/*
meta4a -- Metalink 4.0 checker
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 checker
package main

import (
	"bufio"
	"crypto/sha256"
	"crypto/sha512"
	"encoding/hex"
	"encoding/xml"
	"flag"
	"fmt"
	"hash"
	"io"
	"io/fs"
	"log"
	"os"

	"go.stargrave.org/meta4ra"
)

func main() {
	extractSig := flag.Bool("extract-sig", false, "Extract signature files")
	log.SetFlags(log.Lshortfile)
	flag.Parse()
	sha256Hasher := sha256.New()
	sha512Hasher := sha512.New()
	bad := false
	for _, metaPath := range flag.Args() {
		data, err := os.ReadFile(metaPath)
		if err != nil {
			log.Fatalln(err)
		}
		var meta meta4ra.Metalink
		err = xml.Unmarshal(data, &meta)
		if err != nil {
			log.Fatalln(err)
		}
		for _, f := range meta.Files {
			if f.Signature != nil && *extractSig {
				if err = os.WriteFile(
					f.Name+".asc",
					[]byte(f.Signature.Signature),
					fs.FileMode(0666),
				); err != nil {
					fmt.Println("Error:", f.Name, "can not save signature:", err)
					bad = true
				}
			}
			var sha256Digest string
			var sha512Digest string
			fd, err := os.Open(f.Name)
			if err != nil {
				continue
			}
			for _, h := range f.Hashes {
				switch h.Type {
				case meta4ra.HashSHA256:
					sha256Digest = h.Hash
				case meta4ra.HashSHA512:
					sha512Digest = h.Hash
				}
			}
			var digestTheir string
			var digestName string
			var hasher hash.Hash
			if sha512Digest != "" {
				digestName = meta4ra.HashSHA512
				digestTheir = sha512Digest
				hasher = sha512Hasher
			} else if sha256Digest != "" {
				digestName = meta4ra.HashSHA256
				digestTheir = sha256Digest
				hasher = sha256Hasher
			} else {
				fd.Close()
				fmt.Println("Error:", f.Name, "no satisfiable hash algorithm found")
				bad = true
				continue
			}
			hasher.Reset()
			_, err = io.Copy(hasher, bufio.NewReader(fd))
			fd.Close()
			if err != nil {
				fmt.Println("Error:", f.Name, err)
				bad = true
				continue
			}
			digestOur := hex.EncodeToString(hasher.Sum(nil))
			if digestOur == digestTheir {
				fmt.Println(f.Name, digestName, "good")
			} else {
				fmt.Println(
					"Hash does not match:", f.Name, digestName,
					"our:", digestOur,
					"their:", digestTheir,
				)
				bad = true
				continue
			}
		}
	}
	if bad {
		os.Exit(1)
	}
}