/*
GoCheese -- Python private package repository and caching proxy
Copyright (C) 2019-2020 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 (
	"os"
	"path/filepath"
	"strconv"
	"time"
)

func TempFile(dir string) (*os.File, error) {
	// Assume that probability of suffix collision is negligible
	suffix := strconv.FormatInt(time.Now().UnixNano()+int64(os.Getpid()), 16)
	name := filepath.Join(dir, "nncp"+suffix)
	return os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, os.FileMode(0666))
}

func DirSync(dirPath string) error {
	fd, err := os.Open(dirPath)
	if err != nil {
		return err
	}
	err = fd.Sync()
	if err != nil {
		fd.Close()
		return err
	}
	return fd.Close()
}

func WriteFileSync(dirPath, filePath string, data []byte) error {
	dst, err := TempFile(dirPath)
	if err != nil {
		return err
	}
	if _, err = dst.Write(data); err != nil {
		os.Remove(dst.Name())
		dst.Close()
		return err
	}
	if err = dst.Sync(); err != nil {
		os.Remove(dst.Name())
		dst.Close()
		return err
	}
	dst.Close()
	if err = os.Rename(dst.Name(), filePath); err != nil {
		return err
	}
	return DirSync(dirPath)
}