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package org.aksw.commons.util.slot;

import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collectors;

public class SlottedBuilderImpl
    implements SlottedBuilder
{
    /** The assembler that assembles the 'whole' from the 'parts' */
    protected Function, ? extends W> assembler;

    protected Set> slots = new LinkedHashSet<>();

    public SlottedBuilderImpl(Function, ? extends W> assembler) {
        super();
        this.assembler = assembler;
    }

    public class SlotImpl
        implements Slot
    {
        protected Supplier
 supplier;

        @Override
        public Supplier
 getSupplier() {
            return supplier;
        }

        @Override
        public Slot
 setSupplier(Supplier
 partSupplier) {
            this.supplier = partSupplier;
            return this;
        }

        @Override
        public void close() {
            synchronized (slots) {
                slots.remove(this);
            }
        }

        @Override
        public String toString() {
            return "SlotImpl [suppliedValue=" + supplier.get() + "]";
        }
    }

    @Override
    public synchronized Slot
 newSlot() {
        Slot
 result = new SlotImpl();
        synchronized (slots) {
            slots.add(result);
        }
        return result;
    }

    @Override
    public W build() {
        synchronized (slots) {
            Collection parts = slots.stream()
                .filter(slot -> slot != null)
                .map(Slot::getSupplier)
                .filter(supplier -> supplier != null)
                .map(Supplier::get)
                .filter(part -> part != null)
                .collect(Collectors.toList());

            W result = assembler.apply(parts);
            return result;
        }
    }


    public static  SlottedBuilder create(Function, ? extends W> assembler) {
        return new SlottedBuilderImpl(assembler);
    }
}