Make custom Env flag reliably possible (#8019)

* Make custom Env flag reliably possible

* screw you

* "compatibility" for mods that don't use add()

core/src/mindustry/world/meta/Env.java

@@ -1,26 +1,83 @@
 package mindustry.world.meta;
 
+import arc.struct.*;
+import arc.util.*;
+
 /** Environmental flags for different types of locations. */
 public class Env{
     public static final int
     //is on a planet
-    terrestrial = 1,
+    terrestrial,
     //is in space, no atmosphere
-    space = 1 << 1,
+    space,
     //is underwater, on a planet
-    underwater = 1 << 2,
+    underwater,
     //has a spores
-    spores = 1 << 3,
+    spores,
     //has a scorching env effect
-    scorching = 1 << 4,
+    scorching,
     //has oil reservoirs
-    groundOil = 1 << 5,
+    groundOil,
     //has water reservoirs
-    groundWater = 1 << 6,
+    groundWater,
     //has oxygen in the atmosphere
-    oxygen = 1 << 7,
+    oxygen,
     //all attributes combined, only used for bitmasking purposes
     any = 0xffffffff,
     //no attributes (0)
     none = 0;
+
+    //do NOT modify directly!
+    public static final ObjectIntMap<String> nameToId;
+    public static final IntMap<String> idToName;
+
+    static{
+        //last time i didn't use a static initializer i got a null pointer.
+        //i can probably just move the fields around, but i don't trust java enough for that
+        nameToId = new ObjectIntMap<>();
+        idToName = new IntMap<>();
+
+        terrestrial = add("terrestrial");
+        space = add("space");
+        underwater = add("underwater");
+        spores = add("spores");
+        scorching = add("scorching");
+        groundOil = add("groundOil");
+        groundWater = add("groundWater");
+        oxygen = add("oxygen");
+    }
+
+    public static int add(String key){
+        if(nameToId.containsKey(key)) throw new IllegalArgumentException("'" + key + "' env already exists.");
+        if(nameToId.size >= 32) throw new IllegalStateException("Max env count 32 exceeded.");
+
+        int id = 1 << nameToId.size;
+        nameToId.put(key, id);
+        idToName.put(id, key);
+        return id;
+    }
+
+    public static int remap(int mask, IntMap<String> idToName){
+        int out = 0;
+        for(int i = 0; i < 32; i++){
+            int key = 1 << i;
+            if((mask & key) == key){
+                String name = idToName.get(key);
+                if(name == null){
+                    //if it's unmapped it's probably just some mods using constant value
+                    out |= key;
+                    continue;
+                }
+
+                int id = nameToId.get(name, -1);
+                if(id == -1){
+                    Log.warn("Ignoring '@' env key.", name);
+                }else{
+                    out |= id;
+                }
+            }
+        }
+
+        return out;
+    }
 }