package wire

import (
	"fmt"
	"io"
)

// MsgNotFound defines a bitcoin notfound message which is sent in response to a getdata message if any of the requested
// data in not available on the peer. Each message is limited to a maximum number of inventory vectors, which is
// currently 50,000. Use the AddInvVect function to podbuild up the list of inventory vectors when sending a notfound
// message to another peer.
type MsgNotFound struct {
	InvList []*InvVect
}

// AddInvVect adds an inventory vector to the message.
func (msg *MsgNotFound) AddInvVect(iv *InvVect) (e error) {
	if len(msg.InvList)+1 > MaxInvPerMsg {
		str := fmt.Sprintf(
			"too many invvect in message [max %v]",
			MaxInvPerMsg,
		)
		return messageError("MsgNotFound.AddInvVect", str)
	}
	msg.InvList = append(msg.InvList, iv)
	return nil
}

// BtcDecode decodes r using the bitcoin protocol encoding into the receiver. This is part of the Message interface
// implementation.
func (msg *MsgNotFound) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) (e error) {
	var count uint64
	if count, e = ReadVarInt(r, pver); E.Chk(e) {
		return
	}
	// Limit to max inventory vectors per message.
	if count > MaxInvPerMsg {
		str := fmt.Sprintf("too many invvect in message [%v]", count)
		return messageError("MsgNotFound.BtcDecode", str)
	}
	// Create a contiguous slice of inventory vectors to deserialize into in order to reduce the number of allocations.
	invList := make([]InvVect, count)
	msg.InvList = make([]*InvVect, 0, count)
	for i := uint64(0); i < count; i++ {
		iv := &invList[i]
		if e = readInvVect(r, pver, iv); E.Chk(e) {
			return
		}
		if e = msg.AddInvVect(iv); E.Chk(e) {
		}
	}
	return nil
}

// BtcEncode encodes the receiver to w using the bitcoin protocol encoding. This is part of the Message interface
// implementation.
func (msg *MsgNotFound) BtcEncode(w io.Writer, pver uint32, enc MessageEncoding) (e error) {
	// Limit to max inventory vectors per message.
	count := len(msg.InvList)
	if count > MaxInvPerMsg {
		str := fmt.Sprintf("too many invvect in message [%v]", count)
		return messageError("MsgNotFound.BtcEncode", str)
	}
	if e = WriteVarInt(w, pver, uint64(count)); E.Chk(e) {
		return
	}
	for _, iv := range msg.InvList {
		if e = writeInvVect(w, pver, iv); E.Chk(e) {
			return
		}
	}
	return
}

// Command returns the protocol command string for the message. This is part of the Message interface implementation.
func (msg *MsgNotFound) Command() string {
	return CmdNotFound
}

// MaxPayloadLength returns the maximum length the payload can be for the receiver. This is part of the Message
// interface implementation.
func (msg *MsgNotFound) MaxPayloadLength(pver uint32) uint32 {
	// Max var int 9 bytes + max InvVects at 36 bytes each. Num inventory vectors (varInt) + max allowed inventory
	// vectors.
	return MaxVarIntPayload + (MaxInvPerMsg * maxInvVectPayload)
}

// NewMsgNotFound returns a new bitcoin notfound message that conforms to the Message interface. See MsgNotFound for
// details.
func NewMsgNotFound() *MsgNotFound {
	return &MsgNotFound{
		InvList: make([]*InvVect, 0, defaultInvListAlloc),
	}
}