package types

import (
	"bytes"
	"database/sql/driver"
	"fmt"
	"net"
	"strconv"
)

type (
	// Subnet is used to parse a subnet parameter.
	Subnet net.IPNet
	// IP is used to parse an IP parameter.
	IP net.IP
	// IPVersion represents the two IP versions currently in use.
	IPVersion int
)

// UnmarshalJSON parses a value into a subnet.
//
// It is also checked if the provided IP matches the network address
// of the subnet.
func (s *Subnet) UnmarshalJSON(in []byte) error {
	in = bytes.Trim(in, `"`)

	ip, ipnet, err := net.ParseCIDR(string(in))
	if err != nil {
		return fmt.Errorf("not a valid subnet: %#v", err)
	}
	if !ipnet.IP.Equal(ip) {
		return fmt.Errorf("provided IP '%s' is not network address '%s' of declared subnet", ip.String(), ipnet.IP.String())
	}
	*s = Subnet(*ipnet)
	return nil
}

// String returns the string representation of the subnet.
//
// The subnet is returned as the subnet address and prefix separated by `/`
// as defined in RFC 4632 and RFC 4291.
func (s *Subnet) String() string {
	return (*net.IPNet)(s).String()
}

func (i IP) Is4() bool {
	if a := net.IP(i).To4(); a == nil {
		return false
	}
	return true
}

func (i IP) Is6() bool {
	return !i.Is4()
}

// Value implements the database Value interface.
//
// This function is needed so that a subnet can be inserted into
// the database without much casting.
func (s Subnet) Value() (driver.Value, error) {
	return s.String(), nil
}

func (i *IP) UnmarshalJSON(in []byte) error {
	in = bytes.Trim(in, `"`)

	ip := net.ParseIP(string(in))
	if ip == nil {
		return fmt.Errorf("not a valid ip")
	}
	*i = IP(ip)
	return nil
}

// UnmarshalJSON parses the incoming version from json.
func (v *IPVersion) UnmarshalJSON(in []byte) error {
	raw, err := strconv.Atoi(string(in))
	if err != nil {
		return fmt.Errorf("can't parse ip version: %#v", err)
	}
	if raw != 4 && raw != 6 {
		return fmt.Errorf("only version 4 and 6 are supported")
	}
	*v = IPVersion(raw)
	return nil
}