Use a common funcion for all monster healing

Previously, the code for monster healing was repeated every time it
was needed; this commit sends it all through a common function, which
will make it easier to make changes to how monster healing works in
the future.

This is just a code reorganisation and won't have any gameplay
effect unless I made a mistake.

include/extern.h

@@ -1756,6 +1756,7 @@ extern struct monst *get_iter_mons(boolean (*)(struct monst *));
 extern struct monst *get_iter_mons_xy(boolean (*)(struct monst *,
                                                   coordxy, coordxy),
                                       coordxy, coordxy);
+extern int healmon(struct monst *, int, int) NONNULLARG1;
 extern void rescham(void);
 extern void restartcham(void);
 extern void restore_cham(struct monst *) NONNULLARG1;

src/artifact.c

@@ -1636,9 +1636,7 @@ artifact_hit(
                     healup(drain, 0, FALSE, FALSE);
                 } else {
                     assert(magr != 0);
-                    magr->mhp += drain;
+                    healmon(magr, drain, 0);
-                    if (magr->mhp > magr->mhpmax)
-                        magr->mhp = magr->mhpmax;
                 }
             }
             return vis;
@@ -1664,9 +1662,7 @@ artifact_hit(
             }
             losexp("life drainage");
             if (magr && magr->mhp < magr->mhpmax) {
-                magr->mhp += (abs(oldhpmax - u.uhpmax) + 1) / 2;
+                healmon(magr, (abs(oldhpmax - u.uhpmax) + 1) / 2, 0);
-                if (magr->mhp > magr->mhpmax)
-                    magr->mhp = magr->mhpmax;
             }
             return TRUE;
         }

src/do.c

@@ -876,7 +876,7 @@ engulfer_digests_food(struct obj *obj)
         } else if (could_grow) {
             (void) grow_up(u.ustuck, (struct monst *) 0);
         } else if (could_heal) {
-            u.ustuck->mhp = u.ustuck->mhpmax;
+            healmon(u.ustuck, u.ustuck->mhpmax, 0);
             /* False: don't realize that sight is cured from inside */
             mcureblindness(u.ustuck, FALSE);
         }

src/dog.c

@@ -675,10 +675,7 @@ mon_catchup_elapsed_time(
     /* recover lost hit points */
     if (!regenerates(mtmp->data))
         imv /= 20;
-    if (mtmp->mhp + imv >= mtmp->mhpmax)
+    healmon(mtmp, imv, 0);
-        mtmp->mhp = mtmp->mhpmax;
-    else
-        mtmp->mhp += imv;
 
     set_mon_lastmove(mtmp);
 }

src/mcastu.c

@@ -363,8 +363,7 @@ m_cure_self(struct monst *mtmp, int dmg)
         if (canseemon(mtmp))
             pline_mon(mtmp, "%s looks better.", Monnam(mtmp));
         /* note: player healing does 6d4; this used to do 1d8 */
-        if ((mtmp->mhp += d(3, 6)) > mtmp->mhpmax)
+        healmon(mtmp, d(3, 6), 0);
-            mtmp->mhp = mtmp->mhpmax;
         dmg = 0;
     }
     return dmg;

src/mhitm.c

@@ -1093,7 +1093,7 @@ mdamagem(
                 return (M_ATTK_DEF_DIED
                         | (!DEADMONSTER(magr) ? 0 : M_ATTK_AGR_DIED));
             } else if (pd == &mons[PM_NURSE]) {
-                magr->mhp = magr->mhpmax;
+                healmon(magr, magr->mhpmax, 0);
             }
             mon_givit(magr, pd);
         }
@@ -1390,9 +1390,7 @@ passivemm(
             }
             if (canseemon(magr))
                 pline_mon(magr, "%s is suddenly very cold!", Monnam(magr));
-            mdef->mhp += tmp / 2;
+            healmon(mdef, tmp/2, tmp/2);
-            if (mdef->mhpmax < mdef->mhp)
-                mdef->mhpmax = mdef->mhp;
             if (mdef->mhpmax > ((int) (mdef->m_lev + 1) * 8))
                 (void) split_mon(mdef, magr);
             break;

src/mon.c

@@ -1351,9 +1351,7 @@ m_consume_obj(struct monst *mtmp, struct obj *otmp)
 
     /* non-pet: Heal up to the object's weight in hp */
     if (!ispet && mtmp->mhp < mtmp->mhpmax) {
-        mtmp->mhp += objects[otmp->otyp].oc_weight;
+        healmon(mtmp, objects[otmp->otyp].oc_weight, 0);
-        if (mtmp->mhp > mtmp->mhpmax)
-            mtmp->mhp = mtmp->mhpmax;
     }
     if (Has_contents(otmp))
         meatbox(mtmp, otmp);
@@ -1398,7 +1396,7 @@ m_consume_obj(struct monst *mtmp, struct obj *otmp)
             }
         }
         if (heal)
-            mtmp->mhp = mtmp->mhpmax;
+            healmon(mtmp, mtmp->mhpmax, 0);
         if ((eyes || heal) && !mtmp->mcansee)
             mcureblindness(mtmp, canseemon(mtmp));
         if (ispet && deadmimic)
@@ -4462,6 +4460,44 @@ get_iter_mons_xy(
 }
 
 
+/* Heal the given monster by amt hitpoints, unless it is somehow prevented
+   from healing. "overheal" is the maximum amount by which the max HP will
+   increase to allow for the healing (the resulting HP caps at max HP +
+   overheal, and the max HP stays the some unless it needs to increase to
+   accommodate the new HP). Overhealing the player is not currently
+   implemented by this method.
+
+   This function should only be used for situations which are conceptually
+   heals, rather than other situations where a monster's HP is set, so that
+   "prevent healing" effects work correctly. In particular, it should not
+   be used for cases where a monster's HP is restored upon revival, or when
+   a monster is created. It also shouldn't be used for lifesaving, which
+   overrides "cannot heal" effects.
+
+   amt and overheal must not be negative (0 is allowed, and a very common
+   amount for overheal). Returns the number of hitpoints healed. */
+int
+healmon(struct monst *mtmp, int amt, int overheal)
+{
+    if (mtmp == &gy.youmonst) {
+        int oldhp = Upolyd ? u.mh : u.uhp;
+        healup(amt, 0, 0, 0);
+        return (Upolyd ? u.mh : u.uhp) - oldhp;
+    } else {
+        int oldhp = mtmp->mhp;
+        if (mtmp->mhp + amt > mtmp->mhpmax + overheal) {
+            mtmp->mhpmax += overheal;
+            mtmp->mhp = mtmp->mhpmax;
+        } else {
+            mtmp->mhp += amt;
+            if (mtmp->mhp > mtmp->mhpmax)
+                mtmp->mhpmax = mtmp->mhp;
+        }
+        return mtmp->mhp - oldhp;
+    }
+}
+
+
 /* force all chameleons and mimics to become themselves and werecreatures
    to revert to human form; called when Protection_from_shape_changers gets
    activated via wearing or eating ring or via #wizintrinsic */
@@ -5535,10 +5571,7 @@ golemeffects(struct monst *mon, int damtype, int dam)
             mon_adjust_speed(mon, -1, (struct obj *) 0);
     }
     if (heal) {
-        if (mon->mhp < mon->mhpmax) {
+        if (healmon(mon, heal, 0)) {
-            mon->mhp += heal;
-            if (mon->mhp > mon->mhpmax)
-                mon->mhp = mon->mhpmax;
             if (cansee(mon->mx, mon->my))
                 pline_mon(mon, "%s seems healthier.", Monnam(mon));
         }

src/muse.c

@@ -1139,9 +1139,7 @@ use_defensive(struct monst *mtmp)
     case MUSE_POT_HEALING:
         mquaffmsg(mtmp, otmp);
         i = d(6 + 2 * bcsign(otmp), 4);
-        mtmp->mhp += i;
+        healmon(mtmp, i, 1);
-        if (mtmp->mhp > mtmp->mhpmax)
-            mtmp->mhp = ++mtmp->mhpmax;
         if (!otmp->cursed && !mtmp->mcansee)
             mcureblindness(mtmp, vismon);
         if (vismon)
@@ -1153,9 +1151,7 @@ use_defensive(struct monst *mtmp)
     case MUSE_POT_EXTRA_HEALING:
         mquaffmsg(mtmp, otmp);
         i = d(6 + 2 * bcsign(otmp), 8);
-        mtmp->mhp += i;
+        healmon(mtmp, i, otmp->blessed ? 5 : 2);
-        if (mtmp->mhp > mtmp->mhpmax)
-            mtmp->mhp = (mtmp->mhpmax += (otmp->blessed ? 5 : 2));
         if (!mtmp->mcansee)
             mcureblindness(mtmp, vismon);
         if (vismon)
@@ -1168,7 +1164,7 @@ use_defensive(struct monst *mtmp)
         mquaffmsg(mtmp, otmp);
         if (otmp->otyp == POT_SICKNESS)
             unbless(otmp); /* Pestilence */
-        mtmp->mhp = (mtmp->mhpmax += (otmp->blessed ? 8 : 4));
+        healmon(mtmp, mtmp->mhpmax, otmp->blessed ? 8 : 4);
         if (!mtmp->mcansee && otmp->otyp != POT_SICKNESS)
             mcureblindness(mtmp, vismon);
         if (vismon)

src/potion.c

@@ -1740,7 +1740,7 @@ potionhit(struct monst *mon, struct obj *obj, int how)
  do_healing:
             angermon = FALSE;
             if (mon->mhp < mon->mhpmax) {
-                mon->mhp = mon->mhpmax;
+                healmon(mon, mon->mhpmax, 0);
                 if (canseemon(mon))
                     pline("%s looks sound and hale again.", Monnam(mon));
             }
@@ -1827,9 +1827,7 @@ potionhit(struct monst *mon, struct obj *obj, int how)
                     angermon = FALSE;
                     if (canseemon(mon))
                         pline("%s looks healthier.", Monnam(mon));
-                    mon->mhp += d(2, 6);
+                    healmon(mon, d(2, 6), 0);
-                    if (mon->mhp > mon->mhpmax)
-                        mon->mhp = mon->mhpmax;
                     if (is_were(mon->data) && is_human(mon->data)
                         && !Protection_from_shape_changers)
                         new_were(mon); /* transform into beast */

src/uhitm.c

@@ -5931,9 +5931,7 @@ passive(
                 You("are suddenly very cold!");
                 mdamageu(mon, tmp);
                 /* monster gets stronger with your heat! */
-                mon->mhp += (tmp + rn2(2)) / 2;
+                healmon(mon, (tmp + rn2(2)) / 2, (tmp + 1) / 2);
-                if (mon->mhpmax < mon->mhp)
-                    mon->mhpmax = mon->mhp;
                 /* at a certain point, the monster will reproduce! */
                 if (mon->mhpmax > (((int) mon->m_lev) + 1) * 8)
                     (void) split_mon(mon, &gy.youmonst);

src/were.c

@@ -123,7 +123,7 @@ new_were(struct monst *mon)
         mon->mcanmove = 1;
     }
     /* regenerate by 1/4 of the lost hit points */
-    mon->mhp += (mon->mhpmax - mon->mhp) / 4;
+    healmon(mon, (mon->mhpmax - mon->mhp) / 4, 0);
     newsym(mon->mx, mon->my);
     mon_break_armor(mon, FALSE);
     possibly_unwield(mon, FALSE);

src/wizard.c

@@ -396,7 +396,7 @@ tactics(struct monst *mtmp)
         /* if you're not around, cast healing spells */
         if (distu(mx, my) > (BOLT_LIM * BOLT_LIM))
             if (mtmp->mhp <= mtmp->mhpmax - 8) {
-                mtmp->mhp += rnd(8);
+                healmon(mtmp, rnd(8), 0);
                 return 1;
             }
         FALLTHROUGH;

src/zap.c

@@ -434,9 +434,7 @@ bhitm(struct monst *mtmp, struct obj *otmp)
             int delta = mtmp->mhpmax - mtmp->mhp;
 
             wake = FALSE; /* wakeup() makes the target angry */
-            mtmp->mhp += healamt;
+            healmon(mtmp, healamt, 0);
-            if (mtmp->mhp > mtmp->mhpmax)
-                mtmp->mhp = mtmp->mhpmax;
             /* plain healing must be blessed to cure blindness; extra
                healing only needs to not be cursed, so spell always cures
                [potions quaffed by monsters behave slightly differently;
@@ -4250,10 +4248,9 @@ zhitm(
     case ZT_DEATH:                              /* death/disintegration */
         if (abs(type) != ZT_BREATH(ZT_DEATH)) { /* death */
             if (mon->data == &mons[PM_DEATH]) {
-                mon->mhpmax += mon->mhpmax / 2;
+                healmon(mon, mon->mhpmax * 3 / 2, mon->mhpmax / 2);
                 if (mon->mhpmax >= MAGIC_COOKIE)
                     mon->mhpmax = MAGIC_COOKIE - 1;
-                mon->mhp = mon->mhpmax;
                 tmp = 0;
                 break;
             }