feat(commons): ActorNameRules mirroring Akka path-element validation

src/ZB.MOM.WW.ScadaBridge.Commons/Validation/ActorNameRules.cs

@@ -0,0 +1,62 @@
+using System.Text;
+
+namespace ZB.MOM.WW.ScadaBridge.Commons.Validation;
+
+/// <summary>
+/// Mirrors Akka.NET's <c>ActorPath.IsValidPathElement</c> (Commons does not reference Akka) so
+/// entity names that become actor names can be rejected at save time instead of crashing
+/// the runtime when the actor is created.
+/// </summary>
+public static class ActorNameRules
+{
+    private const string AllowedSymbols = "-_.*$+:@&=,!~';";
+
+    /// <summary>True when <paramref name="name"/> is a legal actor path element.</summary>
+    public static bool IsValid(string? name)
+    {
+        if (string.IsNullOrEmpty(name) || name[0] == '$')
+        {
+            return false;
+        }
+
+        for (var i = 0; i < name.Length; i++)
+        {
+            var c = name[i];
+            if (IsAsciiLetterOrDigit(c) || AllowedSymbols.Contains(c))
+            {
+                continue;
+            }
+
+            // Akka permits percent-encoded octets (%HH).
+            if (c == '%' && i + 2 < name.Length && Uri.IsHexDigit(name[i + 1]) && Uri.IsHexDigit(name[i + 2]))
+            {
+                i += 2;
+                continue;
+            }
+
+            return false;
+        }
+
+        return true;
+    }
+
+    /// <summary>A readable error for an invalid name, or null when the name is valid.</summary>
+    public static string? Describe(string? name)
+    {
+        if (IsValid(name))
+        {
+            return null;
+        }
+
+        if (string.IsNullOrEmpty(name))
+        {
+            return "Name must not be empty.";
+        }
+
+        return $"Name '{name}' contains characters not allowed in a runtime actor name " +
+               $"(allowed: letters, digits and {AllowedSymbols}); it must also not start with '$'.";
+    }
+
+    private static bool IsAsciiLetterOrDigit(char c) =>
+        (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9');
+}

tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Validation/ActorNameRulesTests.cs

@@ -0,0 +1,39 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Validation;
+
+namespace ZB.MOM.WW.ScadaBridge.Commons.Tests.Validation;
+
+public class ActorNameRulesTests
+{
+    [Theory]
+    [InlineData("a b")]
+    [InlineData("Furnace #3")]
+    [InlineData("Ofen Süd")]
+    [InlineData("x/y")]
+    [InlineData("")]
+    [InlineData(null)]
+    [InlineData("$abc")]
+    [InlineData("100%")]
+    public void IsValid_RejectsIllegalNames(string? name)
+    {
+        Assert.False(ActorNameRules.IsValid(name));
+        Assert.NotNull(ActorNameRules.Describe(name));
+    }
+
+    [Theory]
+    [InlineData("Furnace-3")]
+    [InlineData("Line_1.A")]
+    [InlineData("a%20b")]
+    public void IsValid_AcceptsLegalNames(string name)
+    {
+        Assert.True(ActorNameRules.IsValid(name));
+        Assert.Null(ActorNameRules.Describe(name));
+    }
+
+    [Fact]
+    public void Describe_NamesTheOffendingValue()
+    {
+        var msg = ActorNameRules.Describe("Furnace #3");
+        Assert.Contains("'Furnace #3'", msg);
+        Assert.Contains("not allowed in a runtime actor name", msg);
+    }
+}