package main

import (
	"fmt"
	"net"
	"strings"
	"time"
)

// LatencyInfo 延迟信息（均由采集端在本机测量）
type LatencyInfo struct {
	ClientToServer float64           `json:"clientToServer"` // 采集器 → 监控中心 gRPC 地址的 TCP 建连耗时（ms），失败为 -1
	External       map[string]string `json:"external"`       // 采集器对外站点的 TCP 建连耗时（同 checkExternalLatency）
}

// normalizeGRPCDialTarget strips common grpc-go target prefixes; expects host:port or [ipv6]:port.
func normalizeGRPCDialTarget(addr string) string {
	a := strings.TrimSpace(addr)
	a = strings.TrimPrefix(a, "dns:///")
	a = strings.TrimPrefix(a, "dns://")
	return strings.TrimSpace(a)
}

// measureCollectorToCentralTCP returns TCP connect time in ms to the central gRPC dial target, or -1 on failure.
func measureCollectorToCentralTCP(grpcAddr string, timeout time.Duration) float64 {
	target := normalizeGRPCDialTarget(grpcAddr)
	if target == "" || strings.HasPrefix(strings.ToLower(target), "unix:") {
		return -1
	}
	start := time.Now()
	conn, err := net.DialTimeout("tcp", target, timeout)
	if err != nil {
		return -1
	}
	_ = conn.Close()
	return float64(time.Since(start).Microseconds()) / 1000.0
}

// checkExternalLatency 检测外部网站延迟
func checkExternalLatency(host string, timeout time.Duration) string {
	start := time.Now()
	
	// 尝试 TCP 连接 80 端口
	conn, err := net.DialTimeout("tcp", host+":80", timeout)
	if err != nil {
		// 如果 80 端口失败，尝试 443 (HTTPS)
		conn, err = net.DialTimeout("tcp", host+":443", timeout)
		if err != nil {
			return "超时"
		}
	}
	defer conn.Close()

	// 使用微秒换算，避免 Milliseconds() 截断成 0 ms 误导用户
	ms := float64(time.Since(start).Microseconds()) / 1000.0
	if ms < 1 {
		return fmt.Sprintf("%.1f ms", ms)
	}
	return fmt.Sprintf("%.0f ms", ms)
}

// readExternalLatencies 读取外部网站延迟
func readExternalLatencies() map[string]string {
	latencies := make(map[string]string)
	timeout := 3 * time.Second

	// 检测百度
	latencies["baidu.com"] = checkExternalLatency("baidu.com", timeout)

	// 检测谷歌
	latencies["google.com"] = checkExternalLatency("google.com", timeout)

	// 检测 GitHub
	latencies["github.com"] = checkExternalLatency("github.com", timeout)

	return latencies
}