/*
 * Copyright (C) 2012-2014 Dominik Schürmann <dominik@dominikschuermann.de>
 * Copyright (C) 2011-2014 Thialfihar <thi@thialfihar.org>
 * Copyright (C) 2011 Senecaso
 *
 * Licensed 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.sufficientlysecure.keychain.keyimport;



import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import org.sufficientlysecure.keychain.Constants;
import org.sufficientlysecure.keychain.pgp.PgpHelper;
import org.sufficientlysecure.keychain.ui.util.KeyFormattingUtils;
import org.sufficientlysecure.keychain.util.Log;
import org.sufficientlysecure.keychain.util.OkHttpClientFactory;
import org.sufficientlysecure.keychain.util.TlsHelper;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.Proxy;
import java.net.URL;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import android.support.annotation.NonNull;

import de.measite.minidns.Client;
import de.measite.minidns.Question;
import de.measite.minidns.Record;
import de.measite.minidns.record.SRV;

public class HkpKeyserver extends Keyserver {
    private static class HttpError extends Exception {
        private static final long serialVersionUID = 1718783705229428893L;
        private int mCode;
        private String mData;

        public HttpError(int code, String data) {
            super("" + code + ": " + data);
            mCode = code;
            mData = data;
        }

        public int getCode() {
            return mCode;
        }

        public String getData() {
            return mData;
        }
    }

    private String mHost;
    private short mPort;
    private Proxy mProxy;
    private boolean mSecure;

    /**
     * pub:%keyid%:%algo%:%keylen%:%creationdate%:%expirationdate%:%flags%
     * <ul>
     * <li>%<b>keyid</b>% = this is either the fingerprint or the key ID of the key.
     * Either the 16-digit or 8-digit key IDs are acceptable, but obviously the fingerprint is best.
     * </li>
     * <li>%<b>algo</b>% = the algorithm number, (i.e. 1==RSA, 17==DSA, etc).
     * See <a href="http://tools.ietf.org/html/rfc2440#section-9.1">RFC-2440</a></li>
     * <li>%<b>keylen</b>% = the key length (i.e. 1024, 2048, 4096, etc.)</li>
     * <li>%<b>creationdate</b>% = creation date of the key in standard
     * <a href="http://tools.ietf.org/html/rfc2440#section-9.1">RFC-2440</a> form (i.e. number of
     * seconds since 1/1/1970 UTC time)</li>
     * <li>%<b>expirationdate</b>% = expiration date of the key in standard
     * <a href="http://tools.ietf.org/html/rfc2440#section-9.1">RFC-2440</a> form (i.e. number of
     * seconds since 1/1/1970 UTC time)</li>
     * <li>%<b>flags</b>% = letter codes to indicate details of the key, if any. Flags may be in any
     * order. The meaning of "disabled" is implementation-specific. Note that individual flags may
     * be unimplemented, so the absence of a given flag does not necessarily mean the absence of the
     * detail.
     * <ul>
     * <li>r == revoked</li>
     * <li>d == disabled</li>
     * <li>e == expired</li>
     * </ul>
     * </li>
     * </ul>
     *
     * @see <a href="http://tools.ietf.org/html/draft-shaw-openpgp-hkp-00#section-5.2">
     * 5.2. Machine Readable Indexes</a>
     * in Internet-Draft OpenPGP HTTP Keyserver Protocol Document
     */
    public static final Pattern PUB_KEY_LINE = Pattern
            .compile("pub:([0-9a-fA-F]+):([0-9]+):([0-9]+):([0-9]+):([0-9]*):([rde]*)[ \n\r]*" // pub line
                            + "((uid:([^:]*):([0-9]+):([0-9]*):([rde]*)[ \n\r]*)+)", // one or more uid lines
                    Pattern.CASE_INSENSITIVE
            );

    /**
     * uid:%escaped uid string%:%creationdate%:%expirationdate%:%flags%
     * <ul>
     * <li>%<b>escaped uid string</b>% = the user ID string, with HTTP %-escaping for anything that
     * isn't 7-bit safe as well as for the ":" character.  Any other characters may be escaped, as
     * desired.</li>
     * <li>%<b>creationdate</b>% = creation date of the key in standard
     * <a href="http://tools.ietf.org/html/rfc2440#section-9.1">RFC-2440</a> form (i.e. number of
     * seconds since 1/1/1970 UTC time)</li>
     * <li>%<b>expirationdate</b>% = expiration date of the key in standard
     * <a href="http://tools.ietf.org/html/rfc2440#section-9.1">RFC-2440</a> form (i.e. number of
     * seconds since 1/1/1970 UTC time)</li>
     * <li>%<b>flags</b>% = letter codes to indicate details of the key, if any. Flags may be in any
     * order. The meaning of "disabled" is implementation-specific. Note that individual flags may
     * be unimplemented, so the absence of a given flag does not necessarily mean the absence of
     * the detail.
     * <ul>
     * <li>r == revoked</li>
     * <li>d == disabled</li>
     * <li>e == expired</li>
     * </ul>
     * </li>
     * </ul>
     */
    public static final Pattern UID_LINE = Pattern
            .compile("uid:([^:]*):([0-9]+):([0-9]*):([rde]*)",
                    Pattern.CASE_INSENSITIVE);

    private static final short PORT_DEFAULT = 11371;
    private static final short PORT_DEFAULT_HKPS = 443;

    /**
     * @param hostAndPort may be just
     *                    "<code>hostname</code>" (eg. "<code>pool.sks-keyservers.net</code>"), then it will
     *                    connect using {@link #PORT_DEFAULT}. However, port may be specified after colon
     *                    ("<code>hostname:port</code>", eg. "<code>p80.pool.sks-keyservers.net:80</code>").
     */
    public HkpKeyserver(String hostAndPort, Proxy proxy) {
        String host = hostAndPort;
        short port = PORT_DEFAULT;
        boolean secure = false;
        String[] parts = hostAndPort.split(":");
        if (parts.length > 1) {
            if (!parts[0].contains(".")) { // This is not a domain or ip, so it must be a protocol name
                if ("hkps".equalsIgnoreCase(parts[0]) || "https".equalsIgnoreCase(parts[0])) {
                    secure = true;
                    port = PORT_DEFAULT_HKPS;
                } else if (!"hkp".equalsIgnoreCase(parts[0]) && !"http".equalsIgnoreCase(parts[0])) {
                    throw new IllegalArgumentException("Protocol " + parts[0] + " is unknown");
                }
                host = parts[1];
                if (host.startsWith("//")) { // People tend to type https:// and hkps://, so we'll support that as well
                    host = host.substring(2);
                }
                if (parts.length > 2) {
                    port = Short.decode(parts[2]);
                }
            } else {
                host = parts[0];
                port = Short.decode(parts[1]);
            }
        }
        mHost = host;
        mPort = port;
        mProxy = proxy;
        mSecure = secure;
    }

    public HkpKeyserver(String host, short port, Proxy proxy) {
        this(host, port, proxy, false);
    }

    public HkpKeyserver(String host, short port, Proxy proxy, boolean secure) {
        mHost = host;
        mPort = port;
        mProxy = proxy;
        mSecure = secure;
    }

    private String getUrlPrefix() {
        return mSecure ? "https://" : "http://";
    }


    private String query(String request, @NonNull Proxy proxy) throws QueryFailedException, HttpError {
        try {
            URL url = new URL(getUrlPrefix() + mHost + ":" + mPort + request);
            Log.d(Constants.TAG, "hkp keyserver query: " + url + " Proxy: " + proxy);
            OkHttpClient client = OkHttpClientFactory.getClientPinnedIfAvailable(url, proxy);
            Response response = client.newCall(new Request.Builder().url(url).build()).execute();

            String responseBody = response.body().string(); // contains body both in case of success or failure

            if (response.isSuccessful()) {
                return responseBody;
            } else {
                throw new HttpError(response.code(), responseBody);
            }
        } catch (IOException e) {
            Log.e(Constants.TAG, "IOException at HkpKeyserver", e);
            throw new QueryFailedException("Keyserver '" + mHost + "' is unavailable. Check your Internet connection!" +
                    (proxy == Proxy.NO_PROXY ? "" : " Using proxy " + proxy));
        } catch (TlsHelper.TlsHelperException e) {
            Log.e(Constants.TAG, "Exception in pinning certs", e);
            throw new QueryFailedException("Exception in pinning certs");
        }
    }

    /**
     * Results are sorted by creation date of key!
     */
    @Override
    public ArrayList<ImportKeysListEntry> search(String query) throws QueryFailedException,
            QueryNeedsRepairException {
        ArrayList<ImportKeysListEntry> results = new ArrayList<>();

        if (query.length() < 3) {
            throw new QueryTooShortException();
        }

        String encodedQuery;
        try {
            encodedQuery = URLEncoder.encode(query, "UTF8");
        } catch (UnsupportedEncodingException e) {
            return null;
        }
        String request = "/pks/lookup?op=index&options=mr&search=" + encodedQuery;

        String data;
        try {
            data = query(request, mProxy);
        } catch (HttpError e) {
            if (e.getData() != null) {
                Log.d(Constants.TAG, "returned error data: " + e.getData().toLowerCase(Locale.ENGLISH));

                if (e.getData().toLowerCase(Locale.ENGLISH).contains("no keys found")) {
                    // NOTE: This is also a 404 error for some keyservers!
                    return results;
                } else if (e.getData().toLowerCase(Locale.ENGLISH).contains("too many")) {
                    throw new TooManyResponsesException();
                } else if (e.getData().toLowerCase(Locale.ENGLISH).contains("insufficient")) {
                    throw new QueryTooShortException();
                } else if (e.getCode() == 404) {
                    // NOTE: handle this 404 at last, maybe it was a "no keys found" error
                    throw new QueryFailedException("Keyserver '" + mHost + "' not found. Error 404");
                } else {
                    // NOTE: some keyserver do not provide a more detailed error response
                    throw new QueryTooShortOrTooManyResponsesException();
                }
            }

            throw new QueryFailedException("Querying server(s) for '" + mHost + "' failed.");
        }

        final Matcher matcher = PUB_KEY_LINE.matcher(data);
        while (matcher.find()) {
            final ImportKeysListEntry entry = new ImportKeysListEntry();
            entry.setQuery(query);
            entry.addOrigin(getUrlPrefix() + mHost + ":" + mPort);

            // group 1 contains the full fingerprint (v4) or the long key id if available
            // see https://bitbucket.org/skskeyserver/sks-keyserver/pull-request/12/fixes-for-machine-readable-indexes/diff
            String fingerprintOrKeyId = matcher.group(1).toLowerCase(Locale.ENGLISH);
            if (fingerprintOrKeyId.length() == 40) {
                entry.setFingerprintHex(fingerprintOrKeyId);
                entry.setKeyIdHex("0x" + fingerprintOrKeyId.substring(fingerprintOrKeyId.length()
                        - 16, fingerprintOrKeyId.length()));
            } else if (fingerprintOrKeyId.length() == 16) {
                // set key id only
                entry.setKeyIdHex("0x" + fingerprintOrKeyId);
            } else {
                Log.e(Constants.TAG, "Wrong length for fingerprint/long key id.");
                // skip this key
                continue;
            }

            try {
                int bitSize = Integer.parseInt(matcher.group(3));
                entry.setBitStrength(bitSize);
                int algorithmId = Integer.decode(matcher.group(2));
                entry.setAlgorithm(KeyFormattingUtils.getAlgorithmInfo(algorithmId, bitSize, null));

                final long creationDate = Long.parseLong(matcher.group(4));
                final GregorianCalendar tmpGreg = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
                tmpGreg.setTimeInMillis(creationDate * 1000);
                entry.setDate(tmpGreg.getTime());
            } catch (NumberFormatException e) {
                Log.e(Constants.TAG, "Conversation for bit size, algorithm, or creation date failed.", e);
                // skip this key
                continue;
            }

            try {
                entry.setRevoked(matcher.group(6).contains("r"));
                entry.setExpired(matcher.group(6).contains("e"));
            } catch (NullPointerException e) {
                Log.e(Constants.TAG, "Check for revocation or expiry failed.", e);
                // skip this key
                continue;
            }

            ArrayList<String> userIds = new ArrayList<>();
            final String uidLines = matcher.group(7);
            final Matcher uidMatcher = UID_LINE.matcher(uidLines);
            while (uidMatcher.find()) {
                String tmp = uidMatcher.group(1).trim();
                if (tmp.contains("%")) {
                    if (tmp.contains("%%")) {
                        // The server encodes a percent sign as %%, so it is swapped out with its
                        // urlencoded counterpart to prevent errors
                        tmp = tmp.replace("%%", "%25");
                    }
                    try {
                        // converts Strings like "Universit%C3%A4t" to a proper encoding form "Universität".
                        tmp = URLDecoder.decode(tmp, "UTF8");
                    } catch (UnsupportedEncodingException ignored) {
                        // will never happen, because "UTF8" is supported
                    } catch (IllegalArgumentException e) {
                        Log.e(Constants.TAG, "User ID encoding broken", e);
                        // skip this user id
                        continue;
                    }
                }
                userIds.add(tmp);
            }
            entry.setUserIds(userIds);
            entry.setPrimaryUserId(userIds.get(0));

            results.add(entry);
        }
        return results;
    }

    @Override
    public String get(String keyIdHex) throws QueryFailedException {
        String request = "/pks/lookup?op=get&options=mr&search=" + keyIdHex;
        Log.d(Constants.TAG, "hkp keyserver get: " + request + " using Proxy: " + mProxy);
        String data;
        try {
            data = query(request, mProxy);
        } catch (HttpError httpError) {
            Log.d(Constants.TAG, "Failed to get key at HkpKeyserver", httpError);
            throw new QueryFailedException("not found");
        }
        if (data == null) {
            throw new QueryFailedException("data is null");
        }
        Matcher matcher = PgpHelper.PGP_PUBLIC_KEY.matcher(data);
        if (matcher.find()) {
            return matcher.group(1);
        }
        throw new QueryFailedException("data is null");
    }

    @Override
    public void add(String armoredKey) throws AddKeyException {
        try {
            String path = "/pks/add";
            String params;
            try {
                params = "keytext=" + URLEncoder.encode(armoredKey, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                throw new AddKeyException();
            }
            URL url = new URL(getUrlPrefix() + mHost + ":" + mPort + path);

            Log.d(Constants.TAG, "hkp keyserver add: " + url);
            Log.d(Constants.TAG, "params: " + params);


            RequestBody body = RequestBody.create(MediaType.parse("application/x-www-form-urlencoded"), params);

            Request request = new Request.Builder()
                    .url(url)
                    .addHeader("Content-Type", "application/x-www-form-urlencoded")
                    .addHeader("Content-Length", Integer.toString(params.getBytes().length))
                    .post(body)
                    .build();

            Response response = OkHttpClientFactory.getClientPinnedIfAvailable(url, mProxy).newCall(request).execute();

            Log.d(Constants.TAG, "response code: " + response.code());
            Log.d(Constants.TAG, "answer: " + response.body().string());

            if (response.code() != 200) {
                throw new AddKeyException();
            }

        } catch (IOException e) {
            Log.e(Constants.TAG, "IOException", e);
            throw new AddKeyException();
        } catch (TlsHelper.TlsHelperException e) {
            Log.e(Constants.TAG, "Exception in pinning certs", e);
            throw new AddKeyException();
        }
    }

    @Override
    public String toString() {
        return getUrlPrefix() + mHost + ":" + mPort;
    }

    /**
     * Tries to find a server responsible for a given domain
     *
     * @return A responsible Keyserver or null if not found.
     */
    public static HkpKeyserver resolve(String domain, Proxy proxy) {
        try {
            Record[] records = new Client().query(new Question("_hkp._tcp." + domain, Record.TYPE.SRV)).getAnswers();
            if (records.length > 0) {
                Arrays.sort(records, new Comparator<Record>() {
                    @Override
                    public int compare(Record lhs, Record rhs) {
                        if (lhs.getPayload().getType() != Record.TYPE.SRV) return 1;
                        if (rhs.getPayload().getType() != Record.TYPE.SRV) return -1;
                        return ((SRV) lhs.getPayload()).getPriority() - ((SRV) rhs.getPayload()).getPriority();
                    }
                });
                Record record = records[0]; // This is our best choice
                if (record.getPayload().getType() == Record.TYPE.SRV) {
                    return new HkpKeyserver(((SRV) record.getPayload()).getName(),
                            (short) ((SRV) record.getPayload()).getPort(), proxy);
                }
            }
        } catch (Exception ignored) {
        }
        return null;
    }
}