From ddb61bdfc034a683f755dec6ddc80627d2d43522 Mon Sep 17 00:00:00 2001
From: Adam Scarr <adam@vektah.net>
Date: Sun, 13 Aug 2017 22:11:27 +1000
Subject: [PATCH] Add an Until function

---
 combinator.go      | 32 +++++++++++++++++++++++++++++++-
 combinator_test.go | 14 ++++++++++++++
 state.go           |  4 ++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/combinator.go b/combinator.go
index d7be3f9..4e7e4a5 100644
--- a/combinator.go
+++ b/combinator.go
@@ -26,7 +26,7 @@ func NoAutoWS(parser Parserish) Parser {
 	parserfied := Parsify(parser)
 	return func(ps *State, node *Result) {
 		oldWS := ps.WS
-		ps.WS = func(ps *State) {}
+		ps.WS = NoWhitespace
 		parserfied(ps, node)
 		ps.WS = oldWS
 	}
@@ -145,6 +145,36 @@ func Maybe(parser Parserish) Parser {
 	})
 }
 
+// Until will consume all input until one of the given parsers match. This is running every parser over every byte,
+// so its probably going to be slow.
+func Until(parsers ...Parserish) Parser {
+	parserfied := ParsifyAll(parsers...)
+	return NewParser("Until()", func(ps *State, node *Result) {
+		ws := ps.WS
+		ps.WS = NoWhitespace
+		defer func() {
+			ps.WS = ws
+		}()
+		startPos := ps.Pos
+		for ps.Pos < len(ps.Input) {
+			endPos := ps.Pos
+			for _, p := range parserfied {
+				ps.Pos = endPos
+
+				p(ps, node)
+
+				if !ps.Errored() {
+					node.Token = ps.Input[startPos:endPos]
+					return
+				}
+				ps.Recover()
+			}
+			ps.Pos++
+		}
+		node.Token = ps.Input[startPos:ps.Pos]
+	})
+}
+
 // Bind will set the node .Result when the given parser matches
 // This is useful for giving a value to keywords and constant literals
 // like true and false. See the json parser for an example.
diff --git a/combinator_test.go b/combinator_test.go
index c1eedb3..e792c47 100644
--- a/combinator_test.go
+++ b/combinator_test.go
@@ -181,6 +181,20 @@ func TestMap(t *testing.T) {
 	})
 }
 
+func TestUntil(t *testing.T) {
+	parser := Until("world", ".")
+
+	t.Run("success", func(t *testing.T) {
+		result, _ := runParser("this is the end of the world", parser)
+		require.Equal(t, "this is the end of the ", result.Token)
+	})
+
+	t.Run("eof", func(t *testing.T) {
+		result, _ := runParser("this is the end of it all", parser)
+		require.Equal(t, "this is the end of it all", result.Token)
+	})
+}
+
 func TestBind(t *testing.T) {
 	parser := Bind("true", true)
 
diff --git a/state.go b/state.go
index 5d35ac8..9d081cf 100644
--- a/state.go
+++ b/state.go
@@ -44,6 +44,10 @@ func UnicodeWhitespace(s *State) {
 		}
 		s.Pos += w
 	}
+}
+
+// NoWhitespace disables automatic whitespace matching
+func NoWhitespace(s *State) {
 
 }