/*
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"
	"crypto/sha256"
	"crypto/sha512"
	"encoding/hex"
	"encoding/xml"
	"flag"
	"hash"
	"io"
	"log"
	"os"
	"sync"
	"time"

	"go.cypherpunks.ru/gogost/v5/gost34112012256"
	"go.cypherpunks.ru/gogost/v5/gost34112012512"
	"go.stargrave.org/meta4ra"
)

type MultiHasher struct {
	sha256h      hash.Hash
	sha512h      hash.Hash
	streebog256h hash.Hash
	streebog512h hash.Hash
	g            sync.WaitGroup
}

func NewMultiHasher() *MultiHasher {
	return &MultiHasher{
		sha256h:      sha256.New(),
		sha512h:      sha512.New(),
		streebog256h: gost34112012256.New(),
		streebog512h: gost34112012512.New(),
	}
}

func (h *MultiHasher) Write(p []byte) (n int, err error) {
	h.g.Add(4)
	go func() {
		if _, err := h.sha256h.Write(p); err != nil {
			panic(err)
		}
		h.g.Done()
	}()
	go func() {
		if _, err := h.sha512h.Write(p); err != nil {
			panic(err)
		}
		h.g.Done()
	}()
	go func() {
		if _, err := h.streebog256h.Write(p); err != nil {
			panic(err)
		}
		h.g.Done()
	}()
	go func() {
		if _, err := h.streebog512h.Write(p); err != nil {
			panic(err)
		}
		h.g.Done()
	}()
	h.g.Wait()
	return len(p), nil
}

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")
	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})
	}
	br := bufio.NewReaderSize(os.Stdin, 1<<20)
	buf := make([]byte, 1<<20)
	h := NewMultiHasher()
	size, err := io.CopyBuffer(h, br, buf)
	if err != nil {
		log.Fatalln(err)
	}
	f := meta4ra.File{
		Name:        *fn,
		Description: *desc,
		Size:        uint64(size),
		URLs:        urls,
		Hashes: []meta4ra.Hash{
			{Type: meta4ra.HashSHA256, Hash: hex.EncodeToString(h.sha256h.Sum(nil))},
			{Type: meta4ra.HashSHA512, Hash: hex.EncodeToString(h.sha512h.Sum(nil))},
			{Type: meta4ra.HashStreebog256, Hash: hex.EncodeToString(h.streebog256h.Sum(nil))},
			{Type: meta4ra.HashStreebog512, Hash: hex.EncodeToString(h.streebog512h.Sum(nil))},
		},
	}
	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"))
}