package custom_dns_proxy

import (
	"log"
	"net/http"

	"github.com/darkit/goproxy"
	"github.com/darkit/goproxy/pkg/dns"
)

// CustomDNSDelegate 自定义 DNS 代理委托
type CustomDNSDelegate struct {
	goproxy.DefaultDelegate
	dnsResolver dns.Resolver
}

// ResolveBackend 解析后端服务器
func (d *CustomDNSDelegate) ResolveBackend(req *http.Request) (string, error) {
	return d.dnsResolver.Resolve(req.URL.Host)
}

// RunCustomDNSProxy 运行自定义 DNS 代理服务器
func RunCustomDNSProxy() error {
	// 创建自定义 DNS 解析器
	resolver := dns.NewResolver(dns.WithFallback(true))

	// 添加 DNS 记录
	resolver.LoadFromMap(map[string]string{
		"example.com": "http://backend1.example.com",
		"test.com":    "http://backend2.test.com",
	})

	// 创建自定义 DNS 代理委托
	delegate := &CustomDNSDelegate{
		dnsResolver: resolver,
	}

	// 创建代理实例
	proxy := goproxy.NewProxy(
		goproxy.WithDelegate(delegate),
	)

	// 启动代理服务器
	log.Println("自定义 DNS 代理服务器启动在 :8080")
	log.Println("DNS 配置:")
	log.Printf("- example.com -> backend1.example.com\n")
	log.Printf("- test.com -> backend2.test.com\n")
	return http.ListenAndServe(":8080", proxy)
}