package outbound

import (
	"context"
	"crypto/sha256"
	"crypto/tls"
	"encoding/hex"
	"encoding/pem"
	"errors"
	"fmt"
	"net"
	"os"
	"runtime"
	"strconv"

	CN "github.com/Dreamacro/clash/common/net"
	"github.com/Dreamacro/clash/component/dialer"
	"github.com/Dreamacro/clash/component/proxydialer"
	tlsC "github.com/Dreamacro/clash/component/tls"
	C "github.com/Dreamacro/clash/constant"
	tuicCommon "github.com/Dreamacro/clash/transport/tuic/common"

	"github.com/metacubex/sing-quic/hysteria2"

	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
)

func init() {
	hysteria2.SetCongestionController = tuicCommon.SetCongestionController
}

type Hysteria2 struct {
	*Base

	option *Hysteria2Option
	client *hysteria2.Client
	dialer *hy2SingDialer
}

type Hysteria2Option struct {
	BasicOption
	Name           string   `proxy:"name"`
	Server         string   `proxy:"server"`
	Port           int      `proxy:"port"`
	Up             string   `proxy:"up,omitempty"`
	Down           string   `proxy:"down,omitempty"`
	Password       string   `proxy:"password,omitempty"`
	Obfs           string   `proxy:"obfs,omitempty"`
	ObfsPassword   string   `proxy:"obfs-password,omitempty"`
	SNI            string   `proxy:"sni,omitempty"`
	SkipCertVerify bool     `proxy:"skip-cert-verify,omitempty"`
	Fingerprint    string   `proxy:"fingerprint,omitempty"`
	ALPN           []string `proxy:"alpn,omitempty"`
	CustomCA       string   `proxy:"ca,omitempty"`
	CustomCAString string   `proxy:"ca-str,omitempty"`
	CWND           int      `proxy:"cwnd,omitempty"`
}

type hy2SingDialer struct {
	dialer    dialer.Dialer
	proxyName string
}

var _ N.Dialer = (*hy2SingDialer)(nil)

func (d *hy2SingDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
	var cDialer C.Dialer = d.dialer
	if len(d.proxyName) > 0 {
		pd, err := proxydialer.NewByName(d.proxyName, d.dialer)
		if err != nil {
			return nil, err
		}
		cDialer = pd
	}
	return cDialer.DialContext(ctx, network, destination.String())
}

func (d *hy2SingDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
	var cDialer C.Dialer = d.dialer
	if len(d.proxyName) > 0 {
		pd, err := proxydialer.NewByName(d.proxyName, d.dialer)
		if err != nil {
			return nil, err
		}
		cDialer = pd
	}
	return cDialer.ListenPacket(ctx, "udp", "", destination.AddrPort())
}

func (h *Hysteria2) DialContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (_ C.Conn, err error) {
	options := h.Base.DialOptions(opts...)
	h.dialer.dialer = dialer.NewDialer(options...)
	c, err := h.client.DialConn(ctx, M.ParseSocksaddr(metadata.RemoteAddress()))
	if err != nil {
		return nil, err
	}
	return NewConn(CN.NewRefConn(c, h), h), nil
}

func (h *Hysteria2) ListenPacketContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (_ C.PacketConn, err error) {
	options := h.Base.DialOptions(opts...)
	h.dialer.dialer = dialer.NewDialer(options...)
	pc, err := h.client.ListenPacket(ctx)
	if err != nil {
		return nil, err
	}
	if pc == nil {
		return nil, errors.New("packetConn is nil")
	}
	return newPacketConn(CN.NewRefPacketConn(CN.NewThreadSafePacketConn(pc), h), h), nil
}

func closeHysteria2(h *Hysteria2) {
	if h.client != nil {
		_ = h.client.CloseWithError(errors.New("proxy removed"))
	}
}

func NewHysteria2(option Hysteria2Option) (*Hysteria2, error) {
	addr := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
	var salamanderPassword string
	if len(option.Obfs) > 0 {
		if option.ObfsPassword == "" {
			return nil, errors.New("missing obfs password")
		}
		switch option.Obfs {
		case hysteria2.ObfsTypeSalamander:
			salamanderPassword = option.ObfsPassword
		default:
			return nil, fmt.Errorf("unknown obfs type: %s", option.Obfs)
		}
	}

	serverName := option.Server
	if option.SNI != "" {
		serverName = option.SNI
	}

	tlsConfig := &tls.Config{
		ServerName:         serverName,
		InsecureSkipVerify: option.SkipCertVerify,
		MinVersion:         tls.VersionTLS13,
	}

	var bs []byte
	var err error
	if len(option.CustomCA) > 0 {
		bs, err = os.ReadFile(option.CustomCA)
		if err != nil {
			return nil, fmt.Errorf("hysteria %s load ca error: %w", option.Name, err)
		}
	} else if option.CustomCAString != "" {
		bs = []byte(option.CustomCAString)
	}

	if len(bs) > 0 {
		block, _ := pem.Decode(bs)
		if block == nil {
			return nil, fmt.Errorf("CA cert is not PEM")
		}

		fpBytes := sha256.Sum256(block.Bytes)
		if len(option.Fingerprint) == 0 {
			option.Fingerprint = hex.EncodeToString(fpBytes[:])
		}
	}

	if len(option.Fingerprint) != 0 {
		var err error
		tlsConfig, err = tlsC.GetSpecifiedFingerprintTLSConfig(tlsConfig, option.Fingerprint)
		if err != nil {
			return nil, err
		}
	} else {
		tlsConfig = tlsC.GetGlobalTLSConfig(tlsConfig)
	}

	if len(option.ALPN) > 0 {
		tlsConfig.NextProtos = option.ALPN
	}

	singDialer := &hy2SingDialer{dialer: dialer.NewDialer(), proxyName: option.DialerProxy}

	clientOptions := hysteria2.ClientOptions{
		Context:            context.TODO(),
		Dialer:             singDialer,
		ServerAddress:      M.ParseSocksaddrHostPort(option.Server, uint16(option.Port)),
		SendBPS:            StringToBps(option.Up),
		ReceiveBPS:         StringToBps(option.Down),
		SalamanderPassword: salamanderPassword,
		Password:           option.Password,
		TLSConfig:          tlsConfig,
		UDPDisabled:        false,
		CWND:               option.CWND,
	}

	client, err := hysteria2.NewClient(clientOptions)
	if err != nil {
		return nil, err
	}

	outbound := &Hysteria2{
		Base: &Base{
			name:   option.Name,
			addr:   addr,
			tp:     C.Hysteria2,
			udp:    true,
			iface:  option.Interface,
			rmark:  option.RoutingMark,
			prefer: C.NewDNSPrefer(option.IPVersion),
		},
		option: &option,
		client: client,
		dialer: singDialer,
	}
	runtime.SetFinalizer(outbound, closeHysteria2)

	return outbound, nil
}