package org.apidesign.reentrant;

import java.util.Collection;

import java.util.concurrent.atomic.AtomicInteger;

public class CriticalSectionReentrantForLoop<T extends Comparable<T>> implements CriticalSection<T> {

    private volatile T pilot;

    private AtomicInteger cnt = new AtomicInteger();

    public void assignPilot(T pilot) {

        this.pilot = pilot;

    }

    // BEGIN: reentrant.merge.for

    public int sumBigger(Collection<T> args) {

        T pilotCopy = this.pilot;

        for (;;) {

            int previous = cnt.get();

            int own = doCriticalSection(args, pilotCopy);

            // if there was no parallel or reentrant change, 

            // apply and return. Otherwise try once more.

            if (cnt.compareAndSet(previous, own + previous)) {

                return own;

            }

        }

    }

    // END: reentrant.merge.for

    private int doCriticalSection(Collection<T> args, T pilotCopy) {

        int own = 0;

        for (T cmp : args) {

            if (pilotCopy.compareTo(cmp) < 0) {

                own++;

            }

        }

        return own;

    }

    public int getCount() {

        return cnt.get();

    }

}