// Copyright 2015 CoreOS, Inc.
//
// 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 ip

import (
	"encoding/json"
	"math/big"
	"net"
)

// ParseCIDR takes a string like "10.2.3.1/24" and
// return IPNet with "10.2.3.1" and /24 mask
func ParseCIDR(s string) (*net.IPNet, error) {
	ip, ipn, err := net.ParseCIDR(s)
	if err != nil {
		return nil, err
	}

	ipn.IP = ip
	return ipn, nil
}

// NextIP returns IP incremented by 1
func NextIP(ip net.IP) net.IP {
	i := ipToInt(ip)
	return intToIP(i.Add(i, big.NewInt(1)))
}

// PrevIP returns IP decremented by 1
func PrevIP(ip net.IP) net.IP {
	i := ipToInt(ip)
	return intToIP(i.Sub(i, big.NewInt(1)))
}

func ipToInt(ip net.IP) *big.Int {
	if v := ip.To4(); v != nil {
		return big.NewInt(0).SetBytes(v)
	}
	return big.NewInt(0).SetBytes(ip.To16())
}

func intToIP(i *big.Int) net.IP {
	return net.IP(i.Bytes())
}

// Network masks off the host portion of the IP
func Network(ipn *net.IPNet) *net.IPNet {
	return &net.IPNet{
		IP:   ipn.IP.Mask(ipn.Mask),
		Mask: ipn.Mask,
	}
}

// like net.IPNet but adds JSON marshalling and unmarshalling
type IPNet net.IPNet

func (n IPNet) MarshalJSON() ([]byte, error) {
	return json.Marshal((*net.IPNet)(&n).String())
}

func (n *IPNet) UnmarshalJSON(data []byte) error {
	var s string
	if err := json.Unmarshal(data, &s); err != nil {
		return err
	}

	tmp, err := ParseCIDR(s)
	if err != nil {
		return err
	}

	*n = IPNet(*tmp)
	return nil
}