added: GetSecuredApiKeyRemainingValidity

[changelog]

New SearchClient method to get the remaining validity (seconds)
of a securedAPIKey

src/Algolia.Search/Clients/ISearchClient.cs

@@ -29,6 +29,7 @@
 using Algolia.Search.Models.Mcm;
 using Algolia.Search.Models.Personalization;
 using Algolia.Search.Models.Search;
+using System;
 using System.Collections.Generic;
 using System.Net.Http;
 using System.Threading;
@@ -116,6 +117,12 @@ public interface ISearchClient
         /// <returns></returns>
         string GenerateSecuredApiKeys(string parentApiKey, SecuredApiKeyRestriction restriction);
 
+        /// <summary>
+        /// Gets how many seconds are left before the secured API key expires.
+        /// </summary>
+        /// <param name="securedAPIKey">The secured API Key</param>
+        TimeSpan GetSecuredApiKeyRemainingValidity(string securedAPIKey);
+
         /// <summary>
         /// Get the full list of API Keys.
         /// </summary>

src/Algolia.Search/Clients/SearchClient.cs

@@ -34,8 +34,11 @@
 using Algolia.Search.Utils;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Net;
 using System.Net.Http;
+using System.Text;
+using System.Text.RegularExpressions;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -199,6 +202,33 @@ public string GenerateSecuredApiKeys(string parentApiKey, SecuredApiKeyRestricti
             return HmacShaHelper.Base64Encode($"{hash}{queryParams}");
         }
 
+        /// <inheritdoc />
+        public TimeSpan GetSecuredApiKeyRemainingValidity(string securedAPIKey)
+        {
+            if (string.IsNullOrWhiteSpace(securedAPIKey))
+            {
+                throw new ArgumentNullException(nameof(securedAPIKey));
+            }
+
+            var decodedKey = Encoding.UTF8.GetString(Convert.FromBase64String(securedAPIKey));
+
+            var regex = new Regex(@"validUntil=\d+");
+            var matches = regex.Matches(decodedKey);
+
+            if (matches.Count == 0)
+            {
+                throw new AlgoliaException("The SecuredAPIKey doesn't have a validUntil parameter.");
+            }
+
+            // Select the validUntil parameter and its value
+            var validUntilMatch = matches.Cast<Match>().Select(x => x.Value).First();
+
+            // Extracting and converting the timestamp
+            long timeStamp = Convert.ToInt64(validUntilMatch.Replace("validUntil=", string.Empty));
+
+            return TimeSpan.FromSeconds(timeStamp - DateTime.UtcNow.ToUnixTimeSeconds());
+        }
+
         /// <inheritdoc />
         public ListApiKeysResponse ListApiKeys(RequestOptions requestOptions = null) =>
             AsyncHelper.RunSync(() => ListApiKeysAsync(requestOptions));