using System.Text.Json;
using GB5Shared.DTO.Framework.Login;
using Microsoft.AspNetCore.SignalR;
using Microsoft.Extensions.Logging;

namespace ECPSL.Communication.Hubs;

/// <summary>
/// CommunicationHub — real-time push for comment threads/replies/reactions/mentions/status
/// changes (plan's "SignalR hub" section). Hub is transient; no mutable state stored in
/// instance fields. LoginDTO is always reconstructed from the HTTP context — never accepted
/// from client payload. All business logic goes through BLL — no direct DAL access from here.
/// </summary>
public class CommunicationHub(ILogger<CommunicationHub> _logger) : Hub<ICommunicationClient>
{
    // ── Group naming ──────────────────────────────────────────────────
    private static string ObjectGroup(int objectTypeId, int objectId) => $"communication:{objectTypeId}:{objectId}";
    private static string UserGroup(int userId) => $"communication:user:{userId}";

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

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

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        try
        {
            var login = GetLoginDTO();
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, UserGroup(login.UserId));
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "CommunicationHub OnDisconnectedAsync cleanup failed for {ConnectionId}",
                Context.ConnectionId);
        }

        if (exception is not null)
            _logger.LogWarning(exception, "CommunicationHub disconnected with error: {ConnectionId}",
                Context.ConnectionId);

        await base.OnDisconnectedAsync(exception);
    }

    // ── Hub methods (all async Task, never async void) ───────────────

    /// <summary>Client calls this when opening a comment panel for a given business object.</summary>
    public async Task JoinObjectContext(int objectTypeId, int objectId)
    {
        try
        {
            await Groups.AddToGroupAsync(Context.ConnectionId, ObjectGroup(objectTypeId, objectId));
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "JoinObjectContext failed for ObjectType {ObjectTypeId} Object {ObjectId}",
                objectTypeId, objectId);
            await Clients.Caller.ReceiveError("JOIN_FAILED", "Failed to join comment context.");
        }
    }

    /// <summary>Client calls this when closing a comment panel — hygiene only; SignalR also
    /// drops all group membership automatically on disconnect.</summary>
    public async Task LeaveObjectContext(int objectTypeId, int objectId)
    {
        await Groups.RemoveFromGroupAsync(Context.ConnectionId, ObjectGroup(objectTypeId, objectId));
    }

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

    /// <summary>
    /// Reconstructs LoginDTO from the HTTP context "Login" header. Never accepts LoginDTO from
    /// client payload — that would allow impersonation.
    /// </summary>
    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 missing.");
        return JsonSerializer.Deserialize<LoginDTO>(raw)
            ?? throw new InvalidOperationException("Login header is invalid JSON.");
    }
}