// Package dlna provides DLNA server.
package dlna

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"net"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"

	dms_dlna "github.com/anacrolix/dms/dlna"
	"github.com/anacrolix/dms/soap"
	"github.com/anacrolix/dms/ssdp"
	"github.com/anacrolix/dms/upnp"
	"github.com/anacrolix/log"
	"github.com/rclone/rclone/cmd"
	"github.com/rclone/rclone/cmd/serve/dlna/data"
	"github.com/rclone/rclone/cmd/serve/dlna/dlnaflags"
	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/lib/systemd"
	"github.com/rclone/rclone/vfs"
	"github.com/rclone/rclone/vfs/vfscommon"
	"github.com/rclone/rclone/vfs/vfsflags"
	"github.com/spf13/cobra"
)

func init() {
	dlnaflags.AddFlags(Command.Flags())
	vfsflags.AddFlags(Command.Flags())
}

// Command definition for cobra.
var Command = &cobra.Command{
	Use:   "dlna remote:path",
	Short: `Serve remote:path over DLNA`,
	Long: `Run a DLNA media server for media stored in an rclone remote. Many
devices, such as the Xbox and PlayStation, can automatically discover
this server in the LAN and play audio/video from it. VLC is also
supported. Service discovery uses UDP multicast packets (SSDP) and
will thus only work on LANs.

Rclone will list all files present in the remote, without filtering
based on media formats or file extensions. Additionally, there is no
media transcoding support. This means that some players might show
files that they are not able to play back correctly.

Rclone will add external subtitle files (.srt) to videos if they have the same
filename as the video file itself (except the extension), either in the same
directory as the video, or in a "Subs" subdirectory.

` + dlnaflags.Help + vfs.Help(),
	Annotations: map[string]string{
		"versionIntroduced": "v1.46",
		"groups":            "Filter",
	},
	Run: func(command *cobra.Command, args []string) {
		cmd.CheckArgs(1, 1, command, args)
		f := cmd.NewFsSrc(args)

		cmd.Run(false, false, command, func() error {
			s, err := newServer(f, &dlnaflags.Opt)
			if err != nil {
				return err
			}
			if err := s.Serve(); err != nil {
				return err
			}
			defer systemd.Notify()()
			s.Wait()
			return nil
		})
	},
}

const (
	serverField       = "Linux/3.4 DLNADOC/1.50 UPnP/1.0 DMS/1.0"
	rootDescPath      = "/rootDesc.xml"
	resPath           = "/r/"
	serviceControlURL = "/ctl"
)

type server struct {
	// The service SOAP handler keyed by service URN.
	services map[string]UPnPService

	Interfaces []net.Interface

	HTTPConn       net.Listener
	httpListenAddr string
	handler        http.Handler

	RootDeviceUUID string

	FriendlyName string

	// For waiting on the listener to close
	waitChan chan struct{}

	// Time interval between SSPD announces
	AnnounceInterval time.Duration

	f   fs.Fs
	vfs *vfs.VFS
}

func newServer(f fs.Fs, opt *dlnaflags.Options) (*server, error) {
	friendlyName := opt.FriendlyName
	if friendlyName == "" {
		friendlyName = makeDefaultFriendlyName()
	}
	interfaces := make([]net.Interface, 0, len(opt.InterfaceNames))
	for _, interfaceName := range opt.InterfaceNames {
		var err error
		intf, err := net.InterfaceByName(interfaceName)
		if err != nil {
			return nil, fmt.Errorf("failed to resolve interface name '%s': %w", interfaceName, err)
		}
		if !isAppropriatelyConfigured(*intf) {
			return nil, fmt.Errorf("interface '%s' is not appropriately configured (it should be UP, MULTICAST and MTU > 0)", interfaceName)
		}
		interfaces = append(interfaces, *intf)
	}
	if len(interfaces) == 0 {
		interfaces = listInterfaces()
	}

	s := &server{
		AnnounceInterval: time.Duration(opt.AnnounceInterval),
		FriendlyName:     friendlyName,
		RootDeviceUUID:   makeDeviceUUID(friendlyName),
		Interfaces:       interfaces,
		waitChan:         make(chan struct{}),
		httpListenAddr:   opt.ListenAddr,
		f:                f,
		vfs:              vfs.New(f, &vfscommon.Opt),
	}

	s.services = map[string]UPnPService{
		"ContentDirectory": &contentDirectoryService{
			server: s,
		},
		"ConnectionManager": &connectionManagerService{
			server: s,
		},
		"X_MS_MediaReceiverRegistrar": &mediaReceiverRegistrarService{
			server: s,
		},
	}

	// Setup the various http routes.
	r := http.NewServeMux()
	r.Handle(resPath, http.StripPrefix(resPath,
		http.HandlerFunc(s.resourceHandler)))
	if opt.LogTrace {
		r.Handle(rootDescPath, traceLogging(http.HandlerFunc(s.rootDescHandler)))
		r.Handle(serviceControlURL, traceLogging(http.HandlerFunc(s.serviceControlHandler)))
	} else {
		r.HandleFunc(rootDescPath, s.rootDescHandler)
		r.HandleFunc(serviceControlURL, s.serviceControlHandler)
	}
	r.Handle("/static/", http.StripPrefix("/static/",
		withHeader("Cache-Control", "public, max-age=86400",
			http.FileServer(data.Assets))))
	s.handler = logging(withHeader("Server", serverField, r))

	return s, nil
}

// UPnPService is the interface for the SOAP service.
type UPnPService interface {
	Handle(action string, argsXML []byte, r *http.Request) (respArgs map[string]string, err error)
	Subscribe(callback []*url.URL, timeoutSeconds int) (sid string, actualTimeout int, err error)
	Unsubscribe(sid string) error
}

// Formats the server as a string (used for logging.)
func (s *server) String() string {
	return fmt.Sprintf("DLNA server on %v", s.httpListenAddr)
}

// Returns rclone version number as the model number.
func (s *server) ModelNumber() string {
	return fs.Version
}

// Renders the root device descriptor.
func (s *server) rootDescHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	tmpl, err := data.GetTemplate()
	if err != nil {
		serveError(ctx, s, w, "Failed to load root descriptor template", err)
		return
	}

	buffer := new(bytes.Buffer)
	err = tmpl.Execute(buffer, s)
	if err != nil {
		serveError(ctx, s, w, "Failed to render root descriptor XML", err)
		return
	}

	w.Header().Set("content-type", `text/xml; charset="utf-8"`)
	w.Header().Set("cache-control", "private, max-age=60")
	w.Header().Set("content-length", strconv.FormatInt(int64(buffer.Len()), 10))
	_, err = buffer.WriteTo(w)
	if err != nil {
		// Network error
		fs.Debugf(s, "Error writing rootDesc: %v", err)
	}
}

// Handle a service control HTTP request.
func (s *server) serviceControlHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	soapActionString := r.Header.Get("SOAPACTION")
	soapAction, err := upnp.ParseActionHTTPHeader(soapActionString)
	if err != nil {
		serveError(ctx, s, w, "Could not parse SOAPACTION header", err)
		return
	}
	var env soap.Envelope
	if err := xml.NewDecoder(r.Body).Decode(&env); err != nil {
		serveError(ctx, s, w, "Could not parse SOAP request body", err)
		return
	}

	w.Header().Set("Content-Type", `text/xml; charset="utf-8"`)
	w.Header().Set("Ext", "")
	soapRespXML, code := func() ([]byte, int) {
		respArgs, err := s.soapActionResponse(soapAction, env.Body.Action, r)
		if err != nil {
			fs.Errorf(s, "Error invoking %v: %v", soapAction, err)
			upnpErr := upnp.ConvertError(err)
			return mustMarshalXML(soap.NewFault("UPnPError", upnpErr)), http.StatusInternalServerError
		}
		return marshalSOAPResponse(soapAction, respArgs), http.StatusOK
	}()
	bodyStr := fmt.Sprintf(`<?xml version="1.0" encoding="utf-8" standalone="yes"?><s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><s:Body>%s</s:Body></s:Envelope>`, soapRespXML)
	w.WriteHeader(code)
	if _, err := w.Write([]byte(bodyStr)); err != nil {
		fs.Infof(s, "Error writing response: %v", err)
	}
}

// Handle a SOAP request and return the response arguments or UPnP error.
func (s *server) soapActionResponse(sa upnp.SoapAction, actionRequestXML []byte, r *http.Request) (map[string]string, error) {
	service, ok := s.services[sa.Type]
	if !ok {
		// TODO: What's the invalid service error?
		return nil, upnp.Errorf(upnp.InvalidActionErrorCode, "Invalid service: %s", sa.Type)
	}
	return service.Handle(sa.Action, actionRequestXML, r)
}

// Serves actual resources (media files).
func (s *server) resourceHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	remotePath := r.URL.Path
	node, err := s.vfs.Stat(r.URL.Path)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	w.Header().Set("Content-Length", strconv.FormatInt(node.Size(), 10))

	// add some DLNA specific headers
	if r.Header.Get("getContentFeatures.dlna.org") != "" {
		w.Header().Set("contentFeatures.dlna.org", dms_dlna.ContentFeatures{
			SupportRange: true,
		}.String())
	}
	w.Header().Set("transferMode.dlna.org", "Streaming")

	file := node.(*vfs.File)
	in, err := file.Open(os.O_RDONLY)
	if err != nil {
		serveError(ctx, node, w, "Could not open resource", err)
		return
	}
	defer fs.CheckClose(in, &err)

	http.ServeContent(w, r, remotePath, node.ModTime(), in)
}

// Serve runs the server - returns the error only if
// the listener was not started; does not block, so
// use s.Wait() to block on the listener indefinitely.
func (s *server) Serve() (err error) {
	if s.HTTPConn == nil {
		// Currently, the SSDP server only listens on an IPv4 multicast address.
		// Differentiate between two INADDR_ANY addresses,
		// so that 0.0.0.0 can only listen on IPv4 addresses.
		network := "tcp4"
		if strings.Count(s.httpListenAddr, ":") > 1 {
			network = "tcp"
		}
		s.HTTPConn, err = net.Listen(network, s.httpListenAddr)
		if err != nil {
			return
		}
	}

	go func() {
		s.startSSDP()
	}()

	go func() {
		fs.Logf(s.f, "Serving HTTP on %s", s.HTTPConn.Addr().String())

		err := s.serveHTTP()
		if err != nil {
			fs.Logf(s.f, "Error on serving HTTP server: %v", err)
		}
	}()

	return nil
}

// Wait blocks while the listener is open.
func (s *server) Wait() {
	<-s.waitChan
}

func (s *server) Close() {
	err := s.HTTPConn.Close()
	if err != nil {
		fs.Errorf(s.f, "Error closing HTTP server: %v", err)
		return
	}
	close(s.waitChan)
}

// Run SSDP (multicast for server discovery) on all interfaces.
func (s *server) startSSDP() {
	active := 0
	stopped := make(chan struct{})
	for _, intf := range s.Interfaces {
		active++
		go func(intf2 net.Interface) {
			defer func() {
				stopped <- struct{}{}
			}()
			s.ssdpInterface(intf2)
		}(intf)
	}
	for active > 0 {
		<-stopped
		active--
	}
}

// Run SSDP server on an interface.
func (s *server) ssdpInterface(intf net.Interface) {
	// Figure out whether should an ip be announced
	ipfilterFn := func(ip net.IP) bool {
		listenaddr := s.HTTPConn.Addr().String()
		listenip := listenaddr[:strings.LastIndex(listenaddr, ":")]
		switch listenip {
		case "0.0.0.0":
			if strings.Contains(ip.String(), ":") {
				// Any IPv6 address should not be announced
				// because SSDP only listen on IPv4 multicast address
				return false
			}
			return true
		case "[::]":
			// In the @Serve() section, the default settings have been made to not listen on IPv6 addresses.
			// If actually still listening on [::], then allow to announce any address.
			return true
		default:
			if listenip == ip.String() {
				return true
			}
			return false
		}
	}

	// Figure out which HTTP location to advertise based on the interface IP.
	advertiseLocationFn := func(ip net.IP) string {
		url := url.URL{
			Scheme: "http",
			Host: (&net.TCPAddr{
				IP:   ip,
				Port: s.HTTPConn.Addr().(*net.TCPAddr).Port,
			}).String(),
			Path: rootDescPath,
		}
		return url.String()
	}

	_, err := intf.Addrs()
	if err != nil {
		panic(err)
	}
	fs.Logf(s, "Started SSDP on %v", intf.Name)

	// Note that the devices and services advertised here via SSDP should be
	// in agreement with the rootDesc XML descriptor that is defined above.
	ssdpServer := ssdp.Server{
		Interface: intf,
		Devices: []string{
			"urn:schemas-upnp-org:device:MediaServer:1"},
		Services: []string{
			"urn:schemas-upnp-org:service:ContentDirectory:1",
			"urn:schemas-upnp-org:service:ConnectionManager:1",
			"urn:microsoft.com:service:X_MS_MediaReceiverRegistrar:1"},
		IPFilter:       ipfilterFn,
		Location:       advertiseLocationFn,
		Server:         serverField,
		UUID:           s.RootDeviceUUID,
		NotifyInterval: s.AnnounceInterval,
		Logger:         log.Default,
	}

	// An interface with these flags should be valid for SSDP.
	const ssdpInterfaceFlags = net.FlagUp | net.FlagMulticast

	if err := ssdpServer.Init(); err != nil {
		if intf.Flags&ssdpInterfaceFlags != ssdpInterfaceFlags {
			// Didn't expect it to work anyway.
			return
		}
		if strings.Contains(err.Error(), "listen") {
			// OSX has a lot of dud interfaces. Failure to create a socket on
			// the interface are what we're expecting if the interface is no
			// good.
			return
		}
		fs.Errorf(s, "Error creating ssdp server on %s: %s", intf.Name, err)
		return
	}
	defer ssdpServer.Close()
	fs.Infof(s, "Started SSDP on %v", intf.Name)
	stopped := make(chan struct{})
	go func() {
		defer close(stopped)
		if err := ssdpServer.Serve(); err != nil {
			fs.Errorf(s, "%q: %q\n", intf.Name, err)
		}
	}()
	select {
	case <-s.waitChan:
		// Returning will close the server.
	case <-stopped:
	}
}

func (s *server) serveHTTP() error {
	srv := &http.Server{
		Handler: s.handler,
	}
	err := srv.Serve(s.HTTPConn)
	select {
	case <-s.waitChan:
		return nil
	default:
		return err
	}
}