package wire

import (
	"fmt"
	"io"
)

// BloomUpdateType specifies how the filter is updated when a match is found
type BloomUpdateType uint8

const (
	// BloomUpdateNone indicates the filter is not adjusted when a match is found.
	BloomUpdateNone BloomUpdateType = 0
	// BloomUpdateAll indicates if the filter matches any data element in a public
	// key script, the outpoint is serialized and inserted into the filter.
	BloomUpdateAll BloomUpdateType = 1
	// BloomUpdateP2PubkeyOnly indicates if the filter matches a data element in a
	// public key script and the script is of the standard pay-to-pubkey or
	// multisig, the outpoint is serialized and inserted into the filter.
	BloomUpdateP2PubkeyOnly BloomUpdateType = 2
)
const (
	// MaxFilterLoadHashFuncs is the maximum number of hash functions to load into
	// the Bloom filter.
	MaxFilterLoadHashFuncs = 50
	// MaxFilterLoadFilterSize is the maximum size in bytes a filter may be.
	MaxFilterLoadFilterSize = 36000
)

// MsgFilterLoad implements the Message interface and represents a bitcoin
// filterload message which is used to reset a Bloom filter. This message was
// not added until protocol version BIP0037Version.
type MsgFilterLoad struct {
	Filter    []byte
	HashFuncs uint32
	Tweak     uint32
	Flags     BloomUpdateType
}

// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgFilterLoad) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) (e error) {
	if pver < BIP0037Version {
		str := fmt.Sprintf("filterload message invalid for protocol version %d", pver)
		return messageError("MsgFilterLoad.BtcDecode", str)
	}
	if msg.Filter, e = ReadVarBytes(r, pver, MaxFilterLoadFilterSize, "filterload filter size"); E.Chk(e) {
		return
	}
	if e = readElements(r, &msg.HashFuncs, &msg.Tweak, &msg.Flags); E.Chk(e) {
		return
	}
	if msg.HashFuncs > MaxFilterLoadHashFuncs {
		str := fmt.Sprintf(
			"too many filter hash functions for message [count %v, max %v]",
			msg.HashFuncs, MaxFilterLoadHashFuncs,
		)
		return messageError("MsgFilterLoad.BtcDecode", str)
	}
	return
}

// BtcEncode encodes the receiver to w using the bitcoin protocol encoding. This is part of the Message interface
// implementation.
func (msg *MsgFilterLoad) BtcEncode(w io.Writer, pver uint32, enc MessageEncoding) (e error) {
	if pver < BIP0037Version {
		str := fmt.Sprintf(
			"filterload message invalid for protocol "+
				"version %d", pver,
		)
		return messageError("MsgFilterLoad.BtcEncode", str)
	}
	size := len(msg.Filter)
	if size > MaxFilterLoadFilterSize {
		str := fmt.Sprintf(
			"filterload filter size too large for message "+
				"[size %v, max %v]", size, MaxFilterLoadFilterSize,
		)
		return messageError("MsgFilterLoad.BtcEncode", str)
	}
	if msg.HashFuncs > MaxFilterLoadHashFuncs {
		str := fmt.Sprintf(
			"too many filter hash functions for message "+
				"[count %v, max %v]", msg.HashFuncs, MaxFilterLoadHashFuncs,
		)
		return messageError("MsgFilterLoad.BtcEncode", str)
	}
	if e = WriteVarBytes(w, pver, msg.Filter); E.Chk(e) {
		return
	}
	return writeElements(w, msg.HashFuncs, msg.Tweak, msg.Flags)
}

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

// MaxPayloadLength returns the maximum length the payload can be for the receiver. This is part of the Message
// interface implementation.
func (msg *MsgFilterLoad) MaxPayloadLength(pver uint32) uint32 {
	// Num filter bytes (varInt) + filter + 4 bytes hash funcs + 4 bytes tweak + 1 byte flags.
	return uint32(VarIntSerializeSize(MaxFilterLoadFilterSize)) +
		MaxFilterLoadFilterSize + 9
}

// NewMsgFilterLoad returns a new bitcoin filterload message that conforms to the Message interface. See MsgFilterLoad
// for details.
func NewMsgFilterLoad(filter []byte, hashFuncs uint32, tweak uint32, flags BloomUpdateType) *MsgFilterLoad {
	return &MsgFilterLoad{
		Filter:    filter,
		HashFuncs: hashFuncs,
		Tweak:     tweak,
		Flags:     flags,
	}
}