// meta4ra -- Metalink 4.0 utilities
// 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/>.

// Metalink 4.0 checker
package main

import (
	"bufio"
	"encoding/xml"
	"flag"
	"fmt"
	"io"
	"io/fs"
	"log"
	"os"
	"path"
	"strings"

	"go.stargrave.org/meta4ra"
)

func main() {
	hashes := flag.String("hashes",
		strings.Join(meta4ra.HashesDefault, ","), "hash-name:command-s")
	extractSig := flag.Bool("extract-sig", false, "Extract signature files")
	metaPath := flag.String("meta4", "file.meta4", "Metalink file")
	flag.Usage = func() {
		fmt.Fprintf(flag.CommandLine.Output(),
			"Usage: %s [options] [FILE ...]\n", os.Args[0])
		flag.PrintDefaults()
		fmt.Fprint(flag.CommandLine.Output(), `
If no FILEs are specified, then all <file>s from metalink are searched and
verified if they exist. Otherwise only specified FILEs are checked. If you
want to skip any <file> verification (for example only to validate the format
and -extract-sig, then you can just specify empty ("") FILE.
`)
	}
	flag.Parse()
	log.SetFlags(log.Lshortfile)

	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)
	}

	toCheck := make(map[string]string)
	for _, fn := range flag.Args() {
		toCheck[path.Base(fn)] = fn
	}

	bad := false
	for _, f := range meta.Files {
		for _, sig := range f.Signature {
			if !*extractSig {
				continue
			}
			var fn string
			switch sig.MediaType {
			case meta4ra.SigMediaTypePGP:
				fn = f.Name + ".asc"
			case meta4ra.SigMediaTypeSSH:
				fn = f.Name + ".sig"
			}
			if fn == "" {
				continue
			}
			if err = os.WriteFile(
				fn,
				[]byte(strings.TrimPrefix(sig.Signature, "\n")),
				fs.FileMode(0666),
			); err != nil {
				fmt.Println("Error:", f.Name, "can not save signature:", err)
				bad = true
			}
		}
		hasher := meta4ra.NewHasher(*hashes)
		var hashTheir string
		var hashName string
		for i, name := range hasher.Names {
			for _, h := range f.Hashes {
				if h.Type == name {
					hasher.Names = []string{name}
					hasher.Cmds = append(hasher.Cmds[:0], hasher.Cmds[i])
					hasher.Ins = append(hasher.Ins[:0], hasher.Ins[i])
					hasher.Outs = append(hasher.Outs[:0], hasher.Outs[i])
					hashName = name
					hashTheir = h.Hash
					goto HashFound
				}
			}
		}
		log.Fatalln("no common hashes found for:", f.Name)
	HashFound:
		fullPath := toCheck[f.Name]
		if !(len(toCheck) == 0 || fullPath != "") {
			continue
		}
		if fullPath == "" {
			fullPath = f.Name
		}
		fd, err := os.Open(fullPath)
		if err != nil {
			fmt.Println("Error:", f.Name, err)
			bad = true
			continue
		}
		hasher.Start()
		_, err = io.Copy(hasher, bufio.NewReaderSize(fd, 1<<20))
		fd.Close()
		sums := hasher.Sums()
		if err != nil {
			fmt.Println("Error:", f.Name, err)
			bad = true
			continue
		}
		hashOur := sums[0].Hash
		if hashOur == hashTheir {
			fmt.Println(f.Name, hashName, "good")
		} else {
			fmt.Println(
				"Hash does not match:", f.Name, hashName,
				"our:", hashOur,
				"their:", hashTheir,
			)
			bad = true
			continue
		}
	}
	if bad {
		os.Exit(1)
	}
}