Documentation, added Content/ContentDatabase classes

core/src/io/anuke/mindustry/game/Content.java

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+package io.anuke.mindustry.game;
+
+/**Base interface for an unlockable content type.*/
+public interface Content {
+    /**Returns the unqiue name of this piece of content.
+     * The name only needs to be unique for all content of this type.
+     * Do not use IDs for names! Make sure this string stays constant with each update unless removed.
+     * (e.g. having a recipe and a block, both with name "wall" is fine, as they are different types).*/
+    String getContentName();
+
+    /**Returns the type name of this piece of content.
+     * This should return the same value for all instances of this content type.*/
+    String getContentTypeName();
+}

core/src/io/anuke/mindustry/game/ContentDatabase.java

@@ -0,0 +1,27 @@
+package io.anuke.mindustry.game;
+
+import com.badlogic.gdx.utils.ObjectMap;
+import com.badlogic.gdx.utils.ObjectSet;
+
+public class ContentDatabase {
+    private ObjectMap<String, ObjectSet<String>> unlocked = new ObjectMap<>();
+
+    public boolean isUnlocked(Content content){
+        if(!unlocked.containsKey(content.getContentTypeName())){
+            unlocked.put(content.getContentTypeName(), new ObjectSet<>());
+        }
+
+        ObjectSet<String> set = unlocked.get(content.getContentTypeName());
+
+        return set.contains(content.getContentName());
+    }
+
+    private void load(){
+
+    }
+
+    private void save(){
+
+    }
+
+}