Remove all references to WandHelper from GuiSpellDisplay and abstract them behind ISpellCastingItem

src/main/java/electroblob/wizardry/client/gui/GuiSpellDisplay.java

@@ -15,7 +15,6 @@ import electroblob.wizardry.registry.Spells;
 import electroblob.wizardry.registry.WizardryPotions;
 import electroblob.wizardry.spell.Spell;
 import electroblob.wizardry.util.SpellModifiers;
-import electroblob.wizardry.util.WandHelper;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.gui.FontRenderer;
 import net.minecraft.client.renderer.GlStateManager;
@@ -156,7 +155,9 @@ public class GuiSpellDisplay {
 		if(Minecraft.getMinecraft().gameSettings.showDebugInfo) return; // Don't show charge meter in the debug screen
 		if(Minecraft.getMinecraft().gameSettings.thirdPersonView != 0) return; // Don't show in third person
 
-		Spell spell = WandHelper.getCurrentSpell(wand);
+		if(!(wand.getItem() instanceof ISpellCastingItem)) throw new IllegalArgumentException("The given stack must contain an ISpellCastingItem!");
+
+		Spell spell = ((ISpellCastingItem)wand.getItem()).getCurrentSpell(wand);
 
 		int chargeup = spell.getChargeup();
 
@@ -199,6 +200,8 @@ public class GuiSpellDisplay {
 
 		if(!Wizardry.settings.showSpellHUD) return;
 
+		if(!(wand.getItem() instanceof ISpellCastingItem)) throw new IllegalArgumentException("The given stack must contain an ISpellCastingItem!");
+
 		boolean flipX = Wizardry.settings.spellHUDPosition.flipX;
 		boolean flipY = Wizardry.settings.spellHUDPosition.flipY;
 
@@ -245,19 +248,18 @@ public class GuiSpellDisplay {
 			y = MathHelper.ceil(y/scale);
 		}
 
-		// TODO: Maybe convert this to use ISpellCastingItem
-		Spell spell = WandHelper.getCurrentSpell(wand);
-		int cooldown = WandHelper.getCurrentCooldown(wand);
-		int maxCooldown = WandHelper.getCurrentMaxCooldown(wand);
+		Spell spell = ((ISpellCastingItem)wand.getItem()).getCurrentSpell(wand);
+		int cooldown = ((ISpellCastingItem)wand.getItem()).getCurrentCooldown(wand);
+		int maxCooldown = ((ISpellCastingItem)wand.getItem()).getCurrentMaxCooldown(wand);
 
 		if(textLayer){
 
 			float animationProgress = Math.signum(switchTimer) * ((SPELL_SWITCH_TIME - Math.abs(switchTimer) +
 					partialTicks) / SPELL_SWITCH_TIME);
 
-			String prevSpellName = getFormattedSpellName(WandHelper.getPreviousSpell(wand), player, WandHelper.getPreviousCooldown(wand));
+			String prevSpellName = getFormattedSpellName(((ISpellCastingItem)wand.getItem()).getPreviousSpell(wand), player, 0);
 			String spellName = getFormattedSpellName(spell, player, cooldown);
-			String nextSpellName = getFormattedSpellName(WandHelper.getNextSpell(wand), player, WandHelper.getNextCooldown(wand));
+			String nextSpellName = getFormattedSpellName(((ISpellCastingItem)wand.getItem()).getNextSpell(wand), player, 0);
 
 			skin.drawText(x, y, flipX, flipY, prevSpellName, spellName, nextSpellName, animationProgress);
 

src/main/java/electroblob/wizardry/item/ISpellCastingItem.java

@@ -21,7 +21,7 @@ import javax.annotation.Nonnull;
  * This interface is used for the following:<br>
  *     - General-purpose detection of continuous spell casting (see {@link EntityUtils#isCasting(EntityLivingBase, Spell)})<br>
  *     - Display of the arcane workbench tooltip (in conjunction with {@link IManaStoringItem})<br>
- *     - Spell HUD visibility<br>
+ *     - Supplying information to the spell HUD<br>
  *     - Spell switching controls (they won't do anything unless the player is holding an {@code ISpellCastingItem})<br>
  *     - Artefacts that trigger a player's wands/scrolls to cast spells
  * @author Electroblob
@@ -40,6 +40,28 @@ public interface ISpellCastingItem {
 	@Nonnull
 	Spell getCurrentSpell(ItemStack stack);
 
+	/**
+	 * Returns the spell equipped in the next slot on the given itemstack. The given itemstack will be of this item.
+	 * @param stack The itemstack to query.
+	 * @return The next spell, or {@link electroblob.wizardry.registry.Spells#none Spells.none} if no spell is equipped
+	 * in the next slot. Returns the current spell by default (useful for items with only one spell).
+	 */
+	@Nonnull
+	default Spell getNextSpell(ItemStack stack){
+		return getCurrentSpell(stack);
+	}
+
+	/**
+	 * Returns the spell equipped in the previous slot on the given itemstack. The given itemstack will be of this item.
+	 * @param stack The itemstack to query.
+	 * @return The previous spell, or {@link electroblob.wizardry.registry.Spells#none Spells.none} if no spell is
+	 * equipped in the previous slot. Returns the current spell by default (useful for items with only one spell).
+	 */
+	@Nonnull
+	default Spell getPreviousSpell(ItemStack stack){
+		return getCurrentSpell(stack);
+	}
+
 	/**
 	 * Returns all the spells currently bound to the given itemstack. The given itemstack will be of this item.
 	 * @param stack The itemstack to query.
@@ -84,6 +106,24 @@ public interface ISpellCastingItem {
 	 */
 	boolean showSpellHUD(EntityPlayer player, ItemStack stack);
 
+	/**
+	 * Returns the current cooldown to display on the spell HUD for the given itemstack.
+	 * @param stack The itemstack to query.
+	 * @return The current cooldown for the equipped spell.
+	 */
+	default int getCurrentCooldown(ItemStack stack){
+		return 0;
+	}
+
+	/**
+	 * Returns the max cooldown of the current spell to display on the spell HUD for the given itemstack.
+	 * @param stack The itemstack to query.
+	 * @return The max cooldown for the equipped spell.
+	 */
+	default int getCurrentMaxCooldown(ItemStack stack){
+		return 0;
+	}
+
 	/**
 	 * Returns whether this item's spells should be displayed in the arcane workbench tooltip. Only called client-side.
 	 * Ignore this method if this item is not an {@link IWorkbenchItem}.

src/main/java/electroblob/wizardry/item/ItemWand.java

@@ -107,6 +107,16 @@ public class ItemWand extends Item implements IWorkbenchItem, ISpellCastingItem,
 		return WandHelper.getCurrentSpell(stack);
 	}
 
+	@Override
+	public Spell getNextSpell(ItemStack stack){
+		return WandHelper.getNextSpell(stack);
+	}
+
+	@Override
+	public Spell getPreviousSpell(ItemStack stack){
+		return WandHelper.getPreviousSpell(stack);
+	}
+
 	@Override
 	public Spell[] getSpells(ItemStack stack){
 		return WandHelper.getSpells(stack);
@@ -127,6 +137,16 @@ public class ItemWand extends Item implements IWorkbenchItem, ISpellCastingItem,
 		return WandHelper.selectSpell(stack, index);
 	}
 
+	@Override
+	public int getCurrentCooldown(ItemStack stack){
+		return WandHelper.getCurrentCooldown(stack);
+	}
+
+	@Override
+	public int getCurrentMaxCooldown(ItemStack stack){
+		return WandHelper.getCurrentMaxCooldown(stack);
+	}
+
 	@Override
 	public boolean showSpellHUD(EntityPlayer player, ItemStack stack){
 		return true;