Add tests; make finder more efficient

Author: Enkidu93

src/SIL.Machine/PunctuationAnalysis/QuotationMarkFinder.cs

@@ -2,7 +2,6 @@
 using System.Globalization;
 using System.Linq;
 using PCRE;
-using SIL.Extensions;
 
 namespace SIL.Machine.PunctuationAnalysis
 {
@@ -47,15 +46,18 @@ public List<QuotationMarkStringMatch> FindAllPotentialQuotationMarksInTextSegmen
                 )
                 .Select(m =>
                 {
-                    int[] textElementBeginnings = StringInfo.ParseCombiningCharacters(textSegment.Text);
-                    int endIndex = textElementBeginnings.IndexOf(m.Groups[0].EndIndex);
-                    if (endIndex == -1)
-                        endIndex = textElementBeginnings.Length;
-                    return new QuotationMarkStringMatch(
-                        textSegment,
-                        textElementBeginnings.IndexOf(m.Groups[0].Index),
-                        endIndex
-                    );
+                    int[] textElementIndices = StringInfo.ParseCombiningCharacters(textSegment.Text);
+                    int startIndex = 0;
+                    int endIndex = textElementIndices.Length;
+                    for (int textElementIndex = 0; textElementIndex < textElementIndices.Length; textElementIndex++)
+                    {
+                        int stringIndex = textElementIndices[textElementIndex];
+                        if (stringIndex == m.Groups[0].Index)
+                            startIndex = textElementIndex;
+                        if (stringIndex == m.Groups[0].EndIndex)
+                            endIndex = textElementIndex;
+                    }
+                    return new QuotationMarkStringMatch(textSegment, startIndex, endIndex);
                 })
                 .ToList();
         }

tests/SIL.Machine.Tests/PunctuationAnalysis/QuotationMarkFinderTests.cs

@@ -282,6 +282,22 @@ public void ThatAllPossibleQuotationMarksAreIdentified()
                     ]
                 )
         );
+
+        Assert.That(
+            quotationMarkFinder
+                .FindAllPotentialQuotationMarksInTextSegment(
+                    new TextSegment.Builder().SetText("उत्पत्ति \"पुस्तकले").Build()
+                )
+                .SequenceEqual(
+                    [
+                        new QuotationMarkStringMatch(
+                            new TextSegment.Builder().SetText("उत्पत्ति \"पुस्तकले").Build(),
+                            6,
+                            7
+                        ),
+                    ]
+                )
+        );
     }
 
     [Test]

tests/SIL.Machine.Tests/PunctuationAnalysis/TextSegmentTests.cs

@@ -188,6 +188,8 @@ public void Length()
 
         textSegment = new TextSegment.Builder().SetText("new example text").Build();
         Assert.That(textSegment.Length, Is.EqualTo("new example text".Length));
+        textSegment = new TextSegment.Builder().SetText("उत्पत्ति पुस्तकले").Build();
+        Assert.That(textSegment.Length, Is.EqualTo(11));
     }
 
     [Test]