// Package store 负责 SQLite 初始化、敏感字段 AES-GCM 加密存储
package store

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"

	"github.com/glebarez/sqlite"
	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
	gormlogger "gorm.io/gorm/logger"

	"vpn-platform/backend/internal/model"
)

var DB *gorm.DB

var gcm cipher.AEAD

// Init 打开数据库、迁移、初始化加密密钥与默认账号
func Init(dataDir string) error {
	if err := os.MkdirAll(dataDir, 0o700); err != nil {
		return err
	}
	// WAL + busy_timeout：避免 monitor 周期写与 API 写并发时 database is locked
	dsn := filepath.Join(dataDir, "vpn-platform.db") +
		"?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)&_pragma=foreign_keys(1)"
	db, err := gorm.Open(sqlite.Open(dsn), &gorm.Config{
		Logger: gormlogger.Default.LogMode(gormlogger.Warn),
	})
	if err != nil {
		return fmt.Errorf("打开数据库失败: %w", err)
	}
	if sqlDB, err := db.DB(); err == nil {
		sqlDB.SetMaxOpenConns(1) // SQLite 单写者
	}
	// 兼容旧库：VPNUser 唯一约束曾是 username 单列全局唯一
	db.Exec("DROP INDEX IF EXISTS idx_vpn_user")
	if err := db.AutoMigrate(&model.User{}, &model.LDAPConfig{}, &model.MFADevice{}, &model.VPNUser{}, &model.Tunnel{}, &model.Node{}, &model.Plugin{}, &model.AuditLog{}, &model.VPNSession{}, &model.ConnectionLog{}, &model.TrafficPolicy{}, &model.TrafficSample{}, &model.ClientDevice{}, &model.ClientSession{}, &model.IdentityProvider{}, &model.IdentityGrant{}, &model.IdentityProfile{}, &model.FeishuTunnelGrant{}); err != nil {
		return err
	}
	DB = db

	if err := initKey(dataDir); err != nil {
		return err
	}

	// 默认管理员 admin / admin123（首次登录后强制改密） // Logan.Li
	var count int64
	DB.Model(&model.User{}).Count(&count)
	if count == 0 {
		hash, _ := bcrypt.GenerateFromPassword([]byte("admin123"), bcrypt.DefaultCost)
		DB.Create(&model.User{Username: "admin", Password: string(hash), Role: "admin", Source: "local", Enabled: true, MustChangePassword: true})
	} else {
		// 兼容早期单管理员数据：管理员升级后保留完整管理权限。
		DB.Model(&model.User{}).Where("username = ? AND source = ?", "admin", "local").Update("role", "admin")
	}
	// 内置本机节点
	var nodeCount int64
	DB.Model(&model.Node{}).Count(&nodeCount)
	if nodeCount == 0 {
		DB.Create(&model.Node{Name: "本机节点", Address: "127.0.0.1", Port: 22, Kind: "local", Status: "verified", Remark: "平台所在服务器"})
	}
	return nil
}

func initKey(dataDir string) error {
	keyFile := filepath.Join(dataDir, "secret.key")
	raw, err := os.ReadFile(keyFile)
	if err != nil {
		key := make([]byte, 32)
		if _, err := rand.Read(key); err != nil {
			return err
		}
		raw = []byte(hex.EncodeToString(key))
		if err := os.WriteFile(keyFile, raw, 0o600); err != nil {
			return err
		}
	}
	keyBytes, err := hex.DecodeString(string(raw))
	if err != nil || len(keyBytes) != 32 {
		sum := sha256.Sum256(raw)
		keyBytes = sum[:]
	}
	block, err := aes.NewCipher(keyBytes)
	if err != nil {
		return err
	}
	g, err := cipher.NewGCM(block)
	if err != nil {
		return err
	}
	gcm = g
	return nil
}

// EncryptSecret 加密敏感字符串
func EncryptSecret(plain string) (string, error) {
	if plain == "" {
		return "", nil
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err := rand.Read(nonce); err != nil {
		return "", err
	}
	out := gcm.Seal(nonce, nonce, []byte(plain), nil)
	return base64.StdEncoding.EncodeToString(out), nil
}

// DecryptSecret 解密敏感字符串
func DecryptSecret(enc string) (string, error) {
	if enc == "" {
		return "", nil
	}
	raw, err := base64.StdEncoding.DecodeString(enc)
	if err != nil {
		return "", err
	}
	if len(raw) < gcm.NonceSize() {
		return "", fmt.Errorf("密文长度非法")
	}
	plain, err := gcm.Open(nil, raw[:gcm.NonceSize()], raw[gcm.NonceSize():], nil)
	if err != nil {
		return "", err
	}
	return string(plain), nil
}

// Audit 写入操作审计
func Audit(username, action, target, detail string) {
	if DB != nil {
		DB.Create(&model.AuditLog{Username: username, Action: action, Target: target, Detail: detail})
	}
}

// GetTunnel 按 ID 查询专线
func GetTunnel(id uint) (*model.Tunnel, error) {
	var t model.Tunnel
	if err := DB.Preload("Node").First(&t, id).Error; err != nil {
		return nil, err
	}
	return &t, nil
}

// TunnelConfig 解析专线 Config JSON
func TunnelConfig(t *model.Tunnel) (map[string]interface{}, error) {
	cfg := map[string]interface{}{}
	if t.Config != "" {
		if err := json.Unmarshal([]byte(t.Config), &cfg); err != nil {
			return nil, err
		}
	}
	return cfg, nil
}

// TunnelSecrets 解析并解密敏感字段
func TunnelSecrets(t *model.Tunnel) (map[string]interface{}, error) {
	out := map[string]interface{}{}
	plain, err := DecryptSecret(t.Secrets)
	if err != nil || plain == "" {
		return out, nil
	}
	_ = json.Unmarshal([]byte(plain), &out)
	return out, nil
}