// Copyright 2015 flannel authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package vxlan

import (
	"encoding/json"
	"fmt"
	"net"

	"golang.org/x/net/context"

	"github.com/coreos/flannel/backend"
	"github.com/coreos/flannel/pkg/ip"
	"github.com/coreos/flannel/subnet"
)

func init() {
	backend.Register("vxlan", New)
}

const (
	defaultVNI = 1
)

type VXLANBackend struct {
	subnetMgr subnet.Manager
	extIface  *backend.ExternalInterface
}

func New(sm subnet.Manager, extIface *backend.ExternalInterface) (backend.Backend, error) {
	backend := &VXLANBackend{
		subnetMgr: sm,
		extIface:  extIface,
	}

	return backend, nil
}

func newSubnetAttrs(publicIP net.IP, mac net.HardwareAddr) (*subnet.LeaseAttrs, error) {
	data, err := json.Marshal(&vxlanLeaseAttrs{hardwareAddr(mac)})
	if err != nil {
		return nil, err
	}

	return &subnet.LeaseAttrs{
		PublicIP:    ip.FromIP(publicIP),
		BackendType: "vxlan",
		BackendData: json.RawMessage(data),
	}, nil
}

func (be *VXLANBackend) RegisterNetwork(ctx context.Context, config *subnet.Config) (backend.Network, error) {
	// Parse our configuration
	cfg := struct {
		VNI  int
		Port int
		GBP  bool
	}{
		VNI: defaultVNI,
	}

	if len(config.Backend) > 0 {
		if err := json.Unmarshal(config.Backend, &cfg); err != nil {
			return nil, fmt.Errorf("error decoding VXLAN backend config: %v", err)
		}
	}

	devAttrs := vxlanDeviceAttrs{
		vni:       uint32(cfg.VNI),
		name:      fmt.Sprintf("flannel.%v", cfg.VNI),
		vtepIndex: be.extIface.Iface.Index,
		vtepAddr:  be.extIface.IfaceAddr,
		vtepPort:  cfg.Port,
		gbp:       cfg.GBP,
	}

	dev, err := newVXLANDevice(&devAttrs)
	if err != nil {
		return nil, err
	}

	subnetAttrs, err := newSubnetAttrs(be.extIface.ExtAddr, dev.MACAddr())
	if err != nil {
		return nil, err
	}

	lease, err := be.subnetMgr.AcquireLease(ctx, subnetAttrs)
	switch err {
	case nil:

	case context.Canceled, context.DeadlineExceeded:
		return nil, err

	default:
		return nil, fmt.Errorf("failed to acquire lease: %v", err)
	}

	// vxlan's subnet is that of the whole overlay network (e.g. /16)
	// and not that of the individual host (e.g. /24)
	vxlanNet := ip.IP4Net{
		IP:        lease.Subnet.IP,
		PrefixLen: config.Network.PrefixLen,
	}
	if err = dev.Configure(vxlanNet); err != nil {
		return nil, err
	}

	return newNetwork(be.subnetMgr, be.extIface, dev, vxlanNet, lease)
}

// So we can make it JSON (un)marshalable
type hardwareAddr net.HardwareAddr

func (hw hardwareAddr) MarshalJSON() ([]byte, error) {
	return []byte(fmt.Sprintf("%q", net.HardwareAddr(hw))), nil
}

func (hw *hardwareAddr) UnmarshalJSON(bytes []byte) error {
	if len(bytes) < 2 || bytes[0] != '"' || bytes[len(bytes)-1] != '"' {
		return fmt.Errorf("error parsing hardware addr")
	}

	bytes = bytes[1 : len(bytes)-1]

	mac, err := net.ParseMAC(string(bytes))
	if err != nil {
		return err
	}

	*hw = hardwareAddr(mac)
	return nil
}