// Copyright 2016 CNI 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 hwaddr

import (
	"fmt"
	"net"
	"strconv"
	"strings"
)

const (
	// private mac prefix safe to use
	PrivateMACPrefix = "0a:58"
)

type SupportIp4OnlyErr struct{ msg string }

func (e SupportIp4OnlyErr) Error() string { return e.msg }

type MacParseErr struct{ msg string }

func (e MacParseErr) Error() string { return e.msg }

type InvalidPrefixLengthErr struct{ msg string }

func (e InvalidPrefixLengthErr) Error() string { return e.msg }

// GenerateHardwareAddr4 generates 48 bit virtual mac addresses based on the IP4 input.
func GenerateHardwareAddr4(ip net.IP, prefix string) (net.HardwareAddr, error) {
	switch {

	case ip.To4() == nil:
		return nil, SupportIp4OnlyErr{msg: "GenerateHardwareAddr4 only supports valid IPv4 address as input"}

	case len(prefix) != len(PrivateMACPrefix):
		return nil, InvalidPrefixLengthErr{msg: fmt.Sprintf(
			"Prefix has length %d instead  of %d", len(prefix), len(PrivateMACPrefix)),
		}
	}

	mac := prefix
	sections := strings.Split(ip.String(), ".")
	for _, s := range sections {
		i, _ := strconv.Atoi(s)
		mac += fmt.Sprintf(":%02x", i)
	}

	hwAddr, err := net.ParseMAC(mac)
	if err != nil {
		return nil, MacParseErr{msg: fmt.Sprintf(
			"Failed to parse mac address %q generated based on IP %q due to: %v", mac, ip, err),
		}
	}
	return hwAddr, nil
}