using ServiceShared.Crypto;
using ServiceShared.Models.Request;
using ServiceShared.Models.Response;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Security;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

namespace ServiceShared.Https
{
    public static class Request
    {
        /// <summary>
        /// Header filter AES key, value and User-Agent
        /// </summary>
        internal static readonly string HeaderSecureHash = "3HzKQw/&>*VH^?cAR{Qd5pP~6w(V5%aZ";
        internal static readonly string HeaderValueSecureHash = "7*R3P!f:sC4Q8XS:@*J/z:4/sS;V3GnM"; 
        private static readonly string TrustedUserAgent = "BefundApp";

        /// <summary>
        /// Sends https request to the server
        /// </summary>
        /// <typeparam name="T">Type of return object</typeparam>
        /// <param name="host">host of server</param>
        /// <param name="controller">controller of request</param>
        /// <param name="action">action of request</param>
        /// <param name="request">encrypted request, that should be signed and sent</param>
        /// <param name="keyPair">keyPair for encryption/decryption/signing(optional)</param>
        /// <returns>Returns given typed object</returns>
        public static T? Post<T>(string host, string controller, string action, EncryptedRequest request, KeyPair keyPair = null)
        {
            object? result = null;

            try
            {
                string json = Post(host, controller, action, request, keyPair);

                if(!string.IsNullOrEmpty(json))
                {
                    result = JsonSerializer.Deserialize<T>(json, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceShared.Https.Request", "Post<T>(string, string, string, EncryptedRequest, KeyPair");
            }
           
            return (T?)result;
        }

        /// <summary>
        /// Gets Public Key of server
        /// </summary>
        /// <param name="host">host of server</param>
        /// <param name="controller">exchange controller of server(default exchange)</param>
        /// <param name="action">exchange action of controller(default key)</param>
        /// <param name="keyPair">keyPair for encryption/decryption/signing(optional)</param>
        /// <returns>Returns given typed object</returns>
        public static PublicKey GetPublicKey(string host, string controller = "exchange", string action = "key", KeyPair keyPair = null)
        {
            PublicKey result = null;

            try
            {
                string json = Post(host, controller, action, keyPair);

                if (!string.IsNullOrEmpty(json))
                {
                    result = JsonSerializer.Deserialize<PublicKey>(json, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceShared.Https.Request", "GetPublicKey(string, string, string, KeyPair");
            }

            return result;
        }

        /// <summary>
        /// Sends https request to the server
        /// </summary>
        /// <param name="host">host of server</param>
        /// <param name="controller">exchange controller of server(default exchange)</param>
        /// <param name="action">exchange action of controller(default key)</param>
        /// <param name="keyPair">keyPair for encryption/decryption/signing(optional)</param>
        /// <returns>Returns response as string</returns>
        public static string Post(string host, string controller, string action, KeyPair keyPair = null)
        {
            string result = null;

            try
            {
                if (keyPair == null)
                {
                    keyPair = Curve25519.GenerateKeyPair();
                }

                string requestUrl = "https://" + host.Replace("https://", "").Replace("http://", "").TrimEnd('/') + "/" + controller + "/" + action;

                HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(requestUrl);

                string json = JsonSerializer.Serialize(new KeyExchange(), new JsonSerializerOptions
                {
                    PropertyNameCaseInsensitive = true
                });

                webRequest.Method = "POST";
                webRequest.Headers.Add("User-Agent", TrustedUserAgent);
                webRequest.Headers.Add("Client-Hash", AES.Encrypt(HeaderValueSecureHash, AES.GetKey(HeaderSecureHash)));
                webRequest.Headers.Add("Client-Key", keyPair.PublicKey);
                webRequest.Headers.Add("Content-Type", "application/json");
                webRequest.ContentType = "application/json";
                webRequest.ContentLength = json.Length;

                webRequest.ServerCertificateValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; };

                using (Stream stream = webRequest.GetRequestStream())
                {
                    byte[] data = Encoding.UTF8.GetBytes(json);
                    stream.Write(data, 0, data.Length);
                }

                Log.Debug("[REQUEST]: " + json);
                WebResponse response = (HttpWebResponse)webRequest.GetResponse();
                result = new StreamReader(response.GetResponseStream()).ReadToEnd();
                Log.Debug("[RESPONSE]: " + result);
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceShared.Https.Request", "Post(string, string, string, KeyPair)");
            }

            return result;
        }

        /// <summary>
        /// Sends https request to the server
        /// </summary>
        /// <param name="host">host of server</param>
        /// <param name="controller">controller of request</param>
        /// <param name="action">action of request</param>
        /// <param name="request">encrypted request, that should be signed and sent</param>
        /// <param name="keyPair">keyPair for encryption/decryption/signing(optional)</param>
        /// <returns>Returns response as string</returns>
        public static string Post(string host, string controller, string action, EncryptedRequest request, KeyPair keyPair = null)
        {
            string result = null;

            try
            {
                if(request != null && !string.IsNullOrEmpty(request.encrypted_content))
                {
                    if (keyPair == null)
                    {
                        keyPair = Curve25519.GenerateKeyPair();
                    }

                    string requestUrl = "https://" + host.Replace("https://", "").Replace("http://", "").TrimEnd('/') + "/" + controller + "/" + action;

                    HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(requestUrl);

                    string json = JsonSerializer.Serialize(request, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });

                    webRequest.Method = "POST";
                    webRequest.Headers.Add("User-Agent", TrustedUserAgent);
                    webRequest.Headers.Add("Client-Hash", AES.Encrypt(HeaderValueSecureHash, AES.GetKey(HeaderSecureHash)));
                    webRequest.Headers.Add("Client-Key", keyPair.PublicKey);
                    webRequest.Headers.Add("Client-Signature", keyPair.GetSignature((!string.IsNullOrEmpty(request.encrypted_content) ? request.encrypted_content : request.descriptor)));
                    webRequest.Headers.Add("Client-Signature-Key", keyPair.SigningPublicKey);
                    webRequest.Headers.Add("Content-Type", "application/json");
                    webRequest.ContentType = "application/json";
                    webRequest.ContentLength = json.Length;
                    webRequest.ServerCertificateValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; };

                    using (Stream stream = webRequest.GetRequestStream())
                    {
                        byte[] data = Encoding.UTF8.GetBytes(json);
                        stream.Write(data, 0, data.Length);
                    }

                    Log.Debug("[REQUEST]: " + json);
                    WebResponse response = (HttpWebResponse)webRequest.GetResponse();
                    result = new StreamReader(response.GetResponseStream()).ReadToEnd();
                    Log.Debug("[RESPONSE]: " + result);
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceShared.Https.Request", "Post(string, string, string, EncryptedRequest, KeyPair)");
            }

            return result;
        }

        /// <summary>
        /// Sends https request to the server and does not wait for response
        /// </summary>
        /// <param name="host">host of server</param>
        /// <param name="controller">controller of request</param>
        /// <param name="action">action of request</param>
        /// <param name="request">encrypted request, that should be signed and sent</param>
        /// <param name="keyPair">keyPair for encryption/decryption/signing(optional)</param>
        /// <returns>Returns response as string</returns>
        public static async Task PostWithoutResponse(string host, string controller, string action, EncryptedRequest request, KeyPair keyPair = null)
        {
            try
            {
                if (request != null && !string.IsNullOrEmpty(request.encrypted_content))
                {
                    if (keyPair == null)
                    {
                        keyPair = Curve25519.GenerateKeyPair();
                    }

                    string requestUrl = "https://" + host.Replace("https://", "").Replace("http://", "").TrimEnd('/') + "/" + controller + "/" + action;

                    HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(requestUrl);

                    string json = JsonSerializer.Serialize(request, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });

                    webRequest.Method = "POST";
                    webRequest.Headers.Add("User-Agent", TrustedUserAgent);
                    webRequest.Headers.Add("Client-Hash", AES.Encrypt(HeaderValueSecureHash, AES.GetKey(HeaderSecureHash)));
                    webRequest.Headers.Add("Client-Key", keyPair.PublicKey);
                    webRequest.Headers.Add("Client-Signature", keyPair.GetSignature((!string.IsNullOrEmpty(request.encrypted_content) ? request.encrypted_content : request.descriptor)));
                    webRequest.Headers.Add("Client-Signature-Key", keyPair.SigningPublicKey);
                    webRequest.Headers.Add("Content-Type", "application/json");
                    webRequest.ContentType = "application/json";
                    webRequest.ContentLength = json.Length;
                    webRequest.ServerCertificateValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; };

                    using (Stream stream = webRequest.GetRequestStream())
                    {
                        byte[] data = Encoding.UTF8.GetBytes(json);
                        stream.Write(data, 0, data.Length);
                        stream.Flush();
                        stream.Close();
                        webRequest.GetResponseAsync();
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Error(ex, "ServiceShared.Https.Request", "PostWithoutResponse(string, string, string, EncryptedRequest, KeyPair)");
            }
        }

        /// <summary>
        /// Validates user agent
        /// </summary>
        /// <param name="userAgent">User-Agent from header, that should be validated</param>
        /// <returns>returns true if User-Agent is valid</returns>
        public static bool ValidUserAgent(string userAgent)
        {
            return (!string.IsNullOrEmpty(userAgent) && userAgent == TrustedUserAgent);
        }

        /// <summary>
        /// Validates header hash with AES key
        /// </summary>
        /// <param name="headerHash">header hash of client, that should be validated</param>
        /// <returns>returns true if header hash is valid</returns>
        public static bool ValidHeaderHash(string headerHash)
        {
            return (!string.IsNullOrEmpty(headerHash) && AES.Decrypt(headerHash, AES.GetKey(HeaderSecureHash)) == HeaderValueSecureHash);
        }

        /// <summary>
        /// Returns Header Value Secure Hash for Trusted Response(Signature)
        /// </summary>
        /// <returns></returns>
        public static string GeServerHeaderValueSecureHash()
        {
            return HeaderValueSecureHash;
        }

        /// <summary>
        /// Returns Header Secure Hash for Trusted Response
        /// </summary>
        /// <returns></returns>
        public static string GeServerHash()
        {
            return AES.Encrypt(HeaderValueSecureHash, AES.GetKey(HeaderSecureHash));
        }
    }
}