feat: added datetimeoffset support to send_at

Author: LouisWhite15

Smtpapi/HeaderTests/TestHeader.cs

@@ -120,7 +120,7 @@ public void TestSetIpPool()
         }
 
         [Test]
-        public void TestSetSendAt()
+        public void TestSetSendAt_DateTime()
         {
             var test = new Header();
             var now = DateTime.UtcNow;
@@ -130,13 +130,33 @@ public void TestSetSendAt()
         }
 
         [Test]
-        public void TestSetSendEachAt()
+        public void TestSetSendAt_DateTimeOffset()
+        {
+            var test = new Header();
+            var now = DateTimeOffset.UtcNow;
+            test.SetSendAt(now);
+            string result = test.JsonString();
+            Assert.AreEqual("{\"send_at\" : " + Utils.DateTimeOffsetToUnixTimestamp(now) + "}", result);
+        }
+
+        [Test]
+        public void TestSetSendEachAt_DateTime()
         {
             var test = new Header();
             var now = DateTime.UtcNow;
             test.SetSendEachAt(new List<DateTime> { now, now.AddSeconds(10) });
             string result = test.JsonString();
             Assert.AreEqual("{\"send_each_at\" : [" + Utils.DateTimeToUnixTimestamp(now) + "," + Utils.DateTimeToUnixTimestamp(now.AddSeconds(10)) + "]}", result);
         }
+
+        [Test]
+        public void TestSetSendEachAt_DateTimeOffset()
+        {
+            var test = new Header();
+            var now = DateTimeOffset.UtcNow;
+            test.SetSendEachAt(new List<DateTimeOffset> { now, now.AddSeconds(10) });
+            string result = test.JsonString();
+            Assert.AreEqual("{\"send_each_at\" : [" + Utils.DateTimeOffsetToUnixTimestamp(now) + "," + Utils.DateTimeOffsetToUnixTimestamp(now.AddSeconds(10)) + "]}", result);
+        }
     }
 }

Smtpapi/Smtpapi/Header.cs

@@ -181,6 +181,17 @@ public void SetSendAt(DateTime sendTime)
             _settings.AddSetting(keys, Utils.DateTimeToUnixTimestamp(sendTime));
         }
 
+        /// <summary>
+        ///     Schedule the email to be sent in the future. You can find further documentation about scheduled sends here:
+        ///     https://sendgrid.com/docs/API_Reference/SMTP_API/scheduling_parameters.html
+        /// </summary>
+        /// <param name="sendTime">DateTimeOffset representing the time to send the email. See docs for limitations. </param>
+        public void SetSendAt(DateTimeOffset sendTime)
+        {
+            var keys = new List<string> { "send_at" };
+            _settings.AddSetting(keys, Utils.DateTimeOffsetToUnixTimestamp(sendTime));
+        }
+
         /// <summary>
         ///     Schedule each email in your batch to be sent at a specific time in the future. You can find further documentation about scheduled sends here:
         ///     https://sendgrid.com/docs/API_Reference/SMTP_API/scheduling_parameters.html
@@ -191,6 +202,16 @@ public void SetSendEachAt(IEnumerable<DateTime> sendDateTimes)
             _settings.AddArray(new List<string> { "send_each_at" }, sendDateTimes.Select(Utils.DateTimeToUnixTimestamp).Cast<object>().ToArray());
         }
 
+        /// <summary>
+        ///     Schedule each email in your batch to be sent at a specific time in the future. You can find further documentation about scheduled sends here:
+        ///     https://sendgrid.com/docs/API_Reference/SMTP_API/scheduling_parameters.html
+        /// </summary>
+        /// <param name="sendDateTimes">A collection of DateTimeOffsets, with each time corresponding to one recipient in the SMTP API header</param>
+        public void SetSendEachAt(IEnumerable<DateTimeOffset> sendDateTimes)
+        {
+            _settings.AddArray(new List<string> { "send_each_at" }, sendDateTimes.Select(Utils.DateTimeOffsetToUnixTimestamp).Cast<object>().ToArray());
+        }
+
         #endregion
     }
 }

Smtpapi/Smtpapi/Utils.cs

@@ -65,5 +65,16 @@ public static int DateTimeToUnixTimestamp(DateTime dateTime)
             var span = (dateTime - new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc));
             return (int)span.TotalSeconds;
         }
+
+        /// <summary>
+        /// Convert a DateTimeOffset to a UNIX Epoch Timestamp
+        /// </summary>
+        /// <param name="dateTimeOffset">Date to convert to timestamp</param>
+        /// <returns>Timestamp</returns>
+        public static int DateTimeOffsetToUnixTimestamp(DateTimeOffset dateTimeOffset)
+        {
+            var span = (dateTimeOffset - new DateTimeOffset(1970, 1, 1, 0, 0, 0, 0, TimeSpan.Zero));
+            return (int)span.TotalSeconds;
+        }
     }
 }