package adtracking

import (
	"context"
	"errors"
	"fmt"
	"net/url"
	"regexp"
	"strings"
	"time"

	"github.com/redis/go-redis/v9"
)

var (
	ErrLinkNotFound           = errors.New("推广链接不存在")
	ErrLinkDisabled           = errors.New("该推广链接已被停用")
	ErrCodeAlreadyExists      = errors.New("该自定义后缀已被占用，请更换")
	ErrInvalidCodeFormat      = errors.New("后缀格式不正确，仅支持2-64位英文、数字、下划线和连字符")
	ErrReservedCode           = errors.New("该后缀为系统保留字，不可使用")
	ErrDisallowedTargetDomain = errors.New("目标落地页仅允许为 hao858.com 及其子域名或站内路径")
	codePattern               = regexp.MustCompile(`^[a-zA-Z0-9_-]{2,64}$`)
)

var reservedCodes = map[string]bool{
	"admin": true, "api": true, "static": true, "assets": true, "login": true,
	"register": true, "auth": true, "user": true, "order": true, "r": true,
	"pay": true, "notice": true, "chat": true, "dashboard": true,
}

func validateTargetURL(rawURL string, allowLocal bool) (string, error) {
	targetURL := strings.TrimSpace(rawURL)
	if targetURL == "" {
		return "https://hao858.com/", nil
	}
	if strings.HasPrefix(targetURL, "/") {
		return "https://hao858.com" + targetURL, nil
	}
	if !strings.HasPrefix(targetURL, "http://") && !strings.HasPrefix(targetURL, "https://") {
		targetURL = "https://" + targetURL
	}
	u, err := url.Parse(targetURL)
	if err != nil || u.Host == "" {
		return "", errors.New("目标落地页地址不合法")
	}
	scheme := strings.ToLower(u.Scheme)
	if scheme != "http" && scheme != "https" {
		return "", errors.New("目标落地页地址不合法")
	}
	host := strings.ToLower(u.Hostname())
	if host == "localhost" || host == "127.0.0.1" {
		if !allowLocal {
			return "", ErrDisallowedTargetDomain
		}
		return targetURL, nil
	}
	if host != "hao858.com" && !strings.HasSuffix(host, ".hao858.com") {
		return "", ErrDisallowedTargetDomain
	}
	return targetURL, nil
}

type Service struct {
	repo              *Repository
	redis             *redis.Client
	allowLocalTargets bool
}

func NewService(repo *Repository, redisClient *redis.Client, allowLocalTargets bool) *Service {
	return &Service{
		repo:              repo,
		redis:             redisClient,
		allowLocalTargets: allowLocalTargets,
	}
}

func (s *Service) CreateLink(ctx context.Context, adminID uint64, req CreateTrackingLinkRequest) (*AdTrackingLink, error) {
	code := strings.TrimSpace(req.Code)
	if !codePattern.MatchString(code) {
		return nil, ErrInvalidCodeFormat
	}
	if reservedCodes[strings.ToLower(code)] {
		return nil, ErrReservedCode
	}

	// 查重
	existing, _ := s.repo.FindLinkByCode(ctx, code)
	if existing != nil {
		return nil, ErrCodeAlreadyExists
	}

	targetURL, err := validateTargetURL(req.TargetURL, s.allowLocalTargets)
	if err != nil {
		return nil, err
	}

	channelType := strings.TrimSpace(req.ChannelType)
	if channelType == "" {
		channelType = "offline_promo"
	}

	link := &AdTrackingLink{
		Name:        strings.TrimSpace(req.Name),
		Code:        code,
		ChannelType: channelType,
		TargetURL:   targetURL,
		Status:      "active",
		CostCent:    req.CostCent,
		Notes:       strings.TrimSpace(req.Notes),
		CreatedBy:   adminID,
		CreatedAt:   time.Now(),
		UpdatedAt:   time.Now(),
	}

	if err := s.repo.CreateLink(ctx, link); err != nil {
		return nil, fmt.Errorf("创建推广链接失败: %w", err)
	}

	return link, nil
}

func (s *Service) UpdateLink(ctx context.Context, id uint64, req UpdateTrackingLinkRequest) error {
	link, err := s.repo.FindLinkByID(ctx, id)
	if err != nil {
		return ErrLinkNotFound
	}

	targetURL, err := validateTargetURL(req.TargetURL, s.allowLocalTargets)
	if err != nil {
		return err
	}

	channelType := strings.TrimSpace(req.ChannelType)
	if channelType == "" {
		channelType = link.ChannelType
	}

	updates := map[string]interface{}{
		"name":         strings.TrimSpace(req.Name),
		"channel_type": channelType,
		"target_url":   targetURL,
		"cost_cent":    req.CostCent,
		"notes":        strings.TrimSpace(req.Notes),
		"updated_at":   time.Now(),
	}

	return s.repo.UpdateLink(ctx, id, updates)
}

func (s *Service) UpdateStatus(ctx context.Context, id uint64, status string) error {
	if status != "active" && status != "disabled" {
		return errors.New("状态值不合法")
	}
	_, err := s.repo.FindLinkByID(ctx, id)
	if err != nil {
		return ErrLinkNotFound
	}
	return s.repo.UpdateLink(ctx, id, map[string]interface{}{
		"status":     status,
		"updated_at": time.Now(),
	})
}

func (s *Service) ListLinks(ctx context.Context, query ListTrackingLinksQuery, baseURL string) ([]TrackingLinkItem, int64, error) {
	return s.repo.ListLinks(ctx, query, baseURL)
}

func (s *Service) GetOverview(ctx context.Context) (*TrackingOverviewStats, error) {
	return s.repo.GetOverviewStats(ctx)
}

// ResolveRedirect 处理 302 短链跳转，并记录点击流水
func (s *Service) ResolveRedirect(ctx context.Context, code, ip, ua, referer, visitorID string) (string, error) {
	link, err := s.repo.FindLinkByCode(ctx, code)
	if err != nil {
		return "", ErrLinkNotFound
	}
	if link.Status != "active" {
		return "", ErrLinkDisabled
	}

	// 异步记录点击流水，防止写库阻塞跳转
	deviceType, os, browser := parseUserAgent(ua)
	go func() {
		defer func() {
			if r := recover(); r != nil {
				// 保护主进程，防止异步协程 panic
			}
		}()

		bgCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()

		// 防刷：同访客 5 秒去重；同 IP 1 秒去重，避免不带 Cookie 轮换 visitorID 刷库
		if s.redis != nil {
			if isDuplicateClick(bgCtx, s.redis, "adtrack:dedup:v:"+link.Code+":"+visitorID, 5*time.Second) {
				return
			}
			if isDuplicateClick(bgCtx, s.redis, "adtrack:dedup:ip:"+link.Code+":"+ip, time.Second) {
				return
			}
		}

		click := &AdTrackingClick{
			LinkID:     link.ID,
			Code:       link.Code,
			IP:         ip,
			UserAgent:  truncateString(ua, 500),
			DeviceType: deviceType,
			OS:         os,
			Browser:    browser,
			Referer:    truncateString(referer, 500),
			VisitorID:  visitorID,
			CreatedAt:  time.Now(),
		}
		_ = s.repo.RecordClick(bgCtx, click)
	}()

	// 拼接带推广短码的落地页 URL (例如 https://hao858.com/?track_code=wb01)
	finalURL := appendTrackCode(link.TargetURL, link.Code)
	return finalURL, nil
}

func isDuplicateClick(ctx context.Context, rdb *redis.Client, key string, ttl time.Duration) bool {
	if rdb == nil || key == "" || strings.HasSuffix(key, ":") {
		return false
	}
	ok, err := rdb.SetNX(ctx, key, "1", ttl).Result()
	return err == nil && !ok
}

func appendTrackCode(targetURL, code string) string {
	u, err := url.Parse(targetURL)
	if err != nil {
		return targetURL
	}
	q := u.Query()
	q.Set("track_code", code)
	u.RawQuery = q.Encode()
	return u.String()
}

func truncateString(str string, maxLen int) string {
	if len(str) > maxLen {
		return str[:maxLen]
	}
	return str
}

func parseUserAgent(ua string) (deviceType, os, browser string) {
	deviceType = "pc"
	os = "unknown"
	browser = "unknown"

	lowerUA := strings.ToLower(ua)
	if strings.Contains(lowerUA, "mobile") || strings.Contains(lowerUA, "android") || strings.Contains(lowerUA, "iphone") {
		deviceType = "mobile"
	} else if strings.Contains(lowerUA, "ipad") || strings.Contains(lowerUA, "tablet") {
		deviceType = "tablet"
	}

	// OS 检测 (优先移动端避免 iPhone UA 中的 Mac OS X 干扰)
	if strings.Contains(lowerUA, "iphone") || strings.Contains(lowerUA, "ios") {
		os = "iOS"
	} else if strings.Contains(lowerUA, "android") {
		os = "Android"
	} else if strings.Contains(lowerUA, "windows") {
		os = "Windows"
	} else if strings.Contains(lowerUA, "mac os") || strings.Contains(lowerUA, "macintosh") {
		os = "macOS"
	} else if strings.Contains(lowerUA, "linux") {
		os = "Linux"
	}

	// Browser 检测
	if strings.Contains(lowerUA, "micromessenger") {
		browser = "WeChat"
	} else if strings.Contains(lowerUA, "edg/") || strings.Contains(lowerUA, "edge/") {
		browser = "Edge"
	} else if strings.Contains(lowerUA, "chrome") {
		browser = "Chrome"
	} else if strings.Contains(lowerUA, "safari") {
		browser = "Safari"
	} else if strings.Contains(lowerUA, "firefox") {
		browser = "Firefox"
	}

	return deviceType, os, browser
}