Get the URL of HTTP triggered Azure Function including path/query parameters. GetUrl(nameof(FunctionClass.Run))

UrlFunctionsHelper.cs

namespace Namespace.Helpers

using Microsoft.Azure.Functions.Worker;
using Microsoft.AspNetCore.Routing.Template;
using System.Reflection;
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Routing;
using Microsoft.AspNetCore.Routing.Internal;
using Microsoft.Extensions.ObjectPool;
using System.Text.Encodings.Web;

public class UrlFunctionsHelper
{
    private static readonly Lazy<(FunctionAttribute? fnAttr, ParameterInfo[] parameters)[]> FunctionNameAttributesLazy = new (() => Assembly
        .GetExecutingAssembly()
        .GetTypes()
        .SelectMany(x => x.GetMethods())
        .Select(x => (x.GetCustomAttribute<FunctionAttribute>(), x.GetParameters()))
        .Where(x => x.Item1 is not null)
        .ToArray()
    );

    public static Uri GetUrl(string functionName, IDictionary<string, string>? routeValues = default)
    {
        var correspondingAttribute = FunctionNameAttributesLazy.Value
            .FirstOrDefault(x => x.fnAttr?.Name == functionName);

        if (correspondingAttribute.fnAttr is null)
        {
            throw new InvalidOperationException($"'{functionName}' is not a valid Azure Function, please make sure the {nameof(FunctionAttribute)} was set correctly");
        }

#if DEBUG
        const string scheme = "http";
#else
        const string scheme = "https";
#endif

        var hostname = Environment.GetEnvironmentVariable("WEBSITE_HOSTNAME");

        var httpTrigger = correspondingAttribute.parameters
            .Select(x => x.GetCustomAttribute<HttpTriggerAttribute>())
            .SingleOrDefault();

        if (httpTrigger is null)
        {
            throw new InvalidOperationException(
                $"Provided function had no parameter with attribute of type {nameof(HttpTriggerAttribute)}");
        }

        var preparedRoute = ParseRouteTemplate(httpTrigger?.Route ?? functionName, routeValues);

        return new Uri($"{scheme}://{hostname}/api{preparedRoute}");
    }

    private static string? ParseRouteTemplate(string route, IDictionary<string, string>? routeValues)
    {
        var templateRoute = TemplateParser.Parse(route);
        var pool = new DefaultObjectPoolProvider().Create(new UriBuilderContextPooledObjectPolicy());
        var templateBinder = new TemplateBinder(UrlEncoder.Default, pool, templateRoute, defaults: null);
        return templateBinder.BindValues(new RouteValueDictionary(routeValues));
    }
}