/
expansion.go
52 lines (47 loc) · 1.04 KB
/
expansion.go
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package runtime
import (
"errors"
"fmt"
"strings"
)
const (
BeginDelimiter = "{"
EndDelimiter = "}"
)
// Resolver - template parameter name value lookup
type Resolver interface {
Lookup(name string) (string, error)
}
// Expand - templated function to expand a template string, utilizing a resolver
func Expand[T Resolver](t string) (string, error) {
var r T
if t == "" {
return "", nil
}
var buf strings.Builder
tokens := strings.Split(t, BeginDelimiter)
if len(tokens) == 1 {
return t, nil
}
for _, s := range tokens {
sub := strings.Split(s, EndDelimiter)
if len(sub) > 2 {
return "", errors.New(fmt.Sprintf("invalid argument : token has multiple end delimiters: %v", s))
}
// Check case where no end delimiter is found
if len(sub) == 1 && sub[0] == s {
buf.WriteString(s)
continue
}
// Have a valid end delimiter, so lookup the variable
t, err := r.Lookup(sub[0])
if err != nil {
return "", err
}
buf.WriteString(t)
if len(sub) == 2 {
buf.WriteString(sub[1])
}
}
return buf.String(), nil
}