package org.apidesign.singletons.api;

import java.util.Iterator;

import java.util.ServiceLoader;

import org.openide.util.Lookup;

// BEGIN: singletons.injectable.api

public abstract class DialogDisplayer {

    protected DialogDisplayer() {

    }

    /** Ask user a question.

     *

     * @param query the text of the question

     * @return true if user confirmed or false if declined

     */

    public abstract boolean yesOrNo(String query);

    public static DialogDisplayer getDefault() {

        return Impl.DEFAULT;

    }

    // FINISH: singletons.injectable.api

    // BEGIN: singletons.injectable.dummyimpl

    private static final class Impl extends DialogDisplayer {

        private static final DialogDisplayer DEFAULT = initialize();

        @Override

        public boolean yesOrNo(String query) {

            System.err.printf("Saying no to '%s'\n", query);

            return false;

        }

        // FINISH: singletons.injectable.dummyimpl

        private static DialogDisplayer initialize() {

            if (Boolean.getBoolean("singleton.jdk6")) {

                return initializeServiceLoader();

            } else {

                return initializeLookup();

            }

        }

        // BEGIN: singletons.injectable.serviceloader

        private static DialogDisplayer initializeServiceLoader() {

            Iterator<DialogDisplayer> it = null;

            it = ServiceLoader.load(DialogDisplayer.class).iterator();

            return it != null && it.hasNext() ? it.next() : new Impl();

        }

        // END: singletons.injectable.serviceloader

        // BEGIN: singletons.injectable.lookup

        private static DialogDisplayer initializeLookup() {

            final Lookup lkp = Lookup.getDefault();

            DialogDisplayer def = lkp.lookup(DialogDisplayer.class);

            return def != null ? def : new Impl();

        }

        // END: singletons.injectable.lookup

    }

}