package pow

// Verifier handles validation of PoW challenges
type Verifier struct {
	config *Config
}

// NewVerifier creates a new challenge verifier
func NewVerifier(config *Config) *Verifier {
	return &Verifier{
		config: config,
	}
}

// VerifyChallenge validates challenge authenticity and expiration
func (v *Verifier) VerifyChallenge(challenge *Challenge) error {
	// Check expiration first (cheap operation)
	if challenge.IsExpired(v.config.ChallengeTTL) {
		return ErrExpiredChallenge
	}

	// Check HMAC signature (expensive operation)
	if err := challenge.VerifyHMAC(v.config.HMACSecret); err != nil {
		return err
	}

	return nil
}