// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package dns

import "inet.af/netaddr"

// An OSConfigurator applies DNS settings to the operating system.
type OSConfigurator interface {
	// SetDNS updates the OS's DNS configuration to match cfg.
	// If cfg is the zero value, all Tailscale-related DNS
	// configuration is removed.
	// SetDNS must not be called after Close.
	SetDNS(cfg OSConfig) error
	// SupportsSplitDNS reports whether the configurator is capable of
	// installing a resolver only for specific DNS suffixes. If false,
	// the configurator can only set a global resolver.
	SupportsSplitDNS() bool
	// Close removes Tailscale-related DNS configuration from the OS.
	Close() error
}

// OSConfig is an OS DNS configuration.
type OSConfig struct {
	// Nameservers are the IP addresses of the nameservers to use.
	Nameservers []netaddr.IP
	// SearchDomains are the domain suffixes to use when expanding
	// single-label name queries. SearchDomains is additive to
	// whatever non-Tailscale search domains the OS has.
	SearchDomains []string
	// MatchDomains are the DNS suffixes for which Nameservers should
	// be used. If empty, Nameservers is installed as the "primary" resolver.
	// A non-empty MatchDomains requests a "split DNS" configuration
	// from the OS, which will only work with OSConfigurators that
	// report SupportsSplitDNS()=true.
	MatchDomains []string
}