internal/rosa/azalea: improve delimiter insertion

internal/rosa/azalea/azalea.go

@@ -364,17 +364,17 @@ func insertSemicolons(r io.Reader) (io.Reader, error) {
 	var buf strings.Builder
 	nlsemi := false
 	nlcomma := false
-	b := ""
+	b := new(RuneStack)
 
 	tok := s.Scan()
 	for tok != scanner.EOF {
 		switch tok {
 		case '\n':
-			if b[len(b)-1] == '{' && nlsemi {
+			if b.Peek() == '{' && nlsemi {
 				buf.WriteRune(';')
 				nlsemi = false
 			}
-			if b[len(b)-1] == '[' && nlcomma {
+			if b.Peek() == '[' && nlcomma {
 				buf.WriteRune(',')
 				nlcomma = false
 			}
@@ -386,38 +386,40 @@ func insertSemicolons(r io.Reader) (io.Reader, error) {
 			nlcomma = false
 		case '{', '[':
 			nlsemi = false
+			nlcomma = false
 			buf.WriteRune(tok)
-			b += string(tok)
+			b.Push(tok)
 		case '}', ']':
-			if len(b) > 0 && b[len(b)-1] == '{' && nlsemi {
-				buf.WriteRune(';')
-				nlsemi = false
-			}
-			if len(b) > 0 && b[len(b)-1] == '[' && nlcomma {
-				buf.WriteRune(',')
-				nlcomma = false
-			}
-			if len(b) > 1 && b[len(b)-1] == '{' {
-				nlsemi = true
-			}
-			if len(b) > 1 && b[len(b)-1] == '[' {
+			r := b.Pop()
+			if r == '{' {
+				if nlsemi {
+					buf.WriteRune(';')
+				}
 				nlcomma = true
 				nlsemi = true
 			}
-
-			if len(b) > 1 {
-				b = b[:len(b)-1]
+			if r == '[' {
+				if nlcomma {
+					buf.WriteRune(',')
+				}
+				nlsemi = true
 			}
 			buf.WriteRune(tok)
+			if b.Peek() == '}' && nlsemi {
+				buf.WriteRune(';')
+			}
+			if b.Peek() == ']' && nlcomma {
+				buf.WriteRune(',')
+			}
 		case '+', ':', '=':
 			buf.WriteRune(tok)
 			nlsemi = false
 			nlcomma = false
 		case scanner.String, scanner.RawString, scanner.Int, scanner.Ident:
 			buf.WriteString(s.TokenText())
-			if len(b) > 0 && b[len(b)-1] == '{' {
+			if b.Peek() == '{' {
 				nlsemi = true
-			} else if len(b) > 0 && b[len(b)-1] == '[' {
+			} else if b.Peek() == '[' {
 				nlcomma = true
 			}
 		default:
@@ -428,3 +430,40 @@ func insertSemicolons(r io.Reader) (io.Reader, error) {
 	}
 	return strings.NewReader(buf.String()), nil
 }
+
+type Stack[T any] interface {
+	Push(T)
+	Pop() T
+	Peek() T
+	Length() int
+}
+type RuneStack struct {
+	arr []rune
+	Stack[rune]
+}
+
+func (s *RuneStack) Push(r rune) {
+	s.arr = append(s.arr, r)
+}
+
+func (s *RuneStack) String() string {
+	return string(s.arr)
+}
+func (s *RuneStack) Peek() rune {
+	if s.Length() > 0 {
+		return s.arr[s.Length()-1]
+	}
+	return 0
+}
+func (s *RuneStack) Pop() rune {
+	v := s.Peek()
+	if s.Length() > 1 {
+		s.arr = s.arr[:s.Length()-1]
+	} else {
+		s.arr = make([]rune, 0)
+	}
+	return v
+}
+func (s *RuneStack) Length() int {
+	return len(s.arr)
+}