Add validation.

1 files changed, 45 insertions, 0 deletions

diff --git a/Timeline/Models/Validation/UsernameValidator.cs b/Timeline/Models/Validation/UsernameValidator.cs
new file mode 100644
index 00000000..e4891400
--- /dev/null
+++ b/Timeline/Models/Validation/UsernameValidator.cs
@@ -0,0 +1,45 @@
+using System.Linq;

+using System.Text.RegularExpressions;

+

+namespace Timeline.Models.Validation

+{

+    public class UsernameValidator : Validator<string>

+    {

+        public const int MaxLength = 26;

+        public const string RegexPattern = @"^[a-zA-Z0-9_][a-zA-Z0-9-_]*$";

+

+        private readonly Regex _regex = new Regex(RegexPattern);

+

+        protected override bool DoValidate(string value, out string message)

+        {

+            if (value.Length == 0)

+            {

+                message = "An empty string is not permitted.";

+                return false;

+            }

+

+            if (value.Length > 26)

+            {

+                message = $"Too long, more than 26 characters is not premitted, found {value.Length}.";

+                return false;

+            }

+

+            foreach ((char c, int i) in value.Select((c, i) => (c, i)))

+                if (char.IsWhiteSpace(c))

+                {

+                    message = $"A whitespace is found at {i} . Whitespace is not permited.";

+                    return false;

+                }

+

+            var match = _regex.Match(value);

+            if (!match.Success)

+            {

+                message = "Regex match failed.";

+                return false;

+            }

+

+            message = ValidationConstants.SuccessMessage;

+            return true;

+        }

+    }

+}