package config

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

type Config struct {
	DataDir       string
	DatabasePath  string
	UploadDir     string
	JWTSecret     string
	EncryptionKey []byte
}

func New(dataDir string) *Config {
	// 确保data目录存在
	os.MkdirAll(dataDir, 0755)

	// 创建上传目录
	uploadDir := filepath.Join(dataDir, "uploads")
	os.MkdirAll(uploadDir, 0755)

	// 从环境变量获取JWT密钥，如果没有则使用默认值
	jwtSecret := os.Getenv("JWT_SECRET")
	if jwtSecret == "" {
		jwtSecret = "your-secret-key-change-in-production"
	}

	encryptionSource := os.Getenv("CONFIG_ENCRYPTION_KEY")
	if encryptionSource == "" {
		// Keep existing installations decryptable while allowing production deployments
		// to use a dedicated key that is independent from JWT signing.
		encryptionSource = jwtSecret
	}
	encryptionKey := sha256.Sum256([]byte(encryptionSource))

	return &Config{
		DataDir:       dataDir,
		DatabasePath:  filepath.Join(dataDir, "home.db"),
		UploadDir:     uploadDir,
		JWTSecret:     jwtSecret,
		EncryptionKey: encryptionKey[:],
	}
}

// EncryptSecret encrypts a value for storage in the application database.
func (c *Config) EncryptSecret(value string) (string, error) {
	if strings.TrimSpace(value) == "" {
		return "", nil
	}
	block, err := aes.NewCipher(c.EncryptionKey)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	ciphertext := gcm.Seal(nil, nonce, []byte(value), nil)
	encoded := base64.RawStdEncoding.EncodeToString(append(nonce, ciphertext...))
	return "v1:" + encoded, nil
}

// DecryptSecret decrypts a value previously returned by EncryptSecret.
func (c *Config) DecryptSecret(value string) (string, error) {
	if strings.TrimSpace(value) == "" {
		return "", nil
	}
	if !strings.HasPrefix(value, "v1:") {
		return "", errors.New("unsupported encrypted secret format")
	}
	raw, err := base64.RawStdEncoding.DecodeString(strings.TrimPrefix(value, "v1:"))
	if err != nil {
		return "", fmt.Errorf("decode encrypted secret: %w", err)
	}
	block, err := aes.NewCipher(c.EncryptionKey)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	if len(raw) < gcm.NonceSize() {
		return "", errors.New("encrypted secret is too short")
	}
	plaintext, err := gcm.Open(nil, raw[:gcm.NonceSize()], raw[gcm.NonceSize():], nil)
	if err != nil {
		return "", errors.New("encrypted secret authentication failed")
	}
	return string(plaintext), nil
}