Kavita+ Overhaul & New Changelog (#3507)

API/Helpers/JwtHelper.cs

@@ -0,0 +1,40 @@
+using System;
+using System.IdentityModel.Tokens.Jwt;
+using System.Linq;
+
+namespace API.Helpers;
+
+public static class JwtHelper
+{
+    /// <summary>
+    /// Extracts the expiration date from a JWT token.
+    /// </summary>
+    public static DateTime GetTokenExpiry(string jwtToken)
+    {
+        if (string.IsNullOrEmpty(jwtToken))
+            return DateTime.MinValue;
+
+        // Parse the JWT and extract the expiry claim
+        var jwtHandler = new JwtSecurityTokenHandler();
+        var token = jwtHandler.ReadJwtToken(jwtToken);
+        var exp = token.Claims.FirstOrDefault(c => c.Type == "exp")?.Value;
+
+        if (long.TryParse(exp, out var expSeconds))
+        {
+            return DateTimeOffset.FromUnixTimeSeconds(expSeconds).UtcDateTime;
+        }
+
+        return DateTime.MinValue;
+    }
+
+    /// <summary>
+    /// Checks if a JWT token is valid based on its expiry date.
+    /// </summary>
+    public static bool IsTokenValid(string jwtToken)
+    {
+        if (string.IsNullOrEmpty(jwtToken)) return false;
+
+        var expiry = GetTokenExpiry(jwtToken);
+        return expiry > DateTime.UtcNow;
+    }
+}