package service

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

	"gorm.io/gorm"

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

var (
	ErrLicenseNotFound   = errors.New("license not found")
	ErrLicenseInactive   = errors.New("license is inactive")
	ErrLicenseExpired    = errors.New("license has expired")
	ErrDeviceLimitExceed = errors.New("device limit reached — deactivate another device first")
)

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 激活许可证并绑定设备到 license_devices 表。
// 若该设备已绑定，则更新 last_seen_at（幂等）。
// 若是新设备，则校验是否超出 max_devices 上限。
func (s *LicenseService) Activate(shopID uint64, licenseKey, deviceID, deviceName, platform string) (*model.License, error) {
	var lic model.License
	if err := s.db.Where("license_key = ? AND shop_id = ?", licenseKey, shopID).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
	}

	var existing model.LicenseDevice
	err := s.db.Where("license_id = ? AND device_id = ?", lic.ID, deviceID).First(&existing).Error
	if err == nil {
		// Device already bound — just touch last_seen_at (handled by autoUpdateTime)
		if err := s.db.Model(&existing).Update("device_name", deviceName).Error; err != nil {
			return nil, err
		}
		return &lic, nil
	}

	// New device — enforce max_devices
	var count int64
	if err := s.db.Model(&model.LicenseDevice{}).Where("license_id = ?", lic.ID).Count(&count).Error; err != nil {
		return nil, err
	}
	if int(count) >= lic.MaxDevices {
		return nil, ErrDeviceLimitExceed
	}

	dev := model.LicenseDevice{
		LicenseID:  lic.ID,
		ShopID:     shopID,
		DeviceID:   deviceID,
		DeviceName: deviceName,
		Platform:   platform,
	}
	if err := s.db.Create(&dev).Error; err != nil {
		return nil, err
	}
	return &lic, nil
}

// Verify 验证设备许可证（客户端启动时调用）。
// 通过 license_devices 表查找设备，再加载对应的许可证做有效性检查。
func (s *LicenseService) Verify(shopID uint64, deviceID string) (*model.License, error) {
	var dev model.LicenseDevice
	if err := s.db.Where("shop_id = ? AND device_id = ?", shopID, deviceID).First(&dev).Error; err != nil {
		return nil, ErrLicenseNotFound
	}
	var lic model.License
	if err := s.db.Where("id = ? AND shop_id = ? AND is_active = 1", dev.LicenseID, shopID).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
}

// CountDevices 返回指定 license 下已绑定设备数。
func (s *LicenseService) CountDevices(licenseID uint64) (int64, error) {
	var count int64
	err := s.db.Model(&model.LicenseDevice{}).Where("license_id = ?", licenseID).Count(&count).Error
	return count, err
}

// ListDevices 列出许可证下所有已绑定设备。
func (s *LicenseService) ListDevices(shopID uint64) ([]model.LicenseDevice, error) {
	var devs []model.LicenseDevice
	if err := s.db.Where("shop_id = ?", shopID).Order("activated_at DESC").Find(&devs).Error; err != nil {
		return nil, err
	}
	return devs, nil
}

// Deactivate 解绑设备（从 license_devices 删除该条记录）。
func (s *LicenseService) Deactivate(shopID uint64, deviceID string) error {
	return s.db.Where("shop_id = ? AND device_id = ?", shopID, deviceID).
		Delete(&model.LicenseDevice{}).Error
}

// createTrialLicense 在注册事务中为新门店签发 30 天 trial license。
// 私钥未配置时 Fatal，防止生产环境静默跳过导致新注册门店无 license。
func createTrialLicense(tx *gorm.DB, shopID uint64) {
	privKey := config.C.License.Ed25519PrivateKey
	if privKey == "" {
		log.Fatalf("[license] Ed25519 private key not configured — cannot issue trial for shop %d; set License.Ed25519PrivateKey in config", shopID)
	}

	expiresAt := time.Now().Add(30 * 24 * time.Hour)
	expiresUnix := expiresAt.Unix()
	payload := util.LicensePayload{
		ShopID:     shopID,
		Type:       "trial",
		IssuedAt:   time.Now().Unix(),
		ExpiresAt:  &expiresUnix,
		MaxDevices: 1,
	}
	token, err := util.IssueLicenseToken(payload, privKey)
	if err != nil {
		log.Printf("[license] failed to issue trial token for shop %d: %v", shopID, err)
		return
	}

	lic := model.License{
		ShopID:     shopID,
		LicenseKey: token,
		Type:       "trial",
		ExpiresAt:  &expiresAt,
		IsActive:   true,
		MaxDevices: 1,
	}
	if err := tx.Create(&lic).Error; err != nil {
		log.Printf("[license] failed to create trial license for shop %d: %v", shopID, err)
	}
}