/*
meta4a -- Metalink 4.0 creator
Copyright (C) 2021-2023 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/>.
*/

// Metalink 4.0 creator
package main

import (
	"bufio"
	"bytes"
	"encoding/xml"
	"flag"
	"io"
	"log"
	"os"
	"os/exec"
	"path"
	"strings"
	"sync"
	"time"

	"go.stargrave.org/meta4ra"
)

type Hasher struct {
	names []string
	cmds  []*exec.Cmd
	ins   []io.WriteCloser
	outs  []io.ReadCloser
	wg    sync.WaitGroup
}

func NewHasher(hashes string) *Hasher {
	h := Hasher{}
	for _, hc := range strings.Split(hashes, ",") {
		cols := strings.SplitN(hc, ":", 2)
		name, cmdline := cols[0], cols[1]
		cmd := exec.Command(cmdline)
		in, err := cmd.StdinPipe()
		if err != nil {
			log.Fatalln(err)
		}
		out, err := cmd.StdoutPipe()
		if err != nil {
			log.Fatalln(err)
		}
		if err = cmd.Start(); err != nil {
			log.Fatalln(err)
		}
		h.names = append(h.names, name)
		h.ins = append(h.ins, in)
		h.outs = append(h.outs, out)
		h.cmds = append(h.cmds, cmd)
	}
	return &h
}

func (h *Hasher) Write(p []byte) (n int, err error) {
	h.wg.Add(len(h.names))
	for _, in := range h.ins {
		go func(in io.WriteCloser) {
			if _, err := io.Copy(in, bytes.NewReader(p)); err != nil {
				log.Fatalln(err)
			}
			h.wg.Done()
		}(in)
	}
	h.wg.Wait()
	return len(p), nil
}

func (h *Hasher) Sums() []meta4ra.Hash {
	sums := make([]meta4ra.Hash, 0, len(h.names))
	for i, name := range h.names {
		if err := h.ins[i].Close(); err != nil {
			log.Fatalln(err)
		}
		dgst, err := io.ReadAll(h.outs[i])
		if err != nil {
			log.Fatalln(err)
		}
		sums = append(sums, meta4ra.Hash{Type: name, Hash: string(dgst[:len(dgst)-1])})
		if err = h.cmds[i].Wait(); err != nil {
			log.Fatalln(err)
		}
	}
	return sums
}

func main() {
	fn := flag.String("fn", "", "Filename")
	mtime := flag.String("mtime", "", "Take that file's mtime as a Published date")
	desc := flag.String("desc", "", "Description")
	sig := flag.String("sig", "", "Path to signature file")
	hashesDef := []string{
		"sha-256:sha256",
		"sha-512:sha512",
		"shake128:shake128sum",
		"shake256:shake256sum",
		"streebog-256:streebog256sum",
		"streebog-512:streebog512sum",
		"skein-256:skein256",
		"skein-512:skein512",
		"blake3-256:b3sum",
	}
	hashes := flag.String("hashes", strings.Join(hashesDef, ","), "hash-name:command-s")
	torrent := flag.String("torrent", "", "Torrent URL")
	log.SetFlags(log.Lshortfile)
	flag.Parse()
	if *fn == "" {
		log.Fatalln("empty -fn")
	}
	urls := make([]meta4ra.URL, 0, len(flag.Args()))
	for _, u := range flag.Args() {
		urls = append(urls, meta4ra.URL{URL: u})
	}
	h := NewHasher(*hashes)
	br := bufio.NewReaderSize(os.Stdin, 1<<20)
	buf := make([]byte, 1<<20)
	size, err := io.CopyBuffer(h, br, buf)
	if err != nil {
		log.Fatalln(err)
	}
	f := meta4ra.File{
		Name:        path.Base(*fn),
		Description: *desc,
		Size:        uint64(size),
		URLs:        urls,
		Hashes:      h.Sums(),
	}
	if *sig != "" {
		sigData, err := os.ReadFile(*sig)
		if err != nil {
			log.Fatalln(err)
		}
		f.Signature = &meta4ra.Signature{
			MediaType: meta4ra.GPGSigMediaType,
			Signature: "\n" + string(sigData),
		}
	}
	if *torrent != "" {
		f.MetaURLs = []meta4ra.MetaURL{{MediaType: "torrent", URL: *torrent}}
	}
	var published time.Time
	if *mtime == "" {
		published = time.Now()
	} else {
		fi, err := os.Stat(*mtime)
		if err != nil {
			log.Fatalln(err)
		}
		published = fi.ModTime()
	}
	published = published.UTC().Truncate(time.Second)
	m := meta4ra.Metalink{
		Files:     []meta4ra.File{f},
		Generator: meta4ra.Generator,
		Published: published,
	}
	out, err := xml.MarshalIndent(&m, "", "  ")
	if err != nil {
		log.Fatalln(err)
	}
	os.Stdout.Write([]byte(xml.Header))
	os.Stdout.Write(out)
	os.Stdout.Write([]byte("\n"))
}