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expandenv.go
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expandenv.go
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package expandenv
import (
"fmt"
"os"
"regexp"
"strconv"
"strings"
)
type VariableLookup = func(key string) (*string, error)
func ExpandEnv(input interface{}) (interface{}, error) {
return Expand(input, func(key string) (*string, error) {
value, ok := os.LookupEnv(key)
if !ok {
return nil, fmt.Errorf("environment variable %s is missing", key)
}
return &value, nil
})
}
func ExpandMap(input interface{}, values map[string]string) (interface{}, error) {
return Expand(input, func(key string) (*string, error) {
value, ok := values[key]
if !ok {
return nil, fmt.Errorf("variable %s is missing", key)
}
return &value, nil
})
}
func Expand(input interface{}, values VariableLookup) (interface{}, error) {
singleRegex := regexp.MustCompile(`^\$\{[^\}]+\}$`)
detectRegex := regexp.MustCompile(`\\?\$\{[^\}]+\}`)
var recursion func(current interface{}) (interface{}, []error)
recursion = func(current interface{}) (interface{}, []error) {
if current, ok := current.(string); ok {
p := singleRegex.FindStringSubmatch(current)
if p != nil {
expanded, err := expandValue(current, values)
if err != nil {
return current, []error{err}
}
return expanded, nil
}
errs := []error{}
expanded := detectRegex.ReplaceAllStringFunc(current, func(str string) string {
if strings.HasPrefix(str, "\\") {
return str[1:]
}
expanded, err := expandValue(str, values)
if err != nil {
errs = append(errs, err)
return str
}
return fmt.Sprintf("%v", expanded)
})
return expanded, errs
}
if current, ok := current.([]interface{}); ok {
current2 := make([]interface{}, len(current))
errs := []error{}
for i := range current {
v, err := recursion(current[i])
if err != nil {
errs = append(errs, err...)
}
current2[i] = v
}
return current2, errs
}
if current, ok := current.(map[string]interface{}); ok {
errs := []error{}
current2 := map[string]interface{}{}
for k, v := range current {
v, err := recursion(v)
if err != nil {
errs = append(errs, err...)
}
current2[k] = v
}
return current2, errs
}
return current, []error{}
}
output, errs := recursion(input)
if len(errs) > 0 {
errMsgs := []string{}
for _, err := range errs {
errMsgs = append(errMsgs, err.Error())
}
return output, fmt.Errorf(strings.Join(errMsgs, ", "))
}
return output, nil
}
func expandValue(str string, values VariableLookup) (interface{}, error) {
regex := regexp.MustCompile(`^\$\{(?P<name>[^:]+)(?P<hasFormat>:(?P<format>number|boolean|string))?(?P<hasFallback>:-(?P<fallback>.*))?\}$`)
p := regex.FindStringSubmatch(str)
if p == nil {
return nil, fmt.Errorf("could not parse %s", str)
}
name := p[regex.SubexpIndex("name")]
format := p[regex.SubexpIndex("format")]
hasFallback := p[regex.SubexpIndex("hasFallback")] != ""
fallback := p[regex.SubexpIndex("fallback")]
value, err := values(name)
if err != nil {
if !hasFallback {
return nil, err
} else {
value = &fallback
}
}
if value == nil {
return str, nil
}
switch format {
case "":
return *value, nil
case "string":
return *value, nil
case "number":
formatted, err := strconv.Atoi(*value)
if err != nil {
formatted, err := strconv.ParseFloat(*value, 64)
if err != nil {
return nil, fmt.Errorf("%s is not a valid number", *value)
}
return formatted, nil
}
return formatted, nil
case "boolean":
switch *value {
case "0":
return false, nil
case "1":
return true, nil
case "false":
return false, nil
case "true":
return true, nil
case "no":
return false, nil
case "yes":
return true, nil
default:
return nil, fmt.Errorf("%s is not a valid boolean", *value)
}
default:
return nil, fmt.Errorf("format %s is not supported", format)
}
}