package service

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base32"
	"errors"
	"fmt"
	"strings"
	"time"

	"gorm.io/gorm"

	"github.com/wangjia/jiu/backend/config"
	"github.com/wangjia/jiu/backend/internal/model"
)

var (
	ErrLicenseNotFound = errors.New("license not found")
	ErrLicenseInactive = errors.New("license is inactive")
	ErrLicenseExpired  = errors.New("license has expired")
	ErrDeviceMismatch  = errors.New("license is bound to another device")
)

type LicenseService struct {
	db *gorm.DB
}

func NewLicenseService(db *gorm.DB) *LicenseService {
	return &LicenseService{db: db}
}

// GenerateKey 生成许可证激活码
// 格式：HMAC-SHA256(shopID+licenseType+expiry, secret) → base32, 每5字符加'-'
func GenerateKey(shopID uint64, licenseType string, expiresAt *time.Time) string {
	payload := fmt.Sprintf("%d:%s", shopID, licenseType)
	if expiresAt != nil {
		payload += ":" + expiresAt.Format("20060102")
	}
	mac := hmac.New(sha256.New, []byte(config.C.License.HMACSecret))
	mac.Write([]byte(payload))
	raw := base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(mac.Sum(nil))
	// 截取前20字符，分4段，每段5字符
	raw = strings.ToUpper(raw)[:20]
	return fmt.Sprintf("%s-%s-%s-%s", raw[0:5], raw[5:10], raw[10:15], raw[15:20])
}

// Activate 激活许可证（绑定设备）
func (s *LicenseService) Activate(licenseKey, deviceID string) (*model.License, error) {
	var lic model.License
	if err := s.db.Where("license_key = ?", licenseKey).First(&lic).Error; err != nil {
		return nil, ErrLicenseNotFound
	}
	if !lic.IsActive {
		return nil, ErrLicenseInactive
	}
	if lic.ExpiresAt != nil && time.Now().After(*lic.ExpiresAt) {
		return nil, ErrLicenseExpired
	}
	// 若已绑定设备，校验是否一致
	if lic.DeviceID != "" && lic.DeviceID != deviceID {
		return nil, ErrDeviceMismatch
	}

	now := time.Now()
	lic.DeviceID = deviceID
	lic.ActivatedAt = &now
	s.db.Save(&lic)
	return &lic, nil
}

// Verify 验证（客户端启动时调用）
func (s *LicenseService) Verify(shopID uint64, deviceID string) (*model.License, error) {
	var lic model.License
	if err := s.db.Where("shop_id = ? AND device_id = ? AND is_active = 1", shopID, deviceID).
		First(&lic).Error; err != nil {
		return nil, ErrLicenseNotFound
	}
	if lic.ExpiresAt != nil && time.Now().After(*lic.ExpiresAt) {
		return nil, ErrLicenseExpired
	}
	return &lic, nil
}

// ShopInfo 返回门店当前授权信息（取最新一条有效许可证）
func (s *LicenseService) ShopInfo(shopID uint64) (*model.License, error) {
	var lic model.License
	if err := s.db.Where("shop_id = ? AND is_active = 1", shopID).
		Order("id DESC").First(&lic).Error; err != nil {
		return nil, ErrLicenseNotFound
	}
	return &lic, nil
}

// Deactivate 解绑设备（换机时使用）
func (s *LicenseService) Deactivate(shopID uint64, deviceID string) error {
	return s.db.Model(&model.License{}).
		Where("shop_id = ? AND device_id = ?", shopID, deviceID).
		Updates(map[string]interface{}{"device_id": "", "activated_at": nil}).Error
}