package proxy

import (
	"fmt"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"
)

// DynamicProxy 创建指向任意目标 URL 的反向代理
func DynamicProxy(targetURL string) http.Handler {
	target, err := url.Parse(targetURL)
	if err != nil {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			http.Error(w, "Invalid target URL", http.StatusBadRequest)
		})
	}

	p := &httputil.ReverseProxy{
		Director: func(req *http.Request) {
			req.URL.Scheme = target.Scheme
			req.URL.Host = target.Host
			req.Host = target.Host
			req.Header.Set("Host", target.Host)
			if req.Header.Get("User-Agent") == "" {
				req.Header.Set("User-Agent", "MirrorProxy/1.0")
			}
			req.Header.Del("X-Forwarded-For")
		},
		ErrorHandler: func(w http.ResponseWriter, r *http.Request, err error) {
			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
			w.WriteHeader(http.StatusBadGateway)
			fmt.Fprintf(w, "Proxy error: %s", err.Error())
		},
		Transport: &http.Transport{
			MaxIdleConns:        100,
			MaxIdleConnsPerHost: 20,
			IdleConnTimeout:     90 * time.Second,
			TLSHandshakeTimeout: 10 * time.Second,
		},
	}

	return p
}