/*
 * Copyright (c) 2017. slownet5
 *  This file is part of RootPGPExplorer also known as CryptoFM
 *
 *       RootPGPExplorer a is free software: you can redistribute it and/or modify
 *       it under the terms of the GNU General Public License as published by
 *       the Free Software Foundation, either version 3 of the License, or
 *       (at your option) any later version.
 *
 *       RootPGPExplorer 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 for more details.
 *
 *       You should have received a copy of the GNU General Public License
 *       along with RootPGPExplorer.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.slownet5.pgprootexplorer.encryption;

/**
 * Created by tripleheader on 1/8/17.
 * pgp utilities
 */

import org.spongycastle.openpgp.PGPCompressedDataGenerator;
import org.spongycastle.openpgp.PGPException;
import org.spongycastle.openpgp.PGPLiteralData;
import org.spongycastle.openpgp.PGPPrivateKey;
import org.spongycastle.openpgp.PGPPublicKey;
import org.spongycastle.openpgp.PGPPublicKeyRing;
import org.spongycastle.openpgp.PGPPublicKeyRingCollection;
import org.spongycastle.openpgp.PGPSecretKey;
import org.spongycastle.openpgp.PGPSecretKeyRing;
import org.spongycastle.openpgp.PGPSecretKeyRingCollection;
import org.spongycastle.openpgp.PGPUtil;
import org.spongycastle.openpgp.operator.jcajce.JcaKeyFingerprintCalculator;
import org.spongycastle.openpgp.operator.jcajce.JcePBESecretKeyDecryptorBuilder;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.NoSuchProviderException;
import java.util.Iterator;

public class MyPGPUtil
{
    static byte[] compressFile(String fileName, int algorithm) throws IOException
    {
        ByteArrayOutputStream bOut          = new ByteArrayOutputStream();
        PGPCompressedDataGenerator comData  = new PGPCompressedDataGenerator(algorithm);
        PGPUtil.writeFileToLiteralData(comData.open(bOut), PGPLiteralData.BINARY,
                new File(fileName));
        comData.close();
        return bOut.toByteArray();
    }

    /**
     * Search a secret key ring collection for a secret key corresponding to keyID if it
     * exists.
     *
     * @param pgpSec a secret key ring collection.
     * @param keyID keyID we want.
     * @param pass passphrase to decrypt secret key with.
     * @return the private key.
     * @throws PGPException
     * @throws NoSuchProviderException
     */
    static PGPPrivateKey findSecretKey(PGPSecretKeyRingCollection pgpSec, long keyID, char[] pass)
            throws PGPException, NoSuchProviderException
    {
        PGPSecretKey pgpSecKey = pgpSec.getSecretKey(keyID);

        if (pgpSecKey == null)
        {
            return null;
        }

        return pgpSecKey.extractPrivateKey(new JcePBESecretKeyDecryptorBuilder().setProvider("BC").build(pass));
    }

    public static PGPPublicKey readPublicKey(String fileName) throws IOException, PGPException
    {
        InputStream keyIn   = new BufferedInputStream(new FileInputStream(fileName));
        PGPPublicKey pubKey = readPublicKey(keyIn);
        keyIn.close();
        return pubKey;
    }

    /**
     * A simple routine that opens a key ring file and loads the first available key
     * suitable for encryption.
     *
     * @param input data stream containing the public key data
     * @return the first public key found.
     * @throws IOException
     * @throws PGPException
     */
    static PGPPublicKey readPublicKey(InputStream input) throws IOException, PGPException
    {
        PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(
                PGPUtil.getDecoderStream(input), new JcaKeyFingerprintCalculator());

        //
        // we just loop through the collection till we find a key suitable for encryption, in the real
        // world you would probably want to be a bit smarter about this.
        //

        Iterator keyRingIter = pgpPub.getKeyRings();
        while (keyRingIter.hasNext())
        {
            PGPPublicKeyRing keyRing = (PGPPublicKeyRing)keyRingIter.next();

            Iterator keyIter = keyRing.getPublicKeys();
            while (keyIter.hasNext())
            {
                PGPPublicKey key = (PGPPublicKey)keyIter.next();

                if (key.isEncryptionKey())
                {
                    return key;
                }
            }
        }

        throw new IllegalArgumentException("Can't find encryption key in key ring.");
    }

    public static PGPSecretKey readSecretKey(String fileName) throws IOException, PGPException
    {
        InputStream keyIn   = new BufferedInputStream(new FileInputStream(fileName));
        PGPSecretKey secKey = readSecretKey(keyIn);
        keyIn.close();
        return secKey;
    }

    /**
     * A simple routine that opens a key ring file and loads the first available key
     * suitable for signature generation.
     *
     * @param input stream to read the secret key ring collection from.
     * @return a secret key.
     * @throws IOException on a problem with using the input stream.
     * @throws PGPException if there is an issue parsing the input stream.
     */
    public static PGPSecretKey readSecretKey(InputStream input) throws IOException, PGPException
    {
        PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(
                PGPUtil.getDecoderStream(input), new JcaKeyFingerprintCalculator());

        //
        // we just loop through the collection till we find a key suitable for encryption, in the real
        // world you would probably want to be a bit smarter about this.
        //

        Iterator keyRingIter = pgpSec.getKeyRings();
        while (keyRingIter.hasNext())
        {
            PGPSecretKeyRing keyRing = (PGPSecretKeyRing)keyRingIter.next();

            Iterator keyIter = keyRing.getSecretKeys();
            while (keyIter.hasNext())
            {
                PGPSecretKey key = (PGPSecretKey)keyIter.next();

                if (key.isSigningKey())
                {
                    return key;
                }
            }
        }

        throw new IllegalArgumentException("Can't find signing key in key ring.");
    }
}