( "It is %s in size." ),
                          size_names.at( get_size() ) ) + "\n";

src/monster.h

@@ -469,7 +469,9 @@ class monster : public Creature
         // Our faction (species, for most monsters)
         mfaction_id faction;
         // If we're related to a mission
-        int mission_id = 0;
+        std::set<int> mission_ids;
+        // Names of mission monsters fused with this monster
+        std::vector<std::string> mission_fused;
         const mtype *type;
         // If true, don't spawn loot items as part of death.
         bool no_extra_death_drops = false;

src/overmap.cpp

@@ -2047,7 +2047,7 @@ void overmap::move_hordes()
                 type.id == mtype_id( "mon_jabberwock" ) || // Jabberwockies are an exception.
                 this_monster.get_speed() <= 30 || // So are very slow zombies, like crawling zombies.
                 !this_monster.will_join_horde( INT_MAX ) || // So are zombies who won't join a horde of any size.
-                this_monster.mission_id != -1 // We mustn't delete monsters that are related to missions.
+                !this_monster.mission_ids.empty() // We mustn't delete monsters that are related to missions.
             ) {
                 // Don't delete the monster, just increment the iterator.
                 monster_map_it++;

src/savegame_json.cpp

@@ -2135,7 +2135,12 @@ void monster::load( const JsonObject &data )
     }
 
     data.read( "friendly", friendly );
-    data.read( "mission_id", mission_id );
+    if( data.has_member( "mission_ids" ) ) {
+        data.read( "mission_ids", mission_ids );
+    } else if( data.has_member( "mission_id" ) ) {
+        mission_ids = { data.get_int( "mission_id" ) };
+    }
+    data.read( "mission_fused", mission_fused );
     data.read( "no_extra_death_drops", no_extra_death_drops );
     data.read( "dead", dead );
     data.read( "anger", anger );
@@ -2211,7 +2216,8 @@ void monster::store( JsonOut &json ) const
     json.member( "friendly", friendly );
     json.member( "fish_population", fish_population );
     json.member( "faction", faction.id().str() );
-    json.member( "mission_id", mission_id );
+    json.member( "mission_ids", mission_ids );
+    json.member( "mission_fused", mission_fused );
     json.member( "no_extra_death_drops", no_extra_death_drops );
     json.member( "dead", dead );
     json.member( "anger", anger );