package db

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
)

var encryptionKey []byte

func SetEncryptionKey(hexKey string) error {
	key, err := hex.DecodeString(hexKey)
	if err != nil {
		return fmt.Errorf("decode encryption key: %w", err)
	}
	if len(key) != 32 {
		return fmt.Errorf("encryption key must be 32 bytes (64 hex chars), got %d bytes", len(key))
	}
	encryptionKey = key
	return nil
}

func Encrypt(plaintext string) (string, error) {
	if len(encryptionKey) == 0 {
		return plaintext, nil
	}
	block, err := aes.NewCipher(encryptionKey)
	if err != nil {
		return "", err
	}
	aesGCM, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, aesGCM.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	ciphertext := aesGCM.Seal(nonce, nonce, []byte(plaintext), nil)
	return hex.EncodeToString(ciphertext), nil
}

func Decrypt(ciphertextHex string) (string, error) {
	if len(encryptionKey) == 0 {
		return ciphertextHex, nil
	}
	ciphertext, err := hex.DecodeString(ciphertextHex)
	if err != nil {
		return "", err
	}
	block, err := aes.NewCipher(encryptionKey)
	if err != nil {
		return "", err
	}
	aesGCM, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonceSize := aesGCM.NonceSize()
	if len(ciphertext) < nonceSize {
		return "", fmt.Errorf("ciphertext too short")
	}
	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
	plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return "", err
	}
	return string(plaintext), nil
}

func HashSHA256(data string) string {
	h := sha256.Sum256([]byte(data))
	return hex.EncodeToString(h[:])
}