using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using FrameworkBLL.EIPConversation.EIPHandlers.EIPConversationBLL;
using FrameworkDAL.DTO.EIPConversation;
using GB5Shared.DTO.Framework.Login;
using Microsoft.AspNetCore.SignalR;
using Microsoft.Extensions.Logging;

namespace FrameworkSL.Hubs.EIPChat
{
    // ============================================================
    // EIPChatHub — bidirectional SignalR hub for the AppChat channel.
    //
    // Architecture:
    //   • Client calls SendMessage(...) → hub runs full EIP pipeline
    //     via IEIPConversationBLL → response pushed back to the
    //     user's group via ReceiveBotMessage.
    //   • AppChatChannelHandler (BLL layer) is a no-op so the response
    //     engine does not fail; actual delivery is handled here.
    //   • Typing indicator is pushed before and after processing so
    //     the UI can show "bot is typing…".
    //
    // Group convention:
    //   "appchat:user:{userId}:client:{clientId}" — identity-scoped;
    //   survives reconnects and spans multiple browser tabs.
    //
    // LoginDTO:
    //   ALWAYS reconstructed from Context.GetHttpContext() HTTP headers.
    //   NEVER accepted from client payload.
    //
    // Registration (Program.cs):
    //   app.MapHub<EIPChatHub>("/hubs/eip-chat");
    // ============================================================
    public class EIPChatHub : Hub<IEIPChatClient>
    {
        private readonly IEIPConversationBLL _bll;
        private readonly ILogger<EIPChatHub> _logger;

        public EIPChatHub(IEIPConversationBLL bll, ILogger<EIPChatHub> logger)
        {
            _bll    = bll    ?? throw new ArgumentNullException(nameof(bll));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        }

        // ── Group naming ──────────────────────────────────────────────────────────

        public static string UserGroup(int userId, int clientId)
            => $"appchat:user:{userId}:client:{clientId}";

        // ── Connection lifecycle ──────────────────────────────────────────────────

        public override async Task OnConnectedAsync()
        {
            var login = GetLoginDTO();
            var group = UserGroup(login.UserId, login.ClientId);
            await Groups.AddToGroupAsync(Context.ConnectionId, group);
            _logger.LogInformation(
                "EIPChatHub connected: {ConnectionId} user {UserId} tenant {ClientId}",
                Context.ConnectionId, login.UserId, login.ClientId);
            await base.OnConnectedAsync();
        }

        public override async Task OnDisconnectedAsync(Exception? exception)
        {
            var login = GetLoginDTO();
            var group = UserGroup(login.UserId, login.ClientId);
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, group);
            if (exception is not null)
                _logger.LogWarning(exception,
                    "EIPChatHub disconnected with error: {ConnectionId}", Context.ConnectionId);
            await base.OnDisconnectedAsync(exception);
        }

        // ── Hub methods ───────────────────────────────────────────────────────────

        /// <summary>
        /// Processes a user message through the full EIP conversation pipeline and pushes
        /// the bot response back to the user's group via ReceiveBotMessage.
        /// </summary>
        public async Task SendMessage(string message, string? flowCode)
        {
            var ct    = Context.ConnectionAborted;
            var login = GetLoginDTO();
            var group = UserGroup(login.UserId, login.ClientId);

            try
            {
                await Clients.Group(group).ReceiveTypingIndicator(true);

                var payload = new EIPConversationDTO
                {
                    Message        = message,
                    Platform       = "APPCHAT",
                    Channel        = "APPCHAT",
                    ChannelType    = EIPChannelType.AppChat,
                    UserIdentifier = group,
                    TenantId       = login.ClientId,
                    FlowCode       = flowCode ?? string.Empty,
                    ConversationId = 0
                };

                var result = await _bll.HandleIncomingConversationAsync(payload, login, ct)
                    .ConfigureAwait(false);

                await Clients.Group(group).ReceiveTypingIndicator(false);

                if (!result.IsSuccess)
                {
                    await Clients.Group(group).ReceiveError(
                        result.ErrorMessage ?? "An error occurred processing your request.");
                    return;
                }

                await Clients.Group(group).ReceiveBotMessage(new EIPChatMessageDTO
                {
                    Message         = result.ResponseMessage,
                    CurrentStepCode = result.CurrentStepCode,
                    NextStepCode    = result.NextStepCode,
                    IsCompleted     = result.IsCompleted,
                    StructuredData  = result.StructuredData,
                    QrCodeData      = result.QrCodeData,
                    InputHint       = result.InputHint,
                    RatingMax       = result.RatingMax,
                    RequestLocation = result.RequestLocation,
                    Buttons         = result.Buttons?.Count > 0 ? result.Buttons : null
                });
            }
            catch (OperationCanceledException)
            {
                _logger.LogInformation("EIPChatHub.SendMessage cancelled: {ConnectionId}",
                    Context.ConnectionId);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex,
                    "EIPChatHub.SendMessage failed for user {UserId} tenant {ClientId}",
                    login.UserId, login.ClientId);

                try
                {
                    await Clients.Group(group).ReceiveTypingIndicator(false);
                    await Clients.Group(group).ReceiveError("An error occurred. Please try again.");
                }
                catch
                {
                    // Best-effort cleanup — connection may be gone
                }
            }
        }

        // ── Helper ────────────────────────────────────────────────────────────────

        private LoginDTO GetLoginDTO()
        {
            var http = Context.GetHttpContext()
                ?? throw new InvalidOperationException("Hub invoked outside HTTP context.");
            var raw  = http.Request.Headers["Login"].FirstOrDefault()
                ?? throw new InvalidOperationException("Login header is missing.");
            return System.Text.Json.JsonSerializer.Deserialize<LoginDTO>(raw)
                ?? throw new InvalidOperationException("Login header contains invalid JSON.");
        }
    }
}