[Breaking] Enforce case-sensitive date math parsing per Elasticsearch spec

Align DateMath parsing with the Elasticsearch date math specification by
enforcing case-sensitive matching. The anchor 'now' must be lowercase, and
date-math units are case-sensitive (M=months, m=minutes, d=days, D=invalid).

Additionally improve string comparison quality across all parsers by
replacing instance .Equals() and == with String.Equals(), and eliminating
culture-sensitive .ToLower() allocations in favor of String.Equals with
OrdinalIgnoreCase or .ToLowerInvariant() where switch statements require it.

Breaking changes:
- 'Now', 'NOW', and other mixed-case variants of 'now' are no longer valid
- Uppercase units D, Y, W, S are no longer valid (were silently accepted)

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: niemyjski

Exceptionless.DateTimeExtensions.slnx

@@ -2,6 +2,7 @@
   <Folder Name="/Solution Items/">
     <File Path=".github/workflows/build.yml" />
     <File Path="build/common.props" />
+    <File Path="global.json" />
     <File Path="README.md" />
   </Folder>
   <Project Path="src/Exceptionless.DateTimeExtensions/Exceptionless.DateTimeExtensions.csproj" />

src/Exceptionless.DateTimeExtensions/DateMath.cs

@@ -23,10 +23,14 @@ public static class DateMath
     // Match date math expressions with positional and end anchors for flexible matching
     // Uses \G for positional matching and lookahead for boundary detection to support both
     // full string parsing and positional matching within TwoPartFormatParser
+    // NOTE: Case-sensitive matching is intentional per Elasticsearch spec. The anchor 'now' must
+    // be lowercase, and date-math units are case-sensitive: y, M, w, d, h, H, m, s.
+    // Uppercase D is NOT a valid unit. See:
+    // https://www.elastic.co/docs/reference/elasticsearch/rest-apis/common-options
     internal static readonly Regex Parser = new(
         @"\G(?<anchor>now|(?<date>\d{4}-?\d{2}-?\d{2}(?:[T\s](?:\d{1,2}(?::?\d{2}(?::?\d{2})?)?(?:\.\d{1,3})?)?(?:[+-]\d{2}:?\d{2}|Z)?)?)\|\|)" +
         @"(?<operations>(?:[+\-/]\d*[yMwdhHms])*)(?=\s|$|[\]\}])",
-        RegexOptions.Compiled | RegexOptions.IgnoreCase);
+        RegexOptions.Compiled);
 
     // Pre-compiled regex for operation parsing to avoid repeated compilation
     private static readonly Regex _operationRegex = new(@"([+\-/])(\d*)([yMwdhHms])", RegexOptions.Compiled);
@@ -141,7 +145,7 @@ public static bool TryParseFromMatch(Match match, DateTimeOffset relativeBaseTim
             DateTimeOffset baseTime;
             string anchor = match.Groups["anchor"].Value;
 
-            if (anchor.Equals("now", StringComparison.OrdinalIgnoreCase))
+            if (String.Equals(anchor, "now"))
             {
                 baseTime = relativeBaseTime;
             }
@@ -183,7 +187,7 @@ public static bool TryParseFromMatch(Match match, TimeZoneInfo timeZone, bool is
             DateTimeOffset baseTime;
             string anchor = match.Groups["anchor"].Value;
 
-            if (anchor.Equals("now", StringComparison.OrdinalIgnoreCase))
+            if (String.Equals(anchor, "now"))
             {
                 // Use current time in the specified timezone
                 baseTime = TimeZoneInfo.ConvertTime(DateTimeOffset.UtcNow, timeZone);
@@ -463,7 +467,7 @@ public static DateTimeOffset ApplyOperations(DateTimeOffset baseTime, string ope
         for (int i = 0; i < matches.Count; i++)
         {
             string operation = matches[i].Groups[1].Value;
-            if (operation == "/")
+            if (String.Equals(operation, "/"))
             {
                 if (foundRounding)
                 {

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/Helper.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -21,21 +21,26 @@ internal static class Helper
 
     internal static TimeSpan GetTimeSpanFromName(string name)
     {
-        return name.ToLower() switch
-        {
-            "minutes" => TimeSpan.FromMinutes(1),
-            "minute" => TimeSpan.FromMinutes(1),
-            "hours" => TimeSpan.FromHours(1),
-            "hour" => TimeSpan.FromHours(1),
-            "days" => TimeSpan.FromDays(1),
-            "day" => TimeSpan.FromDays(1),
-            _ => TimeSpan.Zero
-        };
+        if (String.Equals(name, "minutes", StringComparison.OrdinalIgnoreCase) ||
+            String.Equals(name, "minute", StringComparison.OrdinalIgnoreCase))
+            return TimeSpan.FromMinutes(1);
+
+        if (String.Equals(name, "hours", StringComparison.OrdinalIgnoreCase) ||
+            String.Equals(name, "hour", StringComparison.OrdinalIgnoreCase))
+            return TimeSpan.FromHours(1);
+
+        if (String.Equals(name, "days", StringComparison.OrdinalIgnoreCase) ||
+            String.Equals(name, "day", StringComparison.OrdinalIgnoreCase))
+            return TimeSpan.FromDays(1);
+
+        return TimeSpan.Zero;
     }
 
     internal static int GetMonthNumber(string name)
     {
-        int index = MonthNames.FindIndex(m => m.Equals(name, StringComparison.OrdinalIgnoreCase) || m.Substring(0, 3).Equals(name, StringComparison.OrdinalIgnoreCase));
+        int index = MonthNames.FindIndex(m =>
+            String.Equals(m, name, StringComparison.OrdinalIgnoreCase) ||
+            String.Equals(m.Substring(0, 3), name, StringComparison.OrdinalIgnoreCase));
         return index >= 0 ? index + 1 : -1;
     }
 

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/MonthRelationFormatParser.cs

@@ -14,7 +14,7 @@ public virtual DateTimeRange Parse(string content, DateTimeOffset relativeBaseTi
         if (!m.Success)
             return null;
 
-        string relation = m.Groups["relation"].Value.ToLower();
+        string relation = m.Groups["relation"].Value.ToLowerInvariant();
         int month = Helper.GetMonthNumber(m.Groups["month"].Value);
         return FromMonthRelation(relation, month, relativeBaseTime);
     }

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/NamedDayFormatParser.cs

@@ -14,12 +14,12 @@ public DateTimeRange Parse(string content, DateTimeOffset relativeBaseTime)
         if (!m.Success)
             return null;
 
-        string value = m.Groups["name"].Value.ToLower();
-        if (value == "today")
+        string value = m.Groups["name"].Value;
+        if (String.Equals(value, "today", StringComparison.OrdinalIgnoreCase))
             return new DateTimeRange(relativeBaseTime.StartOfDay(), relativeBaseTime.EndOfDay());
-        if (value == "yesterday")
+        if (String.Equals(value, "yesterday", StringComparison.OrdinalIgnoreCase))
             return new DateTimeRange(relativeBaseTime.SubtractDays(1).StartOfDay(), relativeBaseTime.SubtractDays(1).EndOfDay());
-        if (value == "tomorrow")
+        if (String.Equals(value, "tomorrow", StringComparison.OrdinalIgnoreCase))
             return new DateTimeRange(relativeBaseTime.AddDays(1).StartOfDay(), relativeBaseTime.AddDays(1).EndOfDay());
 
         return null;

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/PartParsers/AmountTimeRelationPartParser.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Text.RegularExpressions;
 
 namespace Exceptionless.DateTimeExtensions.FormatParsers.PartParsers;
@@ -21,8 +21,7 @@ public class AmountTimeRelationPartParser : IPartParser
 
     protected DateTimeOffset? FromRelationAmountTime(string relation, int amount, string size, DateTimeOffset relativeBaseTime, bool isUpperLimit)
     {
-        relation = relation.ToLower();
-        size = size.ToLower();
+        relation = relation.ToLowerInvariant();
         if (amount < 1)
             throw new ArgumentException("Time amount can't be 0.");
         var intervalSpan = Helper.GetTimeSpanFromName(size);
@@ -38,7 +37,7 @@ public class AmountTimeRelationPartParser : IPartParser
                     return isUpperLimit ? relativeBaseTime.SafeAdd(totalSpan).Ceiling(intervalSpan).SubtractMilliseconds(1) : relativeBaseTime.SafeAdd(totalSpan).Floor(intervalSpan);
             }
         }
-        else if (size == "week" || size == "weeks")
+        else if (String.Equals(size, "week", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "weeks", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {
@@ -48,7 +47,7 @@ public class AmountTimeRelationPartParser : IPartParser
                     return isUpperLimit ? relativeBaseTime.AddWeeks(amount).EndOfDay() : relativeBaseTime.AddWeeks(amount).StartOfDay();
             }
         }
-        else if (size == "month" || size == "months")
+        else if (String.Equals(size, "month", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "months", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {
@@ -58,7 +57,7 @@ public class AmountTimeRelationPartParser : IPartParser
                     return isUpperLimit ? relativeBaseTime.AddMonths(amount).EndOfDay() : relativeBaseTime.AddMonths(amount).StartOfDay();
             }
         }
-        else if (size == "year" || size == "years")
+        else if (String.Equals(size, "year", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "years", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/PartParsers/MonthRelationPartParser.cs

@@ -11,7 +11,7 @@ public class MonthRelationPartParser : IPartParser
 
     public virtual DateTimeOffset? Parse(Match match, DateTimeOffset relativeBaseTime, bool isUpperLimit)
     {
-        string relation = match.Groups["relation"].Value.ToLower();
+        string relation = match.Groups["relation"].Value.ToLowerInvariant();
         int month = Helper.GetMonthNumber(match.Groups["month"].Value);
         return FromMonthRelation(relation, month, relativeBaseTime, isUpperLimit);
     }

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/PartParsers/NamedDayPartParser.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Text.RegularExpressions;
 
 namespace Exceptionless.DateTimeExtensions.FormatParsers.PartParsers;
@@ -12,14 +12,14 @@ public class NamedDayPartParser : IPartParser
 
     public DateTimeOffset? Parse(Match match, DateTimeOffset relativeBaseTime, bool isUpperLimit)
     {
-        string value = match.Groups["name"].Value.ToLower();
-        if (value == "now")
+        string value = match.Groups["name"].Value;
+        if (String.Equals(value, "now", StringComparison.OrdinalIgnoreCase))
             return relativeBaseTime;
-        if (value == "today")
+        if (String.Equals(value, "today", StringComparison.OrdinalIgnoreCase))
             return isUpperLimit ? relativeBaseTime.EndOfDay() : relativeBaseTime.StartOfDay();
-        if (value == "yesterday")
+        if (String.Equals(value, "yesterday", StringComparison.OrdinalIgnoreCase))
             return isUpperLimit ? relativeBaseTime.SubtractDays(1).EndOfDay() : relativeBaseTime.SubtractDays(1).StartOfDay();
-        if (value == "tomorrow")
+        if (String.Equals(value, "tomorrow", StringComparison.OrdinalIgnoreCase))
             return isUpperLimit ? relativeBaseTime.AddDays(1).EndOfDay() : relativeBaseTime.AddDays(1).StartOfDay();
 
         return null;

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/RelationAmountTimeFormatParser.cs

@@ -19,8 +19,7 @@ public virtual DateTimeRange Parse(string content, DateTimeOffset relativeBaseTi
 
     protected DateTimeRange FromRelationAmountTime(string relation, int amount, string size, DateTimeOffset relativeBaseTime)
     {
-        relation = relation.ToLower();
-        size = size.ToLower();
+        relation = relation.ToLowerInvariant();
         if (amount < 1)
             throw new ArgumentException("Time amount can't be 0.");
 
@@ -40,7 +39,7 @@ protected DateTimeRange FromRelationAmountTime(string relation, int amount, stri
                     return new DateTimeRange(relativeBaseTime, relativeBaseTime.SafeAdd(totalSpan).Ceiling(intervalSpan).SubtractMilliseconds(1));
             }
         }
-        else if (size == "week" || size == "weeks")
+        else if (String.Equals(size, "week", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "weeks", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {
@@ -53,7 +52,7 @@ protected DateTimeRange FromRelationAmountTime(string relation, int amount, stri
                     return new DateTimeRange(relativeBaseTime, relativeBaseTime.AddWeeks(amount).EndOfDay());
             }
         }
-        else if (size == "month" || size == "months")
+        else if (String.Equals(size, "month", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "months", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {
@@ -66,7 +65,7 @@ protected DateTimeRange FromRelationAmountTime(string relation, int amount, stri
                     return new DateTimeRange(relativeBaseTime, relativeBaseTime.AddMonths(amount).EndOfDay());
             }
         }
-        else if (size == "year" || size == "years")
+        else if (String.Equals(size, "year", StringComparison.OrdinalIgnoreCase) || String.Equals(size, "years", StringComparison.OrdinalIgnoreCase))
         {
             switch (relation)
             {

src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/TwoPartFormatParser.cs

@@ -102,7 +102,7 @@ private static bool IsValidBracketPair(string opening, string closing)
             return false;
 
         // Check for proper matching pairs
-        return (opening == "[" && closing == "]") ||
-               (opening == "{" && closing == "}");
+        return (String.Equals(opening, "[") && String.Equals(closing, "]")) ||
+               (String.Equals(opening, "{") && String.Equals(closing, "}"));
     }
 }