func (rule *Rule) String() string {
	result := ""
	if rule.Kind == QualifiedRule {
		for i, sel := range rule.Selectors {
			if i != 0 {
				result += ", "
			}
			result += sel
		}
	} else {
		result += fmt.Sprintf("%s", rule.Name)
		if rule.Prelude != "" {
			if result != "" {
				result += " "
			}
			result += fmt.Sprintf("%s", rule.Prelude)
		}
	}
	if (len(rule.Declarations) == 0) && (len(rule.Rules) == 0) {
		result += ";"
	} else {
		result += " {\n"
		if rule.EmbedsRules() {
			for _, subRule := range rule.Rules {
				result += fmt.Sprintf("%s%s\n", rule.indent(), subRule.String())
			}
		} else {
			for _, decl := range rule.Declarations {
				result += fmt.Sprintf("%s%s\n", rule.indent(), decl.String())
			}
		}
		result += fmt.Sprintf("%s}", rule.indentEndBlock())
	}
	return result
}
Returns the string representation of a rule
package css
import (
	"fmt"
	"strings"
)
const (
	indentSpace = 2
)
type RuleKind int
const (
	QualifiedRule RuleKind = iota
	AtRule
)
var atRulesWithRulesBlock = []string{
	"@document", "@font-feature-values", "@keyframes", "@media", "@supports",
}
type Rule struct {
	Kind RuleKind
	Name string
	Prelude string
	Selectors []string
	Declarations []*Declaration
	Rules []*Rule
	EmbedLevel int
}
func NewRule(kind RuleKind) *Rule {
	return &Rule{
		Kind: kind,
	}
}
func (kind RuleKind) String() string {
	switch kind {
	case QualifiedRule:
		return "Qualified Rule"
	case AtRule:
		return "At Rule"
	default:
		return "WAT"
	}
}
func (rule *Rule) EmbedsRules() bool {
	if rule.Kind == AtRule {
		for _, atRuleName := range atRulesWithRulesBlock {
			if rule.Name == atRuleName {
				return true
			}
		}
	}
	return false
}
func (rule *Rule) Equal(other *Rule) bool {
	if (rule.Kind != other.Kind) ||
		(rule.Prelude != other.Prelude) ||
		(rule.Name != other.Name) {
		return false
	}
	if (len(rule.Selectors) != len(other.Selectors)) ||
		(len(rule.Declarations) != len(other.Declarations)) ||
		(len(rule.Rules) != len(other.Rules)) {
		return false
	}
	for i, sel := range rule.Selectors {
		if sel != other.Selectors[i] {
			return false
		}
	}
	for i, decl := range rule.Declarations {
		if !decl.Equal(other.Declarations[i]) {
			return false
		}
	}
	for i, rule := range rule.Rules {
		if !rule.Equal(other.Rules[i]) {
			return false
		}
	}
	return true
}
func (rule *Rule) Diff(other *Rule) []string {
	result := []string{}
	if rule.Kind != other.Kind {
		result = append(result, fmt.Sprintf("Kind: %s | %s", rule.Kind.String(), other.Kind.String()))
	}
	if rule.Prelude != other.Prelude {
		result = append(result, fmt.Sprintf("Prelude: \"%s\" | \"%s\"", rule.Prelude, other.Prelude))
	}
	if rule.Name != other.Name {
		result = append(result, fmt.Sprintf("Name: \"%s\" | \"%s\"", rule.Name, other.Name))
	}
	if len(rule.Selectors) != len(other.Selectors) {
		result = append(result, fmt.Sprintf("Selectors: %v | %v", strings.Join(rule.Selectors, ", "), strings.Join(other.Selectors, ", ")))
	} else {
		for i, sel := range rule.Selectors {
			if sel != other.Selectors[i] {
				result = append(result, fmt.Sprintf("Selector: \"%s\" | \"%s\"", sel, other.Selectors[i]))
			}
		}
	}
	if len(rule.Declarations) != len(other.Declarations) {
		result = append(result, fmt.Sprintf("Declarations Nb: %d | %d", len(rule.Declarations), len(other.Declarations)))
	} else {
		for i, decl := range rule.Declarations {
			if !decl.Equal(other.Declarations[i]) {
				result = append(result, fmt.Sprintf("Declaration: \"%s\" | \"%s\"", decl.String(), other.Declarations[i].String()))
			}
		}
	}
	if len(rule.Rules) != len(other.Rules) {
		result = append(result, fmt.Sprintf("Rules Nb: %d | %d", len(rule.Rules), len(other.Rules)))
	} else {
		for i, rule := range rule.Rules {
			if !rule.Equal(other.Rules[i]) {
				result = append(result, fmt.Sprintf("Rule: \"%s\" | \"%s\"", rule.String(), other.Rules[i].String()))
			}
		}
	}
	return result
}