utxonursery: move spendable output structs to sweep package

This commit moves the output structs to a new package as a
preparation for moving more logic into that package.

sweep/input.go

@@ -0,0 +1,58 @@
+package sweep
+
+import (
+	"github.com/btcsuite/btcd/txscript"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/lnwallet"
+)
+
+// SpendableOutput an interface which can be used by the breach arbiter to
+// construct a transaction spending from outputs we control.
+type SpendableOutput interface {
+	// Amount returns the number of satoshis contained within the output.
+	Amount() btcutil.Amount
+
+	// Outpoint returns the reference to the output being spent, used to
+	// construct the corresponding transaction input.
+	OutPoint() *wire.OutPoint
+
+	// WitnessType returns an enum specifying the type of witness that must
+	// be generated in order to spend this output.
+	WitnessType() lnwallet.WitnessType
+
+	// SignDesc returns a reference to a spendable output's sign descriptor,
+	// which is used during signing to compute a valid witness that spends
+	// this output.
+	SignDesc() *lnwallet.SignDescriptor
+
+	// BuildWitness returns a valid witness allowing this output to be
+	// spent, the witness should be attached to the transaction at the
+	// location determined by the given `txinIdx`.
+	BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx,
+		hashCache *txscript.TxSigHashes,
+		txinIdx int) ([][]byte, error)
+}
+
+// CsvSpendableOutput is a SpendableOutput that contains all of the information
+// necessary to construct, sign, and sweep an output locked with a CSV delay.
+type CsvSpendableOutput interface {
+	SpendableOutput
+
+	// ConfHeight returns the height at which this output was confirmed.
+	// A zero value indicates that the output has not been confirmed.
+	ConfHeight() uint32
+
+	// SetConfHeight marks the height at which the output is confirmed in
+	// the chain.
+	SetConfHeight(height uint32)
+
+	// BlocksToMaturity returns the relative timelock, as a number of
+	// blocks, that must be built on top of the confirmation height before
+	// the output can be spent.
+	BlocksToMaturity() uint32
+
+	// OriginChanPoint returns the outpoint of the channel from which this
+	// output is derived.
+	OriginChanPoint() *wire.OutPoint
+}