Enable untrapping jammed drawbridge

When a drawbridge becomes jammed, it can be unjammed with the #untrap
command, on either the drawbridge itself or the portcullis.

Author: entrez

include/extern.h

@@ -320,11 +320,13 @@ extern boolean is_open_air(int, int);
 extern schar db_under_typ(int);
 extern int is_drawbridge_wall(int, int);
 extern boolean is_db_wall(int, int);
+extern boolean is_jammed_db(int, int);
 extern boolean find_drawbridge(int *, int *);
 extern boolean create_drawbridge(int, int, int, boolean);
 extern void open_drawbridge(int, int);
 extern void close_drawbridge(int, int);
 extern void destroy_drawbridge(int, int);
+extern int unjam_drawbridge(int, int);
 
 /* ### decl.c ### */
 

src/dbridge.c

@@ -181,6 +181,15 @@ is_db_wall(int x, int y)
     return (boolean) (levl[x][y].typ == DBWALL);
 }
 
+boolean
+is_jammed_db(int x, int y)
+{
+    if (!find_drawbridge(&x, &y))
+        return FALSE;
+    else
+        return ((levl[x][y].drawbridgemask & DB_JAM) != 0);
+}
+
 /*
  * Return true with x,y pointing to the drawbridge if x,y initially indicate
  * a drawbridge or drawbridge wall.
@@ -974,4 +983,47 @@ destroy_drawbridge(int x, int y)
     nokiller();
 }
 
+int
+unjam_drawbridge(int x, int y)
+{
+    boolean under_u = (!u.dx && !u.dy);
+    struct monst *mtmp = m_at(x, y);
+
+    if (!is_jammed_db(x, y)) {
+        impossible("unjam_drawbridge: clearing nonexistant jam?");
+        return 0;
+    }
+
+    /* Test for monster first, monsters are displayed instead of trap. */
+    if (mtmp) {
+        pline("%s is in the way.", Monnam(mtmp));
+        return 0;
+    }
+    /* We might be forced to move onto the trap's location. */
+    if (sobj_at(BOULDER, x, y) && !Passes_walls && !under_u) {
+        There("is a boulder in your way.");
+        return 0;
+    }
+    /* duplicate tight-space checks from test_move */
+    if (u.dx && u.dy && bad_rock(g.youmonst.data, u.ux, y)
+        && bad_rock(g.youmonst.data, x, u.uy)) {
+        if ((g.invent && (inv_weight() + weight_cap() > 600))
+            || bigmonst(g.youmonst.data)) {
+            /* don't allow untrap if they can't get thru to it */
+            You("are unable to reach the mechanism!");
+            return 0;
+        }
+    }
+    if (rn2(3)) {
+        You("are having a difficult time clearing the jam.");
+        return 1;
+    }
+
+    /* ok, disarm it. */
+    You("unjam the mechanism.");
+    (void) find_drawbridge(&x, &y);
+    levl[x][y].drawbridgemask &= ~DB_JAM;
+    return 1;
+}
+
 /*dbridge.c*/

src/music.c

@@ -757,8 +757,7 @@ do_play_instrument(struct obj* instr)
                             u.uevent.uheard_tune = 2;
                             record_achievement(ACH_TUNE);
                             if (levl[x][y].typ == DRAWBRIDGE_DOWN) {
-                                boolean jammed =
-                                    (levl[x][y].drawbridgemask & DB_JAM) != 0;
+                                boolean jammed = is_jammed_db(x, y);
                                 if (!rn2(5) || jammed) {
                                     pline("The mechanism seems to %s jammed.",
                                           jammed ? "be" : "get");

src/trap.c

@@ -5449,7 +5449,10 @@ untrap(
                     return 0;
                 }
             }
-        } /* end if */
+        }
+        else if (is_jammed_db(x, y)) {
+            return unjam_drawbridge(x, y);
+        }
 
         if (boxcnt) {
             /* 3.7: this used to allow searching for traps on multiple