Pretty much finished

src/main/java/mc/unraveled/reforged/permission/Group.java

@@ -0,0 +1,63 @@
+package mc.unraveled.reforged.permission;
+
+import lombok.Data;
+import mc.unraveled.reforged.api.Baker;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.entity.Player;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Data
+public class Group implements Baker {
+    private final Rank rank;
+    private Set<String> permissions = new HashSet<>();
+    private Set<OfflinePlayer> players = new HashSet<>();
+    private boolean baked = false;
+
+    public Group(Rank rank) {
+        this.rank = rank;
+    }
+
+    public void insert(String permission) {
+        if (baked) throw new IllegalStateException("Cannot modify a baked group.");
+        permissions.add(permission);
+    }
+
+    public void insert(OfflinePlayer player) {
+        if (baked) throw new IllegalStateException("Cannot modify a baked group.");
+        players.add(player);
+    }
+
+    public void eject(String permission) {
+        if (baked) throw new IllegalStateException("Cannot modify a baked group.");
+        permissions.remove(permission);
+    }
+
+    public void eject(OfflinePlayer player) {
+        if (baked) throw new IllegalStateException("Cannot modify a baked group.");
+        players.remove(player);
+    }
+
+    @Override
+    public void bake() {
+        if (baked) return;
+
+        this.permissions = permissions.stream().collect(Collectors.toUnmodifiableSet());
+        this.players = players.stream().collect(Collectors.toUnmodifiableSet());
+
+        this.baked = true;
+    }
+
+    @Override
+    public void unbake() {
+        if (!baked) return;
+
+        this.permissions = new HashSet<>(permissions);
+        this.players = new HashSet<>(players);
+
+        this.baked = false;
+
+    }
+}