// Copyright (c) 2017 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package wire

import "io"

// FilterType is used to represent a filter type.
type FilterType uint8

const (
	// GCSFilterRegular is the regular filter type.
	GCSFilterRegular FilterType = iota

	// GCSFilterExtended is the extended filter type.
	GCSFilterExtended
)

// MsgCFTypes is the cftypes message.
type MsgCFTypes struct {
	SupportedFilters []FilterType
}

// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgCFTypes) BtcDecode(r io.Reader, pver uint32, _ MessageEncoding) error {
	// Read the number of filter types supported.
	count, err := ReadVarInt(r, pver)
	if err != nil {
		return err
	}

	// Read each filter type.
	msg.SupportedFilters = make([]FilterType, count)
	for i := uint64(0); i < count; i++ {
		var filterType uint8
		err = readElement(r, &filterType)
		if err != nil {
			return err
		}
		msg.SupportedFilters[i] = FilterType(filterType)
	}

	return nil
}

// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgCFTypes) BtcEncode(w io.Writer, pver uint32, _ MessageEncoding) error {
	// Write length of supported filters slice. We assume it's deduplicated.
	err := WriteVarInt(w, pver, uint64(len(msg.SupportedFilters)))
	if err != nil {
		return err
	}

	for i := range msg.SupportedFilters {
		err = writeElement(w, msg.SupportedFilters[i])
		if err != nil {
			return err
		}
	}

	return nil
}

// Deserialize decodes a filter from r into the receiver using a format that is
// suitable for long-term storage such as a database. This function differs
// from BtcDecode in that BtcDecode decodes from the bitcoin wire protocol as
// it was sent across the network.  The wire encoding can technically differ
// depending on the protocol version and doesn't even really need to match the
// format of a stored filter at all. As of the time this comment was written,
// the encoded filter is the same in both instances, but there is a distinct
// difference and separating the two allows the API to be flexible enough to
// deal with changes.
func (msg *MsgCFTypes) Deserialize(r io.Reader) error {
	// At the current time, there is no difference between the wire encoding
	// and the stable long-term storage format.  As a result, make use of
	// BtcDecode.
	return msg.BtcDecode(r, 0, BaseEncoding)
}

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

// MaxPayloadLength returns the maximum length the payload can be for the
// receiver.  This is part of the Message interface implementation.
func (msg *MsgCFTypes) MaxPayloadLength(pver uint32) uint32 {
	// 2 bytes for filter count, and 1 byte for up to 256 filter types.
	return 258
}

// NewMsgCFTypes returns a new bitcoin cftypes message that conforms to the
// Message interface. See MsgCFTypes for details.
func NewMsgCFTypes(filterTypes []FilterType) *MsgCFTypes {
	return &MsgCFTypes{
		SupportedFilters: filterTypes,
	}
}