using Elsa.Authorization;
using Elsa.Diagnostics.OpenTelemetry.Contracts;
using Elsa.Diagnostics.OpenTelemetry.Models;
using Elsa.Diagnostics.OpenTelemetry.Permissions;
using FastEndpoints.Security;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;

namespace Elsa.Diagnostics.OpenTelemetry.RealTime;

[Authorize]
public class OpenTelemetryHub(OpenTelemetrySubscriptionManager subscriptionManager) : Hub<IOpenTelemetryClient>
{
    private static readonly Permission ReadOpenTelemetry = new(OpenTelemetryResourcePermissions.OpenTelemetry, CoreVerbs.View);

    public Task SubscribeAsync(OpenTelemetryTraceFilter? filter)
    {
        EnsureCanReadOpenTelemetry();
        return subscriptionManager.SubscribeAsync(Context.ConnectionId, ValidateFilter(filter), Context.ConnectionAborted);
    }

    public Task UnsubscribeAsync()
    {
        return subscriptionManager.UnsubscribeAsync(Context.ConnectionId);
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        await UnsubscribeAsync().ConfigureAwait(false);
        await base.OnDisconnectedAsync(exception).ConfigureAwait(false);
    }

    private static OpenTelemetryTraceFilter ValidateFilter(OpenTelemetryTraceFilter? filter)
    {
        filter ??= new();

        if (filter.From is { } from && filter.To is { } to && from > to)
            throw new HubException("The OpenTelemetry filter 'from' timestamp must be earlier than or equal to 'to'.");

        return filter;
    }

    private void EnsureCanReadOpenTelemetry()
    {
        var user = Context.User;

        if (user?.Identity?.IsAuthenticated != true || !PermissionEvaluator.Shared.HasPermission(user, ReadOpenTelemetry))
            throw new HubException("Access denied.");
    }
}