package service

import (
	"net/url"
	"strings"
)

// 来源分类常量
const (
	RefKindDirect   = "direct"
	RefKindInternal = "internal"
	RefKindSearch   = "search"
	RefKindSocial   = "social"
	RefKindExternal = "external"
)

// searchHosts 搜索引擎域名（按「等于或以 .子域结尾」匹配）
var searchHosts = []string{"google.com", "bing.com", "baidu.com", "sogou.com", "so.com", "sm.cn", "duckduckgo.com", "yandex.com", "yandex.ru", "yahoo.com"}

// socialHosts 社交/社区域名特征
var socialHosts = []string{
	"weibo.com", "weibo.cn", "zhihu.com", "zhuanlan.zhihu.com", "twitter.com", "x.com",
	"t.me", "telegram.me", "douyin.com", "xiaohongshu.com", "bilibili.com", "b23.tv",
	"qq.com", "tieba.baidu.com", "v2ex.com", "juejin.cn", "csdn.net", "segmentfault.com",
	"github.com", "gitee.com", "reddit.com", "facebook.com", "instagram.com", "discord.com",
}

// hostMatches 按「等于或以 .子域结尾」匹配 host 与域名列表
func hostMatches(host string, list []string) bool {
	for _, d := range list {
		if host == d || strings.HasSuffix(host, "."+d) {
			return true
		}
	}
	return false
}

// ClassifyReferrer 解析并归类 Referer：返回 (来源 host, 来源类别)。
// 空 → direct；本站 → internal；搜索引擎 → search；社交 → social；其余 → external；解析失败按 direct。
func ClassifyReferrer(raw, siteHost string) (string, string) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return "", RefKindDirect
	}
	u, err := url.Parse(raw)
	if err != nil || u.Host == "" {
		return "", RefKindDirect
	}
	host := strings.ToLower(u.Host)
	if i := strings.LastIndex(host, ":"); i >= 0 && !strings.Contains(host, "]") {
		host = host[:i] // 去端口
	}
	if siteHost != "" && (host == siteHost || siteHost == host) {
		return host, RefKindInternal
	}
	if hostMatches(host, searchHosts) {
		return host, RefKindSearch
	}
	if hostMatches(host, socialHosts) {
		return host, RefKindSocial
	}
	return host, RefKindExternal
}