Add script for amulet of finding

These pieces of jewelry help players remember locations on the world
map. Players can bind an amulet at any location on the world map.
Applying a bound amulet shows players a message indicating which
direction they should travel to return to the bound location.

Since this shares some code with the Rhyzian amulet, move the shared
code to CFWorld. While here, improve the getdir() function to round the
direction to the closest compass direction.

python/CFWorld.py

@@ -1,5 +1,7 @@
 #CFWorld.py
 #A small module for checking where is bigworld an object is if it's in bigworld.
+import math
+
 import Crossfire
 
 world_prefix = "/world/world_"
@@ -18,3 +20,18 @@ def loc_from_ob(ob):
     x = (int(strloc[0]) * bigmapxsize) + ob.X
     y = (int(strloc[1]) * bigmapysize) + ob.Y
     return (x, y)
+
+def getdiff(loc1, loc2):
+    return (loc1[0]-loc2[0], loc1[1]-loc2[1])
+
+def getdir(v):
+    x, y = v
+    t = math.atan2(x, y)
+    rt = round(t / (math.pi/4)) # between -4 and 4
+    directions = ["north", "northwest", "west", "southwest", "south", "southeast", "east", "northeast"]
+    dir_str = directions[(rt + 4)%8]
+    return dir_str
+
+#outputs in furlongs (outdoor tiles)
+def getdist(loc):
+    return int(math.sqrt((loc[0]*loc[0])+(loc[1]*loc[1])))

python/items/finding.py

@@ -0,0 +1,83 @@
+# finding.py -- apply event for amulets of finding
+#
+# These pieces of jewelry help players remember locations on the world map.
+# Players can bind an amulet at any location on the world map. Applying a bound
+# amulet shows players a message indicating which direction they should travel
+# to return to the bound location.
+#
+# The bound location is stored in the key-value pair "finding_location", which
+# contains a 2-tuple of global coordinates from the CFWorld module.
+import Crossfire
+import CFWorld
+
+location_key = 'finding_location'
+world_size = 50
+
+def indefinite(ob):
+    """Append 'a' or 'an' to the given object's name."""
+    name = ob.QueryName()
+    if name[0].lower() in {'a', 'e', 'i', 'o'}:
+        article = "an"
+    else:
+        article = "a"
+    return article + " " + name
+
+def auto_identify(ob, pl):
+    """Identify the object if it hasn't already."""
+    if not ob.Identified:
+        ob.Identified = True
+        pl.Message("This is %s!" % indefinite(ob))
+
+def loc_to_str(l):
+    return ",".join(map(str, l))
+
+def str_to_loc(s):
+    return list(map(int, s.split(",")))
+
+def describe_vec(v):
+    dist = CFWorld.getdist(v)
+    if dist < 1:
+        return "here"
+    if dist <= world_size:
+        modifier = "strongly"
+    elif dist <= 5*world_size:
+        modifier = "moderately"
+    else:
+        modifier = "lightly"
+    return modifier + " " + CFWorld.getdir(v)
+
+def on_apply():
+    whoami = Crossfire.WhoAmI()
+    player = Crossfire.WhoIsActivator()
+
+    Crossfire.SetReturnValue(1) # do not allow players to wear this
+    auto_identify(whoami, player)
+
+    if whoami.Env == player:
+        # applied in inventory
+        current_location = CFWorld.loc_from_ob(player)
+    else:
+        # applied on the floor
+        current_location = CFWorld.loc_from_ob(whoami)
+
+    if current_location == False:
+        # can only be used on the world map
+        player.Message("The %s rattles for a moment, then stops." % whoami.QueryName())
+        return
+
+    if whoami.Env == player:
+        # applied in inventory
+        stored_str = whoami.ReadKey(location_key)
+        if stored_str == "":
+            # no location bound
+            player.Message("The %s vibrates for a moment, then stops." % whoami.QueryName())
+            return
+        stored_location = str_to_loc(stored_str)
+        delta = CFWorld.getdiff(stored_location, current_location)
+        player.Message("The %s tugs you %s." % (whoami.QueryName(), describe_vec(delta)))
+    else:
+        # applied on the floor
+        whoami.WriteKey(location_key, loc_to_str(current_location), 1)
+        player.Message("The %s glows blue." % whoami.QueryName())
+
+on_apply()

python/items/rhyzian_amulet.py

@@ -1,43 +1,20 @@
 import Crossfire
 import CFWorld
-import math
 
 scorn_loc = (5272, 5786)
 navar_loc = (6112, 5850)
 
 Crossfire.SetReturnValue( 1 )
 
-def getdiff(loc1, loc2):
-    return (loc1[0]-loc2[0], loc1[1]-loc2[1])
-
-def getdir(loc1, loc2):
-    loc = getdiff(loc1, loc2)
-    if (loc[1] > 0):
-        start="south"
-    elif(loc[1] < 0):
-        start="north"
-    else:
-        start=""
-    if (loc[0] > 0):
-        return start+"east"
-    elif(loc[0] < 0):
-        return start+"west"
-    else:
-        return start
-
-#outputs in furlongs (outdoor tiles)
-def getdist(loc1, loc2):
-    loc = getdiff(loc1, loc2)
-    return int(math.sqrt((loc[0]*loc[0])+(loc[1]*loc[1])))
-
 #outputs in miles
 def getuserdist(dist):
     return (int(dist/8.0+0.5))
 
 def gettext(loc1, loc2, name):
-    loc_raw_dist = getdist(loc1, loc2)
+    diff = CFWorld.getdiff(loc2, loc1)
+    loc_raw_dist = CFWorld.getdist(diff)
     loc_dist = getuserdist(loc_raw_dist)
-    loc_dir = getdir(loc2, loc1)
+    loc_dir = CFWorld.getdir(diff)
     if (abs(loc_dist) > 5):
         loc_distmsg = "A "+name+" arrow flashes "+str(loc_dist)+" times"
     else: