/*
GoCheese -- Python private package repository and caching proxy
Copyright (C) 2019-2021 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/sha256"
	"fmt"
	"hash"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"

	"golang.org/x/crypto/blake2b"
)

func checkFile(
	pkgName, fn, fnHash, hasherName string,
	hasher hash.Hash, digest []byte,
) bool {
	expected, err := ioutil.ReadFile(fnHash)
	if err != nil {
		log.Fatal(err)
	}
	fd, err := os.Open(fn)
	if err != nil {
		if os.IsNotExist(err) {
			return true
		}
		log.Fatal(err)
	}
	_, err = io.Copy(hasher, bufio.NewReader(fd))
	fd.Close()
	if err != nil {
		log.Fatal(err)
	}
	isEqual := bytes.Compare(hasher.Sum(digest[:0]), expected) == 0
	hasher.Reset()
	if isEqual {
		fmt.Println("GOOD", hasherName, pkgName)
		return true
	}
	fmt.Println("BAD", hasherName, pkgName)
	return false
}

func goodIntegrity() bool {
	dirs, err := ioutil.ReadDir(Root)
	if err != nil {
		log.Fatal(err)
	}
	hasherSHA256 := sha256.New()
	hasherBLAKE2b256 := blake2b256New()
	digestSHA256 := make([]byte, sha256.Size)
	digestBLAKE2b256 := make([]byte, blake2b.Size256)
	isGood := true
	var pkgName string
	for _, dir := range dirs {
		files, err := ioutil.ReadDir(filepath.Join(Root, dir.Name()))
		if err != nil {
			log.Fatal(err)
		}
		for _, file := range files {
			if strings.HasSuffix(file.Name(), "."+HashAlgoSHA256) {
				pkgName = strings.TrimSuffix(file.Name(), "."+HashAlgoSHA256)
				if !checkFile(
					pkgName,
					filepath.Join(Root, dir.Name(), pkgName),
					filepath.Join(Root, dir.Name(), file.Name()),
					"SHA256", hasherSHA256, digestSHA256,
				) {
					isGood = false
				}
				continue
			}
			if strings.HasSuffix(file.Name(), "."+HashAlgoBLAKE2b256) {
				pkgName = strings.TrimSuffix(file.Name(), "."+HashAlgoBLAKE2b256)
				if !checkFile(
					pkgName,
					filepath.Join(Root, dir.Name(), pkgName),
					filepath.Join(Root, dir.Name(), file.Name()),
					"BLAKE2b-256", hasherBLAKE2b256, digestBLAKE2b256,
				) {
					isGood = false
				}
			}
		}
	}
	return isGood
}