abzcoding/hget

package main

import (
    "errors"
    "github.com/mattn/go-isatty"
    "net"
    "net/url"
    "os"
    "path/filepath"
    "strings"
)

// FatalCheck panics if err is not nil.
func FatalCheck(err error) {
    if err != nil {
        Errorf("%v", err)
        panic(err)
    }
}

// FilterIPV4 returns parsed ipv4 string.
func FilterIPV4(ips []net.IP) []string {
    var ret = make([]string, 0)
    for _, ip := range ips {
        if ip.To4() != nil {
            ret = append(ret, ip.String())
        }
    }
    return ret
}

// MkdirIfNotExist creates `folder` directory if not available
func MkdirIfNotExist(folder string) error {
    if _, err := os.Stat(folder); err != nil {
        if err = os.MkdirAll(folder, 0700); err != nil {
            return err
        }
    }
    return nil
}

// ExistDir checks if `folder` is available
func ExistDir(folder string) bool {
    _, err := os.Stat(folder)
    return err == nil
}

// DisplayProgressBar shows a fancy progress bar
func DisplayProgressBar() bool {
    return isatty.IsTerminal(os.Stdout.Fd()) && displayProgress
}

// FolderOf makes sure you won't get LFI
func FolderOf(url string) string {
    safePath := filepath.Join(os.Getenv("HOME"), dataFolder)
    fullQualifyPath, err := filepath.Abs(filepath.Join(os.Getenv("HOME"), dataFolder, filepath.Base(url)))
    FatalCheck(err)

    //must ensure full qualify path is CHILD of safe path
    //to prevent directory traversal attack
    //using Rel function to get relative between parent and child
    //if relative join base == child, then child path MUST BE real child
    relative, err := filepath.Rel(safePath, fullQualifyPath)
    FatalCheck(err)

    if strings.Contains(relative, "..") {
        FatalCheck(errors.New("you may be a victim of directory traversal path attack"))
        return "" //return is redundant be cause in fatal check we have panic, but compiler does not able to check
    }
    return fullQualifyPath

}

// TaskFromURL runs when you want to download a single url
func TaskFromURL(url string) string {
    //task is just download file name
    //so we get download file name on url
    filename := filepath.Base(url)
    return filename
}

// IsURL checks if `s` is actually a parsable URL.
func IsURL(s string) bool {
    _, err := url.Parse(s)
    return err == nil
}