/*
NNCP -- Node to Node copy, utilities for store-and-forward data exchange
Copyright (C) 2016-2022 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Parse raw NNCP packet.
package main

import (
	"bufio"
	"bytes"
	"flag"
	"fmt"
	"io"
	"log"
	"os"

	xdr "github.com/davecgh/go-xdr/xdr2"
	"github.com/klauspost/compress/zstd"
	"go.cypherpunks.ru/nncp/v8"
)

func usage() {
	fmt.Fprintf(os.Stderr, nncp.UsageHeader())
	fmt.Fprintf(os.Stderr, "nncp-pkt -- parse raw packet\n\n")
	fmt.Fprintf(os.Stderr, "Usage: %s [options]\nOptions:\n", os.Args[0])
	flag.PrintDefaults()
	fmt.Fprintln(os.Stderr, "Packet is read from stdin.")
}

func doPlain(ctx *nncp.Ctx, pkt nncp.Pkt, dump, decompress bool) {
	if dump {
		bufW := bufio.NewWriter(os.Stdout)
		var r io.Reader
		r = bufio.NewReader(os.Stdin)
		if decompress {
			decompressor, err := zstd.NewReader(r)
			if err != nil {
				log.Fatalln(err)
			}
			r = decompressor
		}
		if _, err := io.Copy(bufW, r); err != nil {
			log.Fatalln(err)
		}
		if err := bufW.Flush(); err != nil {
			log.Fatalln(err)
		}
		return
	}
	payloadType := "unknown"
	switch pkt.Type {
	case nncp.PktTypeFile:
		payloadType = "file"
	case nncp.PktTypeFreq:
		payloadType = "file request"
	case nncp.PktTypeExec:
		payloadType = "exec compressed"
	case nncp.PktTypeTrns:
		payloadType = "transitional"
	case nncp.PktTypeExecFat:
		payloadType = "exec uncompressed"
	case nncp.PktTypeArea:
		payloadType = "area"
	case nncp.PktTypeACK:
		payloadType = "acknowledgement"
	}
	var path string
	switch pkt.Type {
	case nncp.PktTypeExec, nncp.PktTypeExecFat:
		path = string(bytes.Replace(
			pkt.Path[:pkt.PathLen], []byte{0}, []byte(" "), -1,
		))
	case nncp.PktTypeTrns:
		path = nncp.Base32Codec.EncodeToString(pkt.Path[:pkt.PathLen])
		node, err := ctx.FindNode(path)
		if err == nil {
			path = fmt.Sprintf("%s (%s)", path, node.Name)
		}
	case nncp.PktTypeArea:
		path = nncp.Base32Codec.EncodeToString(pkt.Path[:pkt.PathLen])
		if areaId, err := nncp.AreaIdFromString(path); err == nil {
			path = fmt.Sprintf("%s (%s)", path, ctx.AreaName(areaId))
		}
	case nncp.PktTypeACK:
		path = nncp.Base32Codec.EncodeToString(pkt.Path[:pkt.PathLen])
	default:
		path = string(pkt.Path[:pkt.PathLen])
	}
	fmt.Printf(
		"Packet type: plain\nPayload type: %s\nNiceness: %s (%d)\nPath: %s\n",
		payloadType, nncp.NicenessFmt(pkt.Nice), pkt.Nice, path,
	)
	return
}

func doEncrypted(
	ctx *nncp.Ctx,
	pktEnc nncp.PktEnc,
	dump bool,
	beginning []byte,
) {
	senderName := "unknown"
	senderNode := ctx.Neigh[*pktEnc.Sender]
	if senderNode != nil {
		senderName = senderNode.Name
	}

	recipientName := "unknown"
	var area *nncp.Area
	recipientNode := ctx.Neigh[*pktEnc.Recipient]
	if recipientNode == nil {
		area = ctx.AreaId2Area[nncp.AreaId(*pktEnc.Recipient)]
		if area != nil {
			recipientName = "area " + area.Name
		}
	} else {
		recipientName = recipientNode.Name
	}

	if !dump {
		fmt.Printf(`Packet type: encrypted
Niceness: %s (%d)
Sender: %s (%s)
Recipient: %s (%s)
`,
			nncp.NicenessFmt(pktEnc.Nice), pktEnc.Nice,
			pktEnc.Sender, senderName,
			pktEnc.Recipient, recipientName,
		)
		return
	}
	if ctx.Self == nil {
		log.Fatalln("Config lacks private keys")
	}
	bufW := bufio.NewWriter(os.Stdout)
	var err error
	if area == nil {
		_, _, _, err = nncp.PktEncRead(
			ctx.Self, ctx.Neigh,
			io.MultiReader(bytes.NewReader(beginning), bufio.NewReader(os.Stdin)),
			bufW, senderNode != nil, nil,
		)
	} else {
		areaNode := nncp.NodeOur{Id: new(nncp.NodeId), ExchPrv: new([32]byte)}
		copy(areaNode.Id[:], area.Id[:])
		copy(areaNode.ExchPrv[:], area.Prv[:])
		_, _, _, err = nncp.PktEncRead(
			&areaNode, ctx.Neigh,
			io.MultiReader(bytes.NewReader(beginning), bufio.NewReader(os.Stdin)),
			bufW, senderNode != nil, nil,
		)
	}
	if err != nil {
		log.Fatalln(err)
	}
	if err = bufW.Flush(); err != nil {
		log.Fatalln(err)
	}
}

func main() {
	var (
		overheads  = flag.Bool("overheads", false, "Print packet overheads")
		dump       = flag.Bool("dump", false, "Write decrypted/parsed payload to stdout")
		decompress = flag.Bool("decompress", false, "Try to zstd decompress dumped data")
		cfgPath    = flag.String("cfg", nncp.DefaultCfgPath, "Path to configuration file")
		version    = flag.Bool("version", false, "Print version information")
		warranty   = flag.Bool("warranty", false, "Print warranty information")
	)
	log.SetFlags(log.Lshortfile)
	flag.Usage = usage
	flag.Parse()
	if *warranty {
		fmt.Println(nncp.Warranty)
		return
	}
	if *version {
		fmt.Println(nncp.VersionGet())
		return
	}

	ctx, err := nncp.CtxFromCmdline(*cfgPath, "", "", false, false, false, false)
	if err != nil {
		log.Fatalln("Error during initialization:", err)
	}

	if *overheads {
		fmt.Printf(
			"Plain: %d\nEncrypted: %d\nSize: %d\n",
			nncp.PktOverhead,
			nncp.PktEncOverhead,
			nncp.PktSizeOverhead,
		)
		return
	}

	beginning := make([]byte, nncp.PktOverhead)
	if _, err := io.ReadFull(os.Stdin, beginning[:nncp.PktEncOverhead]); err != nil {
		log.Fatalln("Not enough data to read")
	}
	var pktEnc nncp.PktEnc
	if _, err := xdr.Unmarshal(bytes.NewReader(beginning), &pktEnc); err == nil {
		switch pktEnc.Magic {
		case nncp.MagicNNCPEv1.B:
			log.Fatalln(nncp.MagicNNCPEv1.TooOld())
		case nncp.MagicNNCPEv2.B:
			log.Fatalln(nncp.MagicNNCPEv2.TooOld())
		case nncp.MagicNNCPEv3.B:
			log.Fatalln(nncp.MagicNNCPEv3.TooOld())
		case nncp.MagicNNCPEv4.B:
			log.Fatalln(nncp.MagicNNCPEv4.TooOld())
		case nncp.MagicNNCPEv5.B:
			log.Fatalln(nncp.MagicNNCPEv5.TooOld())
		case nncp.MagicNNCPEv6.B:
			doEncrypted(ctx, pktEnc, *dump, beginning[:nncp.PktEncOverhead])
			return
		}
	}

	if _, err := io.ReadFull(os.Stdin, beginning[nncp.PktEncOverhead:]); err != nil {
		log.Fatalln("Not enough data to read")
	}
	var pkt nncp.Pkt
	if _, err := xdr.Unmarshal(bytes.NewReader(beginning), &pkt); err == nil {
		switch pkt.Magic {
		case nncp.MagicNNCPPv1.B:
			log.Fatalln(nncp.MagicNNCPPv1.TooOld())
		case nncp.MagicNNCPPv2.B:
			log.Fatalln(nncp.MagicNNCPPv2.TooOld())
		case nncp.MagicNNCPPv3.B:
			doPlain(ctx, pkt, *dump, *decompress)
			return
		}
	}
	log.Fatalln("Unable to determine packet type")
}