format/mdext: add single-character bold, italic and strikethrough parsers

format/mdext/shortemphasis.go

@@ -0,0 +1,96 @@
+// Copyright (c) 2024 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package mdext
+
+import (
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var ShortEmphasis goldmark.Extender = &shortEmphasisExtender{}
+
+type shortEmphasisExtender struct{}
+
+func (s *shortEmphasisExtender) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithInlineParsers(
+		util.Prioritized(&italicsParser{}, 500),
+		util.Prioritized(&boldParser{}, 500),
+	))
+}
+
+type italicsDelimiterProcessor struct{}
+
+func (p *italicsDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '_'
+}
+
+func (p *italicsDelimiterProcessor) CanOpenCloser(opener, closer *parser.Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *italicsDelimiterProcessor) OnMatch(consumes int) ast.Node {
+	return ast.NewEmphasis(1)
+}
+
+var defaultItalicsDelimiterProcessor = &italicsDelimiterProcessor{}
+
+type italicsParser struct{}
+
+func (s *italicsParser) Trigger() []byte {
+	return []byte{'_'}
+}
+
+func (s *italicsParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := parser.ScanDelimiter(line, before, 1, defaultItalicsDelimiterProcessor)
+	if node == nil || node.OriginalLength > 1 || before == '_' {
+		return nil
+	}
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}
+
+type boldDelimiterProcessor struct{}
+
+func (p *boldDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '*'
+}
+
+func (p *boldDelimiterProcessor) CanOpenCloser(opener, closer *parser.Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *boldDelimiterProcessor) OnMatch(consumes int) ast.Node {
+	return ast.NewEmphasis(2)
+}
+
+var defaultBoldDelimiterProcessor = &boldDelimiterProcessor{}
+
+type boldParser struct{}
+
+func (s *boldParser) Trigger() []byte {
+	return []byte{'*'}
+}
+
+func (s *boldParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := parser.ScanDelimiter(line, before, 1, defaultBoldDelimiterProcessor)
+	if node == nil || node.OriginalLength > 1 || before == '*' {
+		return nil
+	}
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}

format/mdext/shortstrike.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2024 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package mdext
+
+import (
+	"github.com/yuin/goldmark"
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/extension"
+	"github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var ShortStrike goldmark.Extender = &shortStrikeExtender{length: 1}
+var LongStrike goldmark.Extender = &shortStrikeExtender{length: 2}
+
+type shortStrikeExtender struct {
+	length int
+}
+
+func (s *shortStrikeExtender) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithInlineParsers(
+		util.Prioritized(&strikethroughParser{length: s.length}, 500),
+	))
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(extension.NewStrikethroughHTMLRenderer(), 500),
+	))
+}
+
+type strikethroughDelimiterProcessor struct{}
+
+func (p *strikethroughDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '~'
+}
+
+func (p *strikethroughDelimiterProcessor) CanOpenCloser(opener, closer *parser.Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *strikethroughDelimiterProcessor) OnMatch(consumes int) gast.Node {
+	return ast.NewStrikethrough()
+}
+
+var defaultStrikethroughDelimiterProcessor = &strikethroughDelimiterProcessor{}
+
+type strikethroughParser struct {
+	length int
+}
+
+func (s *strikethroughParser) Trigger() []byte {
+	return []byte{'~'}
+}
+
+func (s *strikethroughParser) Parse(parent gast.Node, block text.Reader, pc parser.Context) gast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := parser.ScanDelimiter(line, before, 1, defaultStrikethroughDelimiterProcessor)
+	if node == nil || node.OriginalLength != s.length || before == '~' {
+		return nil
+	}
+
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}
+
+func (s *strikethroughParser) CloseBlock(parent gast.Node, pc parser.Context) {
+	// nothing to do
+}