From 829f9f65f7f5fe0e6c036c1f40ec540ca9fc4625 Mon Sep 17 00:00:00 2001
From: Pasi Kallinen <paxed@alt.org>
Date: Tue, 23 Jan 2024 19:01:31 +0200
Subject: [PATCH] Split out harmless-to-monster trap

Also make the code much easier to understand, and
more-or-less match hero trap triggering.
---
 include/extern.h |  1 +
 src/mon.c        | 19 +----------
 src/trap.c       | 82 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 18 deletions(-)

diff --git a/include/extern.h b/include/extern.h
index 67544d1b1..6e637b2e3 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -3099,6 +3099,7 @@ extern struct monst *activate_statue_trap(struct trap *, coordxy, coordxy,
 extern int immune_to_trap(struct monst *, unsigned) NO_NNARGS; /* revisit */
 extern void set_utrap(unsigned, unsigned);
 extern void reset_utrap(boolean);
+extern boolean m_harmless_trap(struct monst *, struct trap *);
 extern void dotrap(struct trap *, unsigned) NONNULLARG1;
 extern void seetrap(struct trap *) NONNULLARG1;
 extern void feeltrap(struct trap *) NONNULLARG1;
diff --git a/src/mon.c b/src/mon.c
index c3e44b590..b6c0bff0e 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -2128,24 +2128,7 @@ mfndpos(
                                    ttmp->ttyp);
                             continue;
                     }
-                    if ((ttmp->ttyp != RUST_TRAP
-                         || mdat == &mons[PM_IRON_GOLEM])
-                        && ttmp->ttyp != STATUE_TRAP
-                        && ttmp->ttyp != VIBRATING_SQUARE
-                        && ((!is_pit(ttmp->ttyp) && !is_hole(ttmp->ttyp))
-                            || (!is_flyer(mdat) && !is_floater(mdat)
-                                && !is_clinger(mdat)) || Sokoban)
-                        && (ttmp->ttyp != SLP_GAS_TRAP || !resists_sleep(mon))
-                        && (ttmp->ttyp != BEAR_TRAP
-                            || (mdat->msize > MZ_SMALL && !amorphous(mdat)
-                                && !is_flyer(mdat) && !is_floater(mdat)
-                                && !is_whirly(mdat) && !unsolid(mdat)))
-                        && (ttmp->ttyp != FIRE_TRAP || !resists_fire(mon))
-                        && (ttmp->ttyp != SQKY_BOARD || !is_flyer(mdat))
-                        && (ttmp->ttyp != WEB
-                            || (!amorphous(mdat) && !webmaker(mdat)
-                                && !is_whirly(mdat) && !unsolid(mdat)))
-                        && (ttmp->ttyp != ANTI_MAGIC || !resists_magm(mon))) {
+                    if (!m_harmless_trap(mon, ttmp)) {
                         if (!(flag & ALLOW_TRAPS)) {
                             if (mon_knows_traps(mon, ttmp->ttyp))
                                 continue;
diff --git a/src/trap.c b/src/trap.c
index f14590290..5e46a03b6 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -1049,6 +1049,88 @@ check_in_air(struct monst *mtmp, unsigned trflags)
             || ((is_you ? Flying : is_flyer(mtmp->data)) && !plunged));
 }
 
+/* is trap ttmp harmless to monster mtmp? */
+boolean
+m_harmless_trap(struct monst *mtmp, struct trap *ttmp)
+{
+    struct permonst *mdat = mtmp->data;
+
+    /* this handles most of the traps, but those are still included
+       in the switch case below for completeness */
+    if (!Sokoban && floor_trigger(ttmp->ttyp) && check_in_air(mtmp, 0L))
+        return TRUE;
+
+    switch (ttmp->ttyp) {
+    case ARROW_TRAP:
+        break;
+    case DART_TRAP:
+        break;
+    case ROCKTRAP:
+        break;
+    case SQKY_BOARD:
+        break;
+    case BEAR_TRAP:
+        if (mdat->msize <= MZ_SMALL || amorphous(mdat)
+            || is_whirly(mdat) || unsolid(mdat))
+            return TRUE;
+        break;
+    case LANDMINE:
+        break;
+    case ROLLING_BOULDER_TRAP:
+        break;
+    case SLP_GAS_TRAP:
+        if (resists_sleep(mtmp) || defended(mtmp, AD_SLEE))
+            return TRUE;
+        break;
+    case RUST_TRAP:
+        if (mdat != &mons[PM_IRON_GOLEM])
+            return TRUE;
+        break;
+    case FIRE_TRAP:
+        if (resists_fire(mtmp) || defended(mtmp, AD_FIRE))
+            return TRUE;
+        break;
+    case PIT:
+        /*FALLTHRU*/
+    case SPIKED_PIT:
+        /*FALLTHRU*/
+    case HOLE:
+        /*FALLTHRU*/
+    case TRAPDOOR:
+        if (is_clinger(mdat) && !Sokoban)
+            return TRUE;
+        break;
+    case TELEP_TRAP:
+        break;
+    case LEVEL_TELEP:
+        break;
+    case MAGIC_PORTAL:
+        break;
+    case WEB:
+        if (amorphous(mdat) || webmaker(mdat)
+            || is_whirly(mdat) || unsolid(mdat))
+            return TRUE;
+        break;
+    case STATUE_TRAP:
+        return TRUE;
+    case MAGIC_TRAP:
+        return TRUE; /* usually */
+    case ANTI_MAGIC:
+        if (resists_magm(mtmp) || defended(mtmp, AD_MAGM))
+            return TRUE;
+        break;
+    case POLY_TRAP:
+        break;
+    case VIBRATING_SQUARE:
+        return TRUE;
+    default:
+        impossible("m_harmless_trap: unknown trap %i", ttmp->ttyp);
+        break;
+    }
+
+    return FALSE;
+}
+
 static int
 trapeffect_arrow_trap(
     struct monst *mtmp,