package go_environment

import (
	"encoding/json"
	"os"
)

// EnvironmentString describes a (readonly) string which is
// defined as an environment variable.
type EnvironmentString struct {
	Variable string
}

// MarshalJSON returns the JSON encoding of es.
func (es EnvironmentString) MarshalJSON() ([]byte, error) {
	return json.Marshal(es.Variable)
}

// UnmarshalJSON parses the JSON-encoded data and stores the
// result in es.
func (es *EnvironmentString) UnmarshalJSON(data []byte) error {
	return json.Unmarshal(data, &es.Variable)
}

// String returns the string representation of es.
func (es EnvironmentString) String() (value string) {
	return os.Getenv(es.Variable)
}

// Key returns the key of the underlying environment
// variable of es.
func (es EnvironmentString) Key() (value string) {
	return es.Variable
}

// String determines the validity of the underlying
// environment variable of es.
func (es EnvironmentString) Valid() (valid bool) {
	if es.Variable == "" {
		return false
	}
	var value string
	value, valid = os.LookupEnv(es.Variable)
	return valid && (value != "")
}