create SurfaceLocator

common/addons/config-locators/src/main/java/com/dfsek/terra/addons/feature/locator/locators/SurfaceLocator.java

@@ -0,0 +1,31 @@
+package com.dfsek.terra.addons.feature.locator.locators;
+
+import com.dfsek.terra.api.TerraPlugin;
+import com.dfsek.terra.api.block.state.BlockState;
+import com.dfsek.terra.api.structure.feature.Locator;
+import com.dfsek.terra.api.util.ConstantRange;
+import com.dfsek.terra.api.world.Column;
+
+import java.util.Collections;
+import java.util.List;
+
+public class SurfaceLocator implements Locator {
+    private final ConstantRange search;
+
+    private final BlockState air;
+
+    public SurfaceLocator(ConstantRange search, TerraPlugin main) {
+        this.search = search;
+        this.air = main.getWorldHandle().air();
+    }
+
+    @Override
+    public List<Integer> getSuitableCoordinates(Column column) {
+        for(int y : search) {
+            if(column.getBlock(y).matches(air) && !column.getBlock(y-1).matches(air)) {
+                return Collections.singletonList(y);
+            }
+        }
+        return Collections.emptyList();
+    }
+}