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rconfig/autoenv.go
Knut Ahlers f2a0efe97c
Add AutoEnv feature
to automatically derive environment variable names from struct field
names

Signed-off-by: Knut Ahlers <knut@ahlers.me>
2018-08-02 12:02:47 +02:00

64 lines
1.3 KiB
Go

package rconfig
import "strings"
type characterClass [2]rune
func (c characterClass) Contains(r rune) bool {
return c[0] <= r && c[1] >= r
}
type characterClasses []characterClass
func (c characterClasses) Contains(r rune) bool {
for _, cc := range c {
if cc.Contains(r) {
return true
}
}
return false
}
var (
charGroupUpperLetter = characterClass{'A', 'Z'}
charGroupLowerLetter = characterClass{'a', 'z'}
charGroupNumber = characterClass{'0', '9'}
charGroupLowerNumber = characterClasses{charGroupLowerLetter, charGroupNumber}
)
func deriveEnvVarName(s string) string {
var (
words []string
word []rune
)
for _, l := range s {
switch {
case charGroupUpperLetter.Contains(l):
if len(word) > 0 && charGroupLowerNumber.Contains(word[len(word)-1]) {
words = append(words, string(word))
word = []rune{}
}
word = append(word, l)
case charGroupLowerLetter.Contains(l):
if len(word) > 1 && charGroupUpperLetter.Contains(word[len(word)-1]) {
words = append(words, string(word[0:len(word)-1]))
word = word[len(word)-1:]
}
word = append(word, l)
case charGroupNumber.Contains(l):
word = append(word, l)
default:
if len(word) > 0 {
words = append(words, string(word))
}
word = []rune{}
}
}
words = append(words, string(word))
return strings.ToUpper(strings.Join(words, "_"))
}