package resolver

import "errors"

// NoAnswerError is returned when the walk to a name's nameservers
// reached a zone through a referral and none of that zone's
// nameservers, Nameservers as the referral names them, answered. Err
// says why they did not.
type NoAnswerError struct {
	Nameservers []string
	Err         error
}

func (e *NoAnswerError) Error() string {
	return e.Err.Error()
}

func (e *NoAnswerError) Unwrap() error {
	return e.Err
}

// Sentinel errors returned by the resolver.
var (
	// ErrNoNameservers is returned when no authoritative NS
	// could be discovered for a domain.
	ErrNoNameservers = errors.New(
		"no authoritative nameservers found",
	)

	// ErrNXDomain is returned when the servers of the zone a domain
	// is in answer NXDOMAIN: the domain does not exist.
	ErrNXDomain = errors.New("domain does not exist")

	// ErrNoNameserverAnswered is returned when every nameserver
	// asked about a name timed out, failed or returned a referral,
	// so whether the name has addresses is unknown.
	ErrNoNameserverAnswered = errors.New("no nameserver answered")

	// ErrNoNameserverAddress is returned when a nameserver is to be
	// asked and no address for it was given.
	ErrNoNameserverAddress = errors.New("nameserver has no address")

	// ErrUnusableReply is returned when a server replied with an
	// error such as SERVFAIL, or with a referral that leads no
	// closer to the name asked about.
	ErrUnusableReply = errors.New(
		"reply is an error or a referral that leads no closer",
	)

	// ErrTruncated is the reason given for a reply too large for UDP
	// whose retry over TCP failed.
	ErrTruncated = errors.New(
		"reply truncated and its retry over TCP failed",
	)

	// ErrRecursionAvailable is the reason a reply from a root server's
	// address marked recursion available is not used. Root servers offer
	// no recursion, so the reply came from something on the network
	// answering in their place.
	ErrRecursionAvailable = errors.New(
		"reply marked recursion available, so not from a root server",
	)

	// ErrIntercepted is returned when every root server refused a
	// query or gave a reply marked recursion available. Root servers do
	// neither, so those replies came from something on the network
	// answering in their place. On such a network dnswatcher fails with
	// it, by design: nothing works around the interception.
	ErrIntercepted = errors.New("this network intercepts DNS queries")

	// ErrCNAMEDepthExceeded is returned when a CNAME chain
	// exceeds MaxCNAMEDepth.
	ErrCNAMEDepthExceeded = errors.New(
		"CNAME chain depth exceeded",
	)

	// ErrLookupDepthExceeded is returned when nameserver addresses
	// were not looked up because lookups were already maxLookupDepth
	// deep, one inside another.
	ErrLookupDepthExceeded = errors.New(
		"lookups of nameserver addresses go too deep",
	)

	// ErrContextCanceled wraps context cancellation for the
	// resolver's iterative queries.
	ErrContextCanceled = errors.New("context canceled")
)