package idp

import (
	"encoding/base64"
	"encoding/json"
	"strings"
)

type hintContext struct{}

func hintSubject(raw string) string {
	const invalid = "!"
	parts := strings.Split(raw, ".")
	if len(parts) != 3 {
		return invalid
	}
	payload, err := base64.RawURLEncoding.Strict().DecodeString(parts[1])
	if err != nil {
		return invalid
	}
	var claims struct {
		Subject string `json:"sub"`
	}
	if err := json.Unmarshal(payload, &claims); err != nil || claims.Subject == "" {
		return invalid
	}
	return claims.Subject
}