implemented custom check function

src/main/java/org/kapelle/multiblock/BlockComponent.java

@@ -7,14 +7,14 @@ import org.bukkit.block.Block;
 import java.util.Collections;
 import java.util.Set;
 
+interface CheckFunction {
+    boolean apply(Location location);
+}
+
 public class BlockComponent {
     private final BlockComponentMode mode;
     private final Set<Material> blocks;
-
+    private CheckFunction customCheckFunction;
-    public BlockComponent(){
-        this.mode = BlockComponentMode.ANY;
-        this.blocks = Collections.emptySet();
-    }
 
     public BlockComponent(BlockComponentMode mode){
         if(mode == BlockComponentMode.SET){
@@ -30,11 +30,19 @@ public class BlockComponent {
         this.blocks = validBlocks;
     }
 
-    // TODO: custom check function constructor
+    public BlockComponent(CheckFunction customCheckFunction){
+        this.mode = BlockComponentMode.CUSTOM;
+        this.blocks = Collections.emptySet();
+        this.customCheckFunction = customCheckFunction;
+    }
 
     public boolean isValidBlock(Location location){
+        if(this.mode == BlockComponentMode.CUSTOM){
+            return this.customCheckFunction.apply(location);
+        }else{
             return isValidType(location.getBlock().getType());
         }
+    }
 
     private boolean isValidType(Material type){
         switch (this.mode){
@@ -44,8 +52,6 @@ public class BlockComponent {
                 return true;
             case SET:
                 return blocks.contains(type);
-            case CUSTOM:
-                return false; // TODO custom function
             default:
                 return false;