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customflags.go
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customflags.go
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package cmd
import (
"flag"
"fmt"
"os"
"os/user"
"path"
"strings"
)
// DirectoryString -- Custom type which is registered in the flags library
// which cli uses for argument parsing. This allows us to expand Value to
// an absolute path when the argument is parsed.
type DirectoryString struct {
Value string
}
func (d *DirectoryString) String() string {
return d.Value
}
// Set directory string value
func (d *DirectoryString) Set(value string) error {
d.Value = expandPath(value)
return nil
}
func prefixFor(name string) (prefix string) {
if len(name) == 1 {
prefix = "-"
} else {
prefix = "--"
}
return prefix
}
func prefixedNames(fullName string) (prefixed string) {
parts := strings.Split(fullName, ",")
for i, name := range parts {
name = strings.Trim(name, " ")
prefixed += prefixFor(name) + name
if i < len(parts)-1 {
prefixed += ", "
}
}
return prefixed
}
// DirectoryFlag expands the received string to an absolute path.
// e.g. ~/.ethereum -> /home/username/.ethereum
type DirectoryFlag struct {
Name string
Value DirectoryString
Usage string
}
func (d DirectoryFlag) String() string {
fmtString := "%s %v\t%v"
if len(d.Value.Value) > 0 {
fmtString = "%s \"%v\"\t%v"
}
return fmt.Sprintf(fmtString, prefixedNames(d.Name), d.Value.Value, d.Usage)
}
func eachName(longName string, fn func(string)) {
parts := strings.Split(longName, ",")
for _, name := range parts {
name = strings.Trim(name, " ")
fn(name)
}
}
// Apply is called by cli library, grabs variable from environment (if in env)
// and adds variable to flag set for parsing.
func (d DirectoryFlag) Apply(set *flag.FlagSet) {
eachName(d.Name, func(name string) {
set.Var(&d.Value, d.Name, d.Usage)
})
}
// GetName of directory.
func (d DirectoryFlag) GetName() string {
return d.Name
}
// Set flag value.
func (d *DirectoryFlag) Set(value string) {
d.Value.Value = value
}
// Expands a file path
// 1. replace tilde with users home dir
// 2. expands embedded environment variables
// 3. cleans the path, e.g. /a/b/../c -> /a/c
// Note, it has limitations, e.g. ~someuser/tmp will not be expanded
func expandPath(p string) string {
if strings.HasPrefix(p, "~/") || strings.HasPrefix(p, "~\\") {
if home := homeDir(); home != "" {
p = home + p[1:]
}
}
return path.Clean(os.ExpandEnv(p))
}
func homeDir() string {
if home := os.Getenv("HOME"); home != "" {
return home
}
if usr, err := user.Current(); err == nil {
return usr.HomeDir
}
return ""
}