Authentication¶

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

public class P21SessionClient : IAsyncDisposable
{
    private readonly HttpClient _client;
    private readonly string _baseUrl;
    private string? _sessionToken;

    public P21SessionClient(string serverHost, string username, string password)
    {
        _baseUrl = $"https://{serverHost}/uiserver0/ui";
        _client = new HttpClient();

        // Set Basic auth for the initial session creation request
        var credentials = Convert.ToBase64String(
            Encoding.ASCII.GetBytes($"{username}:{password}"));
        _client.DefaultRequestHeaders.Authorization =
            new AuthenticationHeaderValue("Basic", credentials);
        _client.DefaultRequestHeaders.Accept.Add(
            new MediaTypeWithQualityHeaderValue("application/json"));
    }

    /// <summary>
    /// Creates a P21 session and stores the session token for subsequent calls.
    /// </summary>
    public async Task LoginAsync(string workstationId = "API-Client")
    {
        var sessionParams = new
        {
            SessionType = "User",
            WorkstationID = workstationId,
            PrintMode = "Browser",
            SessionTimeout = 2147483647
        };

        var json = JsonSerializer.Serialize(sessionParams);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        var response = await _client.PostAsync(
            $"{_baseUrl}/common/v1/sessions/", content);

        response.EnsureSuccessStatusCode();

        var responseBody = await response.Content.ReadAsStringAsync();
        var result = JsonSerializer.Deserialize<JsonElement>(responseBody);

        // Extract the session token from the response
        // The exact property name depends on your P21 version — check your server's response
        _sessionToken = result.GetProperty("SessionID").GetString()
            ?? throw new InvalidOperationException("No session token in response.");

        // Set the session token on all future requests
        _client.DefaultRequestHeaders.Remove("X-SessionToken");
        _client.DefaultRequestHeaders.Add("X-SessionToken", _sessionToken);

        Console.WriteLine($"Session established: {_sessionToken}");
    }

    /// <summary>
    /// Sends a keep-alive ping to prevent session timeout.
    /// </summary>
    public async Task PingAsync()
    {
        if (_sessionToken is null)
            throw new InvalidOperationException("Not logged in.");

        var response = await _client.PostAsync(
            $"{_baseUrl}/common/v1/sessions/ping",
            new StringContent(string.Empty));

        response.EnsureSuccessStatusCode();
    }

    /// <summary>
    /// Retrieves current session state.
    /// </summary>
    public async Task<string> GetSessionStateAsync()
    {
        if (_sessionToken is null)
            throw new InvalidOperationException("Not logged in.");

        var response = await _client.GetAsync(
            $"{_baseUrl}/common/v1/sessions/state");

        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }

    /// <summary>
    /// Closes the session. Always call this when done.
    /// </summary>
    public async Task LogoutAsync()
    {
        if (_sessionToken is null) return;

        try
        {
            var response = await _client.DeleteAsync(
                $"{_baseUrl}/common/v1/sessions/");
            response.EnsureSuccessStatusCode();
            Console.WriteLine("Session closed.");
        }
        finally
        {
            _sessionToken = null;
        }
    }

    public async ValueTask DisposeAsync()
    {
        await LogoutAsync();
        _client.Dispose();
    }
}

await using var p21 = new P21SessionClient("p21-dev.yourcompany.com", "apiuser", "password");

await p21.LoginAsync("OrderSync-Prod");

var state = await p21.GetSessionStateAsync();
Console.WriteLine(state);

// ... make additional API calls using the shared HttpClient ...

// Session is closed automatically by DisposeAsync