using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Threading.Tasks;
using Akari.Prototype.Server.Utils;
using Microsoft.Extensions.Logging;

namespace Akari.Prototype.Server.Services
{
    public sealed class KeyManager : IKeyManager
    {
        public const string KeysPath = "Keys";
        public const int KeyLength = 256 / 8;

        private readonly ILogger<KeyManager> _logger;
        private readonly IMasterKeyService _masterKeyService;
        private readonly AkariPath _akariPath;

        public KeyManager(ILogger<KeyManager> logger, IMasterKeyService masterKeyService, AkariPath akariPath)
        {
            _logger = logger;
            _masterKeyService = masterKeyService;
            _akariPath = akariPath;

            CheckConfig();
        }

        private void CheckConfig()
        {
            string path = _akariPath.GetPath(KeysPath);

            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }
        }

        public bool AddFingerprint(string applicationName, string fingerprintName, AesGcm fingerprintKey)
        {
            if (!Directory.Exists(GetKeyDirectoryPath(applicationName)) || !_masterKeyService.TryGetKey(out var masterKey))
            {
                return false;
            }

            // Read key
            var encryptedKeyBytes = File.ReadAllBytes(GetMasterKeyPath(applicationName));

            var decryptedKeyBytes = Security.AesGcmDecrypt(masterKey, encryptedKeyBytes);

            var newEncryptedKeyBytes = Security.AesGcmEncrypt(fingerprintKey, decryptedKeyBytes);

            File.WriteAllBytes(GetKeyPath(applicationName, fingerprintName), newEncryptedKeyBytes);

            _logger.LogDebug($"Fingerprint '{fingerprintName}' added for {applicationName}");

            return true;
        }

        public void Clear(string applicationName)
        {
            _logger.LogDebug($"Deleted keys for {applicationName}");

            _logger.LogDebug($"Going to delete {GetKeyDirectoryPath(applicationName)}");
            //Directory.Delete(GetKeyDirectoryPath(applicationName));
        }

        public bool Create(string applicationName)
        {
            if (!_masterKeyService.TryGetKey(out var masterKey))
            {
                _logger.LogDebug("Can't create key if master not logged in");

                return false;
            }

            Directory.CreateDirectory(GetKeyDirectoryPath(applicationName));

            Span<byte> keyBytes = KeyLength <= 1024 ? stackalloc byte[KeyLength]
                                                                 : new byte[KeyLength];

            RandomNumberGenerator.Fill(keyBytes);

            var encryptedKeyBytes = Security.AesGcmEncrypt(masterKey, keyBytes);

            File.WriteAllBytes(GetMasterKeyPath(applicationName), encryptedKeyBytes);

            _logger.LogDebug($"Key created for {applicationName}");

            return true;
        }

        public AesGcm RetrieveKey(string applicationName, string fingerprintName, AesGcm fingerprintKey)
        {
            if (!Directory.Exists(GetKeyDirectoryPath(applicationName)))
            {
                throw new IOException($"Can't find key files for {applicationName}");
            }

            // Read key
            var encryptedKeyBytes = File.ReadAllBytes(GetKeyPath(applicationName, fingerprintName));

            var decryptedKeyBytes = Security.AesGcmDecrypt(fingerprintKey, encryptedKeyBytes);

            _logger.LogDebug($"Key retrieved for {applicationName} using {fingerprintName}");

            return new AesGcm(decryptedKeyBytes);
        }

        private string GetKeyDirectoryPath(string applicationName) => Path.Combine(_akariPath.GetPath(KeysPath), applicationName);

        private string GetMasterKeyPath(string applicationName) => Path.Combine(GetKeyDirectoryPath(applicationName), "key");

        private string GetKeyPath(string applicationName, string fingerprintName) => $"{GetMasterKeyPath(applicationName)}-{fingerprintName}";
    }
}