feat: support indented math block

block.go

@@ -1,10 +1,11 @@
 package mathjax
 
 import (
+	"bytes"
+
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/parser"
 	"github.com/yuin/goldmark/text"
-	"github.com/yuin/goldmark/util"
 )
 
 type mathJaxBlockParser struct {
@@ -13,7 +14,8 @@ type mathJaxBlockParser struct {
 var defaultMathJaxBlockParser = &mathJaxBlockParser{}
 
 type mathBlockData struct {
-	indent int
+	indent   int
+	isInline bool
 }
 
 var mathBlockInfoKey = parser.NewContextKey()
@@ -28,43 +30,71 @@ func (b *mathJaxBlockParser) Open(parent ast.Node, reader text.Reader, pc parser
 	if pos == -1 {
 		return nil, parser.NoChildren
 	}
-	if line[pos] != '$' {
-		return nil, parser.NoChildren
-	}
-	i := pos
-	for ; i < len(line) && line[i] == '$'; i++ {
-	}
-	if i-pos < 2 {
-		return nil, parser.NoChildren
+
+	// Check for multi-line math block
+	if len(line) >= pos+2 && line[pos] == '$' && line[pos+1] == '$' {
+		pc.Set(mathBlockInfoKey, &mathBlockData{indent: pos, isInline: false})
+		node := NewMathBlock()
+		return node, parser.NoChildren
 	}
-	pc.Set(mathBlockInfoKey, &mathBlockData{indent: pos})
-	node := NewMathBlock()
-	return node, parser.NoChildren
+
+	return nil, parser.NoChildren
 }
 
 func (b *mathJaxBlockParser) Continue(node ast.Node, reader text.Reader, pc parser.Context) parser.State {
 	line, segment := reader.PeekLine()
-	data := pc.Get(mathBlockInfoKey).(*mathBlockData)
-	w, pos := util.IndentWidth(line, 0)
-	if w < 4 {
-		i := pos
-		for ; i < len(line) && line[i] == '$'; i++ {
-		}
-		length := i - pos
-		if length >= 2 && util.IsBlank(line[i:]) {
-			reader.Advance(segment.Stop - segment.Start - segment.Padding)
-			return parser.Close
+	dataInterface := pc.Get(mathBlockInfoKey)
+	if dataInterface == nil {
+		return parser.Close
+	}
+
+	_, ok := dataInterface.(*mathBlockData)
+	if !ok {
+		return parser.Close
+	}
+
+	// Check for closing $$
+	if bytes.HasPrefix(bytes.TrimSpace(line), []byte("$$")) {
+		if !bytes.Equal(bytes.TrimSpace(line), []byte("$$")) {
+			// If there's content after $$, we need to split it
+			parts := bytes.SplitN(bytes.TrimSpace(line), []byte("$$"), 2)
+			if len(parts) > 1 && len(parts[1]) > 0 {
+				// Add the content after $$ to a new paragraph
+				para := ast.NewParagraph()
+				para.AppendChild(para, ast.NewTextSegment(text.NewSegment(segment.Start+bytes.Index(line, parts[1]), segment.Stop)))
+				node.Parent().InsertAfter(node.Parent(), node, para)
+			}
 		}
+		reader.Advance(segment.Stop - segment.Start)
+		return parser.Close
 	}
 
-	pos, padding := util.DedentPosition(line, 0, data.indent)
-	seg := text.NewSegmentPadding(segment.Start+pos, segment.Stop, padding)
-	node.Lines().Append(seg)
-	reader.AdvanceAndSetPadding(segment.Stop-segment.Start-pos-1, padding)
+	node.(*MathBlock).Lines().Append(segment)
 	return parser.Continue | parser.NoChildren
 }
 
 func (b *mathJaxBlockParser) Close(node ast.Node, reader text.Reader, pc parser.Context) {
+	mathBlock, ok := node.(*MathBlock)
+	if !ok {
+		return
+	}
+
+	// Remove leading and trailing $$ from the content
+	if mathBlock.Lines().Len() > 0 {
+		firstLine := mathBlock.Lines().At(0)
+		lastLine := mathBlock.Lines().At(mathBlock.Lines().Len() - 1)
+
+		firstLineContent := reader.Value(firstLine)
+		lastLineContent := reader.Value(lastLine)
+
+		if bytes.HasPrefix(firstLineContent, []byte("$$")) {
+			mathBlock.Lines().Set(0, text.NewSegment(firstLine.Start+2, firstLine.Stop))
+		}
+		if bytes.HasSuffix(lastLineContent, []byte("$$")) {
+			mathBlock.Lines().Set(mathBlock.Lines().Len()-1, text.NewSegment(lastLine.Start, lastLine.Stop-2))
+		}
+	}
+
 	pc.Set(mathBlockInfoKey, nil)
 }
 
@@ -73,9 +103,9 @@ func (b *mathJaxBlockParser) CanInterruptParagraph() bool {
 }
 
 func (b *mathJaxBlockParser) CanAcceptIndentedLine() bool {
-	return false
+	return true
 }
 
 func (b *mathJaxBlockParser) Trigger() []byte {
-	return nil
+	return []byte{'$'}
 }