/*

 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 */

package java.net.http;

import java.io.IOException;

import static java.net.Authenticator.RequestorType.PROXY;

import static java.net.Authenticator.RequestorType.SERVER;

import java.net.PasswordAuthentication;

import java.net.URI;

import java.net.InetSocketAddress;

import java.net.URISyntaxException;

import java.util.Base64;

import java.util.HashMap;

import java.util.LinkedList;

import static java.nio.charset.StandardCharsets.ISO_8859_1;

/**

 * Implementation of Http Basic authentication.

 */

class AuthenticationFilter implements HeaderFilter {

    static private final Base64.Encoder encoder = Base64.getEncoder();

    static final int DEFAULT_RETRY_LIMIT = 3;

    static final int retry_limit = Utils.getIntegerNetProperty(

            "sun.net.httpclient.auth.retrylimit", DEFAULT_RETRY_LIMIT);

    static final int UNAUTHORIZED = 401;

    static final int PROXY_UNAUTHORIZED = 407;

    private PasswordAuthentication getCredentials(String header,

                                                  boolean proxy,

                                                  HttpRequestImpl req)

        throws IOException

    {

        HttpClientImpl client = req.client();

        java.net.Authenticator auth =

                client.authenticator()

                      .orElseThrow(() -> new IOException("No authenticator set"));

        URI uri = req.uri();

        HeaderParser parser = new HeaderParser(header);

        String authscheme = parser.findKey(0);

        String realm = parser.findValue("realm");

        java.net.Authenticator.RequestorType rtype = proxy ? PROXY : SERVER;

        // needs to be instance method in Authenticator

        return auth.requestPasswordAuthenticationInstance(uri.getHost(),

                                                          null,

                                                          uri.getPort(),

                                                          uri.getScheme(),

                                                          realm,

                                                          authscheme,

                                                          uri.toURL(),

                                                          rtype

        );

    }

    private URI getProxyURI(HttpRequestImpl r) {

        InetSocketAddress proxy = r.proxy();

        if (proxy == null) {

            return null;

        }

        // our own private scheme for proxy URLs

        // eg. proxy.http://host:port/

        String scheme = "proxy." + r.uri().getScheme();

        try {

            return new URI(scheme,

                           null,

                           proxy.getHostString(),

                           proxy.getPort(),

                           null,

                           null,

                           null);

        } catch (URISyntaxException e) {

            throw new InternalError(e);

        }

    }

    @Override

    public void request(HttpRequestImpl r) throws IOException {

        // use preemptive authentication if an entry exists.

        Cache cache = getCache(r);

        // Proxy

        if (r.exchange.proxyauth == null) {

            URI proxyURI = getProxyURI(r);

            if (proxyURI != null) {

                CacheEntry ca = cache.get(proxyURI, true);

                if (ca != null) {

                    r.exchange.proxyauth = new AuthInfo(true, ca.scheme, null, ca);

                    addBasicCredentials(r, true, ca.value);

                }

            }

        }

        // Server

        if (r.exchange.serverauth == null) {

            CacheEntry ca = cache.get(r.uri(), false);

            if (ca != null) {

                r.exchange.serverauth = new AuthInfo(true, ca.scheme, null, ca);

                addBasicCredentials(r, false, ca.value);

            }

        }

    }

    // TODO: refactor into per auth scheme class

    static private void addBasicCredentials(HttpRequestImpl r,

                                            boolean proxy,

                                            PasswordAuthentication pw) {

        String hdrname = proxy ? "Proxy-Authorization" : "Authorization";

        StringBuilder sb = new StringBuilder(128);

        sb.append(pw.getUserName()).append(':').append(pw.getPassword());

        String s = encoder.encodeToString(sb.toString().getBytes(ISO_8859_1));

        String value = "Basic " + s;

        r.setSystemHeader(hdrname, value);

    }

    // Information attached to a HttpRequestImpl relating to authentication

    static class AuthInfo {

        final boolean fromcache;

        final String scheme;

        int retries;

        PasswordAuthentication credentials; // used in request

        CacheEntry cacheEntry; // if used

        AuthInfo(boolean fromcache,

                 String scheme,

                 PasswordAuthentication credentials) {

            this.fromcache = fromcache;

            this.scheme = scheme;

            this.credentials = credentials;

            this.retries = 1;

        }

        AuthInfo(boolean fromcache,

                 String scheme,

                 PasswordAuthentication credentials,

                 CacheEntry ca) {

            this(fromcache, scheme, credentials);

            assert credentials == null || (ca != null && ca.value == null);

            cacheEntry = ca;

        }

    }

    @Override

    public HttpRequestImpl response(HttpResponseImpl r) throws IOException {

        Cache cache = getCache(r.request);

        int status = r.statusCode();

        HttpHeaders hdrs = r.headers();

        HttpRequestImpl req = r.request();

        if (status != UNAUTHORIZED && status != PROXY_UNAUTHORIZED) {

            // check if any authentication succeeded for first time

            if (req.exchange.serverauth != null && !req.exchange.serverauth.fromcache) {

                AuthInfo au = req.exchange.serverauth;

                cache.store(au.scheme, req.uri(), false, au.credentials);

            }

            if (req.exchange.proxyauth != null && !req.exchange.proxyauth.fromcache) {

                AuthInfo au = req.exchange.proxyauth;

                cache.store(au.scheme, req.uri(), false, au.credentials);

            }

            return null;

        }

        boolean proxy = status == PROXY_UNAUTHORIZED;

        String authname = proxy ? "Proxy-Authentication" : "WWW-Authenticate";

        String authval = hdrs.firstValue(authname).orElseThrow(() -> {

            return new IOException("Invalid auth header");

        });

        HeaderParser parser = new HeaderParser(authval);

        String scheme = parser.findKey(0);

        // TODO: Need to generalise from Basic only. Delegate to a provider class etc.

        if (!scheme.equalsIgnoreCase("Basic")) {

            return null;   // error gets returned to app

        }

        String realm = parser.findValue("realm");

        AuthInfo au = proxy ? req.exchange.proxyauth : req.exchange.serverauth;

        if (au == null) {

            PasswordAuthentication pw = getCredentials(authval, proxy, req);

            if (pw == null) {

                throw new IOException("No credentials provided");

            }

            // No authentication in request. Get credentials from user

            au = new AuthInfo(false, "Basic", pw);

            if (proxy)

                req.exchange.proxyauth = au;

            else

                req.exchange.serverauth = au;

            addBasicCredentials(req, proxy, pw);

            return req;

        } else if (au.retries > retry_limit) {

            throw new IOException("too many authentication attempts");

        } else {

            // we sent credentials, but they were rejected

            if (au.fromcache) {

                cache.remove(au.cacheEntry);

            }

            // try again

            au.credentials = getCredentials(authval, proxy, req);

            addBasicCredentials(req, proxy, au.credentials);

            au.retries++;

            return req;

        }

    }

    static final HashMap<HttpClientImpl,Cache> caches = new HashMap<>();

    static synchronized Cache getCache(HttpRequestImpl req) {

        HttpClientImpl client = req.client();

        Cache c = caches.get(client);

        if (c == null) {

            c = new Cache();

            caches.put(client, c);

        }

        return c;

    }

    static class Cache {

        final LinkedList<CacheEntry> entries = new LinkedList<>();

        synchronized CacheEntry get(URI uri, boolean proxy) {

            for (CacheEntry entry : entries) {

                if (entry.equalsKey(uri, proxy)) {

                    return entry;

                }

            }

            return null;

        }

        synchronized void remove(String authscheme, URI domain, boolean proxy) {

            for (CacheEntry entry : entries) {

                if (entry.equalsKey(domain, proxy)) {

                    entries.remove(entry);

                }

            }

        }

        synchronized void remove(CacheEntry entry) {

            entries.remove(entry);

        }

        synchronized void store(String authscheme,

                                URI domain,

                                boolean proxy,

                                PasswordAuthentication value) {

            remove(authscheme, domain, proxy);

            entries.add(new CacheEntry(authscheme, domain, proxy, value));

        }

    }

    static class CacheEntry {

        final String root;

        final String scheme;

        final boolean proxy;

        final PasswordAuthentication value;

        CacheEntry(String authscheme,

                   URI uri,

                   boolean proxy,

                   PasswordAuthentication value) {

            this.scheme = authscheme;

            this.root = uri.resolve(".").toString(); // remove extraneous components

            this.proxy = proxy;

            this.value = value;

        }

        public PasswordAuthentication value() {

            return value;

        }

        public boolean equalsKey(URI uri, boolean proxy) {

            if (this.proxy != proxy) {

                return false;

            }

            String other = uri.toString();

            return other.startsWith(root);

        }

    }

}