fetchUserIds.cs

using System.Net.Http.Headers;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

public class FetchUserIds
{

    private readonly ILogger<FetchUserIds> _logger;

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

    [Function("FetchUserIds")]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", Route = "FetchUserIds/{product}")] HttpRequest req,
        string product)
    {
        _logger.LogInformation("C# HTTP trigger function processed a request.");

        if (string.IsNullOrEmpty(product))
        {
            string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            dynamic data = JsonConvert.DeserializeObject(requestBody);
            product = data?.product;
        }

        if (!string.IsNullOrEmpty(product))
        {
            var azureToken = await GetAzureAccessTokenAsync();
            if (string.IsNullOrEmpty(azureToken))
            {
                return new BadRequestObjectResult("Failed to acquire Azure access token.");
            }

            var subscriptionId = Environment.GetEnvironmentVariable("SUB_ID");
            var resourceGroup = Environment.GetEnvironmentVariable("RG");
            var apimName = Environment.GetEnvironmentVariable("APIM_NAME");
            var ownerId = await GetProductSubscriptionOwnerIdAsync(azureToken, subscriptionId, resourceGroup, apimName, product, _logger);
            if (string.IsNullOrEmpty(ownerId))
            {
                return new NotFoundObjectResult($"Product '{product}' not found ");
            }

            return new OkObjectResult(ownerId);
        }
        else
        {
            return null;
        }
    }
    private static async Task<string> GetAzureAccessTokenAsync()
    {
        string clientId = Environment.GetEnvironmentVariable("CLIENT_ID");
        string clientSecret = Environment.GetEnvironmentVariable("CLIENT_SECRET");
        string tenantId = Environment.GetEnvironmentVariable("TENANT_ID");

        var httpClient = new HttpClient();

        var tokenEndpoint = $"https://login.microsoftonline.com/{tenantId}/oauth2/token";
        var tokenRequestBody = $"grant_type=client_credentials&client_id={clientId}&client_secret={clientSecret}&resource=https://management.azure.com/";

        var tokenRequest = new HttpRequestMessage(HttpMethod.Post, tokenEndpoint)
        {
            Content = new StringContent(tokenRequestBody, System.Text.Encoding.UTF8, "application/x-www-form-urlencoded")
        };

        var tokenResponse = await httpClient.SendAsync(tokenRequest);
        if (!tokenResponse.IsSuccessStatusCode)
        {
            return null;
        }

        var responseBody = await tokenResponse.Content.ReadAsStringAsync();
        dynamic tokenData = Newtonsoft.Json.JsonConvert.DeserializeObject(responseBody);
        string accessToken = tokenData?.access_token;

        return accessToken;
    }

    private static List<string> handleUserIds(string responseBody, string product, List<String> users )
     {
        var subscriptions = JsonConvert.DeserializeObject<SubscriptionListResult>(responseBody);
        var subProducts = subscriptions?.Value?.FindAll(s => s.properties.scope.Contains(product));
        if (subProducts != null)
        {
            foreach (Subscription sub in subProducts)
            {
                int i = sub.properties.OwnerId.LastIndexOf('/');
                if(i >= 0 && i < sub.properties.OwnerId.Length) {
                    string id = sub.properties.OwnerId.Substring(i + 1);
                    users.Add(id);
                }
            }
        }
        return users;
    }

    private static async Task<List<string>> handleResponse(string response, string product, List<String> users, HttpClient client, ILogger log)
    {
        handleUserIds(response, product, users);
        JObject jsonObj = JObject.Parse(response);
        string nextLink = (string)jsonObj["nextLink"];
        if(!string.IsNullOrEmpty(nextLink)) {
            var newResponse = await client.GetAsync(nextLink);

            if( newResponse.IsSuccessStatusCode) {
                var responseBody = await newResponse.Content.ReadAsStringAsync();
               return await handleResponse(responseBody, product, users, client, log);
            }
        }
        return users;
    }
    private static async Task<string> GetProductSubscriptionOwnerIdAsync(string azureToken, string subscriptionId, string resourceGroup, string apimName, string product, ILogger log)
    {
        List<String> returnStr = new List<string>();
        using (var client = new HttpClient())
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", azureToken);

            var apiUrl = $"https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroup}/providers/Microsoft.ApiManagement/service/{apimName}/subscriptions?api-version=2020-06-01-preview";
            var response = await client.GetAsync(apiUrl);

            if (response.IsSuccessStatusCode)
            {
                var responseBody = await response.Content.ReadAsStringAsync();
                returnStr = await handleResponse(responseBody, product, returnStr, client, log);
                return JsonConvert.SerializeObject(returnStr);

            }

            return null;
        }
    }
}
    public class Subscription
    {
        public string type {get; set;}
        public string name {get; set;}

        public string id {get; set;}
        public Properties properties { get; set; }
    }

    public class Properties
    {
     public string OwnerId {get; set;}
     public string scope {get; set;}
     public string displayName {get; set;}
     public string state {get; set;}
     public string createdDate {get; set;}
     public string startDate {get; set;}
     public string expirationDate {get; set;}
     public string endDate {get; set;}
     public string notificationDate {get; set;}
     public string stateComment {get; set;}
     public string allowTracing {get; set;}
     public string allowTracingTill {get; set;}
    }

    public class SubscriptionListResult
    {
        public List<Subscription> Value { get; set; }
    }