package main

import (
	"flag"
	"fmt"
	"github.com/vishvananda/netlink"
	"log"
	"os"
)

func main() {
	var (
		err         error
		mainlog     = log.New(os.Stderr, "net-predictable: ", log.Lmsgprefix|log.Ltime)
		ifnparam    string
		force, info bool
		main        IfNameType
	)
	flag.StringVar(&ifnparam, "ifname", "", "Interface name to rename")
	flag.BoolVar(&force, "force", false, "Force update name of interface")
	flag.BoolVar(&info, "info", false, "Show interface details")
	flag.IntVar((*int)(&main), "main", int(IfNameLoc), fmt.Sprintf("Main interface name to use: %v",
		map[string]IfNameType{
			"Kernel":   IfNameKern,
			"MAC":      IfNameMAC,
			"Location": IfNameLoc,
		},
	))
	flag.Parse()

	// Probe different methods to get interface name
	var ifname = ""
	for _, v := range []string{
		ifnparam,
		os.Getenv("INTERFACE"),
		os.Getenv("MDEV"),
		os.Getenv("IFNAME"),
	} {
		if v != "" {
			ifname = v
			break
		}
	}

	if ifname == "" {
		mainlog.Println("No interface name provided")
		return
	}

	mainlog.SetPrefix(fmt.Sprintf("net-predictable (%s): ", ifname))
	var l netlink.Link
	if l, err = netlink.LinkByName(ifname); err != nil {
		mainlog.Fatalln("Interface", ifname, "doesn't exist or disappeared before it could be selected")
	}

	var cif iface
	if cif, err = New(ifname); err != nil {
		mainlog.Println("Failed creating interface data:", err)
		return
	}

	var should bool
	if should, err = cif.shouldRun(); err != nil {
		mainlog.Println(err)
	}
	if !info && (!force && !should) {
		mainlog.Println("Interface is already renamed, exiting")
		return
	}

	if err = cif.ProcMAC(); err != nil {
		mainlog.Println("Failed to process interface MAC path:", err)
	}

	if err = cif.ProcLoc(); err != nil {
		mainlog.Println("Failed to process interface HW Location path:", err)
	}

	// Just print information
	if info {
		mainlog.Println("Selected Interface:", ifname)
		mainlog.Println("HW Location Name:", cif.names[IfNameLoc])
		mainlog.Println("MAC Name:", cif.names[IfNameMAC])
		return
	}

	// Main name
	// This must be set before the next are following as altname cannot be added if a interface with the same name exists
	if ifname == cif.names[main] {
		mainlog.Println("Interface already named correctly, skipping")
	} else if cif.names[main] != "" {
		mainlog.Printf("Renaming %s to %s\n", ifname, cif.names[main])
		if err = netlink.LinkSetName(l, cif.names[main]); err != nil {
			mainlog.Fatalf("Could not rename interface %s: %s\n", ifname, err)
		}
	} else {
		mainlog.Println("Main interface naming method is unavailable for this interface, skipping")
	}

	// Alt names
	var result = make(map[string]int)
	for k, v := range cif.names {
		if k != main {
			result[v]++
		}
	}

	// Invalidate main name
	result[cif.names[main]]--

	// Invalidate already present alternative names
	for _, v := range l.Attrs().AltNames {
		result[v]--
	}

	for k, v := range result {
		if v != 1 {
			continue
		}

		mainlog.Printf("Adding altname %s for %s\n", k, ifname)
		if err = netlink.LinkAddAltName(l, k); err != nil {
			mainlog.Printf("Adding altname %s failed for %s: %s\n", k, ifname, err)
		}
	}
}