package rewrite

import (
	"context"
	"fmt"
	"strings"

	"github.com/miekg/dns"
)

type classRule struct {
	fromClass  uint16
	toClass    uint16
	NextAction string
}

// newClassRule creates a class matching rule
func newClassRule(nextAction string, args ...string) (Rule, error) {
	var from, to uint16
	var ok bool
	if from, ok = dns.StringToClass[strings.ToUpper(args[0])]; !ok {
		return nil, fmt.Errorf("invalid class %q", strings.ToUpper(args[0]))
	}
	if to, ok = dns.StringToClass[strings.ToUpper(args[1])]; !ok {
		return nil, fmt.Errorf("invalid class %q", strings.ToUpper(args[1]))
	}
	return &classRule{from, to, nextAction}, nil
}

// Rewrite rewrites the the current request.
func (rule *classRule) Rewrite(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) Result {
	if rule.fromClass > 0 && rule.toClass > 0 {
		if r.Question[0].Qclass == rule.fromClass {
			r.Question[0].Qclass = rule.toClass
			return RewriteDone
		}
	}
	return RewriteIgnored
}

// Mode returns the processing mode
func (rule *classRule) Mode() string {
	return rule.NextAction
}

// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *classRule) GetResponseRule() ResponseRule {
	return ResponseRule{}
}