// netstring -- netstring format serialization library
// Copyright (C) 2015-2024 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/>.

package main

import (
	"flag"
	"fmt"
	"io"
	"os"
	"strconv"

	"go.cypherpunks.ru/netstring/v2"
)

func usage() {
	fmt.Fprintf(os.Stderr, "ns -- Work with netstring encoded files\n\n")
	fmt.Fprintf(os.Stderr, "Usage: %s list FILE\n", os.Args[0])
	fmt.Fprintf(os.Stderr, "       %s read FILE CHUNK > data\n", os.Args[0])
	fmt.Fprintf(os.Stderr, "       %s write FILE ... > data\n", os.Args[0])
	fmt.Fprintf(os.Stderr, "FILE can be \"-\" for reading from stdin\n")
	os.Exit(1)
}

func fileRead(path string) io.Reader {
	if path == "-" {
		return os.Stdin
	}
	fd, err := os.Open(path)
	if err != nil {
		panic(err)
	}
	return fd
}

func main() {
	flag.Usage = usage
	flag.Parse()
	if len(os.Args) < 3 {
		usage()
	}
	switch os.Args[1] {
	case "list":
		r := netstring.NewReader(fileRead(os.Args[2]))
		for i := 0; ; i++ {
			size, err := r.Next()
			if err == io.EOF {
				break
			}
			if err != nil {
				panic(err)
			}
			fmt.Printf("%d\t%d\n", i, size)
			r.Discard()
		}
	case "read":
		if len(os.Args) != 4 {
			usage()
		}
		chunk, err := strconv.Atoi(os.Args[3])
		if err != nil {
			panic(err)
		}
		r := netstring.NewReader(fileRead(os.Args[2]))
		for i := 0; i < chunk; i++ {
			_, err = r.Next()
			if err != nil {
				panic(err)
			}
			r.Discard()
		}
		_, err = r.Next()
		if err != nil {
			panic(err)
		}
		if _, err = io.Copy(os.Stdout, r); err != nil {
			panic(err)
		}
	case "write":
		w := netstring.NewWriter(os.Stdout)
		for i, fn := range os.Args[2:] {
			fd, err := os.Open(fn)
			if err != nil {
				panic(err)
			}
			fi, err := fd.Stat()
			if err != nil {
				panic(err)
			}
			size := uint64(fi.Size())
			if _, err = w.WriteSize(size); err != nil {
				panic(err)
			}
			if _, err = io.Copy(w, fd); err != nil {
				panic(err)
			}
			fmt.Fprintf(os.Stderr, "%d\t%d\t%s\n", i, size, fn)
		}
	}
}