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package org.netbeans.modules.openide.util;

import java.lang.ref.Reference;

import java.lang.ref.WeakReference;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;

import org.openide.util.Lookup;

import org.openide.util.lookup.Lookups;

/** Interface for core/startup and core/settings

 * to provide lookup over system filesystem.

 *

 * @author Jaroslav Tulach

 */

public abstract class NamedServicesProvider {

    private static final Map<String,Reference<Lookup>> map = Collections.synchronizedMap(new HashMap<String,Reference<Lookup>>());

    public abstract Lookup create(String path);

    public static Lookup find(String path) {

        if (!path.endsWith("/")) {

            path = path + "/";

        }

        Reference<Lookup> ref = map.get(path);

        Lookup lkp = ref == null ? null : ref.get();

        if (lkp != null) {

            return lkp;

        }

        NamedServicesProvider prov = Lookup.getDefault().lookup(NamedServicesProvider.class);

        if (prov != null && /* avoid stack overflow during initialization */ !path.equals("URLStreamHandler/nbres/")) { // NOI18N

            lkp = prov.create(path);

        } else {

            ClassLoader l = Lookup.getDefault().lookup(ClassLoader.class);

            if (l == null) {

                l = Thread.currentThread().getContextClassLoader();

                if (l == null) {

                    l = NamedServicesProvider.class.getClassLoader();

                }

            }

            lkp = Lookups.metaInfServices(l, "META-INF/namedservices/" + path);

        }

        map.put(path, new WeakReference<Lookup>(lkp));

        return lkp;

    }

}