That's one heck of a commit you've got there...

I may have got a bit behind with version control. A lot behind, in fact. Maybe I'll go back and split this sometime - then again, I probably won't. But hey, at least it's here!

src/main/java/electroblob/wizardry/advancement/SpellPredicate.java

@@ -0,0 +1,117 @@
+package electroblob.wizardry.advancement;
+
+import com.google.common.collect.Streams;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
+import electroblob.wizardry.constants.Element;
+import electroblob.wizardry.constants.Tier;
+import electroblob.wizardry.spell.Spell;
+import net.minecraft.util.JsonUtils;
+
+import javax.annotation.Nullable;
+import java.util.Arrays;
+
+/** Predicate used by advancement triggers to match spells. */
+public class SpellPredicate {
+
+	public static final SpellPredicate ANY = new SpellPredicate();
+	private final Spell spell;
+	private final Tier[] tiers;
+	private final Element[] elements;
+
+	public SpellPredicate(){
+		this.spell = null;
+		this.tiers = Tier.values();
+		this.elements = Element.values();
+	}
+
+	public SpellPredicate(@Nullable Spell spell, Tier[] tiers, Element[] elements){
+		this.spell = spell;
+		this.tiers = tiers;
+		this.elements = elements;
+	}
+
+	public boolean test(Spell spell){
+
+		if(this.spell != null && spell != this.spell){
+			return false;
+		}else if(!Arrays.asList(this.tiers).contains(spell.getTier())){
+			return false;
+		}else if(!Arrays.asList(this.elements).contains(spell.getElement())){
+			return false;
+		}
+
+		return true;
+	}
+
+	public static SpellPredicate deserialize(@Nullable JsonElement element){
+
+		if(element != null && !element.isJsonNull()){
+
+			JsonObject jsonobject = JsonUtils.getJsonObject(element, "spell");
+
+			Spell spell = null;
+
+			if(jsonobject.has("spell")){
+
+				String s = JsonUtils.getString(jsonobject, "spell");
+				spell = Spell.get(s);
+
+				if(spell == null){
+					throw new JsonSyntaxException("Unknown spell id '" + s + "'");
+				}
+			}
+
+			Tier[] tiers = Tier.values();
+
+			if(jsonobject.has("tiers")){
+				try{
+					JsonArray array = JsonUtils.getJsonArray(jsonobject, "tiers");
+					tiers = Streams.stream(array)
+							.map(je -> Tier.fromName(JsonUtils.getString(je, "element of array tiers")))
+							.toArray(Tier[]::new);
+				}catch(IllegalArgumentException e){
+					throw new JsonSyntaxException("Incorrect spell predicate value", e);
+				}
+			}
+
+			Element[] elements = Element.values();
+
+			if(jsonobject.has("elements")){
+				try{
+					JsonArray array = JsonUtils.getJsonArray(jsonobject, "elements");
+					elements = Streams.stream(array)
+							.map(je -> Element.fromName(JsonUtils.getString(je, "element of array elements")))
+							.toArray(Element[]::new);
+				}catch(IllegalArgumentException e){
+					throw new JsonSyntaxException("Incorrect spell predicate value", e);
+				}
+			}
+
+			return new SpellPredicate(spell, tiers, elements);
+
+		}else{
+			return ANY;
+		}
+	}
+
+	public static SpellPredicate[] deserializeArray(@Nullable JsonElement element){
+
+		if(element != null && !element.isJsonNull()){
+
+			JsonArray jsonarray = JsonUtils.getJsonArray(element, "spells");
+			SpellPredicate[] predicates = new SpellPredicate[jsonarray.size()];
+
+			for(int i = 0; i < predicates.length; ++i){
+				predicates[i] = deserialize(jsonarray.get(i));
+			}
+
+			return predicates;
+
+		}else{
+			return new SpellPredicate[0];
+		}
+	}
+}