--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vendor/github.com/yosssi/gcss/mixin_declaration.go	Sun Jul 23 13:18:53 2023 +0000
@@ -0,0 +1,85 @@
+package gcss
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+// mixinDeclaration represents a mixin declaration.
+type mixinDeclaration struct {
+	elementBase
+	name       string
+	paramNames []string
+}
+
+// WriteTo writes the selector to the writer.
+func (md *mixinDeclaration) WriteTo(w io.Writer) (int64, error) {
+	return 0, nil
+}
+
+// mixinNP extracts a mixin name and parameters from the line.
+func mixinNP(ln *line, isDeclaration bool) (string, []string, error) {
+	s := strings.TrimSpace(ln.s)
+
+	if !strings.HasPrefix(s, dollarMark) {
+		return "", nil, fmt.Errorf("mixin must start with %q [line: %d]", dollarMark, ln.no)
+	}
+
+	s = strings.TrimPrefix(s, dollarMark)
+
+	np := strings.Split(s, openParenthesis)
+
+	if len(np) != 2 {
+		return "", nil, fmt.Errorf("mixin's format is invalid [line: %d]", ln.no)
+	}
+
+	paramsS := strings.TrimSpace(np[1])
+
+	if !strings.HasSuffix(paramsS, closeParenthesis) {
+		return "", nil, fmt.Errorf("mixin must end with %q [line: %d]", closeParenthesis, ln.no)
+	}
+
+	paramsS = strings.TrimSuffix(paramsS, closeParenthesis)
+
+	if strings.Index(paramsS, closeParenthesis) != -1 {
+		return "", nil, fmt.Errorf("mixin's format is invalid [line: %d]", ln.no)
+	}
+
+	var params []string
+
+	if paramsS != "" {
+		params = strings.Split(paramsS, comma)
+	}
+
+	for i, p := range params {
+		p = strings.TrimSpace(p)
+
+		if isDeclaration {
+			if !strings.HasPrefix(p, dollarMark) {
+				return "", nil, fmt.Errorf("mixin's parameter must start with %q [line: %d]", dollarMark, ln.no)
+			}
+
+			p = strings.TrimPrefix(p, dollarMark)
+		}
+
+		params[i] = p
+	}
+
+	return np[0], params, nil
+}
+
+// newMixinDeclaration creates and returns a mixin declaration.
+func newMixinDeclaration(ln *line, parent element) (*mixinDeclaration, error) {
+	name, paramNames, err := mixinNP(ln, true)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &mixinDeclaration{
+		elementBase: newElementBase(ln, parent),
+		name:        name,
+		paramNames:  paramNames,
+	}, nil
+}