package main

import (
	"fmt"
	"io"
	"os"
	"path/filepath"

	log "github.com/sirupsen/logrus"
)


/*help to copy the file, ioutil doesn't offer the feature*/

func copyFileContents(src, dst string) (err error) {
	in, err := os.Open(src)
	if err != nil {
		return
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return
	}
	defer func() {
		cerr := out.Close()
		if err == nil {
			err = cerr
		}
	}()
	if _, err = io.Copy(out, in); err != nil {
		return
	}
	err = out.Sync()
	return
}

/*copy the file, ioutile doesn't offer the feature*/
func CopyFile(sourceSymLink, destinationFile string) (err error) {
	sourceFile, err := filepath.EvalSymlinks(sourceSymLink)
	if err != nil {
		log.Infof("Not a symlink : %s", err)
		sourceFile = sourceSymLink
	}

	sourceFileStat, err := os.Stat(sourceFile)
	if err != nil {
		return
	}
	if !sourceFileStat.Mode().IsRegular() {
		// cannot copy non-regular files (e.g., directories,
		// symlinks, devices, etc.)
		return fmt.Errorf("copyFile: non-regular source file %s (%q)", sourceFileStat.Name(), sourceFileStat.Mode().String())
	}
	destinationFileStat, err := os.Stat(destinationFile)
	if err != nil {
		if !os.IsNotExist(err) {
			return
		}
	} else {
		if !(destinationFileStat.Mode().IsRegular()) {
			return fmt.Errorf("copyFile: non-regular destination file %s (%q)", destinationFileStat.Name(), destinationFileStat.Mode().String())
		}
		if os.SameFile(sourceFileStat, destinationFileStat) {
			return
		}
	}
	if err = os.Link(sourceFile, destinationFile); err != nil {
		err = copyFileContents(sourceFile, destinationFile)
	}
	return
}