From 8dfd2fcf9bdfe9957106d4ded4cec39b864ce8af Mon Sep 17 00:00:00 2001
From: hugmouse <mysh@tuta.io>
Date: Fri, 5 Mar 2021 14:34:56 +0800
Subject: [PATCH 1/2] Fix lexer for "----" (<hr/>) case

The point is that there may be another character in the string.
For example, a space or a line break.

Because we check the whole string, not the first 4 characters - we can ignore the variant where it can be "----\s" or "----\r\n" and make the wrong markup.

Alternatively: use `startsWith("----")`, but this is a bit more expensive operation.
---
 markup/lexer.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/markup/lexer.go b/markup/lexer.go
index 607393f..fbd87fc 100644
--- a/markup/lexer.go
+++ b/markup/lexer.go
@@ -235,7 +235,7 @@ normalState:
 	case startsWith("<="):
 		addParagraphIfNeeded()
 		addLine(parseTransclusion(line, state.name))
-	case line == "----":
+	case line[:4] == "----":
 		addParagraphIfNeeded()
 		*ast = append(*ast, Line{id: -1, contents: "<hr/>"})
 	case MatchesImg(line):

From 62c616985d8bb70898fc13093d2bccb454ea82bd Mon Sep 17 00:00:00 2001
From: hugmouse <mysh@tuta.io>
Date: Fri, 5 Mar 2021 16:29:39 +0800
Subject: [PATCH 2/2] Replace old method with new that is a little
 overcomplicated

---
 markup/hr.go    | 34 ++++++++++++++++++++++++++++++++++
 markup/lexer.go |  2 +-
 2 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 markup/hr.go

diff --git a/markup/hr.go b/markup/hr.go
new file mode 100644
index 0000000..278138a
--- /dev/null
+++ b/markup/hr.go
@@ -0,0 +1,34 @@
+package markup
+
+import (
+	"unicode"
+)
+
+// MatchesHorizontalLine checks if the string can be interpreted as suitable for rendering as <hr/>.
+//
+// The rule is: if there are more than 4 characters "-" in the string, then make it a horizontal line.
+// Otherwise it is a paragraph (<p>).
+func MatchesHorizontalLine(line string) bool {
+	counter := 0
+
+	// Check initially that the symbol is "-". If it is not a "-", it is most likely a space or another character.
+	// With unicode.IsLetter() we can separate spaces and characters.
+	for _, ch := range line {
+		if ch == '-' {
+			counter++
+			continue
+		}
+		// If we bump into any other character (letter) in the line, it is immediately an incorrect horizontal line.
+		// There is no point in counting further, we end the loop.
+		if unicode.IsLetter(ch) {
+			counter = 0
+			break
+		}
+	}
+
+	if counter >= 4 {
+		return true
+	}
+
+	return false
+}
diff --git a/markup/lexer.go b/markup/lexer.go
index fbd87fc..bf077e7 100644
--- a/markup/lexer.go
+++ b/markup/lexer.go
@@ -235,7 +235,7 @@ normalState:
 	case startsWith("<="):
 		addParagraphIfNeeded()
 		addLine(parseTransclusion(line, state.name))
-	case line[:4] == "----":
+	case MatchesHorizontalLine(line):
 		addParagraphIfNeeded()
 		*ast = append(*ast, Line{id: -1, contents: "<hr/>"})
 	case MatchesImg(line):