From eb1fad93330ff9b51f51a63e457a63f8190c8587 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dawid=20P=C4=85gowski?= <dawidpag@protonmail.com>
Date: Wed, 23 Aug 2023 00:27:55 +0200
Subject: [PATCH] Add IEC date DataType

---
 S7.Net/Enums.cs                     |  5 +++
 S7.Net/Helper/DateTimeExtensions.cs | 23 ++++++++++
 S7.Net/Types/Date.cs                | 70 +++++++++++++++++++++++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 S7.Net/Helper/DateTimeExtensions.cs
 create mode 100644 S7.Net/Types/Date.cs

diff --git a/S7.Net/Enums.cs b/S7.Net/Enums.cs
index 080dce6..3eb7e4b 100644
--- a/S7.Net/Enums.cs
+++ b/S7.Net/Enums.cs
@@ -202,6 +202,11 @@
         /// DateTIme variable type
         /// </summary>
         DateTime,
+        
+        /// <summary>
+        /// IEC date (legacy) variable type
+        /// </summary>
+        Date,
 
         /// <summary>
         /// DateTimeLong variable type
diff --git a/S7.Net/Helper/DateTimeExtensions.cs b/S7.Net/Helper/DateTimeExtensions.cs
new file mode 100644
index 0000000..7e128c1
--- /dev/null
+++ b/S7.Net/Helper/DateTimeExtensions.cs
@@ -0,0 +1,23 @@
+using System;
+using S7.Net.Types;
+using DateTime = System.DateTime;
+
+namespace S7.Net.Helper
+{
+    public static class DateTimeExtensions
+    {
+        public static ushort GetDaysSinceIecDateStart(this DateTime dateTime)
+        {
+            if (dateTime < Date.IecMinDate)
+            {
+                throw new ArgumentException($"DateTime must be at least {Date.IecMinDate:d}");
+            }
+            if (dateTime > Date.IecMaxDate)
+            {
+                throw new ArgumentException($"DateTime must be lower than {Date.IecMaxDate:d}");
+            }
+
+            return (ushort)(dateTime - Date.IecMinDate).TotalDays;
+        }
+    }
+}
\ No newline at end of file
diff --git a/S7.Net/Types/Date.cs b/S7.Net/Types/Date.cs
new file mode 100644
index 0000000..980742e
--- /dev/null
+++ b/S7.Net/Types/Date.cs
@@ -0,0 +1,70 @@
+using System;
+using S7.Net.Helper;
+
+namespace S7.Net.Types
+{
+    /// <summary>
+    /// Contains the conversion methods to convert Words from S7 plc to C#.
+    /// </summary>
+    public static class Date
+    {
+        /// <summary>
+        /// Minimum allowed date for the IEC date type
+        /// </summary>
+        public static readonly System.DateTime IecMinDate = new(year: 1990, month: 01, day: 01);
+        
+        /// <summary>
+        /// Maximum allowed date for the IEC date type
+        /// </summary>
+        public static readonly System.DateTime IecMaxDate = new(year: 2168, month: 12, day: 31);
+        
+        /// <summary>
+        /// Converts a word (2 bytes) to IEC date (<see cref="System.DateTime"/>)
+        /// </summary>
+        public static System.DateTime FromByteArray(byte[] bytes)
+        {
+            if (bytes.Length != 2)
+            {
+                throw new ArgumentException("Wrong number of bytes. Bytes array must contain 2 bytes.");
+            }
+
+            var daysSinceDateStart = Word.FromByteArray(bytes);
+            return IecMinDate.AddDays(daysSinceDateStart);
+        }
+
+        /// <summary>
+        /// Converts a <see cref="System.DateTime"/> to word (2 bytes)
+        /// </summary>
+        public static byte[] ToByteArray(System.DateTime dateTime) => Word.ToByteArray(dateTime.GetDaysSinceIecDateStart());
+
+        /// <summary>
+        /// Converts an array of <see cref="System.DateTime"/>s to an array of bytes
+        /// </summary>
+        public static byte[] ToByteArray(System.DateTime[] value)
+        {
+            var arr = new ByteArray();
+            foreach (var date in value)
+                arr.Add(ToByteArray(date));
+            return arr.Array;
+        }
+
+        /// <summary>
+        /// Converts an array of bytes to an array of <see cref="System.DateTime"/>s
+        /// </summary>
+        public static System.DateTime[] ToArray(byte[] bytes)
+        {
+            var values = new System.DateTime[bytes.Length / sizeof(ushort)];
+
+            for (int i = 0; i < values.Length; i++)
+            {
+                values[i] = FromByteArray(
+                    new[]
+                    {
+                        bytes[i], bytes[i + 1]
+                    });
+            }
+
+            return values;
+        }
+    }
+}
\ No newline at end of file