TokenGenerator.cs

/**
 * FCS API - Token Generator (C#)
 *
 * Generate secure tokens for frontend JavaScript authentication
 *
 * Usage:
 * 1. Set your accessKey and publicKey
 * 2. Call GenerateToken()
 * 3. Pass the token data to your frontend JavaScript
 *
 * @package FcsApi
 * @author FCS API <support@fcsapi.com>
 * @link https://fcsapi.com
 */

using System;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;

namespace FcsApi
{
    public class TokenGenerator
    {
        // Token expiry options (in seconds):
        // 300 (5min), 900 (15min), 1800 (30min), 3600 (1hr), 86400 (24hr)

        private readonly string _accessKey;
        private readonly string _publicKey;
        private readonly int _tokenExpiry;

        /// <summary>
        /// Initialize token generator
        /// </summary>
        /// <param name="accessKey">Your API access key (get from https://fcsapi.com/dashboard)</param>
        /// <param name="publicKey">Your public key (get from https://fcsapi.com/dashboard)</param>
        /// <param name="tokenExpiry">Token expiry in seconds (default: 3600 = 1 hour)</param>
        public TokenGenerator(string accessKey = "YOUR_ACCESS_KEY_HERE", string publicKey = "YOUR_PUBLIC_KEY_HERE", int tokenExpiry = 3600)
        {
            _accessKey = accessKey;
            _publicKey = publicKey;
            _tokenExpiry = tokenExpiry;
        }

        /// <summary>
        /// Generate token for frontend authentication
        /// </summary>
        /// <returns>Dictionary with _token, _expiry, _public_key</returns>
        public Dictionary<string, object> GenerateToken()
        {
            var expiry = DateTimeOffset.UtcNow.ToUnixTimeSeconds() + _tokenExpiry;
            var message = _publicKey + expiry.ToString();
            var token = ComputeHmacSha256(message, _accessKey);

            return new Dictionary<string, object>
            {
                { "_token", token },
                { "_expiry", expiry },
                { "_public_key", _publicKey }
            };
        }

        /// <summary>
        /// Generate token and return as JSON string
        /// </summary>
        /// <returns>JSON string of token data</returns>
        public string ToJson()
        {
            return JsonSerializer.Serialize(GenerateToken());
        }

        /// <summary>
        /// Generate HTML meta tags for token
        /// </summary>
        /// <returns>HTML meta tags string</returns>
        public string GetMetaTags()
        {
            var token = GenerateToken();
            return $"<meta name=\"fcs-public-key\" content=\"{token["_public_key"]}\">\n" +
                   $"<meta name=\"fcs-token\" content=\"{token["_token"]}\">\n" +
                   $"<meta name=\"fcs-token-expiry\" content=\"{token["_expiry"]}\">";
        }

        private static string ComputeHmacSha256(string message, string key)
        {
            var keyBytes = Encoding.UTF8.GetBytes(key);
            var messageBytes = Encoding.UTF8.GetBytes(message);

            using var hmac = new HMACSHA256(keyBytes);
            var hashBytes = hmac.ComputeHash(messageBytes);
            return BitConverter.ToString(hashBytes).Replace("-", "").ToLower();
        }
    }
}

// ============================================
// USAGE EXAMPLES
// ============================================

// Example 1: Generate token
// var generator = new TokenGenerator("your_access_key", "your_public_key");
// var tokenData = generator.GenerateToken();
// Console.WriteLine($"Token: {tokenData["_token"]}");

// Example 2: Get as JSON
// Console.WriteLine(generator.ToJson());

// Example 3: Get meta tags
// Console.WriteLine(generator.GetMetaTags());

// ASP.NET Core example:
// [ApiController]
// [Route("api/[controller]")]
// public class FcsTokenController : ControllerBase
// {
//     [HttpGet]
//     public IActionResult GetToken()
//     {
//         var generator = new TokenGenerator(
//             Environment.GetEnvironmentVariable("FCS_ACCESS_KEY"),
//             Environment.GetEnvironmentVariable("FCS_PUBLIC_KEY")
//         );
//         return Ok(generator.GenerateToken());
//     }
// }