package tls

import (
	ctls "crypto/tls"

	"github.com/coredns/coredns/core/dnsserver"
	"github.com/coredns/coredns/plugin"
	"github.com/coredns/coredns/plugin/pkg/tls"

	"github.com/caddyserver/caddy"
)

func init() { plugin.Register("tls", setup) }

func setup(c *caddy.Controller) error {
	err := parseTLS(c)
	if err != nil {
		return plugin.Error("tls", err)
	}
	return nil
}

func setTLSDefaults(tls *ctls.Config) {
	tls.MinVersion = ctls.VersionTLS12
	tls.MaxVersion = ctls.VersionTLS13
	tls.CipherSuites = []uint16{
		ctls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
		ctls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
		ctls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
		ctls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
		ctls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
		ctls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
		ctls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
		ctls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
		ctls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
	}
	tls.PreferServerCipherSuites = true
}

func parseTLS(c *caddy.Controller) error {
	config := dnsserver.GetConfig(c)

	if config.TLSConfig != nil {
		return plugin.Error("tls", c.Errf("TLS already configured for this server instance"))
	}

	for c.Next() {
		args := c.RemainingArgs()
		if len(args) < 2 || len(args) > 3 {
			return plugin.Error("tls", c.ArgErr())
		}
		clientAuth := ctls.NoClientCert
		for c.NextBlock() {
			switch c.Val() {
			case "client_auth":
				authTypeArgs := c.RemainingArgs()
				if len(authTypeArgs) != 1 {
					return c.ArgErr()
				}
				switch authTypeArgs[0] {
				case "nocert":
					clientAuth = ctls.NoClientCert
				case "request":
					clientAuth = ctls.RequestClientCert
				case "require":
					clientAuth = ctls.RequireAnyClientCert
				case "verify_if_given":
					clientAuth = ctls.VerifyClientCertIfGiven
				case "require_and_verify":
					clientAuth = ctls.RequireAndVerifyClientCert
				default:
					return c.Errf("unknown authentication type '%s'", authTypeArgs[0])
				}
			default:
				return c.Errf("unknown option '%s'", c.Val())
			}
		}
		tls, err := tls.NewTLSConfigFromArgs(args...)
		if err != nil {
			return err
		}
		tls.ClientAuth = clientAuth
		// NewTLSConfigFromArgs only sets RootCAs, so we need to let ClientCAs refer to it.
		tls.ClientCAs = tls.RootCAs

		setTLSDefaults(tls)

		config.TLSConfig = tls
	}
	return nil
}
