// Package secret encrypts provider credentials at rest using an environment-owned key.
package secret

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"fmt"

	"git.sundynix.cn/Blizzard/Veyra/internal/apperror"
)

type Vault struct{ aead cipher.AEAD }

func NewVault(encodedKey string) (*Vault, error) {
	if encodedKey == "" {
		return &Vault{}, nil
	}
	key, err := base64.StdEncoding.DecodeString(encodedKey)
	if err != nil || len(key) != 32 {
		return nil, fmt.Errorf("SECRET_ENCRYPTION_KEY must be base64 of 32 bytes")
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, fmt.Errorf("initialize secret cipher")
	}
	aead, err := cipher.NewGCM(block)
	if err != nil {
		return nil, fmt.Errorf("initialize secret encryption")
	}
	return &Vault{aead: aead}, nil
}
func (v *Vault) Encrypt(value, binding string) ([]byte, error) {
	if v == nil || v.aead == nil {
		return nil, apperror.ErrUnavailable
	}
	nonce := make([]byte, v.aead.NonceSize())
	if _, err := rand.Read(nonce); err != nil {
		return nil, apperror.ErrUnavailable
	}
	return v.aead.Seal(nonce, nonce, []byte(value), []byte(binding)), nil
}
func (v *Vault) Decrypt(encrypted []byte, binding string) (string, error) {
	if len(encrypted) == 0 {
		return "", nil
	}
	if v == nil || v.aead == nil || len(encrypted) < v.aead.NonceSize() {
		return "", apperror.ErrUnavailable
	}
	value, err := v.aead.Open(nil, encrypted[:v.aead.NonceSize()], encrypted[v.aead.NonceSize():], []byte(binding))
	if err != nil {
		return "", apperror.ErrUnavailable
	}
	return string(value), nil
}