Return number of matching lines when finding nearest

Author: jcansdale

src/GitHub.App/Services/NavigationService.cs

@@ -32,7 +32,7 @@ public IVsTextView NavigateToEquivalentPosition(IVsTextView sourceView, string t
 
             var fromLines = ReadLines(text1);
             var toLines = ReadLines(text2);
-            var matchingLine = FindNearestMatchingLine(fromLines, toLines, line);
+            var matchingLine = FindMatchingLine(fromLines, toLines, line);
             if (matchingLine == -1)
             {
                 // If we can't match line use orignal as best guess.
@@ -54,32 +54,52 @@ public IVsTextView FindActiveView()
             return hresult == VSConstants.S_OK ? view : null;
         }
 
-        public int FindNearestMatchingLine(IList<string> fromLines, IList<string> toLines, int line)
+        public int FindMatchingLine(IList<string> fromLines, IList<string> toLines, int line)
+        {
+            int matchedLines;
+            return FindNearestMatchingLine(fromLines, toLines, line, out matchedLines);
+        }
+
+        public int FindNearestMatchingLine(IList<string> fromLines, IList<string> toLines, int line, out int matchedLines)
         {
             line = line < fromLines.Count ? line : fromLines.Count - 1; // VS shows one extra line at end
             var fromLine = fromLines[line];
 
+            matchedLines = 0;
+            var matchingLine = -1;
             for (var offset = 0; true; offset++)
             {
                 var lineAbove = line + offset;
                 var checkAbove = lineAbove < toLines.Count;
                 if (checkAbove && toLines[lineAbove] == fromLine)
                 {
-                    return lineAbove;
+                    if (matchedLines == 0)
+                    {
+                        matchingLine = lineAbove;
+                    }
+
+                    matchedLines++;
                 }
 
                 var lineBelow = line - offset;
                 var checkBelow = lineBelow >= 0;
-                if (checkBelow && lineBelow < toLines.Count && toLines[lineBelow] == fromLine)
+                if (checkBelow && offset > 0 && lineBelow < toLines.Count && toLines[lineBelow] == fromLine)
                 {
-                    return lineBelow;
+                    if (matchedLines == 0)
+                    {
+                        matchingLine = lineBelow;
+                    }
+
+                    matchedLines++;
                 }
 
                 if (!checkAbove && !checkBelow)
                 {
-                    return -1;
+                    break;
                 }
             }
+
+            return matchingLine;
         }
 
         string GetText(IVsTextView textView)

test/UnitTests/GitHub.App/Services/NavigationServiceTests.cs

@@ -8,21 +8,24 @@ public class NavigationServiceTests
 {
     public class TheFindNearestMatchingLineMethod
     {
-        [TestCase(new[] { "line" }, new[] { "line" }, 0, 0, Description = "Match same line")]
-        [TestCase(new[] { "line" }, new[] { "line_no_match" }, 0, -1, Description = "No matching line")]
-        [TestCase(new[] { "line" }, new[] { "", "line" }, 0, 1, Description = "Match line moved up")]
-        [TestCase(new[] { "", "line" }, new[] { "line" }, 1, 0, Description = "Match line moved down")]
-        [TestCase(new[] { "line", "line" }, new[] { "line", "line" }, 0, 0, Description = "Match nearest line")]
-        [TestCase(new[] { "line", "line" }, new[] { "line", "line" }, 1, 1, Description = "Match nearest line")]
-        [TestCase(new[] { "line" }, new[] { "line" }, 1, 0, Description = "Treat after last line the same as last line")]
-        public void FindNearestMatching(IList<string> fromLines, IList<string> toLines, int line, int expectLine)
+        [TestCase(new[] { "line" }, new[] { "line" }, 0, 0, 1, Description = "Match same line")]
+        [TestCase(new[] { "line" }, new[] { "line_no_match" }, 0, -1, 0, Description = "No matching line")]
+        [TestCase(new[] { "line" }, new[] { "", "line" }, 0, 1, 1, Description = "Match line moved up")]
+        [TestCase(new[] { "", "line" }, new[] { "line" }, 1, 0, 1, Description = "Match line moved down")]
+        [TestCase(new[] { "line", "line" }, new[] { "line", "line" }, 0, 0, 2, Description = "Match nearest line")]
+        [TestCase(new[] { "line", "line" }, new[] { "line", "line" }, 1, 1, 2, Description = "Match nearest line")]
+        [TestCase(new[] { "line" }, new[] { "line" }, 1, 0, 1, Description = "Treat after last line the same as last line")]
+        public void FindNearestMatchingLine(IList<string> fromLines, IList<string> toLines, int line,
+            int expectNearestLine, int expectMatchingLines)
         {
             var sp = Substitute.For<IServiceProvider>();
             var target = new NavigationService(sp);
 
-            var matchingLine = target.FindNearestMatchingLine(fromLines, toLines, line);
+            int matchedLines;
+            var nearestLine = target.FindNearestMatchingLine(fromLines, toLines, line, out matchedLines);
 
-            Assert.That(matchingLine, Is.EqualTo(expectLine));
+            Assert.That(nearestLine, Is.EqualTo(expectNearestLine));
+            Assert.That(matchedLines, Is.EqualTo(expectMatchingLines));
         }
     }
 }