// ollie-9p-mount — per-session FUSE proxy that attaches to olliesrv with a custom uname.
//
// Each agent session gets its own mount. Tools running inside the session see
// the full ollie namespace through $OLLIE, but all 9P operations carry the
// session's identity (Uname). The server can then enforce access control
// (e.g. rejecting self-prompts).
//
// Usage:
//
//	ollie-9p-mount [-u uname] [-s service] [-addr address] <mountpoint>
//
// If -u is not given, $OLLIE_SESSION_ID is used.
package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"syscall"

	"9fans.net/go/plan9/client"
	"github.com/hanwen/go-fuse/v2/fs"
	"github.com/hanwen/go-fuse/v2/fuse"
)

var (
	userFlag    = flag.String("u", "", "uname for 9P attach (default: $OLLIE_SESSION_ID)")
	serviceFlag = flag.String("s", "ollie", "9P service name")
	netFlag     = flag.String("net", "", "network type (unix, tcp); empty = namespace")
	addrFlag    = flag.String("addr", "", "9P address; empty = namespace service")
)

func main() {
	flag.Parse()
	if flag.NArg() != 1 {
		fmt.Fprintf(os.Stderr, "usage: ollie-9p-mount [-u uname] [-s service] <mountpoint>\n")
		os.Exit(1)
	}
	mnt := flag.Arg(0)

	uname := *userFlag
	if uname == "" {
		uname = os.Getenv("OLLIE_SESSION_ID")
	}
	if uname == "" {
		fmt.Fprintf(os.Stderr, "ollie-9p-mount: no uname (-u or $OLLIE_SESSION_ID)\n")
		os.Exit(1)
	}

	fsys, err := dial(uname)
	if err != nil {
		log.Fatalf("dial: %v", err)
	}

	os.MkdirAll(mnt, 0755)
	root := &p9Dir{fsys: fsys, path: ""}
	server, err := fs.Mount(mnt, root, &fs.Options{
		MountOptions: fuse.MountOptions{
			FsName:        "ollie-9p",
			Name:          "ollie",
			DisableXAttrs: true,
		},
	})
	if err != nil {
		log.Fatalf("mount: %v", err)
	}

	// Unmount on signal.
	sig := make(chan os.Signal, 1)
	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		<-sig
		server.Unmount()
	}()

	server.Wait()
}

func dial(uname string) (*client.Fsys, error) {
	var conn *client.Conn
	var err error
	if *addrFlag != "" {
		n := *netFlag
		if n == "" {
			n = "tcp"
		}
		conn, err = client.Dial(n, *addrFlag)
	} else {
		conn, err = client.DialService(*serviceFlag)
	}
	if err != nil {
		return nil, err
	}
	return conn.Attach(nil, uname, "")
}