using System;
using gehGassi.Core.Interfaces;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;

namespace gehGassi.Core.Services
{
    /// <summary>
    /// Service der eine Kombination aus private und public Key erstellen kann
    /// </summary>
    public class KeyGeneratorService : IKeyGeneratorService
    {
        /// <summary>
        /// Erstellt einen public und einen Private key mit Standard 1024 bit Verschlüsselung
        /// </summary>
        /// <returns>PrivateKey und Public Key</returns>
        public Tuple<string, string> GenerateKeys()
        {
            return GenerateKeys(1024);
        }

        /// <summary>
        /// Erstellt einen public und einen Private key
        /// </summary>
        /// <param name="keySize">Schlüssel Größe</param>
        /// <returns>PrivateKey und Public Key</returns>
        public Tuple<string, string> GenerateKeys(int keySize)
        {
            var secureRandom = new SecureRandom();
            return GenerateKeys(keySize, secureRandom.GenerateSeed(32));
        }

        /// <summary>
        /// Erstellt einen public und einen Private key
        /// </summary>
        /// <param name="keySize">Schlüssel Größe</param>
        /// <param name="seed">Seed</param>
        /// <returns>PrivateKey und Public Key</returns>
        public Tuple<string, string> GenerateKeys(int keySize, byte[] seed)
        {
            var generator = new RsaKeyPairGenerator();
            var secureRandom = new SecureRandom();
            secureRandom.SetSeed(seed);
            generator.Init(new KeyGenerationParameters(secureRandom, keySize));
            var pair = generator.GenerateKeyPair();

            var privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(pair.Private);
            var serializedPrivateBytes = privateKeyInfo.ToAsn1Object().GetDerEncoded();
            var serializedPrivate = Convert.ToBase64String(serializedPrivateBytes);

            var publicKeyInfo = SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(pair.Public);
            var serializedPublicBytes = publicKeyInfo.ToAsn1Object().GetDerEncoded();
            var serializedPublic = Convert.ToBase64String(serializedPublicBytes);

            return new Tuple<string, string>(serializedPrivate, serializedPublic);
        }
    }
}