Refactor melee randart brand selection.

The chained pile of enum arithmetic was hard to read and hard to modify.
There should be no functional change wrt old code (other that slight
rounding errors in probabilities).  I preserved calculations of
"power_level" as well, even if its behaviour for demon items and
distortion looks strange.

1 files changed, 35 insertions, 59 deletions

diff --git a/crawl-ref/source/artefact.cc b/crawl-ref/source/artefact.cc
index 27e0ed51be..3f7dd749f2 100644
--- a/crawl-ref/source/artefact.cc
+++ b/crawl-ref/source/artefact.cc
@@ -702,30 +702,6 @@ static void _get_randart_properties(const item_def &item,
 
     if (aclass == OBJ_WEAPONS) // Only weapons get brands, of course.
     {
-#if TAG_MAJOR_VERSION == 34
-        proprt[ARTP_BRAND] = SPWPN_FLAMING + random2(16);        // brand
-#else
-        proprt[ARTP_BRAND] = SPWPN_FLAMING + random2(15);        // brand
-#endif
-
-        if (one_chance_in(6))
-            proprt[ARTP_BRAND] = SPWPN_FLAMING + random2(2);
-
-        if (one_chance_in(6))
-            proprt[ARTP_BRAND] = SPWPN_DRAGON_SLAYING + random2(4);
-
-        if (one_chance_in(6))
-            proprt[ARTP_BRAND] = SPWPN_VORPAL;
-
-        if (proprt[ARTP_BRAND] == SPWPN_PROTECTION || proprt[ARTP_BRAND] == SPWPN_EVASION)
-            proprt[ARTP_BRAND] = SPWPN_NORMAL;      // no protection or evasion
-
-#if TAG_MAJOR_VERSION == 34
-        // orc slaying removed
-        if (proprt[ARTP_BRAND] == SPWPN_ORC_SLAYING)
-            proprt[ARTP_BRAND] = SPWPN_NORMAL;
-#endif
-
         if (is_range_weapon(item))
         {
             proprt[ARTP_BRAND] = random_choose_weighted(
@@ -747,49 +723,49 @@ static void _get_randart_properties(const item_def &item,
                 else if (one_chance_in(5))
                     proprt[ARTP_BRAND] = SPWPN_PENETRATION;
             }
-        }
 
-        // Quarter of the chance of distortion elsewhere.
-        if (!is_range_weapon(item) && one_chance_in(100))
-            proprt[ARTP_BRAND] = SPWPN_DISTORTION;
-        else if (is_demonic(item))
+            power_level++;
+        }
+        else if (is_demonic(item) && x_chance_in_y(7, 9))
         {
-            switch (random2(9))
-            {
-            case 0:
-                proprt[ARTP_BRAND] = SPWPN_DRAINING;
-                break;
-            case 1:
-                proprt[ARTP_BRAND] = SPWPN_FLAMING;
-                break;
-            case 2:
-                proprt[ARTP_BRAND] = SPWPN_FREEZING;
-                break;
-            case 3:
-                proprt[ARTP_BRAND] = SPWPN_ELECTROCUTION;
-                break;
-            case 4:
-                proprt[ARTP_BRAND] = SPWPN_VAMPIRICISM;
-                break;
-            case 5:
-                proprt[ARTP_BRAND] = SPWPN_PAIN;
-                break;
-            case 6:
-                proprt[ARTP_BRAND] = SPWPN_VENOM;
-                break;
-            default:
-                power_level -= 2;
-            }
+            proprt[ARTP_BRAND] = random_choose(
+                SPWPN_DRAINING,
+                SPWPN_FLAMING,
+                SPWPN_FREEZING,
+                SPWPN_ELECTROCUTION,
+                SPWPN_VAMPIRICISM,
+                SPWPN_PAIN,
+                SPWPN_VENOM,
+                -1);
             power_level += 2;
+            // fall back to regular melee brands 2/9 of the time
         }
         else
-            power_level++;
+        {
+            proprt[ARTP_BRAND] = random_choose_weighted(
+                34, SPWPN_FLAMING,
+                34, SPWPN_FREEZING,
+                13, SPWPN_HOLY_WRATH,
+                13, SPWPN_ELECTROCUTION,
+                26, SPWPN_DRAGON_SLAYING,
+                26, SPWPN_VENOM,
+                26, SPWPN_DRAINING,
+                13, SPWPN_SPEED,
+                73, SPWPN_VORPAL,
+                13, SPWPN_VAMPIRICISM,
+                13, SPWPN_PAIN,
+                13, SPWPN_ANTIMAGIC,
+                 3, SPWPN_DISTORTION,
+                 0);
+
+            // What's the point in this logic?
+            if (!is_demonic(item) && proprt[ARTP_BRAND] != SPWPN_DISTORTION)
+                power_level++;
+        }
 
+        // no brand = magic flag to reject and retry
         if (!is_weapon_brand_ok(atype, proprt[ARTP_BRAND], true))
-        {
             proprt[ARTP_BRAND] = SPWPN_NORMAL;
-            power_level--;
-        }
     }
 
     if (!one_chance_in(5))