using System;
using System.IO;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using PolyTraderSharp.Models;
using IcgSoftware.Threema.CoreMsgApi;
using IcgSoftware.Threema.CoreMsgApi.Exceptions;

namespace PolyTraderSharp.Services
{
    public class ThreemaService : BackgroundService
    {
        public event Action<string>? OnCommandReceived;

        private readonly TerminalLogger _logger;
        private ServerSettings _settings;
        private readonly string _settingsPath = "server_settings.xml";

        private readonly JobStatusRow _jobStatus;
        private HttpListener? _httpListener;
        private APIConnector? _apiConnector;

        public ThreemaService(TerminalLogger logger, JobManager jobManager)
        {
            _logger = logger;
            _settings = ServerSettings.Load(_settingsPath);

            _jobStatus = new JobStatusRow
            {
                JobName = "Threema Webhook Listener",
                Description = "Listens for incoming Threema Gateway Webhooks on the configured port.",
                StatusText = "Pending Initial Delay..."
            };

            _jobStatus.ManualTriggerAction = async () =>
            {
                _jobStatus.StatusText = "Manual trigger not supported for Webhook";
                await Task.Delay(2000);
            };

            jobManager.RegisterJob(_jobStatus);
            InitConnector();
        }

        public void ReloadSettings()
        {
            _settings = ServerSettings.Load(_settingsPath);
            InitConnector();
        }

        private void InitConnector()
        {
            if (_settings.ThreemaEnabled && !string.IsNullOrEmpty(_settings.ThreemaGatewayId) && !string.IsNullOrEmpty(_settings.ThreemaSecret))
            {
                // Initialize the pt-icg SDK APIConnector
                _apiConnector = new APIConnector(_settings.ThreemaGatewayId, _settings.ThreemaSecret, new PublicKeyStoreNone());
            }
        }

        public async Task<bool> SendMessageAsync(string text, string parseMode = "")
        {
            if (!_settings.ThreemaEnabled || _apiConnector == null)
            {
                return false;
            }

            // Using the GroupID field as the target (could be a Threema ID)
            string targetId = _settings.ThreemaGroupId;
            if (string.IsNullOrEmpty(targetId))
            {
                _logger.Error("Threema send failed: Target ID (Group ID) is not configured.");
                return false;
            }

            try
            {
                return await Task.Run(() =>
                {
                    // If no private key is configured, fallback to Basic mode (SendTextMessageSimple)
                    // Note: Basic mode does not support actual Group messaging, so targetId must be a personal Threema ID.
                    // If a private key IS configured, we would use E2E mode, but without the official 2.0 SDK's 
                    // SendGroupTextMessage, we just send a direct E2E message.
                    
                    if (string.IsNullOrEmpty(_settings.ThreemaPrivateKey))
                    {
                        string msgId = _apiConnector.SendTextMessageSimple(targetId, text);
                        if (!string.IsNullOrEmpty(msgId))
                        {
                            _logger.Info($"Threema basic message sent. ID: {msgId}");
                            return true;
                        }
                    }
                    else
                    {
                        // E2E Mode Direct Message
                        byte[] privateKey = DataUtils.HexStringToByteArray(_settings.ThreemaPrivateKey);
                        byte[] publicKey = _apiConnector.LookupKey(targetId);
                        
                        if (publicKey == null)
                        {
                            _logger.Error($"Threema E2E failed: Could not lookup public key for {targetId}");
                            return false;
                        }

                        byte[] nonce = CryptTool.RandomNonce();
                        var encryptResult = CryptTool.EncryptTextMessage(text, privateKey, publicKey);
                        
                        if (encryptResult != null && encryptResult.Result != null)
                        {
                            byte[] box = encryptResult.Result;
                            string msgId = _apiConnector.SendE2EMessage(targetId, encryptResult.Nonce, box);
                            if (!string.IsNullOrEmpty(msgId))
                            {
                                _logger.Info($"Threema E2E message sent. ID: {msgId}");
                                return true;
                            }
                        }
                    }
                    return false;
                });
            }
            catch (Exception ex)
            {
                _logger.Error($"Threema send failed: {ex.Message}");
                return false;
            }
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            _jobStatus.StatusText = "Idle";

            while (!stoppingToken.IsCancellationRequested)
            {
                if (!_settings.ThreemaEnabled || !_jobStatus.IsEnabled)
                {
                    _jobStatus.StatusText = "Paused / Disabled";
                    if (_httpListener != null && _httpListener.IsListening)
                    {
                        _httpListener.Stop();
                    }
                    await Task.Delay(5000, stoppingToken);
                    continue;
                }
                
                try
                {
                    if (_httpListener == null || !_httpListener.IsListening)
                    {
                        _httpListener = new HttpListener();
                        _httpListener.Prefixes.Add($"http://*:{_settings.ThreemaWebhookPort}/");
                        _httpListener.Start();
                        _jobStatus.StatusText = $"Listening on port {_settings.ThreemaWebhookPort}...";
                        _logger.Info($"[Threema] Webhook listener started on port {_settings.ThreemaWebhookPort}");
                    }

                    _jobStatus.LastRun = DateTime.Now;

                    var getContextTask = _httpListener.GetContextAsync();
                    var delayTask = Task.Delay(5000, stoppingToken);

                    var completedTask = await Task.WhenAny(getContextTask, delayTask);

                    if (completedTask == getContextTask)
                    {
                        var context = await getContextTask;
                        _ = Task.Run(() => HandleIncomingWebhook(context), stoppingToken);
                    }
                }
                catch (TaskCanceledException) { }
                catch (Exception ex)
                {
                    if (ex is HttpListenerException hle && hle.ErrorCode == 5)
                    {
                        _logger.Error($"[Threema] Access Denied starting Webhook. Try running as Administrator or run: netsh http add urlacl url=http://*:{_settings.ThreemaWebhookPort}/ user=Everyone");
                    }
                    else
                    {
                        _logger.Error($"[Threema] Listener error: {ex.Message}");
                    }
                    
                    _jobStatus.StatusText = "Error! Retrying in 5s...";
                    if (_httpListener != null)
                    {
                        try { _httpListener.Close(); } catch { }
                        _httpListener = null;
                    }
                    await Task.Delay(5000, stoppingToken);
                }

                _jobStatus.NextRun = DateTime.Now;
            }

            if (_httpListener != null)
            {
                try { _httpListener.Close(); } catch { }
            }
        }

        private void HandleIncomingWebhook(HttpListenerContext context)
        {
            try
            {
                var request = context.Request;
                var response = context.Response;

                if (request.HttpMethod == "POST")
                {
                    using (var reader = new StreamReader(request.InputStream, request.ContentEncoding))
                    {
                        string body = reader.ReadToEnd();
                        var parsedParams = System.Web.HttpUtility.ParseQueryString(body);

                        string? from = parsedParams["from"];
                        string? to = parsedParams["to"];
                        string? nonceStr = parsedParams["nonce"];
                        string? boxStr = parsedParams["box"];
                        string? macStr = parsedParams["mac"];

                        // Decrypt the message if E2E
                        if (!string.IsNullOrEmpty(from) && !string.IsNullOrEmpty(nonceStr) && !string.IsNullOrEmpty(boxStr) && !string.IsNullOrEmpty(_settings.ThreemaPrivateKey) && _apiConnector != null)
                        {
                            try
                            {
                                byte[] privateKey = DataUtils.HexStringToByteArray(_settings.ThreemaPrivateKey);
                                byte[] publicKey = _apiConnector.LookupKey(from);
                                byte[] nonce = DataUtils.HexStringToByteArray(nonceStr);
                                byte[] box = DataUtils.HexStringToByteArray(boxStr);

                                if (publicKey != null)
                                {
                                    var msg = CryptTool.DecryptMessage(box, privateKey, publicKey, nonce);
                                    if (msg is IcgSoftware.Threema.CoreMsgApi.Messages.TextMessage textMsg)
                                    {
                                        string text = textMsg.Text;
                                        string logText = text.Length > 200 ? text.Substring(0, 200) + "..." : text;
                                        _logger.Info($"[Threema] Empfangen von {from}: {logText}");
                                        
                                        if (text.StartsWith("/"))
                                        {
                                            OnCommandReceived?.Invoke(text);
                                        }
                                    }
                                }
                            }
                            catch (Exception dex)
                            {
                                _logger.Warning($"[Threema] Failed to decrypt incoming message: {dex.Message}");
                            }
                        }
                        else
                        {
                            _logger.Info($"[Threema] Received webhook, but cannot process (Basic mode doesn't support incoming, or missing E2E keys).");
                        }
                    }
                }

                response.StatusCode = 200;
                response.Close();
            }
            catch (Exception ex)
            {
                _logger.Error($"[Threema] Webhook handling error: {ex.Message}");
            }
        }
    }
}