Validation for Grok patterns

src/Grok.Net.Tests/UnitTests.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Reflection;
 using GrokNet;
 using PCRE;
 using Xunit;
@@ -395,5 +396,33 @@ public void GrokResult_To_Dictionary()
             Assert.True(grokResult.ContainsKey("email"));
             Assert.True(grokResult.ContainsKey("comment"));
         }
+
+        [Fact]
+        public void InvalidPattern_ThrowsException()
+        {
+            // Arrange
+            const string logs = @"06-21-19 21:00:13:589241;15;INFO;main;DECODED: 775233900043 DECODED BY: 18500738 DISTANCE: 1.5165
+            06-22-19 22:00:13:589265;156;WARN;main;DECODED: 775233900043 EMPTY DISTANCE: --------";
+
+            var sut = new Grok("%{MONTHDA:month}-%{MONTHDAY:day}-%{MONTHDAY:year} %{TIME:timestamp};%{WORD:id};%{LOGLEVEL:loglevel};%{WORD:func};%{GREEDYDATA:msg}");
+
+            // Act & Assert
+            FormatException exception = Assert.Throws<FormatException>(() => sut.Parse(logs));
+            Assert.Contains("Invalid Grok pattern: Pattern 'MONTHDA' not found.", exception.Message);
+        }
+
+        [Fact]
+        public void InvaidPattern_With_Custom_Patterns()
+        {
+            // Arrange
+            const string zipcode = "122001";
+            const string email = "Bob.Davis@microsoft.com";
+
+            var sut = new Grok("%{ZIPCOD:zipcode}:%{EMAILADDRESS:email}", ReadCustomFile());
+
+            // Act & Assert
+            FormatException exception = Assert.Throws<FormatException>(() => sut.Parse($"{zipcode}:{email}"));
+            Assert.Contains("Invalid Grok pattern: Pattern 'ZIPCOD' not found.", exception.Message);
+        }
     }
 }

src/Grok.Net/Grok.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -104,6 +104,7 @@ public GrokResult Parse(string text)
         {
             if (_compiledRegex == null)
             {
+                ValidateGrokPattern();
                 ParsePattern();
             }
 
@@ -286,5 +287,20 @@ private string ReplaceWithoutName(PcreMatch match)
 
             return "()";
         }
+
+        private void ValidateGrokPattern()
+        {
+            var grokPatternRegex = new PcreRegex("%\\{([^:}]+)(?::[^}]+)?(?::[^}]+)?\\}");
+            IEnumerable<PcreMatch> matches = grokPatternRegex.Matches(_grokPattern);
+
+            foreach (PcreMatch match in matches)
+            {
+                var patternName = match.Groups[1].Value;
+                if (!_patterns.ContainsKey(patternName))
+                {
+                    throw new FormatException($"Invalid Grok pattern: Pattern '{patternName}' not found.");
+                }
+            }
+        }
     }
 }