package handler

import (
	"net/url"
	"strings"
	"unicode/utf8"
)

const (
	maxPageURLLen   = 1000
	maxPageTitleLen = 200
	// 单会话最多保留轨迹条数（超出删最旧）
	maxPageViewsPerSession = 50
)

// 常见敏感 query 参数，上报 URL 时剥离
var sensitiveQueryKeys = map[string]bool{
	"token": true, "access_token": true, "refresh_token": true,
	"password": true, "passwd": true, "pwd": true,
	"phone": true, "mobile": true, "tel": true,
	"idcard": true, "id_card": true, "secret": true, "key": true,
	"authorization": true, "auth": true, "session": true, "sid": true,
	"code": true, "otp": true, "verify": true,
}

func truncateRunes(s string, max int) string {
	s = strings.TrimSpace(s)
	if max <= 0 || s == "" {
		return s
	}
	if utf8.RuneCountInString(s) <= max {
		return s
	}
	r := []rune(s)
	return string(r[:max])
}

// sanitizePageURL 规范化并脱敏 URL，非法则返回空。
func sanitizePageURL(raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return ""
	}
	if utf8.RuneCountInString(raw) > maxPageURLLen*2 {
		raw = string([]rune(raw)[:maxPageURLLen*2])
	}
	u, err := url.Parse(raw)
	if err != nil || u.Scheme == "" || u.Host == "" {
		// 允许无 scheme 的相对路径拼不成绝对时，若已是 http(s) 失败则截断原文
		if strings.HasPrefix(raw, "http://") || strings.HasPrefix(raw, "https://") {
			return truncateRunes(raw, maxPageURLLen)
		}
		return ""
	}
	if u.Scheme != "http" && u.Scheme != "https" {
		return ""
	}
	q := u.Query()
	changed := false
	for k := range q {
		lk := strings.ToLower(k)
		if sensitiveQueryKeys[lk] || strings.Contains(lk, "token") || strings.Contains(lk, "password") {
			q.Del(k)
			changed = true
		}
	}
	if changed {
		u.RawQuery = q.Encode()
	}
	// 保留 hash：大量 SPA（含演示站 demo-shop）靠 #/path 区分页面；
	// 若去掉 fragment，换页后 URL 相同会被服务端当成重复而丢弃轨迹。
	// 仅截断过长 hash，避免异常数据撑爆字段。
	if utf8.RuneCountInString(u.Fragment) > 200 {
		u.Fragment = string([]rune(u.Fragment)[:200])
	}
	out := u.String()
	return truncateRunes(out, maxPageURLLen)
}

func sanitizePageTitle(raw string) string {
	return truncateRunes(raw, maxPageTitleLen)
}