using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

namespace HotDocsAdvanceApiExamples
{
    public class ResourceOwnerAuthorization
    {
        // These are the credentials required for retrieving an access token using the resource owner flow.
        // You will replace these credentials with those for a client you create yourself,
        // using the Advance Client Management Application. See the API help guide for more information.
        private string clientName = "ab3e4544-b595-4681-b0ea-c7c18c9b63f6";
        private string servicePrincipalName = "ExampleServicePrincipalA";
        private string servicePrincipalPassword = "examplePassword";

        public async Task<string> GetResourceOwnerToken()
        {
            // Create the access token request            
            var request = CreateHttpRequestMessage();

            //Send token request to Advance
            using (var client = new HttpClient())
            {
                var response = await client.SendAsync(request);

                // Return the retrieved access token
                return response.Content.ReadAsStringAsync().Result;
            }
        }

        private HttpRequestMessage CreateHttpRequestMessage()
        {
            var tokenUrl = string.Format("https://yourtenancy.yourorganization.com/HdaAuth/Authorize/ServicePrincipalLogIn");

            return new HttpRequestMessage
            {
                RequestUri = new Uri(tokenUrl),
                Method = HttpMethod.Post,
                Content = GetRequestContent()
            };
        }

        private StringContent GetRequestContent()
        {
            var json = "{" + string.Format("'ClientName' : '{0}', 'PrincipalName' : '{1}', 'PrincipalPassword' : '{2}'", clientName, servicePrincipalName, servicePrincipalPassword) + "}";
            return new StringContent(json, Encoding.UTF8, "application/json");
        }
    }
}

$body = @{
    ClientName = "ExampleClientA"
    PrincipalName = "ExampleServicePrincipalA"
    PrincipalPassword = "examplePassword"
} | ConvertTo-Json

$header = @{
 "Accept"="application/json"
 "Content-Type"="application/json"
} 

$result = Invoke-RestMethod -Uri "https://yourtenancy.yourorganization.com/HdaAuth/Authorize/ServicePrincipalLogIn" -Method 'Post' -Body $body -Headers $header

Write-Host $result