package funding

import (
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/lightningnetwork/lnd/channeldb"
	"github.com/lightningnetwork/lnd/fn"
	"github.com/lightningnetwork/lnd/lnwallet"
	"github.com/lightningnetwork/lnd/protofsm"
)

// AuxFundingController permits the implementation of the funding of custom
// channels types. The controller serves as a MsgEndpoint which allows it to
// intercept custom messages, or even the regular funding messages. The
// controller might also pass along an aux funding desc based on an existing
// pending channel ID.
type AuxFundingController interface {
	// MsgEndpoint is the embedded interface that signals that the funding
	// controller is also a message endpoint. This'll allow it to handle
	// custom messages specific to the funding type.
	protofsm.MsgEndpoint

	// DescFromPendingChanID takes a pending channel ID, that may already be
	// known due to prior custom channel messages, and maybe returns an aux
	// funding desc which can be used to modify how a channel is funded.
	DescFromPendingChanID(pid PendingChanID,
		openChan *channeldb.OpenChannel,
		localKeyRing, remoteKeyRing lnwallet.CommitmentKeyRing,
		initiator bool) (fn.Option[lnwallet.AuxFundingDesc], error)

	// DeriveTapscriptRoot takes a pending channel ID and maybe returns a
	// tapscript root that should be used when creating any MuSig2 sessions
	// for a channel.
	DeriveTapscriptRoot(PendingChanID) (fn.Option[chainhash.Hash], error)

	// ChannelReady is called when a channel has been fully opened (multiple
	// confirmations) and is ready to be used. This can be used to perform
	// any final setup or cleanup.
	ChannelReady(openChan *channeldb.OpenChannel) error

	// ChannelFinalized is called when a channel has been fully finalized.
	// In this state, we've received the commitment sig from the remote
	// party, so we are safe to broadcast the funding transaction.
	ChannelFinalized(PendingChanID) error
}

// descFromPendingChanID takes a pending channel ID, that may already be known
// due to prior custom channel messages, and maybe returns an aux funding desc
// which can be used to modify how a channel is funded.
func descFromPendingChanID(controller fn.Option[AuxFundingController],
	chanID PendingChanID, openChan *channeldb.OpenChannel,
	localKeyRing, remoteKeyRing lnwallet.CommitmentKeyRing,
	initiator bool) (fn.Option[lnwallet.AuxFundingDesc], error) {

	var result fn.Option[lnwallet.AuxFundingDesc]
	mapErr := fn.MapOptionZ(controller, func(c AuxFundingController) error {
		var err error
		result, err = c.DescFromPendingChanID(
			chanID, openChan, localKeyRing, remoteKeyRing,
			initiator,
		)

		return err
	})

	return result, mapErr
}

// deriveTapscriptRoot takes a pending channel ID and maybe returns a
// tapscript root that should be used when creating any MuSig2 sessions for a
// channel.
func deriveTapscriptRoot(controller fn.Option[AuxFundingController],
	chanID PendingChanID) (fn.Option[chainhash.Hash], error) {

	var result fn.Option[chainhash.Hash]
	mapErr := fn.MapOptionZ(controller, func(c AuxFundingController) error {
		var err error
		result, err = c.DeriveTapscriptRoot(chanID)
		return err
	})

	return result, mapErr
}