package outbound

import (
	"context"
	"crypto/tls"
	"errors"
	"fmt"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"

	tlsC "github.com/Dreamacro/clash/component/tls"
	vmess "github.com/sagernet/sing-vmess"

	"github.com/Dreamacro/clash/component/dialer"
	"github.com/Dreamacro/clash/component/resolver"
	C "github.com/Dreamacro/clash/constant"
	"github.com/Dreamacro/clash/transport/gun"
	clashVMess "github.com/Dreamacro/clash/transport/vmess"

	"github.com/sagernet/sing-vmess/packetaddr"
	M "github.com/sagernet/sing/common/metadata"
)

var ErrUDPRemoteAddrMismatch = errors.New("udp packet dropped due to mismatched remote address")

type Vmess struct {
	*Base
	client *vmess.Client
	option *VmessOption

	// for gun mux
	gunTLSConfig *tls.Config
	gunConfig    *gun.Config
	transport    *gun.TransportWrap
}

type VmessOption struct {
	BasicOption
	Name                string       `proxy:"name"`
	Server              string       `proxy:"server"`
	Port                int          `proxy:"port"`
	UUID                string       `proxy:"uuid"`
	AlterID             int          `proxy:"alterId"`
	Cipher              string       `proxy:"cipher"`
	UDP                 bool         `proxy:"udp,omitempty"`
	Network             string       `proxy:"network,omitempty"`
	TLS                 bool         `proxy:"tls,omitempty"`
	SkipCertVerify      bool         `proxy:"skip-cert-verify,omitempty"`
	Fingerprint         string       `proxy:"fingerprint,omitempty"`
	ServerName          string       `proxy:"servername,omitempty"`
	HTTPOpts            HTTPOptions  `proxy:"http-opts,omitempty"`
	HTTP2Opts           HTTP2Options `proxy:"h2-opts,omitempty"`
	GrpcOpts            GrpcOptions  `proxy:"grpc-opts,omitempty"`
	WSOpts              WSOptions    `proxy:"ws-opts,omitempty"`
	PacketAddr          bool         `proxy:"packet-addr,omitempty"`
	XUDP                bool         `proxy:"xudp,omitempty"`
	PacketEncoding      string       `proxy:"packet-encoding,omitempty"`
	GlobalPadding       bool         `proxy:"global-padding,omitempty"`
	AuthenticatedLength bool         `proxy:"authenticated-length,omitempty"`
}

type HTTPOptions struct {
	Method  string              `proxy:"method,omitempty"`
	Path    []string            `proxy:"path,omitempty"`
	Headers map[string][]string `proxy:"headers,omitempty"`
}

type HTTP2Options struct {
	Host []string `proxy:"host,omitempty"`
	Path string   `proxy:"path,omitempty"`
}

type GrpcOptions struct {
	GrpcServiceName string `proxy:"grpc-service-name,omitempty"`
}

type WSOptions struct {
	Path                string            `proxy:"path,omitempty"`
	Headers             map[string]string `proxy:"headers,omitempty"`
	MaxEarlyData        int               `proxy:"max-early-data,omitempty"`
	EarlyDataHeaderName string            `proxy:"early-data-header-name,omitempty"`
}

// StreamConn implements C.ProxyAdapter
func (v *Vmess) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
	var err error
	switch v.option.Network {
	case "ws":

		host, port, _ := net.SplitHostPort(v.addr)
		wsOpts := &clashVMess.WebsocketConfig{
			Host:                host,
			Port:                port,
			Path:                v.option.WSOpts.Path,
			MaxEarlyData:        v.option.WSOpts.MaxEarlyData,
			EarlyDataHeaderName: v.option.WSOpts.EarlyDataHeaderName,
			Headers:             http.Header{},
		}

		if len(v.option.WSOpts.Headers) != 0 {
			for key, value := range v.option.WSOpts.Headers {
				wsOpts.Headers.Add(key, value)
			}
		}

		if v.option.TLS {
			wsOpts.TLS = true
			tlsConfig := &tls.Config{
				ServerName:         host,
				InsecureSkipVerify: v.option.SkipCertVerify,
				NextProtos:         []string{"http/1.1"},
			}

			if len(v.option.Fingerprint) == 0 {
				wsOpts.TLSConfig = tlsC.GetGlobalTLSConfig(tlsConfig)
			} else {
				if wsOpts.TLSConfig, err = tlsC.GetSpecifiedFingerprintTLSConfig(tlsConfig, v.option.Fingerprint); err != nil {
					return nil, err
				}
			}

			if v.option.ServerName != "" {
				wsOpts.TLSConfig.ServerName = v.option.ServerName
			} else if host := wsOpts.Headers.Get("Host"); host != "" {
				wsOpts.TLSConfig.ServerName = host
			}
		}
		c, err = clashVMess.StreamWebsocketConn(c, wsOpts)
	case "http":
		// readability first, so just copy default TLS logic
		if v.option.TLS {
			host, _, _ := net.SplitHostPort(v.addr)
			tlsOpts := &clashVMess.TLSConfig{
				Host:           host,
				SkipCertVerify: v.option.SkipCertVerify,
			}

			if v.option.ServerName != "" {
				tlsOpts.Host = v.option.ServerName
			}

			c, err = clashVMess.StreamTLSConn(c, tlsOpts)
			if err != nil {
				return nil, err
			}
		}

		host, _, _ := net.SplitHostPort(v.addr)
		httpOpts := &clashVMess.HTTPConfig{
			Host:    host,
			Method:  v.option.HTTPOpts.Method,
			Path:    v.option.HTTPOpts.Path,
			Headers: v.option.HTTPOpts.Headers,
		}

		c = clashVMess.StreamHTTPConn(c, httpOpts)
	case "h2":
		host, _, _ := net.SplitHostPort(v.addr)
		tlsOpts := clashVMess.TLSConfig{
			Host:           host,
			SkipCertVerify: v.option.SkipCertVerify,
			NextProtos:     []string{"h2"},
		}

		if v.option.ServerName != "" {
			tlsOpts.Host = v.option.ServerName
		}

		c, err = clashVMess.StreamTLSConn(c, &tlsOpts)
		if err != nil {
			return nil, err
		}

		h2Opts := &clashVMess.H2Config{
			Hosts: v.option.HTTP2Opts.Host,
			Path:  v.option.HTTP2Opts.Path,
		}

		c, err = clashVMess.StreamH2Conn(c, h2Opts)
	case "grpc":
		c, err = gun.StreamGunWithConn(c, v.gunTLSConfig, v.gunConfig)
	default:
		// handle TLS
		if v.option.TLS {
			host, _, _ := net.SplitHostPort(v.addr)
			tlsOpts := &clashVMess.TLSConfig{
				Host:           host,
				SkipCertVerify: v.option.SkipCertVerify,
			}

			if v.option.ServerName != "" {
				tlsOpts.Host = v.option.ServerName
			}

			c, err = clashVMess.StreamTLSConn(c, tlsOpts)
		}
	}

	if err != nil {
		return nil, err
	}
	if metadata.NetWork == C.UDP {
		if v.option.XUDP {
			return v.client.DialXUDPPacketConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
		} else {
			return v.client.DialPacketConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
		}
	} else {
		return v.client.DialConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
	}
}

// DialContext implements C.ProxyAdapter
func (v *Vmess) DialContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (_ C.Conn, err error) {
	// gun transport
	if v.transport != nil && len(opts) == 0 {
		c, err := gun.StreamGunWithTransport(v.transport, v.gunConfig)
		if err != nil {
			return nil, err
		}
		defer func(c net.Conn) {
			safeConnClose(c, err)
		}(c)

		c, err = v.client.DialConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
		if err != nil {
			return nil, err
		}

		return NewConn(c, v), nil
	}
	return v.DialContextWithDialer(ctx, dialer.NewDialer(v.Base.DialOptions(opts...)...), metadata)
}

// DialContextWithDialer implements C.ProxyAdapter
func (v *Vmess) DialContextWithDialer(ctx context.Context, dialer C.Dialer, metadata *C.Metadata) (_ C.Conn, err error) {
	c, err := dialer.DialContext(ctx, "tcp", v.addr)
	if err != nil {
		return nil, fmt.Errorf("%s connect error: %s", v.addr, err.Error())
	}
	tcpKeepAlive(c)
	defer func(c net.Conn) {
		safeConnClose(c, err)
	}(c)

	c, err = v.StreamConn(c, metadata)
	return NewConn(c, v), err
}

// ListenPacketContext implements C.ProxyAdapter
func (v *Vmess) ListenPacketContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (_ C.PacketConn, err error) {
	// vmess use stream-oriented udp with a special address, so we needs a net.UDPAddr
	if !metadata.Resolved() {
		ip, err := resolver.ResolveIP(ctx, metadata.Host)
		if err != nil {
			return nil, errors.New("can't resolve ip")
		}
		metadata.DstIP = ip
	}

	if v.option.PacketAddr {
		_metadata := *metadata // make a copy
		metadata = &_metadata
		metadata.Host = packetaddr.SeqPacketMagicAddress
		metadata.DstPort = "443"
	}

	var c net.Conn
	// gun transport
	if v.transport != nil && len(opts) == 0 {
		c, err = gun.StreamGunWithTransport(v.transport, v.gunConfig)
		if err != nil {
			return nil, err
		}
		defer func(c net.Conn) {
			safeConnClose(c, err)
		}(c)

		if v.option.XUDP {
			c, err = v.client.DialXUDPPacketConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
		} else {
			c, err = v.client.DialPacketConn(c, M.ParseSocksaddr(metadata.RemoteAddress()))
		}

		if err != nil {
			return nil, fmt.Errorf("new vmess client error: %v", err)
		}
		return v.ListenPacketOnStreamConn(c, metadata)
	}
	return v.ListenPacketWithDialer(ctx, dialer.NewDialer(v.Base.DialOptions(opts...)...), metadata)
}

// ListenPacketWithDialer implements C.ProxyAdapter
func (v *Vmess) ListenPacketWithDialer(ctx context.Context, dialer C.Dialer, metadata *C.Metadata) (_ C.PacketConn, err error) {
	// vmess use stream-oriented udp with a special address, so we needs a net.UDPAddr
	if !metadata.Resolved() {
		ip, err := resolver.ResolveIP(ctx, metadata.Host)
		if err != nil {
			return nil, errors.New("can't resolve ip")
		}
		metadata.DstIP = ip
	}

	c, err := dialer.DialContext(ctx, "tcp", v.addr)
	if err != nil {
		return nil, fmt.Errorf("%s connect error: %s", v.addr, err.Error())
	}
	tcpKeepAlive(c)
	defer func(c net.Conn) {
		safeConnClose(c, err)
	}(c)

	c, err = v.StreamConn(c, metadata)
	if err != nil {
		return nil, fmt.Errorf("new vmess client error: %v", err)
	}
	return v.ListenPacketOnStreamConn(c, metadata)
}

// SupportWithDialer implements C.ProxyAdapter
func (v *Vmess) SupportWithDialer() bool {
	return true
}

// ListenPacketOnStreamConn implements C.ProxyAdapter
func (v *Vmess) ListenPacketOnStreamConn(c net.Conn, metadata *C.Metadata) (_ C.PacketConn, err error) {
	if v.option.PacketAddr {
		return newPacketConn(&threadSafePacketConn{PacketConn: packetaddr.NewBindConn(c)}, v), nil
	} else if pc, ok := c.(net.PacketConn); ok {
		return newPacketConn(&threadSafePacketConn{PacketConn: pc}, v), nil
	}
	return newPacketConn(&vmessPacketConn{Conn: c, rAddr: metadata.UDPAddr()}, v), nil
}

// SupportUOT implements C.ProxyAdapter
func (v *Vmess) SupportUOT() bool {
	return true
}

func NewVmess(option VmessOption) (*Vmess, error) {
	security := strings.ToLower(option.Cipher)
	var options []vmess.ClientOption
	if option.GlobalPadding {
		options = append(options, vmess.ClientWithGlobalPadding())
	}
	if option.AuthenticatedLength {
		options = append(options, vmess.ClientWithAuthenticatedLength())
	}
	client, err := vmess.NewClient(option.UUID, security, option.AlterID, options...)
	if err != nil {
		return nil, err
	}

	switch option.PacketEncoding {
	case "packetaddr", "packet":
		option.PacketAddr = true
	case "xudp":
		option.XUDP = true
	}
	if option.XUDP {
		option.PacketAddr = false
	}

	switch option.Network {
	case "h2", "grpc":
		if !option.TLS {
			option.TLS = true
		}
	}

	v := &Vmess{
		Base: &Base{
			name:   option.Name,
			addr:   net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
			tp:     C.Vmess,
			udp:    option.UDP,
			xudp:   option.XUDP,
			iface:  option.Interface,
			rmark:  option.RoutingMark,
			prefer: C.NewDNSPrefer(option.IPVersion),
		},
		client: client,
		option: &option,
	}

	switch option.Network {
	case "h2":
		if len(option.HTTP2Opts.Host) == 0 {
			option.HTTP2Opts.Host = append(option.HTTP2Opts.Host, "www.example.com")
		}
	case "grpc":
		dialFn := func(network, addr string) (net.Conn, error) {
			c, err := dialer.DialContext(context.Background(), "tcp", v.addr, v.Base.DialOptions()...)
			if err != nil {
				return nil, fmt.Errorf("%s connect error: %s", v.addr, err.Error())
			}
			tcpKeepAlive(c)
			return c, nil
		}

		gunConfig := &gun.Config{
			ServiceName: v.option.GrpcOpts.GrpcServiceName,
			Host:        v.option.ServerName,
		}
		tlsConfig := &tls.Config{
			InsecureSkipVerify: v.option.SkipCertVerify,
			ServerName:         v.option.ServerName,
		}

		if v.option.ServerName == "" {
			host, _, _ := net.SplitHostPort(v.addr)
			tlsConfig.ServerName = host
			gunConfig.Host = host
		}

		v.gunTLSConfig = tlsConfig
		v.gunConfig = gunConfig
		v.transport = gun.NewHTTP2Client(dialFn, tlsConfig)
	}
	return v, nil
}

type threadSafePacketConn struct {
	net.PacketConn
	access sync.Mutex
}

func (c *threadSafePacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
	c.access.Lock()
	defer c.access.Unlock()
	return c.PacketConn.WriteTo(b, addr)
}

type vmessPacketConn struct {
	net.Conn
	rAddr  net.Addr
	access sync.Mutex
}

// WriteTo implments C.PacketConn.WriteTo
// Since VMess doesn't support full cone NAT by design, we verify if addr matches uc.rAddr, and drop the packet if not.
func (uc *vmessPacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
	allowedAddr := uc.rAddr.(*net.UDPAddr)
	destAddr := addr.(*net.UDPAddr)
	if !(allowedAddr.IP.Equal(destAddr.IP) && allowedAddr.Port == destAddr.Port) {
		return 0, ErrUDPRemoteAddrMismatch
	}
	uc.access.Lock()
	defer uc.access.Unlock()
	return uc.Conn.Write(b)
}

func (uc *vmessPacketConn) ReadFrom(b []byte) (int, net.Addr, error) {
	n, err := uc.Conn.Read(b)
	return n, uc.rAddr, err
}