package libcontainer

import (
	"fmt"
	"math"

	"github.com/vishvananda/netlink/nl"
	"golang.org/x/sys/unix"
)

// list of known message types we want to send to bootstrap program
// The number is randomly chosen to not conflict with known netlink types
const (
	InitMsg          uint16 = 62000
	CloneFlagsAttr   uint16 = 27281
	NsPathsAttr      uint16 = 27282
	UidmapAttr       uint16 = 27283
	GidmapAttr       uint16 = 27284
	SetgroupAttr     uint16 = 27285
	OomScoreAdjAttr  uint16 = 27286
	RootlessEUIDAttr uint16 = 27287
	UidmapPathAttr   uint16 = 27288
	GidmapPathAttr   uint16 = 27289
	TimeOffsetsAttr  uint16 = 27290
)

type Int32msg struct {
	Type  uint16
	Value uint32
}

// Serialize serializes the message.
// Int32msg has the following representation
// | nlattr len | nlattr type |
// | uint32 value             |
func (msg *Int32msg) Serialize() []byte {
	buf := make([]byte, msg.Len())
	native := nl.NativeEndian()
	native.PutUint16(buf[0:2], uint16(msg.Len()))
	native.PutUint16(buf[2:4], msg.Type)
	native.PutUint32(buf[4:8], msg.Value)
	return buf
}

func (msg *Int32msg) Len() int {
	return unix.NLA_HDRLEN + 4
}

// Bytemsg has the following representation
// | nlattr len | nlattr type |
// | value              | pad |
type Bytemsg struct {
	Type  uint16
	Value []byte
}

func (msg *Bytemsg) Serialize() []byte {
	l := msg.Len()
	if l > math.MaxUint16 {
		// We cannot return nil nor an error here, so we panic with
		// a specific type instead, which is handled via recover in
		// bootstrapData.
		panic(netlinkError{fmt.Errorf("netlink: cannot serialize bytemsg of length %d (larger than UINT16_MAX)", l)})
	}
	buf := make([]byte, (l+unix.NLA_ALIGNTO-1) & ^(unix.NLA_ALIGNTO-1))
	native := nl.NativeEndian()
	native.PutUint16(buf[0:2], uint16(l))
	native.PutUint16(buf[2:4], msg.Type)
	copy(buf[4:], msg.Value)
	return buf
}

func (msg *Bytemsg) Len() int {
	return unix.NLA_HDRLEN + len(msg.Value) + 1 // null-terminated
}

type Boolmsg struct {
	Type  uint16
	Value bool
}

func (msg *Boolmsg) Serialize() []byte {
	buf := make([]byte, msg.Len())
	native := nl.NativeEndian()
	native.PutUint16(buf[0:2], uint16(msg.Len()))
	native.PutUint16(buf[2:4], msg.Type)
	if msg.Value {
		native.PutUint32(buf[4:8], uint32(1))
	} else {
		native.PutUint32(buf[4:8], uint32(0))
	}
	return buf
}

func (msg *Boolmsg) Len() int {
	return unix.NLA_HDRLEN + 4 // alignment
}