package main

// Upnp code taken from Taipei Torrent license is below:
// Copyright (c) 2010 Jack Palevich. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Just enough UPnP to be able to forward ports
//

import (
	"bytes"
	"context"
	"encoding/xml"
	"errors"
	"fmt"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"
)

type upnpNAT struct {
	serviceURL string
	ourIP      string
}

// discover searches the local network for a UPnP router returning a NAT
// for the network if so, nil if not.
func discover(ctx context.Context) (*upnpNAT, error) {
	ssdp, err := net.ResolveUDPAddr("udp4", "239.255.255.250:1900")
	if err != nil {
		return nil, err
	}
	var l net.ListenConfig
	conn, err := l.ListenPacket(ctx, "udp4", ":0")
	if err != nil {
		return nil, err
	}
	socket := conn.(*net.UDPConn)
	defer socket.Close()

	err = socket.SetDeadline(time.Now().Add(3 * time.Second))
	if err != nil {
		return nil, err
	}

	st := "ST: urn:schemas-upnp-org:device:InternetGatewayDevice:1\r\n"
	buf := bytes.NewBufferString(
		"M-SEARCH * HTTP/1.1\r\n" +
			"HOST: 239.255.255.250:1900\r\n" +
			st +
			"MAN: \"ssdp:discover\"\r\n" +
			"MX: 2\r\n\r\n")
	message := buf.Bytes()
	answerBytes := make([]byte, 1024)
	for i := 0; i < 3; i++ {
		_, err = socket.WriteToUDP(message, ssdp)
		if err != nil {
			return nil, err
		}
		var n int
		n, _, err = socket.ReadFromUDP(answerBytes)
		if err != nil {
			continue
			// socket.Close()
			// return
		}
		answer := string(answerBytes[0:n])
		if !strings.Contains(answer, "\r\n"+st) {
			continue
		}
		// HTTP header field names are case-insensitive.
		// https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2
		locString := "\r\nlocation: "
		locIndex := strings.Index(strings.ToLower(answer), locString)
		if locIndex < 0 {
			continue
		}
		loc := answer[locIndex+len(locString):]
		endIndex := strings.Index(loc, "\r\n")
		if endIndex < 0 {
			continue
		}
		locURL := loc[0:endIndex]
		var serviceURL string
		serviceURL, err = getServiceURL(locURL)
		if err != nil {
			return nil, err
		}
		serviceIP := getServiceIP(serviceURL)
		var ourIP string
		ourIP, err = getOurIP(serviceIP)
		if err != nil {
			return nil, err
		}
		return &upnpNAT{serviceURL: serviceURL, ourIP: ourIP}, nil
	}
	return nil, errors.New("UPnP port discovery failed")
}

// service represents the Service type in an UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type service struct {
	ServiceType string `xml:"serviceType"`
	ControlURL  string `xml:"controlURL"`
}

// deviceList represents the deviceList type in an UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type deviceList struct {
	XMLName xml.Name `xml:"deviceList"`
	Device  []device `xml:"device"`
}

// serviceList represents the serviceList type in an UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type serviceList struct {
	XMLName xml.Name  `xml:"serviceList"`
	Service []service `xml:"service"`
}

// device represents the device type in an UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type device struct {
	XMLName     xml.Name    `xml:"device"`
	DeviceType  string      `xml:"deviceType"`
	DeviceList  deviceList  `xml:"deviceList"`
	ServiceList serviceList `xml:"serviceList"`
}

// specVersion represents the specVersion in a UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type specVersion struct {
	XMLName xml.Name `xml:"specVersion"`
	Major   int      `xml:"major"`
	Minor   int      `xml:"minor"`
}

// root represents the Root document for a UPnP xml description.
// Only the parts we care about are present and thus the xml may have more
// fields than present in the structure.
type root struct {
	XMLName     xml.Name `xml:"root"`
	SpecVersion specVersion
	Device      device
}

// getChildDevice searches the children of device for a device with the given
// type.
func getChildDevice(d *device, deviceType string) *device {
	for i := range d.DeviceList.Device {
		if d.DeviceList.Device[i].DeviceType == deviceType {
			return &d.DeviceList.Device[i]
		}
	}
	return nil
}

// getChildService searches the service list of device for a service with the
// given type.
func getChildService(d *device, serviceType string) *service {
	for i := range d.ServiceList.Service {
		if d.ServiceList.Service[i].ServiceType == serviceType {
			return &d.ServiceList.Service[i]
		}
	}
	return nil
}

func getServiceIP(serviceURL string) (routerIP string) {
	url, _ := url.Parse(serviceURL)
	return url.Hostname()
}

// getOurIP returns the local IP that is on the same subnet as the serviceIP.
func getOurIP(serviceIP string) (ip string, err error) {
	_, serviceNet, _ := net.ParseCIDR(serviceIP + "/24")
	addrs, err := net.InterfaceAddrs()
	for _, addr := range addrs {
		ip, _, _ := net.ParseCIDR(addr.String())
		if serviceNet.Contains(ip) {
			return ip.String(), nil
		}
	}
	return
}

// getServiceURL parses the xml description at the given root url to find the
// url for the WANIPConnection service to be used for port forwarding.
func getServiceURL(rootURL string) (url string, err error) {
	r, err := http.Get(rootURL)
	if err != nil {
		return
	}
	defer r.Body.Close()
	if r.StatusCode >= 400 {
		err = fmt.Errorf("%d", r.StatusCode)
		return
	}
	var root root
	err = xml.NewDecoder(r.Body).Decode(&root)
	if err != nil {
		return
	}
	a := &root.Device
	if a.DeviceType != "urn:schemas-upnp-org:device:InternetGatewayDevice:1" {
		err = errors.New("no internet gateway device")
		return
	}
	b := getChildDevice(a, "urn:schemas-upnp-org:device:WANDevice:1")
	if b == nil {
		err = errors.New("no WAN device")
		return
	}
	c := getChildDevice(b, "urn:schemas-upnp-org:device:WANConnectionDevice:1")
	if c == nil {
		err = errors.New("no WAN connection device")
		return
	}
	d := getChildService(c, "urn:schemas-upnp-org:service:WANIPConnection:1")
	if d == nil {
		err = errors.New("no WAN IP connection")
		return
	}
	url = combineURL(rootURL, d.ControlURL)
	return
}

// combineURL appends subURL onto rootURL.
func combineURL(rootURL, subURL string) string {
	protocolEnd := "://"
	protoEndIndex := strings.Index(rootURL, protocolEnd)
	a := rootURL[protoEndIndex+len(protocolEnd):]
	rootIndex := strings.Index(a, "/")
	return rootURL[0:protoEndIndex+len(protocolEnd)+rootIndex] + subURL
}

// soapBody represents the <s:Body> element in a SOAP reply.
// fields we don't care about are elided.
type soapBody struct {
	XMLName xml.Name `xml:"Body"`
	Data    []byte   `xml:",innerxml"`
}

// soapEnvelope represents the <s:Envelope> element in a SOAP reply.
// fields we don't care about are elided.
type soapEnvelope struct {
	XMLName xml.Name `xml:"Envelope"`
	Body    soapBody `xml:"Body"`
}

// soapRequest performs a soap request with the given parameters and returns
// the xml replied stripped of the soap headers. in the case that the request is
// unsuccessful the an error is returned.
func soapRequest(url, function, message string) (replyXML []byte, err error) {
	fullMessage := "<?xml version=\"1.0\" ?>" +
		"<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\" s:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\">\r\n" +
		"<s:Body>" + message + "</s:Body></s:Envelope>"

	req, err := http.NewRequest(http.MethodPost, url, strings.NewReader(fullMessage))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "text/xml ; charset=\"utf-8\"")
	req.Header.Set("User-Agent", "Darwin/10.0.0, UPnP/1.0, MiniUPnPc/1.3")
	//req.Header.Set("Transfer-Encoding", "chunked")
	req.Header.Set("SOAPAction", "\"urn:schemas-upnp-org:service:WANIPConnection:1#"+function+"\"")
	req.Header.Set("Connection", "Close")
	req.Header.Set("Cache-Control", "no-cache")
	req.Header.Set("Pragma", "no-cache")

	r, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	if r.Body != nil {
		defer r.Body.Close()
	}

	if r.StatusCode >= 400 {
		// log.Stderr(function, r.StatusCode)
		err = errors.New("error " + strconv.Itoa(r.StatusCode) + " for " + function)
		r = nil
		return
	}
	var reply soapEnvelope
	err = xml.NewDecoder(r.Body).Decode(&reply)
	if err != nil {
		return nil, err
	}
	return reply.Body.Data, nil
}

// getExternalIPAddressResponse represents the XML response to a
// GetExternalIPAddress SOAP request.
type getExternalIPAddressResponse struct {
	XMLName           xml.Name `xml:"GetExternalIPAddressResponse"`
	ExternalIPAddress string   `xml:"NewExternalIPAddress"`
}

// GetExternalAddress implements the NAT interface by fetching the external IP
// from the UPnP router.
func (n *upnpNAT) GetExternalAddress() (addr net.IP, err error) {
	message := "<u:GetExternalIPAddress xmlns:u=\"urn:schemas-upnp-org:service:WANIPConnection:1\"/>\r\n"
	response, err := soapRequest(n.serviceURL, "GetExternalIPAddress", message)
	if err != nil {
		return nil, err
	}

	var reply getExternalIPAddressResponse
	err = xml.Unmarshal(response, &reply)
	if err != nil {
		return nil, err
	}

	addr = net.ParseIP(reply.ExternalIPAddress)
	if addr == nil {
		return nil, errors.New("unable to parse ip address")
	}
	return addr, nil
}

// AddPortMapping implements the NAT interface by setting up a port forwarding
// from the UPnP router to the local machine with the given ports and protocol.
func (n *upnpNAT) AddPortMapping(protocol string, externalPort, internalPort int, description string, timeout int) (mappedExternalPort int, err error) {
	// A single concatenation would break ARM compilation.
	message := "<u:AddPortMapping xmlns:u=\"urn:schemas-upnp-org:service:WANIPConnection:1\">\r\n" +
		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort)
	message += "</NewExternalPort><NewProtocol>" + strings.ToUpper(protocol) + "</NewProtocol>"
	message += "<NewInternalPort>" + strconv.Itoa(internalPort) + "</NewInternalPort>" +
		"<NewInternalClient>" + n.ourIP + "</NewInternalClient>" +
		"<NewEnabled>1</NewEnabled><NewPortMappingDescription>"
	message += description +
		"</NewPortMappingDescription><NewLeaseDuration>" + strconv.Itoa(timeout) +
		"</NewLeaseDuration></u:AddPortMapping>"

	response, err := soapRequest(n.serviceURL, "AddPortMapping", message)
	if err != nil {
		return
	}

	// TODO: check response to see if the port was forwarded
	// If the port was not wildcard we don't get a reply with the port in
	// it. Not sure about wildcard yet. miniupnpc just checks for error
	// codes here.
	mappedExternalPort = externalPort
	_ = response
	return
}

// DeletePortMapping implements the NAT interface by removing up a port forwarding
// from the UPnP router to the local machine with the given ports and.
func (n *upnpNAT) DeletePortMapping(protocol string, externalPort, internalPort int) (err error) {

	message := "<u:DeletePortMapping xmlns:u=\"urn:schemas-upnp-org:service:WANIPConnection:1\">\r\n" +
		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort) +
		"</NewExternalPort><NewProtocol>" + strings.ToUpper(protocol) + "</NewProtocol>" +
		"</u:DeletePortMapping>"

	response, err := soapRequest(n.serviceURL, "DeletePortMapping", message)
	if err != nil {
		return
	}

	// TODO: check response to see if the port was deleted
	// log.Println(message, response)
	_ = response
	return
}
