cleanup ability cost into separate cost file

lib/std/ability.c

@@ -412,22 +412,10 @@ private void handle_ability_use (object source, object *targets) {
 
     // determine cost
     cost = query_cost();
-    // check source vitals
-    if (cost["sp"] > 0 && source->query_sp() < cost["sp"]) {
-        message("action", "You are too drained to " + query_name() + ".", source);
+    if (!verify_cost(source, cost)) {
         return;
     }
-    if (cost["mp"] > 0 && source->query_mp() < cost["mp"]) {
-        message("action", "You are too tired to " + query_name() + ".", source);
-        return;
-    }
-    // update source vitals
-    if (cost["sp"] > 0) {
-        source->add_sp(-(cost["sp"]*3/4 + (random(cost["sp"]/4) + 1)));
-    }
-    if (cost["mp"]) {
-        source->add_mp(-(cost["mp"]*3/4 + (random(cost["mp"]/4) + 1)));
-    }
+    apply_cost(source, cost);
 
     // update statuses
     source->set_busy(1);

lib/std/ability/cost.c

@@ -1,5 +1,10 @@
 // @this_object /std/ability.c
 
+/**
+ * Determine how much this ability costs to cast.
+ *
+ * @returns a mapping of vitals
+ */
 mapping query_cost () {
     string vitalType;
     mapping cost = ([
@@ -19,4 +24,39 @@ mapping query_cost () {
         cost[vitalType] += value;
     }
     return cost;
+}
+
+/**
+ * Verifies the source has enough vitals to cast this ability.
+ *
+ * @param {STD_LIVING} source
+ * @param cost from query_cost function
+ * @returns 0 or 1 for being able to cast
+ */
+int verify_cost (object source, mapping cost) {
+    // check source vitals
+    if (cost["sp"] > 0 && source->query_sp() < cost["sp"]) {
+        message("action", "You are too drained to " + this_object()->query_name() + ".", source);
+        return;
+    }
+    if (cost["mp"] > 0 && source->query_mp() < cost["mp"]) {
+        message("action", "You are too tired to " + this_object()->query_name() + ".", source);
+        return;
+    }
+}
+
+/**
+ * Applies the cost to the source's vitals.
+ *
+ * @param {STD_LIVING} source
+ * @param cost from query_cost function
+ */
+void apply_cost (object source, mapping cost) {
+    // update source vitals
+    if (cost["sp"] > 0) {
+        source->add_sp(-(cost["sp"]*3/4 + (random(cost["sp"]/4) + 1)));
+    }
+    if (cost["mp"]) {
+        source->add_mp(-(cost["mp"]*3/4 + (random(cost["mp"]/4) + 1)));
+    }
 }