package lnwire

import (
	"bytes"
	"io"

	"github.com/btcsuite/btcd/btcec/v2"
	"github.com/lightningnetwork/lnd/tlv"
)

// ChannelReady is the message that both parties to a new channel creation
// send once they have observed the funding transaction being confirmed on the
// blockchain. ChannelReady contains the signatures necessary for the channel
// participants to advertise the existence of the channel to the rest of the
// network.
type ChannelReady struct {
	// ChanID is the outpoint of the channel's funding transaction. This
	// can be used to query for the channel in the database.
	ChanID ChannelID

	// NextPerCommitmentPoint is the secret that can be used to revoke the
	// next commitment transaction for the channel.
	NextPerCommitmentPoint *btcec.PublicKey

	// AliasScid is an alias ShortChannelID used to refer to the underlying
	// channel. It can be used instead of the confirmed on-chain
	// ShortChannelID for forwarding.
	AliasScid *ShortChannelID

	// ExtraData is the set of data that was appended to this message to
	// fill out the full maximum transport message size. These fields can
	// be used to specify optional data such as custom TLV fields.
	ExtraData ExtraOpaqueData
}

// NewChannelReady creates a new ChannelReady message, populating it with the
// necessary IDs and revocation secret.
func NewChannelReady(cid ChannelID, npcp *btcec.PublicKey) *ChannelReady {
	return &ChannelReady{
		ChanID:                 cid,
		NextPerCommitmentPoint: npcp,
		ExtraData:              make([]byte, 0),
	}
}

// A compile time check to ensure ChannelReady implements the lnwire.Message
// interface.
var _ Message = (*ChannelReady)(nil)

// Decode deserializes the serialized ChannelReady message stored in the
// passed io.Reader into the target ChannelReady using the deserialization
// rules defined by the passed protocol version.
//
// This is part of the lnwire.Message interface.
func (c *ChannelReady) Decode(r io.Reader, pver uint32) error {
	// Read all the mandatory fields in the message.
	err := ReadElements(r,
		&c.ChanID,
		&c.NextPerCommitmentPoint,
		&c.ExtraData,
	)
	if err != nil {
		return err
	}

	// Next we'll parse out the set of known records. For now, this is just
	// the AliasScidRecordType.
	var aliasScid ShortChannelID
	typeMap, err := c.ExtraData.ExtractRecords(&aliasScid)
	if err != nil {
		return err
	}

	// We'll only set AliasScid if the corresponding TLV type was included
	// in the stream.
	if val, ok := typeMap[AliasScidRecordType]; ok && val == nil {
		c.AliasScid = &aliasScid
	}

	return nil
}

// Encode serializes the target ChannelReady message into the passed io.Writer
// implementation. Serialization will observe the rules defined by the passed
// protocol version.
//
// This is part of the lnwire.Message interface.
func (c *ChannelReady) Encode(w *bytes.Buffer, pver uint32) error {
	if err := WriteChannelID(w, c.ChanID); err != nil {
		return err
	}

	if err := WritePublicKey(w, c.NextPerCommitmentPoint); err != nil {
		return err
	}

	// We'll only encode the AliasScid in a TLV segment if it exists.
	if c.AliasScid != nil {
		recordProducers := []tlv.RecordProducer{c.AliasScid}
		err := EncodeMessageExtraData(&c.ExtraData, recordProducers...)
		if err != nil {
			return err
		}
	}

	return WriteBytes(w, c.ExtraData)
}

// MsgType returns the uint32 code which uniquely identifies this message as a
// ChannelReady message on the wire.
//
// This is part of the lnwire.Message interface.
func (c *ChannelReady) MsgType() MessageType {
	return MsgChannelReady
}