using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using API_NetFramework.Models;
using Swashbuckle.Application;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using System.Web;
using System.Web.Configuration;

namespace SecuringWebApiUsingApiKey.Middleware
{
    public static class StringCipher
    {
        // This constant is used to determine the keysize of the encryption algorithm in bits.
        // We divide this by 8 within the code below to get the equivalent number of bytes.
        private const int Keysize = 256;

        // This constant determines the number of iterations for the password bytes generation function.
        private const int DerivationIterations = 1000;

        public static string Encrypt(string plainText, string passPhrase)
        {
            // Salt and IV is randomly generated each time, but is preprended to encrypted cipher text
            // so that the same Salt and IV values can be used when decrypting.  
            var saltStringBytes = Generate256BitsOfRandomEntropy();
            var ivStringBytes = Generate256BitsOfRandomEntropy();
            var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
            using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
            {
                var keyBytes = password.GetBytes(Keysize / 8);
                using (var symmetricKey = new RijndaelManaged())
                {
                    symmetricKey.BlockSize = 256;
                    symmetricKey.Mode = CipherMode.CBC;
                    symmetricKey.Padding = PaddingMode.PKCS7;
                    using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
                    {
                        using (var memoryStream = new MemoryStream())
                        {
                            using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                            {
                                cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                                cryptoStream.FlushFinalBlock();
                                // Create the final bytes as a concatenation of the random salt bytes, the random iv bytes and the cipher bytes.
                                var cipherTextBytes = saltStringBytes;
                                cipherTextBytes = cipherTextBytes.Concat(ivStringBytes).ToArray();
                                cipherTextBytes = cipherTextBytes.Concat(memoryStream.ToArray()).ToArray();
                                memoryStream.Close();
                                cryptoStream.Close();
                                return Convert.ToBase64String(cipherTextBytes);
                            }
                        }
                    }
                }
            }
        }

        public static string Decrypt(string cipherText, string passPhrase)
        {
            // Get the complete stream of bytes that represent:
            // [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]
            var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);
            // Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.
            var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();
            // Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.
            var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();
            // Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.
            var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();

            using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
            {
                var keyBytes = password.GetBytes(Keysize / 8);
                using (var symmetricKey = new RijndaelManaged())
                {
                    symmetricKey.BlockSize = 256;
                    symmetricKey.Mode = CipherMode.CBC;
                    symmetricKey.Padding = PaddingMode.PKCS7;
                    using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))
                    {
                        using (var memoryStream = new MemoryStream(cipherTextBytes))
                        {
                            using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                            using (var streamReader = new StreamReader(cryptoStream, Encoding.UTF8))
                            {
                                return streamReader.ReadToEnd();
                            }
                        }
                    }
                }
            }
        }

        private static byte[] Generate256BitsOfRandomEntropy()
        {
            var randomBytes = new byte[32]; // 32 Bytes will give us 256 bits.
            using (var rngCsp = new RNGCryptoServiceProvider())
            {
                // Fill the array with cryptographically secure random bytes.
                rngCsp.GetBytes(randomBytes);
            }
            return randomBytes;
        }
    }
    public static class ApiKeyMiddleware
    {
        public static string[] apikeys;
        
        public static string GetValue( string key)
        {
            string res = WebConfigurationManager.AppSettings[key];
            return res;
        }

        private static bool checkfunction(string apikey, string function)
        {
            string decryptstring = SecuringWebApiUsingApiKey.Middleware.StringCipher.Decrypt(apikey, "OnDoc01");
            if ( decryptstring.Contains(function))
                { return true; }
            else return false;
        }
        public static Boolean Authorized(HttpRequestMessage request, string function)
        {
            
            if (GetValue("AuthCheck") == "Yes")
            {
                apikeys = GetValue("APIKeys").ToString().Split(',');
                for (int i = 0; i < apikeys.Length; i++)
                {
                    apikeys[i] = apikeys[i].Replace(Environment.NewLine, "");
                }
                IEnumerable<KeyValuePair<string, string>> queryParams = request.GetQueryNameValuePairs();
                var key = queryParams.FirstOrDefault(x => x.Key == "api_key");
                if (apikeys.Contains(key.Value) && checkfunction(key.Value,function)==true) { return true; }
                try
                {
                    IEnumerable<string> headerValues = request.Headers.GetValues("api_key");
                    string apikey = headerValues.FirstOrDefault();
                   
                    if (apikeys.Contains(apikey) && checkfunction(apikey,function)==true) { return true; }
                }
                catch { }
                try
                {
                    if (request.Headers.Authorization.Scheme == "Bearer" && apikeys.Contains(request.Headers.Authorization.Parameter.ToString()) && checkfunction(request.Headers.Authorization.Parameter.ToString(),function)==true)
                    {
                        return true;
                    }
                }
                catch {
                    APILogging.Log(request, "Unberechtigter Zugriff", LogLevelType.Error);
                    return false; }
            }
            APILogging.Log(request, "Unberechtigter Zugriff", LogLevelType.Error);
            return false;
        }
        //private readonly RequestDelegate _next;
        //private const string APIKEYNAME = "ApiKey";
        //public ApiKeyMiddleware(RequestDelegate next)
        //{
        //    _next = next;
        //}
        //public async Task InvokeAsync(Microsoft.AspNetCore.Http.HttpContext context)
        //{
        //    var appSettings = context.RequestServices.GetRequiredService<IConfiguration>();
        //    string apiCheck = GetValue("ApiCheck");
        //    if (apiCheck == "e913aab4-c2c5-4e33-ad24-d25848f748e7")
        //    {
        //        await _next(context);
        //        return;
        //    }
        //    if (!context.Request.Headers.TryGetValue(APIKEYNAME, out var extractedApiKey))
        //    {
        //        context.Response.StatusCode = 401;
        //        await context.Response.WriteAsync("Api Key was not provided. (Using ApiKeyMiddleware) ");
        //        return;
        //    }



        //    var apiKey = GetValue(APIKEYNAME);
        //    string[] keys =  apiKey.Split(',');

        //    bool tokenok = false;
        //    for (int i = 0; i < keys.Length; i++)
        //        if (keys[i] == extractedApiKey)
        //        {
        //            tokenok = true;
        //            break;
        //        }

        //    //if (!apiKey.Equals(extractedApiKey))
        //    if (!tokenok)
        //    {
        //        context.Response.StatusCode = 401;
        //        await context.Response.WriteAsync
        //              ("Unauthorized client. (Using ApiKeyMiddleware)");
        //        return;
        //    }

        //    await _next(context);
        //}
    }
}