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

namespace RecruitmentSL.Hubs
{
    // Server-push-only hub: pipeline-stage changes on an Application (kanban board) and
    // interview-scheduling notifications to assigned interviewers. Driven entirely by
    // IHubContext pushes from ApplicationBLL/InterviewBLL via IRecruitmentHubNotifier — this
    // Hub itself defines no client-invoked RPCs (YAGNI, per CLAUDE.md's guidance for a
    // server-push-only module).
    public class RecruitmentHub : Hub<IRecruitmentClient>
    {
        private readonly ILogger<RecruitmentHub> _logger;

        public RecruitmentHub(ILogger<RecruitmentHub> logger)
        {
            _logger = logger;
        }

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

        public override async Task OnConnectedAsync()
        {
            var login = GetLoginDTO();

            // Tenant-wide group — a kanban board watching all applications for the org.
            await Groups.AddToGroupAsync(Context.ConnectionId, ClientGroup(login.ClientId));

            // Per-user group — an interviewer's personal notification stream.
            await Groups.AddToGroupAsync(Context.ConnectionId, UserGroup(login.UserId));

            _logger.LogInformation(
                "RecruitmentHub connected: {ConnectionId} user {UserId} client {ClientId}",
                Context.ConnectionId, login.UserId, login.ClientId);

            await base.OnConnectedAsync();
        }

        public override async Task OnDisconnectedAsync(Exception? exception)
        {
            var login = GetLoginDTO();

            await Groups.RemoveFromGroupAsync(Context.ConnectionId, ClientGroup(login.ClientId));
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, UserGroup(login.UserId));

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

            await base.OnDisconnectedAsync(exception);
        }

        // ── Group naming (CLAUDE.md convention) ─────────────────────────────
        // Per tenant/client: {module}:client:{clientId}
        // Per user:          {module}:user:{userId}
        public static string ClientGroup(int clientId) => $"recruitment:client:{clientId}";
        public static string UserGroup(int userId) => $"recruitment:user:{userId}";

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

        // ALWAYS reconstruct LoginDTO from the HTTP context — never accept it from a client
        // payload. This module's real per-request identity convention is the serialized "Login"
        // header (see every FastEndpoint's `[FromHeader] string Login` under
        // RecruitmentSL/EndPoints) — there is no ClaimsPrincipal-based authentication wired up
        // for this host, so a claims-based lookup would silently resolve every field to its
        // default. Mirrors FLSSL.Hubs.FlsMonitorHub.GetLoginDTO exactly.
        private LoginDTO GetLoginDTO()
        {
            var httpContext = Context.GetHttpContext()
                ?? throw new InvalidOperationException("Hub invoked outside HTTP context.");

            var raw = httpContext.Request.Headers["Login"].FirstOrDefault()
                ?? throw new InvalidOperationException("Login header missing.");

            return JsonSerializer.Deserialize<LoginDTO>(raw)
                ?? throw new InvalidOperationException("Login header is invalid JSON.");
        }
    }
}