Identifying indeces of numerical arguments

That will be used to preformat those args.

Author: par.dahlman

Common.Logging.Serilog.Tests/SerilogPreformatterTests.cs

@@ -49,7 +49,7 @@ public void Should_Return_Same_Template_String_If_No_Args_Provided()
         public void Should_Format_Entire_String_If_Only_Numeric_Formatting_Is_Used()
         {
             /* Setup */
-            const string originalTemplate = "Look at this,a {0} formatted string!";
+            const string originalTemplate = "Look at this, a {0} formatted string!";
             var args = new object[] {"nicely "};
             var expected = string.Format(originalTemplate, args);
 
@@ -60,5 +60,34 @@ public void Should_Format_Entire_String_If_Only_Numeric_Formatting_Is_Used()
             Assert.That(result, Is.True);
             Assert.That(_resultTemplate, Is.EqualTo(expected));
         }
+
+        public class When_Calling_GetIndecesOfNumericalFormatting : SerilogPreformatterTests
+        {
+            [Test]
+            public void Should_Return_Empty_List_If_Template_String_Is_Not_Formatted()
+            {
+                /* Setup */
+                const string originalTemplate = "This is a template without any args";
+
+                /* Test */
+                var result = _preformatter.GetIndecesOfNumericalFormatting(originalTemplate);
+
+                /* Assert */
+                Assert.That(result, Is.Empty);
+            }
+
+            [TestCase("A pure numeric string with {0} and {1}.", new[] {0,1})]
+            [TestCase("A pure {@Serilog} formatted string", new int[0])]
+            [TestCase("A mixed string with both {@Seri} and numeric {1} formatting", new[] {1})]
+            public void Should_Return_Expected_Indeces(string originalTemplate, int[] expectedResult)
+            {
+                /* Setup */
+                /* Test */
+                var result = _preformatter.GetIndecesOfNumericalFormatting(originalTemplate);
+
+                /* Assert */
+                Assert.That(result, Is.EquivalentTo(expectedResult));
+            }
+        }
     }
 }

src/Properties/AssemblyInfo.cs

@@ -18,6 +18,7 @@
 // to COM components.  If you need to access a type in this assembly from 
 // COM, set the ComVisible attribute to true on that type.
 [assembly: ComVisible(false)]
+[assembly: InternalsVisibleTo("Common.Logging.Serilog.Tests")]
 
 // The following GUID is for the ID of the typelib if this project is exposed to COM
 [assembly: Guid("f3753a5f-71d4-4fd5-9208-f79beb1de08c")]

src/SerilogPreformatter.cs

@@ -1,9 +1,13 @@
-using System.Linq;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
 
 namespace Common.Logging.Serilog
 {
     public class SerilogPreformatter
     {
+        private readonly Regex _numericFormattedRegex = new Regex(@"{(\d)}", RegexOptions.Compiled);
+
         public bool TryPreformat(string templateString, object[] args, out string newTemplate, out object[] newArgs)
         {
             if (string.IsNullOrEmpty(templateString))
@@ -24,5 +28,21 @@ public bool TryPreformat(string templateString, object[] args, out string newTem
             newArgs = null;
             return true;
         }
+
+        internal IEnumerable<int> GetIndecesOfNumericalFormatting(string templateString)
+        {
+            var matches = _numericFormattedRegex.Matches(templateString);
+
+            for (var i = 0; i < matches.Count; i++)
+            {
+                var numericMatch = matches[i].Groups
+                    .OfType<Group>()
+                    .Skip(1)
+                    .First()
+                    .Value;
+
+                yield return int.Parse(numericMatch);
+            }
+        }
     }
 }