main.go

// 文件传输 — 局域网文件共享与直传工具
//
// 两种模式：
//   1. 共享模式 - 上传到服务器，局域网内设备均可下载（文件持久化）
//   2. 直传模式 - 上传后即时转发给指定设备，对方自动下载，文件不保留
//
// 设备通过 localStorage 中持久化的设备 ID 自动识别，无需手动输入 token。
// 数据明文 HTTP 传输，面向信任局域网环境。
package main

import (
	"embed"
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"strings"
)

//go:embed static/*
var staticFS embed.FS

func main() {
	port := flag.String("port", "8080", "server port")
	flag.Parse()

	os.MkdirAll("uploads", 0755)

	serverAddr := getLanIP(*port)

	h := NewHandler("uploads")

	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		path := r.URL.Path
		switch {
		case path == "/api/events" && r.Method == "GET":
			h.sseEvents(w, r)
		case path == "/api/devices" && r.Method == "GET":
			h.listDevices(w, r)
		case path == "/api/name" && r.Method == "POST":
			h.setName(w, r)
		case path == "/api/send" && r.Method == "POST":
			h.sendFile(w, r)
		case path == "/api/files" && r.Method == "GET":
			h.listFiles(w, r)
		case path == "/api/upload" && r.Method == "POST":
			h.uploadFile(w, r)
		case strings.HasPrefix(path, "/api/download/") && r.Method == "GET":
			h.downloadFile(w, r)
		case strings.HasPrefix(path, "/api/inbox/") && r.Method == "GET":
			h.serveInbox(w, r)
		default:
			serveStaticFile(w, r, serverAddr)
		}
	})

	printAccessInfo(*port, serverAddr)

	log.Fatal(http.ListenAndServe(":"+*port, mux))
}

func serveStaticFile(w http.ResponseWriter, r *http.Request, serverAddr string) {
	path := r.URL.Path
	if path == "/" {
		path = "/index.html"
	}

	data, err := staticFS.ReadFile("static" + path)
	if err != nil {
		data, _ = staticFS.ReadFile("static/index.html")
	}

	if strings.HasSuffix(path, ".html") {
		data = []byte(strings.Replace(string(data), "__SERVER_ADDR__", serverAddr, 1))
	}

	switch {
	case strings.HasSuffix(path, ".css"):
		w.Header().Set("Content-Type", "text/css; charset=utf-8")
	case strings.HasSuffix(path, ".js"):
		w.Header().Set("Content-Type", "application/javascript; charset=utf-8")
	default:
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
	}
	w.Write(data)
}

func getLanIP(port string) string {
	ip := pickBestIP()
	if ip == "" {
		return fmt.Sprintf("http://localhost:%s", port)
	}
	return fmt.Sprintf("http://%s:%s", ip, port)
}

func isPrivateIP(ip net.IP) bool {
	return ip[0] == 10 ||
		(ip[0] == 172 && ip[1] >= 16 && ip[1] <= 31) ||
		(ip[0] == 192 && ip[1] == 168)
}

func isLinkLocal(ip net.IP) bool {
	return ip[0] == 169 && ip[1] == 254
}

func pickBestIP() string {
	addrs, _ := net.InterfaceAddrs()
	var firstPrivate, firstOther string
	for _, addr := range addrs {
		ipnet, ok := addr.(*net.IPNet)
		if !ok {
			continue
		}
		ip4 := ipnet.IP.To4()
		if ip4 == nil || ip4.IsLoopback() || isLinkLocal(ip4) {
			continue
		}
		s := ip4.String()
		if isPrivateIP(ip4) {
			if firstPrivate == "" {
				firstPrivate = s
			}
		} else {
			if firstOther == "" {
				firstOther = s
			}
		}
	}
	if firstPrivate != "" {
		return firstPrivate
	}
	return firstOther
}

func printAccessInfo(port, serverAddr string) {
	fmt.Println()
	fmt.Println("  ╔══════════════════════════════════════╗")
	fmt.Println("  ║       📁 文件传输服务 已启动        ║")
	fmt.Println("  ╠══════════════════════════════════════╣")

	best := pickBestIP()
	addrs, _ := net.InterfaceAddrs()
	for _, addr := range addrs {
		if ipnet, ok := addr.(*net.IPNet); ok {
			if ip4 := ipnet.IP.To4(); ip4 != nil && !ip4.IsLoopback() {
				marker := "  "
				if ip4.String() == best {
					marker = "★ "
				}
				addrStr := fmt.Sprintf("%shttp://%s:%s", marker, ip4, port)
				pad := 32 - len(addrStr)
				if pad < 1 {
					pad = 1
				}
				fmt.Printf("  ║  %s%s║\n", addrStr, strings.Repeat(" ", pad))
			}
		}
	}

	addrStr := fmt.Sprintf("http://localhost:%s", port)
	pad := 30 - len(addrStr)
	if pad < 1 {
		pad = 1
	}
	fmt.Printf("  ║  %s%s║\n", addrStr, strings.Repeat(" ", pad))
	fmt.Println("  ╚══════════════════════════════════════╝")
	fmt.Println()
}