Magic Hunter fix and optimization

There was a small bug in magic hunter, where it tried to apply an
enchantment level between 1 and the Enchantment.getMaxLevel(), however
it didn't take into account Enchantment.getStartLevel(), so when it
tried to apply an enchantment level below the start level, an
IllegalArgumentException was being thrown and the magic hunter event
wasn't happening.

Also, it's potentially inefficient to recalculate which enchantments
are possible for each ItemStack every time, so I added a HashMap to
cache the possibleEnchantments for each material type, then check this
cache instead of just looping to regenerate the list each time.

src/main/java/com/gmail/nossr50/skills/fishing/FishingManager.java

@@ -2,6 +2,7 @@ package com.gmail.nossr50.skills.fishing;
 
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 
 import org.bukkit.ChatColor;
@@ -48,6 +49,7 @@ import com.gmail.nossr50.util.skills.CombatUtils;
 import com.gmail.nossr50.util.skills.SkillUtils;
 
 public class FishingManager extends SkillManager {
+    private static HashMap<Material, List<Enchantment>> enchantableCache = new HashMap<Material, List<Enchantment>>();
     private final long FISHING_COOLDOWN_SECONDS = 1000L;
 
     private int fishingTries = 0;
@@ -411,7 +413,14 @@ public class FishingManager extends SkillManager {
             return false;
         }
 
-        List<Enchantment> possibleEnchantments = new ArrayList<Enchantment>();
+        // When calculating the possible enchantments, we should cache the possible enchantments to minimize
+        // looping every time someone fishes.
+        List<Enchantment> possibleEnchantments;
+
+        if (enchantableCache.containsKey(treasureDrop.getType())) { // Check if possible enchantments is already cached for this item.
+            possibleEnchantments = enchantableCache.get(treasureDrop.getType());
+        } else { // If not, check which enchantments are possible
+            possibleEnchantments = new ArrayList<Enchantment>();
 
             for (Enchantment enchantment : Enchantment.values()) {
                 if (enchantment.canEnchantItem(treasureDrop)) {
@@ -419,6 +428,9 @@ public class FishingManager extends SkillManager {
                 }
             }
         	
+            enchantableCache.put(treasureDrop.getType(), possibleEnchantments); // Cache these enchantments.
+        }
+
         // This make sure that the order isn't always the same, for example previously Unbreaking had a lot more chance to be used than any other enchant
         Collections.shuffle(possibleEnchantments, Misc.getRandom());
 
@@ -427,7 +439,10 @@ public class FishingManager extends SkillManager {
 
         for (Enchantment possibleEnchantment : possibleEnchantments) {
             if (!treasureDrop.getItemMeta().hasConflictingEnchant(possibleEnchantment) && Misc.getRandom().nextInt(specificChance) == 0) {
-                treasureDrop.addEnchantment(possibleEnchantment, Misc.getRandom().nextInt(possibleEnchantment.getMaxLevel()) + 1);
+                // We need our random enchantment level to fall in the range between getStartLevel() and getMaxLevel()
+                // so we take a random number in the range of their difference, then add the start level.
+                final int levelDiff = possibleEnchantment.getMaxLevel() - possibleEnchantment.getStartLevel();
+                treasureDrop.addEnchantment(possibleEnchantment, Misc.getRandom().nextInt(levelDiff + 1) + possibleEnchantment.getStartLevel());
 
                 specificChance++;
                 enchanted = true;