Merge branch 'Ellested-dev' into dev

datalust · Apr 13, 2021 · 21f53b2 · 21f53b2
2 parents 886c160 + 5f48738
commit 21f53b2
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diff --git a/src/Superpower/Parsers/Span.cs b/src/Superpower/Parsers/Span.cs
@@ -258,5 +258,37 @@ public static TextParser<TextSpan> MatchedBy<T>(TextParser<T> parser)
                     result.Remainder);
             };
         }
+
+        /// <summary>
+        /// Parse input until the <paramref name="text"/> string is present.
+        /// </summary>
+        /// <param name="text">The string to match until. The content of the <paramref name="text"/> is not included in the result.</param>
+        /// <returns>A parser that will match anything until the <paramref name="text"/> string argument is present in the Span.</returns>
+        /// <exception cref="ArgumentNullException">The <paramref name="text"/> is null.</exception>
+        public static TextParser<TextSpan> Except(string text)
+        {
+            if (text == null) throw new ArgumentNullException(nameof(text));
+
+            return (TextSpan input) =>
+            {
+                TextSpan remainder = input;
+                var matchIndex = 0;
+
+                while (remainder.Length>0)
+                {
+                    var current = remainder.ConsumeChar();
+                    remainder = current.Remainder;
+                    if (current.Value != text[matchIndex++]) matchIndex = 0;
+                    if (matchIndex == text.Length)
+                    {
+                        var foundPosition = remainder.Position.Absolute - input.Position.Absolute - text.Length;
+                        var found = input.Skip(foundPosition);
+                        return Result.Value(input.Until(found), found, found);
+                    }
+                }
+
+                return Result.Empty<TextSpan>(input);
+            };
+        }
     }
 }
diff --git a/test/Superpower.Tests/Parsers/SpanTests.cs b/test/Superpower.Tests/Parsers/SpanTests.cs
@@ -4,6 +4,7 @@
 
 namespace Superpower.Tests.Parsers
 {
+    using System;
     using System.Text.RegularExpressions;
 
     public class SpanTests
@@ -83,5 +84,38 @@ public void RegexMatches()
             var r = parser(input);
             Assert.Equal("Foo", r.Value.ToStringValue());
         }
+
+        [Theory]
+        [InlineData("STOP", "")]
+        [InlineData("123STOP", "123")]
+        [InlineData("STOP123", "")]
+        [InlineData("123STOP456STOP789", "123")]
+        public void ExceptMatchesUntilStopwordIsPresent(string text, string expected)
+        {
+            var result = Span.Except("STOP").Parse(text);
+            Assert.Equal(expected, result.ToStringValue());
+        }
+
+        [Theory]
+        [InlineData(null)]
+        public void ExceptFailsWhenArgumentIsNull(string text)
+        {
+            Assert.Throws<ArgumentNullException>(() => Span.Except(text).Parse(""));
+        }
+
+        [Theory]
+        [InlineData("Begin123STOPEnd")]
+        public void ExceptMatchesWhenTheInputAbsolutePositionIsNonZero(string text)
+        {
+            var test =
+                from begin in Span.EqualTo("Begin")
+                from value in Span.Except("STOP")
+                from stop in Span.EqualTo("STOP")
+                from end in Span.EqualTo("End")
+                select value;
+            var result = test.Parse(text).ToStringValue();
+
+            Assert.Equal("123", result);
+        }
     }
 }