package service

import (
	"context"
	"net"
	"strings"

	"kefu-cloud/server/internal/geoip"
	"kefu-cloud/server/internal/model"
)

const visitorGeoBackfillBatch = 500

var visitorGeoLookup = geoip.Lookup

// BackfillVisitorGeoIP 使用历史会话保存的 IP 补齐旧数据中的国家/省市信息。
func BackfillVisitorGeoIP(ctx context.Context) (int, error) {
	var lastID uint
	updated := 0
	for {
		select {
		case <-ctx.Done():
			return updated, ctx.Err()
		default:
		}

		var sessions []model.Session
		if err := model.DB.
			Select("id", "visitor_ip").
			Where("id > ? AND visitor_ip <> ''", lastID).
			Where("visitor_country = '' AND (visitor_region = '' OR visitor_region = ?)", "未知").
			Order("id asc").Limit(visitorGeoBackfillBatch).Find(&sessions).Error; err != nil {
			return updated, err
		}
		if len(sessions) == 0 {
			return updated, nil
		}

		for _, session := range sessions {
			lastID = session.ID
			location, ok := visitorGeoLookup(session.VisitorIP)
			if !ok {
				if isPrivateIP(session.VisitorIP) {
					if err := model.DB.Model(&model.Session{}).Where("id = ?", session.ID).
						Update("visitor_region", "内网").Error; err != nil {
						return updated, err
					}
					updated++
				}
				continue
			}
			if strings.TrimSpace(location.Region) == "" {
				continue
			}
			if err := model.DB.Model(&model.Session{}).Where("id = ?", session.ID).Updates(map[string]interface{}{
				"visitor_region":   location.Region,
				"visitor_country":  location.Country,
				"visitor_province": location.Province,
				"visitor_city":     location.City,
			}).Error; err != nil {
				return updated, err
			}
			updated++
		}
		if len(sessions) < visitorGeoBackfillBatch {
			return updated, nil
		}
	}
}

func isPrivateIP(raw string) bool {
	ip := net.ParseIP(strings.TrimSpace(raw))
	return ip != nil && (ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast())
}