package contact

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"errors"
	"io"
	"strings"
)

var ErrChannelKeyUnavailable = errors.New("联系人通道加密密钥未配置或格式错误")

func ParseChannelKey(value string) ([]byte, error) {
	key, err := base64.StdEncoding.DecodeString(strings.TrimSpace(value))
	if err != nil || len(key) != 32 {
		return nil, ErrChannelKeyUnavailable
	}
	return key, nil
}

func encryptAddress(key []byte, value string) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, ErrChannelKeyUnavailable
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}
	return gcm.Seal(nonce, nonce, []byte(value), nil), nil
}

func decryptAddress(key, encoded []byte) (string, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", ErrChannelKeyUnavailable
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	if len(encoded) < gcm.NonceSize() {
		return "", errors.New("通道密文已损坏")
	}
	plain, err := gcm.Open(nil, encoded[:gcm.NonceSize()], encoded[gcm.NonceSize():], nil)
	return string(plain), err
}

func fingerprint(value string) string {
	sum := sha256.Sum256([]byte(value))
	return base64.RawURLEncoding.EncodeToString(sum[:])
}