// paster -- paste service
// Copyright (C) 2021-2024 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 (
	"bufio"
	"bytes"
	"crypto/rand"
	_ "embed"
	"encoding/base32"
	"encoding/hex"
	"flag"
	"fmt"
	"html/template"
	"io"
	"os"

	"go.cypherpunks.ru/netstring/v2"
	"lukechampine.com/blake3"
)

const MaxExtLen = 9

var (
	//go:embed asciicast.tmpl
	ASCIICastHTMLTmplRaw string
	ASCIICastHTMLTmpl    = template.Must(template.New("asciicast").Parse(
		ASCIICastHTMLTmplRaw,
	))
)

func fatal(s string) {
	fmt.Println(s)
	os.Exit(1)
}

func asciicastHTML(playerPath, cast string) error {
	var buf bytes.Buffer
	err := ASCIICastHTMLTmpl.Execute(&buf, struct {
		PlayerPath string
		Cast       string
	}{
		PlayerPath: playerPath,
		Cast:       cast,
	})
	if err != nil {
		return err
	}
	fn := cast + ".html"
	fd, err := os.OpenFile(fn, os.O_WRONLY|os.O_CREATE|os.O_EXCL, os.FileMode(0666))
	if err != nil {
		return err
	}
	if _, err = fd.Write(buf.Bytes()); err != nil {
		os.Remove(fn)
		return err
	}
	return fd.Close()
}

func main() {
	maxSize := flag.Uint64("max-size", 1<<20, "Maximal upload size")
	asciicastPath := flag.String("asciicast-path", "", "Generate HTMLs for .cast asciicasts, specify \"asciinema-player-v2.6.1\"")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: paster [options] URL [URL ...]\n")
		flag.PrintDefaults()
	}
	flag.Parse()
	if len(flag.Args()) == 0 {
		flag.Usage()
		os.Exit(1)
	}
	r := netstring.NewReader(os.Stdin)
	size, err := r.Next()
	if err != nil {
		fatal(err.Error())
	}
	if size > MaxExtLen {
		fatal("too long extension length")
	}
	data, err := io.ReadAll(r)
	if err != nil {
		fatal(err.Error())
	}
	var ext string
	if len(data) == 0 {
		ext = ".txt"
	} else {
		ext = "." + string(data)
	}
	size, err = r.Next()
	if err != nil {
		fatal(err.Error())
	}
	if size == 0 {
		fatal("empty paste")
	}
	if size > *maxSize {
		fatal("too big")
	}
	rnd := make([]byte, 12)
	if _, err = io.ReadFull(rand.Reader, rnd); err != nil {
		fatal(err.Error())
	}
	fn := "." + base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(rnd) + ext
	fd, err := os.OpenFile(fn, os.O_RDWR|os.O_CREATE|os.O_EXCL, os.FileMode(0666))
	if err != nil {
		fatal(err.Error())
	}
	h := blake3.New(32, nil)
	bfd := bufio.NewWriter(fd)
	mw := io.MultiWriter(bfd, h)
	buf := make([]byte, 1)
	_, err = io.CopyN(mw, r, int64(size-1))
	if err != nil {
		goto Failed
	}
	_, err = r.Read(buf)
	if err != nil {
		goto Failed
	}
	_, err = mw.Write(buf)
	if err != nil {
		goto Failed
	}
	if (ext == ".txt" || ext == ".url") && buf[0] != '\n' {
		err = bfd.WriteByte('\n')
		if err != nil {
			goto Failed
		}
	}
	err = bfd.Flush()
	if err != nil {
		goto Failed
	}
	err = fd.Close()
	if err != nil {
		goto Failed
	}
	err = os.Rename(fn, fn[1:])
	if err != nil {
		goto Failed
	}
	for _, u := range flag.Args() {
		fmt.Println(u + fn[1:])
	}
	fmt.Println("BLAKE3-256:", hex.EncodeToString(h.Sum(nil)))
	if ext == ".cast" && *asciicastPath != "" {
		if err = asciicastHTML(*asciicastPath, fn[1:]); err != nil {
			goto Failed
		}
		for _, u := range flag.Args() {
			fmt.Println(u + fn[1:] + ".html")
		}
	}
	fmt.Fprintf(
		os.Stderr,
		"[%s]:%s %s %d\n",
		os.Getenv("TCPREMOTEIP"),
		os.Getenv("TCPREMOTEPORT"),
		fn[1:], size,
	)
	return
Failed:
	os.Remove(fn)
	fatal(err.Error())
}