ASP.NET Core tag helper for Sentry

SentryTagHelper.cs

namespace Website.TagHelpers
{
    using System.Security.Claims;
    using System.Text;
    using System.Text.Encodings.Web;

    using Microsoft.AspNetCore.Mvc.Rendering;
    using Microsoft.AspNetCore.Mvc.ViewFeatures;
    using Microsoft.AspNetCore.Razor.TagHelpers;
    using Microsoft.Extensions.Options;

    using Sentry;
    using Sentry.AspNetCore;

    [HtmlTargetElement("head")]
    public class SentryTagHelper : TagHelper
    {
        // ToDo: try to get this added to SentryAspNetCoreOptions so it can be easily injected
        private const string SentryVersion = "3.26.4";

        private readonly IHtmlHelper _htmlHelper;
        private readonly IHub _sentry;
        private readonly JavaScriptEncoder _encoder;
        private readonly SentryAspNetCoreOptions _settings;

        public SentryTagHelper(
            IHtmlHelper htmlHelper,
            IHub sentry,
            JavaScriptEncoder encoder,
            IOptions<SentryAspNetCoreOptions> settings)
        {
            _htmlHelper = htmlHelper ?? throw new ArgumentNullException(nameof(htmlHelper));
            _sentry = sentry ?? throw new ArgumentNullException(nameof(sentry));
            _encoder = encoder ?? throw new ArgumentNullException(nameof(encoder));
            _settings = settings?.Value ?? throw new ArgumentNullException(nameof(settings));
        }

        public override int Order => 1;

        [ViewContext]
        public ViewContext ViewContext { get; set; }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (!_sentry.IsEnabled)
            {
                return;
            }

            ((IViewContextAware) _htmlHelper).Contextualize(ViewContext);

            var js = new StringBuilder();

            js.AppendLine("window.SENTRY_SDK = {");
            js.AppendFormat("    url: 'https://cdn.ravenjs.com/{0}/raven.min.js',", _encoder.Encode(SentryVersion)).AppendLine();
            js.AppendFormat("    dsn: '{0}',", _encoder.Encode(_settings.Dsn)).AppendLine();
            js.AppendLine("    options: {");
            js.AppendFormat("        environment: '{0}',", _encoder.Encode(_settings.Environment ?? string.Empty)).AppendLine();
            js.AppendFormat("        release: '{0}'", _encoder.Encode(_settings.Release ?? string.Empty)).AppendLine();
            js.AppendLine("    }");

            if (ViewContext.HttpContext?.User?.Identity is ClaimsIdentity identity && identity.IsAuthenticated)
            {
                var email = identity.FindFirst(ClaimTypes.Email)?.Value;
                var firstName = identity.FindFirst(ClaimTypes.GivenName)?.Value;
                var lastName = identity.FindFirst(ClaimTypes.Surname)?.Value;

                js.AppendLine("    , setup: function() {");
                js.AppendLine("        Raven.setUserContext({");
                js.AppendFormat("            id: '{0}',", _encoder.Encode(identity.Name));
                js.AppendFormat("            username: '{0}',", _encoder.Encode($"{firstName} {lastName}"));
                js.AppendFormat("            email: '{0}'", _encoder.Encode(email));
                js.Append("        });");
                js.Append("    }");
            }

            js.AppendLine("};");

            // This MUST be added immediately after the .install() call: 'undefined'!=typeof k.setup&&k.setup();
            js.AppendLine("(function(a,b,g,e,h){var k=a.SENTRY_SDK,f=function(a){f.data.push(a)};f.data=[];var l=a[e];a[e]=function(c,b,e,d,h){f({e:[].slice.call(arguments)});l&&l.apply(a,arguments)};var m=a[h];a[h]=function(c){f({p:c.reason});m&&m.apply(a,arguments)};var n=b.getElementsByTagName(g)[0];b=b.createElement(g);b.src=k.url;b.crossorigin=\"anonymous\";b.addEventListener(\"load\",function(){try{a[e]=l;a[h]=m;var c=f.data,b=a.Raven;b.config(k.dsn,k.options).install();'undefined'!=typeof k.setup&&k.setup();var g=a[e];if(c.length)for(var d=0;d<c.length;d++)c[d].e?g.apply(b.TraceKit,c[d].e):c[d].p&&b.captureException(c[d].p)}catch(p){console.log(p)}});n.parentNode.insertBefore(b,n)})(window,document,\"script\",\"onerror\",\"onunhandledrejection\");");

            var tag = new TagBuilder("script");
            tag.InnerHtml.AppendHtml(js.ToString());

            output.PostContent.AppendHtml(tag);
        }
    }
}