/*
 * 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.eclipse.aether.util.repository;

import java.net.Authenticator;
import java.net.InetSocketAddress;
import java.net.PasswordAuthentication;
import java.net.SocketAddress;
import java.net.URI;
import java.net.URL;
import java.util.List;
import java.util.Map;
import java.util.UUID;

import org.eclipse.aether.repository.Authentication;
import org.eclipse.aether.repository.AuthenticationContext;
import org.eclipse.aether.repository.AuthenticationDigest;
import org.eclipse.aether.repository.Proxy;
import org.eclipse.aether.repository.ProxySelector;
import org.eclipse.aether.repository.RemoteRepository;

import static java.util.Objects.requireNonNull;

/**
 * A proxy selector that uses the {@link java.net.ProxySelector#getDefault() JRE's global proxy selector}. In
 * combination with the system property {@code java.net.useSystemProxies}, this proxy selector can be employed to pick
 * up the proxy configuration from the operating system, see <a
 * href="http://docs.oracle.com/javase/6/docs/technotes/guides/net/proxies.html">Java Networking and Proxies</a> for
 * details. The {@link java.net.Authenticator JRE's global authenticator} is used to look up credentials for a proxy
 * when needed.
 */
public final class JreProxySelector implements ProxySelector {

    /**
     * Creates a new proxy selector that delegates to {@link java.net.ProxySelector#getDefault()}.
     */
    public JreProxySelector() {}

    public Proxy getProxy(RemoteRepository repository) {
        requireNonNull(repository, "repository cannot be null");
        List<java.net.Proxy> proxies = null;
        try {
            URI uri = new URI(repository.getUrl()).parseServerAuthority();
            proxies = java.net.ProxySelector.getDefault().select(uri);
        } catch (Exception e) {
            // URL invalid or not accepted by selector or no selector at all, simply use no proxy
        }
        if (proxies != null) {
            for (java.net.Proxy proxy : proxies) {
                if (java.net.Proxy.Type.DIRECT.equals(proxy.type())) {
                    break;
                }
                if (java.net.Proxy.Type.HTTP.equals(proxy.type()) && isValid(proxy.address())) {
                    InetSocketAddress addr = (InetSocketAddress) proxy.address();
                    return new Proxy(
                            Proxy.TYPE_HTTP, addr.getHostName(), addr.getPort(), JreProxyAuthentication.INSTANCE);
                }
            }
        }
        return null;
    }

    private static boolean isValid(SocketAddress address) {
        if (address instanceof InetSocketAddress) {
            /*
             * NOTE: On some platforms with java.net.useSystemProxies=true, unconfigured proxies show up as proxy
             * objects with empty host and port 0.
             */
            InetSocketAddress addr = (InetSocketAddress) address;
            if (addr.getPort() <= 0) {
                return false;
            }
            if (addr.getHostName() == null || addr.getHostName().isEmpty()) {
                return false;
            }
            return true;
        }
        return false;
    }

    private static final class JreProxyAuthentication implements Authentication {

        public static final Authentication INSTANCE = new JreProxyAuthentication();

        public void fill(AuthenticationContext context, String key, Map<String, String> data) {
            requireNonNull(context, "context cannot be null");
            Proxy proxy = context.getProxy();
            if (proxy == null) {
                return;
            }
            if (!AuthenticationContext.USERNAME.equals(key) && !AuthenticationContext.PASSWORD.equals(key)) {
                return;
            }

            try {
                URL url;
                try {
                    url = new URL(context.getRepository().getUrl());
                } catch (Exception e) {
                    url = null;
                }

                PasswordAuthentication auth = Authenticator.requestPasswordAuthentication(
                        proxy.getHost(),
                        null,
                        proxy.getPort(),
                        "http",
                        "Credentials for proxy " + proxy,
                        null,
                        url,
                        Authenticator.RequestorType.PROXY);
                if (auth != null) {
                    context.put(AuthenticationContext.USERNAME, auth.getUserName());
                    context.put(AuthenticationContext.PASSWORD, auth.getPassword());
                } else {
                    context.put(AuthenticationContext.USERNAME, System.getProperty("http.proxyUser"));
                    context.put(AuthenticationContext.PASSWORD, System.getProperty("http.proxyPassword"));
                }
            } catch (SecurityException e) {
                // oh well, let's hope the proxy can do without auth
            }
        }

        public void digest(AuthenticationDigest digest) {
            requireNonNull(digest, "digest cannot be null");
            // we don't know anything about the JRE's current authenticator, assume the worst (i.e. interactive)
            digest.update(UUID.randomUUID().toString());
        }

        @Override
        public boolean equals(Object obj) {
            return this == obj || (obj != null && getClass().equals(obj.getClass()));
        }

        @Override
        public int hashCode() {
            return getClass().hashCode();
        }
    }
}
