Start work on the new and improved PlayerKnowledge system

src/main/java/com/pahimar/ee3/knowledge/PlayerKnowledge.java

@@ -0,0 +1,62 @@
+package com.pahimar.ee3.knowledge;
+
+import com.pahimar.ee3.reference.Comparators;
+import com.pahimar.ee3.util.ItemHelper;
+import net.minecraft.item.ItemStack;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Set;
+import java.util.TreeSet;
+
+public class PlayerKnowledge {
+
+    private static final int VERSION = 1;
+
+    private int version;
+    private Set<ItemStack> knownItemStacks;
+
+    public PlayerKnowledge() {
+        this(Collections.EMPTY_SET);
+    }
+
+    public PlayerKnowledge(Collection<ItemStack> itemStacks) {
+
+        version = VERSION;
+        knownItemStacks = new TreeSet<>(Comparators.idComparator);
+
+        if (itemStacks != null) {
+            for (ItemStack itemStack : itemStacks) {
+                knownItemStacks.add(ItemHelper.clone(itemStack, 1));
+            }
+        }
+    }
+
+    public boolean isKnown(ItemStack itemStack) {
+        return knownItemStacks.contains(ItemHelper.clone(itemStack, 1));
+    }
+
+    public Set<ItemStack> get() {
+        return knownItemStacks;
+    }
+
+    public void learn(ItemStack itemStack) {
+
+        if (itemStack != null) {
+            ItemStack unitItemStack = ItemHelper.clone(itemStack, 1);
+            knownItemStacks.add(unitItemStack);
+        }
+    }
+
+    public void forget(ItemStack itemStack) {
+
+        if (itemStack != null) {
+            ItemStack unitItemStack = ItemHelper.clone(itemStack, 1);
+            knownItemStacks.remove(unitItemStack);
+        }
+    }
+
+    public void forgetAll() {
+        knownItemStacks.clear();
+    }
+}