Improve enchant weapon selection (#8407, #8552)

Now you are not prompted for, or allowed to select, weapons which
are enchantable but not by this scroll---for example, a +9,+0 weapon
with EW_I.  Take care to handle blowguns correctly: they have no +dam,
but EW_II increases their +acc.

The message "You aren't carrying any weapons that can be enchanted."
isn't quite right anymore, but I can't think of a good way to make it
more pendant-friendly without being too wordy.

1 files changed, 29 insertions, 9 deletions

diff --git a/crawl-ref/source/invent.cc b/crawl-ref/source/invent.cc
index b651fb2a75..e3df65d0e5 100644
--- a/crawl-ref/source/invent.cc
+++ b/crawl-ref/source/invent.cc
@@ -527,7 +527,10 @@ static string _no_selectables_message(int item_selector)
         return "You aren't wearing any piece of uncursed jewellery.";
     case OSEL_BRANDABLE_WEAPON:
         return "You aren't carrying any weapons that can be branded.";
-    case OSEL_ENCHANTABLE_WEAPON:
+    case OSEL_ENCHANTABLE_WEAPON_I:
+    case OSEL_ENCHANTABLE_WEAPON_II:
+    case OSEL_ENCHANTABLE_WEAPON_III:
+        // TODO: this message isn't quite right for _I and _II
         return "You aren't carrying any weapons that can be enchanted.";
     }
 
@@ -1240,14 +1243,31 @@ static bool _item_class_selected(const item_def &i, int selector)
     case OSEL_BRANDABLE_WEAPON:
         return is_brandable_weapon(i, true);
 
-    case OSEL_ENCHANTABLE_WEAPON:
-        return is_weapon(i)
-               && (itype == OBJ_WEAPONS
-                    && !is_artefact(i)
-                    && (i.plus < MAX_WPN_ENCHANT
-                        || i.plus2 < MAX_WPN_ENCHANT
-                        || !(item_ident(i, ISFLAG_KNOW_PLUSES)))
-                   || i.cursed());
+    case OSEL_ENCHANTABLE_WEAPON_I:
+    case OSEL_ENCHANTABLE_WEAPON_II:
+    case OSEL_ENCHANTABLE_WEAPON_III:
+    {
+        if (!is_weapon(i))
+            return false;
+        if (i.cursed())
+            return true;
+        if (itype != OBJ_WEAPONS || is_artefact(i))
+            return false;
+        if (!item_ident(i, ISFLAG_KNOW_PLUSES))
+            return true;
+
+        // Might this enchant +acc?
+        const bool acc = selector != OSEL_ENCHANTABLE_WEAPON_II
+                         || i.sub_type == WPN_BLOWGUN;
+        const bool dam = selector != OSEL_ENCHANTABLE_WEAPON_I
+                         && i.sub_type != WPN_BLOWGUN;
+
+        if (acc && i.plus < MAX_WPN_ENCHANT)
+            return true;
+        if (dam && i.plus2 < MAX_WPN_ENCHANT)
+            return true;
+        return false;
+    }
 
     default:
         return false;