Bionics no longer block conflicting mutations

Instead, the mutation can fail, inflicting some internal damage, or
destroy the bionic, causing large internal damage.

Most of the damage is through bleeding and pain, unless it's a
particularly severe injury, in which case limb damage is applied.

The exact numbers and chance in particular, don't have a particularly
strong backing.

data/json/effects.json

@@ -4064,6 +4064,46 @@
     ],
     "flags": [ "EFFECT_LIMB_SCORE_MOD", "NO_PSIONICS" ]
   },
+  {
+    "type": "effect_type",
+    "id": "mutation_internal_damage",
+    "max_intensity": 3,
+    "name": [ "Botched Mutation", "Botched Mutation", "Destroyed Bionic" ],
+    "desc": [ "Your changing body did not cope well with your bionics." ],
+    "apply_message": [
+      [ "Your twisting flesh strains against the bionics invading your body.", "bad" ],
+      [ "Your twisting flesh strains against the bionics invading your body.", "bad" ],
+      [ "Your twisting flesh strains against the bionics invading your body.", "bad" ]
+    ],
+    "apply_memorial_log": "Had a mutation botched due to their installed bionics.",
+    "int_decay_tick": 25200,
+    "int_decay_remove": true,
+    "show_intensity": false,
+    "main_parts_only": true,
+    "//": "Internal bleeding",
+    "vitamins": [
+      { "vitamin": "redcells", "rate": [ [ -2, -5 ], [ -2, -5 ], [ -4, -8 ] ], "tick": [ "30s", "30s", "15s" ] },
+      { "vitamin": "blood", "rate": [ [ -2, -5 ], [ -2, -5 ], [ -4, -8 ] ], "tick": [ "30s", "30s", "15s" ] }
+    ],
+    "base_mods": {
+      "pain_min": [ 1 ],
+      "pain_max": [ 2 ],
+      "pain_chance": [ 24 ],
+      "pain_tick": [ 36 ],
+      "hurt_max": [ 1 ],
+      "hurt_chance": [ 24 ],
+      "hurt_tick": [ 40 ]
+    },
+    "scaling_mods": {
+      "pain_min": [ 1 ],
+      "pain_max": [ 4 ],
+      "pain_chance": [ -8 ],
+      "pain_tick": [ -15 ],
+      "hurt_max": [ 0 ],
+      "hurt_chance": [ -8 ],
+      "hurt_tick": [ 40 ]
+    }
+  },
   {
     "type": "effect_type",
     "id": "anemia",

src/character.h

@@ -1375,6 +1375,8 @@ class Character : public Creature, public visitable
          *  Defaults to true
          */
         bool purifiable( const trait_id &flag ) const;
+        /** Returns true if a conflict has destroyed a bionic */
+        bool handle_bio_mut_conflict( const bionic_id &bio, const trait_id &mut );
         /** Returns a dream's description selected randomly from the player's highest mutation category */
         std::string get_category_dream( const mutation_category_id &cat, int strength ) const;
         /** Returns true if the player has the entered trait in cached_mutations */

src/mutation.cpp

@@ -49,6 +49,8 @@
 static const activity_id ACT_PULL_CREATURE( "ACT_PULL_CREATURE" );
 static const activity_id ACT_TREE_COMMUNION( "ACT_TREE_COMMUNION" );
 
+static const efftype_id effect_mutation_internal_damage( "mutation_internal_damage" );
+
 static const flag_id json_flag_INTEGRATED( "INTEGRATED" );
 
 static const itype_id itype_fake_burrowing( "fake_burrowing" );
@@ -1073,13 +1075,6 @@ bool Character::mutation_ok( const trait_id &mutation, bool allow_good, bool all
                 return false;
             }
         }
-
-        if( bid->mutation_conflicts.count( mutation ) != 0 ) {
-            add_msg_debug( debugmode::DF_MUTATION,
-                           "mutation_ok( %s ): failed, bionic conflict (conflicting mutation on %s)", mutation.c_str(),
-                           bid.c_str() );
-            return false;
-        }
     }
 
     const mutation_branch &mdata = mutation.obj();
@@ -1687,17 +1682,11 @@ bool Character::mutate_towards( const trait_id &mut, const mutation_category_id
         return false;
     }
 
-    // Just prevent it when it conflicts with a CBM, for now
-    // TODO: Consequences?
     for( const bionic_id &bid : get_bionics() ) {
         if( bid->mutation_conflicts.count( mut ) != 0 ) {
-            add_msg_debug( debugmode::DF_MUTATION,
-                           "mutate_towards: failed, bionic %s prevents mutation (mutation conflict)", bid.c_str() );
-            add_msg_if_player(
-                _( "Your churning flesh strains painfully against your %1$s for a moment, then the feeling fades." ),
-                bid->name );
-            return false;
+            return handle_bio_mut_conflict( bid, mut );
         }
+        // We shouldn't ever get here, because of mutation_ok
         for( const trait_id &mid : bid->canceled_mutations ) {
             if( mid == mut ) {
                 add_msg_debug( debugmode::DF_MUTATION,
@@ -2345,6 +2334,61 @@ void Character::test_crossing_threshold( const mutation_category_id &mutation_ca
     }
 }
 
+static void fail_mutation_wounds( Character &guy, const bionic_id &bio, bool catastrophic )
+{
+    std::map<bodypart_str_id, int> main_bps;
+    for( const std::pair<const bodypart_str_id, size_t> &bp : bio->occupied_bodyparts ) {
+        main_bps.emplace( bp.first->main_part, 1 ).first->second += 1;
+    }
+    for( const std::pair<const bodypart_str_id, int> bp : main_bps ) {
+        int intensity = catastrophic ? 3 : bp.second > 1 ? 2 : 1;
+        guy.add_effect( effect_mutation_internal_damage, intensity * 7 * 1_hours, bp.first.id(), false,
+                        intensity );
+        if( catastrophic ) {
+            guy.apply_damage( nullptr, bp.first.id(), rng( 12, 36 ) );
+        }
+    }
+}
+
+bool Character::handle_bio_mut_conflict( const bionic_id &bio, const trait_id &mut )
+{
+    int bio_slots = 0;
+    std::set<bodypart_str_id> bio_parts;
+    for( const std::pair<const bodypart_str_id, size_t> &bp : bio->occupied_bodyparts ) {
+        bio_slots += bp.second;
+        bio_parts.emplace( bp.first->main_part );
+    }
+    // Occupying more body parts decreases chance of destruction (less invasive overall)
+    // Occupying more slots increases chance of desctruction (more invasive)
+    // More mutation points increase chance of destruction (more invasive mutation)
+    // because there must be more slots than parts, decrease slots with sqrt
+    int deviation = bio_parts.size() + std::abs( mut->points ) - std::sqrt( bio_slots );
+    if( deviation < 2 ) {
+        deviation = 2;
+    }
+    add_msg_debug( debugmode::DF_MUTATION,
+                   "Chance of %s to destroy %s: (dev: %d = %d - %g + %d) %.1f%%",
+                   mut->name(), bio->name, deviation, bio_parts.size(), std::sqrt( bio_slots ),
+                   std::abs( mut->points ), normal_roll_chance( 0, deviation, 2 ) * 100.0 );
+    if( normal_roll( 0, deviation ) > 2 ) {
+        std::optional<bionic *> ret = find_bionic_by_type( bio );
+        if( !ret ) {
+            debugmsg( "Mutation conflicts with bionic (%s) that is not installed?", bio.str() );
+            return false;
+        }
+        remove_bionic( *( *ret ) );
+        // massive wounds
+        fail_mutation_wounds( *this, bio, true );
+        add_msg( m_bad, _( "The changes in your body destroy your %s." ), bio->name );
+        return true;
+    }
+    add_msg( m_bad, _( "Your body strains against your %s and it hurts!" ), bio->name );
+    add_msg_debug( debugmode::DF_MUTATION, "Tried to mutate %s but blocked by %s.",
+                   mut->name(), bio->name );
+    fail_mutation_wounds( *this, bio, false );
+    return false;
+}
+
 bool are_conflicting_traits( const trait_id &trait_a, const trait_id &trait_b )
 {
     return are_opposite_traits( trait_a, trait_b ) || b_is_lower_trait_of_a( trait_a, trait_b )