package network

import (
	"fmt"
	"github.com/docker/libcontainer"
	"github.com/docker/libcontainer/utils"
)

// Veth is a network strategy that uses a bridge and creates
// a veth pair, one that stays outside on the host and the other
// is placed inside the container's namespace
type Veth struct {
}

const defaultDevice = "eth0"

func (v *Veth) Create(n *libcontainer.Network, nspid int, context libcontainer.Context) error {
	var (
		bridge string
		prefix string
		exists bool
	)
	if bridge, exists = n.Context["bridge"]; !exists {
		return fmt.Errorf("bridge does not exist in network context")
	}
	if prefix, exists = n.Context["prefix"]; !exists {
		return fmt.Errorf("veth prefix does not exist in network context")
	}
	name1, name2, err := createVethPair(prefix)
	if err != nil {
		return err
	}
	context["veth-host"] = name1
	context["veth-child"] = name2
	if err := SetInterfaceMaster(name1, bridge); err != nil {
		return err
	}
	if err := SetMtu(name1, n.Mtu); err != nil {
		return err
	}
	if err := InterfaceUp(name1); err != nil {
		return err
	}
	if err := SetInterfaceInNamespacePid(name2, nspid); err != nil {
		return err
	}
	return nil
}

func (v *Veth) Initialize(config *libcontainer.Network, context libcontainer.Context) error {
	var (
		vethChild string
		exists    bool
	)
	if vethChild, exists = context["veth-child"]; !exists {
		return fmt.Errorf("vethChild does not exist in network context")
	}
	if err := InterfaceDown(vethChild); err != nil {
		return fmt.Errorf("interface down %s %s", vethChild, err)
	}
	if err := ChangeInterfaceName(vethChild, defaultDevice); err != nil {
		return fmt.Errorf("change %s to %s %s", vethChild, defaultDevice, err)
	}
	if err := SetInterfaceIp(defaultDevice, config.Address); err != nil {
		return fmt.Errorf("set %s ip %s", defaultDevice, err)
	}
	if err := SetMtu(defaultDevice, config.Mtu); err != nil {
		return fmt.Errorf("set %s mtu to %d %s", defaultDevice, config.Mtu, err)
	}
	if err := InterfaceUp(defaultDevice); err != nil {
		return fmt.Errorf("%s up %s", defaultDevice, err)
	}
	if config.Gateway != "" {
		if err := SetDefaultGateway(config.Gateway, defaultDevice); err != nil {
			return fmt.Errorf("set gateway to %s on device %s failed with %s", config.Gateway, defaultDevice, err)
		}
	}
	return nil
}

// createVethPair will automatically generage two random names for
// the veth pair and ensure that they have been created
func createVethPair(prefix string) (name1 string, name2 string, err error) {
	name1, err = utils.GenerateRandomName(prefix, 4)
	if err != nil {
		return
	}
	name2, err = utils.GenerateRandomName(prefix, 4)
	if err != nil {
		return
	}
	if err = CreateVethPair(name1, name2); err != nil {
		return
	}
	return
}