Fixes #1006: conjunctions etc lower case in Title Case

src/Humanizer.Tests.Shared/InflectorTests.cs

@@ -75,9 +75,9 @@ public void SingularizeSkipSimpleWords(string singular, string plural)
         [InlineData("some title", "Some Title")]
         [InlineData("some-title", "Some Title")]
         [InlineData("sometitle", "Sometitle")]
-        [InlineData("some-title: The begining", "Some Title: The Begining")]
-        [InlineData("some_title:_the_begining", "Some Title: The Begining")]
-        [InlineData("some title: The_begining", "Some Title: The Begining")]
+        [InlineData("some-title: The beginning", "Some Title: The Beginning")]
+        [InlineData("some_title:_the_beginning", "Some Title: the Beginning")]
+        [InlineData("some title: The_beginning", "Some Title: The Beginning")]
         public void Titleize(string input, string expectedOuput)
         {
             Assert.Equal(expectedOuput, input.Titleize());

src/Humanizer.Tests.Shared/StringHumanizeTests.cs

@@ -71,6 +71,7 @@ public void CanHumanizeStringWithAcronyms(string input, string expectedValue)
         [Theory]
         [InlineData("CanReturnTitleCase", "Can Return Title Case")]
         [InlineData("Can_return_title_Case", "Can Return Title Case")]
+        [InlineData("In titles use lower case for prepositions an article or conjunctions", "In Titles Use Lower Case for Prepositions an Article or Conjunctions")]
         [InlineData("Title_humanization_Honors_ALLCAPS", "Title Humanization Honors ALLCAPS")]
         [InlineData("MühldorferStraße23", "Mühldorfer Straße 23")]
         [InlineData("mühldorfer_STRAẞE_23", "Mühldorfer STRAẞE 23")]

src/Humanizer.Tests.Shared/TransformersTests.cs

@@ -9,7 +9,7 @@ public class TransformersTests
         [InlineData("Sentence casing", "Sentence Casing")]
         [InlineData("honors UPPER case", "Honors UPPER Case")]
         [InlineData("INvalid caSEs arE corrected", "Invalid Cases Are Corrected")]
-        [InlineData("Can deal w 1 letter words as i do", "Can Deal W 1 Letter Words As I Do")]
+        [InlineData("Can deal w 1 letter words as i do", "Can Deal W 1 Letter Words as I Do")]
         [InlineData("  random spaces   are HONORED    too ", "  Random Spaces   Are HONORED    Too ")]
         [InlineData("Title Case", "Title Case")]
         [InlineData("apostrophe's aren't capitalized", "Apostrophe's Aren't Capitalized")]

src/Humanizer/Transformer/ToTitleCase.cs

@@ -1,4 +1,5 @@
-using System.Globalization;
+using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Text.RegularExpressions;
 
@@ -17,12 +18,14 @@ public string Transform(string input, CultureInfo culture)
 
             var result = input;
             var matches = Regex.Matches(input, @"(\w|[^\u0000-\u007F])+'?\w*");
+            var firstWord = true;
             foreach (Match word in matches)
             {
                 if (!AllCapitals(word.Value))
                 {
-                    result = ReplaceWithTitleCase(word, result, culture);
+                    result = ReplaceWithTitleCase(word, result, culture, firstWord);
                 }
+                firstWord = false;
             }
 
             return result;
@@ -33,10 +36,28 @@ private static bool AllCapitals(string input)
             return input.ToCharArray().All(char.IsUpper);
         }
 
-        private static string ReplaceWithTitleCase(Match word, string source, CultureInfo culture)
+        private static string ReplaceWithTitleCase(Match word, string source, CultureInfo culture, bool firstWord)
         {
+            var articles = new List<string> { "a", "an", "the" };
+            var conjunctions = new List<string> { "and", "as", "but", "if", "nor", "or", "so", "yet" };
+            var prepositions = new List<string> { "as", "at", "by", "for", "in", "of", "off", "on", "to", "up", "via" };
+
             var wordToConvert = word.Value;
-            var replacement = culture.TextInfo.ToUpper(wordToConvert[0]) + culture.TextInfo.ToLower(wordToConvert.Remove(0, 1));
+            string replacement;
+
+
+            if (firstWord || 
+                (!articles.Contains(wordToConvert) &&
+                !conjunctions.Contains(wordToConvert) &&
+                !prepositions.Contains(wordToConvert)))
+            {
+                replacement = culture.TextInfo.ToUpper(wordToConvert[0]) + culture.TextInfo.ToLower(wordToConvert.Remove(0, 1));
+
+            }
+            else
+            {
+                replacement = culture.TextInfo.ToLower(wordToConvert);
+            }
             return source.Substring(0, word.Index) + replacement + source.Substring(word.Index + word.Length);
         }
     }