/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server.auth;

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import org.apache.zookeeper.server.ZooKeeperServer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ProviderRegistry {

    private static final Logger LOG = LoggerFactory.getLogger(ProviderRegistry.class);

    public static final String AUTHPROVIDER_PROPERTY_PREFIX = "zookeeper.authProvider.";

    private static boolean initialized = false;
    private static final Map<String, AuthenticationProvider> authenticationProviders = new HashMap<>();

    //VisibleForTesting
    public static void reset() {
        synchronized (ProviderRegistry.class) {
            initialized = false;
            authenticationProviders.clear();
        }
    }

    public static void initialize() {
        synchronized (ProviderRegistry.class) {
            if (initialized) {
                return;
            }
            IPAuthenticationProvider ipp = new IPAuthenticationProvider();
            authenticationProviders.put(ipp.getScheme(), ipp);

            if (DigestAuthenticationProvider.isEnabled()) {
                DigestAuthenticationProvider digp = new DigestAuthenticationProvider();
                authenticationProviders.put(digp.getScheme(), digp);
            }

            Enumeration<Object> en = System.getProperties().keys();
            while (en.hasMoreElements()) {
                String k = (String) en.nextElement();
                addOrUpdateProvider(k);
            }
            initialized = true;
        }
    }

    public static void addOrUpdateProvider(String authKey) {
        synchronized (ProviderRegistry.class) {
            if (authKey.startsWith(AUTHPROVIDER_PROPERTY_PREFIX)) {
                String className = System.getProperty(authKey);
                try {
                    Class<?> c = ZooKeeperServer.class.getClassLoader().loadClass(className);
                    AuthenticationProvider ap = (AuthenticationProvider) c.getDeclaredConstructor().newInstance();
                    authenticationProviders.put(ap.getScheme(), ap);
                } catch (Exception e) {
                    LOG.warn("Problems loading {}", className, e);
                }
            }
        }
    }

    public static ServerAuthenticationProvider getServerProvider(String scheme) {
        return WrappedAuthenticationProvider.wrap(getProvider(scheme));
    }

    public static AuthenticationProvider getProvider(String scheme) {
        if (!initialized) {
            initialize();
        }
        return authenticationProviders.get(scheme);
    }

    public static void removeProvider(String scheme) {
        authenticationProviders.remove(scheme);
    }

    public static String listProviders() {
        StringBuilder sb = new StringBuilder();
        for (String s : authenticationProviders.keySet()) {
            sb.append(s).append(" ");
        }
        return sb.toString();
    }

}

@@ -1685,77 +1685,8 @@
 ) %7B%0A
-            if (initialized) %7B%0A                return;%0A            %7D%0A
     

Revert "ZOOKEEPER-4549: ProviderRegistry may be repeatedly initialized"