using System;
using System.Collections.Generic;
using System.IO;

using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
using Org.BouncyCastle.Utilities.Collections;

namespace Org.BouncyCastle.Bcpg.OpenPgp
{
    /// <remarks>
    /// Class to hold a single master secret key and its subkeys.
    /// <p>
    /// Often PGP keyring files consist of multiple master keys, if you are trying to process
    /// or construct one of these you should use the <c>PgpSecretKeyRingBundle</c> class.
    /// </p>
    /// </remarks>
    public class PgpSecretKeyRing
        : PgpKeyRing
    {
        private readonly IList<PgpSecretKey> keys;
        private readonly IList<PgpPublicKey> extraPubKeys;

        internal PgpSecretKeyRing(
            IList<PgpSecretKey> keys)
            : this(keys, new List<PgpPublicKey>())
        {
        }

        private PgpSecretKeyRing(
            IList<PgpSecretKey> keys,
            IList<PgpPublicKey> extraPubKeys)
        {
            this.keys = keys;
            this.extraPubKeys = extraPubKeys;
        }

        public PgpSecretKeyRing(
            byte[] encoding)
            : this(new MemoryStream(encoding))
        {
        }

        public PgpSecretKeyRing(
            Stream inputStream)
        {
            this.keys = new List<PgpSecretKey>();
            this.extraPubKeys = new List<PgpPublicKey>();

            BcpgInputStream bcpgInput = BcpgInputStream.Wrap(inputStream);

            PacketTag initialTag = bcpgInput.SkipMarkerPackets();
            if (initialTag != PacketTag.SecretKey && initialTag != PacketTag.SecretSubkey)
            {
                throw new IOException("secret key ring doesn't start with secret key tag: "
                    + "tag 0x" + ((int)initialTag).ToString("X"));
            }

            SecretKeyPacket secret = (SecretKeyPacket) bcpgInput.ReadPacket();

            //
            // ignore GPG comment packets if found.
            //
            while (bcpgInput.NextPacketTag() == PacketTag.Experimental2)
            {
                bcpgInput.ReadPacket();
            }

            TrustPacket trust = ReadOptionalTrustPacket(bcpgInput);

            // revocation and direct signatures
            var keySigs = ReadSignaturesAndTrust(bcpgInput);

            ReadUserIDs(bcpgInput, out var ids, out var idTrusts, out var idSigs);

            keys.Add(new PgpSecretKey(secret,
                new PgpPublicKey(secret.PublicKeyPacket, trust, keySigs, ids, idTrusts, idSigs)));

            // Read subkeys
            while (bcpgInput.NextPacketTag() == PacketTag.SecretSubkey
                || bcpgInput.NextPacketTag() == PacketTag.PublicSubkey)
            {
                if (bcpgInput.NextPacketTag() == PacketTag.SecretSubkey)
                {
                    SecretSubkeyPacket sub = (SecretSubkeyPacket) bcpgInput.ReadPacket();

                    //
                    // ignore GPG comment packets if found.
                    //
                    while (bcpgInput.NextPacketTag() == PacketTag.Experimental2)
                    {
                        bcpgInput.ReadPacket();
                    }

                    TrustPacket subTrust = ReadOptionalTrustPacket(bcpgInput);
                    var sigList = ReadSignaturesAndTrust(bcpgInput);

                    keys.Add(new PgpSecretKey(sub, new PgpPublicKey(sub.PublicKeyPacket, subTrust, sigList)));
                }
                else
                {
                    PublicSubkeyPacket sub = (PublicSubkeyPacket) bcpgInput.ReadPacket();

                    TrustPacket subTrust = ReadOptionalTrustPacket(bcpgInput);
                    var sigList = ReadSignaturesAndTrust(bcpgInput);

                    extraPubKeys.Add(new PgpPublicKey(sub, subTrust, sigList));
                }
            }
        }

        /// <summary>Return the public key for the master key.</summary>
        public PgpPublicKey GetPublicKey()
        {
            return keys[0].PublicKey;
        }

        /**
         * Return any keys carrying a signature issued by the key represented by keyID.
         *
         * @param keyID the key id to be matched against.
         * @return an iterator (possibly empty) of PGPPublicKey objects carrying signatures from keyID.
         */
        public IEnumerable<PgpPublicKey> GetKeysWithSignaturesBy(long keyID)
        {
            var keysWithSigs = new List<PgpPublicKey>();

            foreach (var k in GetPublicKeys())
            {
                var sigIt = k.GetSignaturesForKeyID(keyID).GetEnumerator();

                if (sigIt.MoveNext())
                {
                    keysWithSigs.Add(k);
                }
            }

            return CollectionUtilities.Proxy(keysWithSigs);
        }

        public IEnumerable<PgpPublicKey> GetPublicKeys()
        {
            var pubKeys = new List<PgpPublicKey>();

            foreach (var secretKey in keys)
            {
                pubKeys.Add(secretKey.PublicKey);
            }

            pubKeys.AddRange(extraPubKeys);

            return CollectionUtilities.Proxy(pubKeys);
        }

        /// <summary>Return the master private key.</summary>
        public PgpSecretKey GetSecretKey()
        {
            return keys[0];
        }

        /// <summary>Allows enumeration of the secret keys.</summary>
        /// <returns>An <c>IEnumerable</c> of <c>PgpSecretKey</c> objects.</returns>
        public IEnumerable<PgpSecretKey> GetSecretKeys()
        {
            return CollectionUtilities.Proxy(keys);
        }

        public PgpSecretKey GetSecretKey(long keyId)
        {
            foreach (PgpSecretKey k in keys)
            {
                if (keyId == k.KeyId)
                    return k;
            }

            return null;
        }

        /// <summary>
        /// Return an iterator of the public keys in the secret key ring that
        /// have no matching private key. At the moment only personal certificate data
        /// appears in this fashion.
        /// </summary>
        /// <returns>An <c>IEnumerable</c> of unattached, or extra, public keys.</returns>
        public IEnumerable<PgpPublicKey> GetExtraPublicKeys()
        {
            return CollectionUtilities.Proxy(extraPubKeys);
        }

        public byte[] GetEncoded()
        {
            var bOut = new MemoryStream();
            Encode(bOut);
            return bOut.ToArray();
        }

        public void Encode(
            Stream outStr)
        {
            if (outStr == null)
                throw new ArgumentNullException(nameof(outStr));

            foreach (PgpSecretKey key in keys)
            {
                key.Encode(outStr);
            }
            foreach (PgpPublicKey extraPubKey in extraPubKeys)
            {
                extraPubKey.Encode(outStr);
            }
        }

        /// <summary>
        /// Replace the public key set on the secret ring with the corresponding key off the public ring.
        /// </summary>
        /// <param name="secretRing">Secret ring to be changed.</param>
        /// <param name="publicRing">Public ring containing the new public key set.</param>
        public static PgpSecretKeyRing ReplacePublicKeys(PgpSecretKeyRing secretRing, PgpPublicKeyRing publicRing)
        {
            var newList = new List<PgpSecretKey>(secretRing.keys.Count);

            foreach (PgpSecretKey sk in secretRing.keys)
            {
                PgpPublicKey pk = publicRing.GetPublicKey(sk.KeyId);

                newList.Add(PgpSecretKey.ReplacePublicKey(sk, pk));
            }

            return new PgpSecretKeyRing(newList);
        }

        /// <summary>
        /// Return a copy of the passed in secret key ring, with the master key and sub keys encrypted
        /// using a new password and the passed in algorithm.
        /// </summary>
        /// <param name="ring">The <c>PgpSecretKeyRing</c> to be copied.</param>
        /// <param name="oldPassPhrase">The current password for key.</param>
        /// <param name="newPassPhrase">The new password for the key.</param>
        /// <param name="newEncAlgorithm">The algorithm to be used for the encryption.</param>
        /// <param name="rand">Source of randomness.</param>
        public static PgpSecretKeyRing CopyWithNewPassword(
            PgpSecretKeyRing			ring,
            char[]						oldPassPhrase,
            char[]						newPassPhrase,
            SymmetricKeyAlgorithmTag	newEncAlgorithm,
            SecureRandom				rand)
        {
            var newKeys = new List<PgpSecretKey>(ring.keys.Count);

            foreach (PgpSecretKey secretKey in ring.GetSecretKeys())
            {
                if (secretKey.IsPrivateKeyEmpty)
                {
                    newKeys.Add(secretKey);
                }
                else
                {
                    newKeys.Add(PgpSecretKey.CopyWithNewPassword(secretKey, oldPassPhrase, newPassPhrase,
                        newEncAlgorithm, rand));
                }
            }

            return new PgpSecretKeyRing(newKeys, ring.extraPubKeys);
        }

        /// <summary>
        /// Returns a new key ring with the secret key passed in either added or
        /// replacing an existing one with the same key ID.
        /// </summary>
        /// <param name="secRing">The secret key ring to be modified.</param>
        /// <param name="secKey">The secret key to be inserted.</param>
        /// <returns>A new <c>PgpSecretKeyRing</c></returns>
        public static PgpSecretKeyRing InsertSecretKey(
            PgpSecretKeyRing  secRing,
            PgpSecretKey      secKey)
        {
            var keys = new List<PgpSecretKey>(secRing.keys);
            bool found = false;
            bool masterFound = false;

            for (int i = 0; i != keys.Count; i++)
            {
                PgpSecretKey key = (PgpSecretKey) keys[i];

                if (key.KeyId == secKey.KeyId)
                {
                    found = true;
                    keys[i] = secKey;
                }
                if (key.IsMasterKey)
                {
                    masterFound = true;
                }
            }

            if (!found)
            {
                if (secKey.IsMasterKey)
                {
                    if (masterFound)
                        throw new ArgumentException("cannot add a master key to a ring that already has one");

                    keys.Insert(0, secKey);
                }
                else
                {
                    keys.Add(secKey);
                }
            }

            return new PgpSecretKeyRing(keys, secRing.extraPubKeys);
        }

        /// <summary>Returns a new key ring with the secret key passed in removed from the key ring.</summary>
        /// <param name="secRing">The secret key ring to be modified.</param>
        /// <param name="secKey">The secret key to be removed.</param>
        /// <returns>A new <c>PgpSecretKeyRing</c>, or null if secKey is not found.</returns>
        public static PgpSecretKeyRing RemoveSecretKey(
            PgpSecretKeyRing  secRing,
            PgpSecretKey      secKey)
        {
            var keys = new List<PgpSecretKey>(secRing.keys);
            bool found = false;

            for (int i = 0; i < keys.Count; i++)
            {
                PgpSecretKey key = (PgpSecretKey)keys[i];

                if (key.KeyId == secKey.KeyId)
                {
                    found = true;
                    keys.RemoveAt(i);
                }
            }

            return found ? new PgpSecretKeyRing(keys, secRing.extraPubKeys) : null;
        }
    }
}