1 files changed, 161 insertions, 0 deletions
diff --git a/src/cmd/vendor/rsc.io/markdown/heading.go b/src/cmd/vendor/rsc.io/markdown/heading.go
new file mode 100644
index 0000000000..7be6a473aa
--- /dev/null
+++ b/src/cmd/vendor/rsc.io/markdown/heading.go
@@ -0,0 +1,161 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package markdown
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+)
+
+type Heading struct {
+	Position
+	Level int
+	Text  *Text
+	// The HTML id attribute. The parser populates this field if
+	// [Parser.HeadingIDs] is true and the heading ends with text like "{#id}".
+	ID string
+}
+
+func (b *Heading) PrintHTML(buf *bytes.Buffer) {
+	fmt.Fprintf(buf, "<h%d", b.Level)
+	if b.ID != "" {
+		fmt.Fprintf(buf, ` id="%s"`, htmlQuoteEscaper.Replace(b.ID))
+	}
+	buf.WriteByte('>')
+	b.Text.PrintHTML(buf)
+	fmt.Fprintf(buf, "</h%d>\n", b.Level)
+}
+
+func (b *Heading) printMarkdown(buf *bytes.Buffer, s mdState) {
+	// TODO: handle setext headings properly.
+	buf.WriteString(s.prefix)
+	for i := 0; i < b.Level; i++ {
+		buf.WriteByte('#')
+	}
+	buf.WriteByte(' ')
+	// The prefix has already been printed for this line of text.
+	s.prefix = ""
+	b.Text.printMarkdown(buf, s)
+	if b.ID != "" {
+		// A heading text is a block, so it ends in a newline. Move the newline
+		// after the ID.
+		buf.Truncate(buf.Len() - 1)
+		fmt.Fprintf(buf, " {#%s}\n", b.ID)
+	}
+}
+
+func newATXHeading(p *parseState, s line) (line, bool) {
+	peek := s
+	var n int
+	if peek.trimHeading(&n) {
+		s := peek.string()
+		s = trimRightSpaceTab(s)
+		// Remove trailing '#'s.
+		if t := strings.TrimRight(s, "#"); t != trimRightSpaceTab(t) || t == "" {
+			s = t
+		}
+		var id string
+		if p.HeadingIDs {
+			// Parse and remove ID attribute.
+			// It must come before trailing '#'s to more closely follow the spec:
+			//    The optional closing sequence of #s must be preceded by spaces or tabs
+			//    and may be followed by spaces or tabs only.
+			// But Goldmark allows it to come after.
+			id, s = extractID(p, s)
+
+			// Goldmark is strict about the id syntax.
+			for _, c := range id {
+				if c >= 0x80 || !isLetterDigit(byte(c)) {
+					p.corner = true
+				}
+			}
+		}
+		pos := Position{p.lineno, p.lineno}
+		p.doneBlock(&Heading{pos, n, p.newText(pos, s), id})
+		return line{}, true
+	}
+	return s, false
+}
+
+// extractID removes an ID attribute from s if one is present.
+// It returns the attribute value and the resulting string.
+// The attribute has the form "{#...}", where the "..." can contain
+// any character other than '}'.
+// The attribute must be followed only by whitespace.
+func extractID(p *parseState, s string) (id, s2 string) {
+	i := strings.LastIndexByte(s, '{')
+	if i < 0 {
+		return "", s
+	}
+	if i+1 >= len(s) || s[i+1] != '#' {
+		p.corner = true // goldmark accepts {}
+		return "", s
+	}
+	j := i + strings.IndexByte(s[i:], '}')
+	if j < 0 || trimRightSpaceTab(s[j+1:]) != "" {
+		return "", s
+	}
+	id = strings.TrimSpace(s[i+2 : j])
+	if id == "" {
+		p.corner = true // goldmark accepts {#}
+		return "", s
+	}
+	return s[i+2 : j], s[:i]
+}
+
+func newSetextHeading(p *parseState, s line) (line, bool) {
+	var n int
+	peek := s
+	if p.nextB() == p.para() && peek.trimSetext(&n) {
+		p.closeBlock()
+		para, ok := p.last().(*Paragraph)
+		if !ok {
+			return s, false
+		}
+		p.deleteLast()
+		p.doneBlock(&Heading{Position{para.StartLine, p.lineno}, n, para.Text, ""})
+		return line{}, true
+	}
+	return s, false
+}
+
+func (s *line) trimHeading(width *int) bool {
+	t := *s
+	t.trimSpace(0, 3, false)
+	if !t.trim('#') {
+		return false
+	}
+	n := 1
+	for n < 6 && t.trim('#') {
+		n++
+	}
+	if !t.trimSpace(1, 1, true) {
+		return false
+	}
+	*width = n
+	*s = t
+	return true
+}
+
+func (s *line) trimSetext(n *int) bool {
+	t := *s
+	t.trimSpace(0, 3, false)
+	c := t.peek()
+	if c == '-' || c == '=' {
+		for t.trim(c) {
+		}
+		t.skipSpace()
+		if t.eof() {
+			if c == '=' {
+				*n = 1
+			} else {
+				*n = 2
+			}
+			return true
+		}
+	}
+	return false
+}