Add deadpool, a pool of recorded deaths

src/meld/game/DeadPool.java

@@ -0,0 +1,87 @@
+package meld.game;
+
+import java.io.*;
+import arc.*;
+import arc.math.geom.*;
+import arc.struct.*;
+import arc.util.*;
+import mindustry.game.EventType.*;
+import mindustry.io.*;
+import static mindustry.io.SaveVersion.*;
+
+public final class DeadPool implements CustomChunk{
+    private static final DeadPool instance = new DeadPool();
+    private static final Seq<Death> deaths = new Seq<>();
+
+    private DeadPool(){}
+
+    public static void init(){
+        SaveVersion.addCustomChunk("meld-dead-pool", instance);
+        Events.on(UnitDestroyEvent.class, it -> addDeath(Death.from(it)));
+    }
+
+    public static void addDeath(Death death){
+        deaths.add(death);
+    }
+
+    public static Seq<Death> deaths(){
+        return deaths;
+    }
+
+    @Override
+    public void read(DataInput stream) throws IOException{
+        deaths.clear();
+
+        var count = stream.readInt();
+        for(var i = 0; i < count; i++){
+            var death = readDeath(stream);
+            deaths.add(death);
+        }
+    }
+
+    private Death readDeath(DataInput stream) throws IOException{
+        var unit = stream.readUTF();
+        var x = stream.readFloat();
+        var y = stream.readFloat();
+        var time = stream.readLong();
+
+        return new Death(unit, new Vec2(x, y), time);
+    }
+
+    @Override
+    public void write(DataOutput stream) throws IOException{
+        // TODO: might need to synchronize on the list or make a read-only clone
+        stream.writeInt(deaths.size);
+        for(var death: deaths){
+            writeDeath(stream, death);
+        }
+    }
+
+    private void writeDeath(DataOutput stream, Death death) throws IOException{
+        stream.writeUTF(death.unit);
+        stream.writeFloat(death.pos.getX());
+        stream.writeFloat(death.pos.getY());
+        stream.writeLong(death.time);
+    }
+
+    // TODO: this should be a record, but i can't get jabel to compile them correctly
+    public static class Death{
+        public final String unit;
+        public final Position pos;
+        public final long time;
+
+        public Death(String u, Position p, long t){
+            unit = u;
+            pos = p;
+            time = t;
+        }
+
+        public static Death from(UnitDestroyEvent event){
+            return new Death(
+                event.unit.type.name,
+                event.unit,
+                Time.millis()
+            );
+        }
+    }
+}