package transport

import (
	"context"
	"net"

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/common/dialer"
	"github.com/sagernet/sing-box/common/tls"
	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing-box/dns"
	"github.com/sagernet/sing-box/log"
	"github.com/sagernet/sing-box/option"
	"github.com/sagernet/sing/common"
	E "github.com/sagernet/sing/common/exceptions"
	"github.com/sagernet/sing/common/logger"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"

	mDNS "github.com/miekg/dns"
)

var _ adapter.DNSTransport = (*TLSTransport)(nil)

func RegisterTLS(registry *dns.TransportRegistry) {
	dns.RegisterTransport[option.RemoteTLSDNSServerOptions](registry, C.DNSTypeTLS, NewTLS)
}

type TLSTransport struct {
	dns.TransportAdapter
	logger      logger.ContextLogger
	dialer      tls.Dialer
	serverAddr  M.Socksaddr
	multiplexer *queryMultiplexer
}

func NewTLS(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteTLSDNSServerOptions) (adapter.DNSTransport, error) {
	transportDialer, err := dns.NewRemoteDialer(ctx, options.RemoteDNSServerOptions)
	if err != nil {
		return nil, err
	}
	tlsOptions := common.PtrValueOrDefault(options.TLS)
	tlsOptions.Enabled = true
	tlsConfig, err := tls.NewClient(ctx, logger, options.Server, tlsOptions)
	if err != nil {
		return nil, err
	}
	serverAddr := options.DNSServerAddressOptions.Build()
	if serverAddr.Port == 0 {
		serverAddr.Port = 853
	}
	if !serverAddr.IsValid() {
		return nil, E.New("invalid server address: ", serverAddr)
	}
	return NewTLSRaw(logger, dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeTLS, tag, options.RemoteDNSServerOptions), transportDialer, serverAddr, tlsConfig), nil
}

func NewTLSRaw(logger logger.ContextLogger, adapter dns.TransportAdapter, dialer N.Dialer, serverAddr M.Socksaddr, tlsConfig tls.Config) *TLSTransport {
	t := &TLSTransport{
		TransportAdapter: adapter,
		logger:           logger,
		dialer:           tls.NewDialer(dialer, tlsConfig),
		serverAddr:       serverAddr,
	}
	t.multiplexer = newQueryMultiplexer(queryMultiplexerOptions{
		dial: func(ctx context.Context) (net.Conn, error) {
			conn, err := t.dialer.DialTLSContext(ctx, t.serverAddr)
			if err != nil {
				return nil, E.Cause(err, "dial TLS connection")
			}
			return conn, nil
		},
		write: func(conn net.Conn, message *mDNS.Msg, queryId uint16) error {
			return WriteMessage(conn, queryId, message)
		},
		readNext: func(conn net.Conn) (*mDNS.Msg, error) {
			return ReadMessage(conn)
		},
		retryReadError: true,
		probeReuse:     true,
	})
	return t
}

func (t *TLSTransport) Start(stage adapter.StartStage) error {
	if stage != adapter.StartStateStart {
		return nil
	}
	return dialer.InitializeDetour(t.dialer)
}

func (t *TLSTransport) Close() error {
	return t.multiplexer.Close()
}

func (t *TLSTransport) Reset() {
	t.multiplexer.Reset()
}

func (t *TLSTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
	return t.multiplexer.Exchange(ctx, message)
}

func (t *TLSTransport) ExchangeAsync(ctx context.Context, message *mDNS.Msg, callback func(response *mDNS.Msg, err error)) {
	t.multiplexer.ExchangeAsync(ctx, message, callback)
}