chanstate: move forwarding package types

diff --git a/channeldb/forwarding_package.go b/channeldb/forwarding_package.go
index 8ba2c95..31ec1cc 100644
--- a/channeldb/forwarding_package.go
+++ b/channeldb/forwarding_package.go
@@ -2,10 +2,7 @@ package channeldb
 
 import (
 	"bytes"
-	"encoding/binary"
 	"errors"
-	"fmt"
-	"io"
 
 	cstate "github.com/lightningnetwork/lnd/chanstate"
 	"github.com/lightningnetwork/lnd/kvdb"
@@ -19,33 +16,44 @@ type (
 	// SettleFailRef is used to locate a Settle/Fail in another channel's
 	// FwdPkg.
 	SettleFailRef = cstate.SettleFailRef
-)
 
-// ErrCorruptedFwdPkg signals that the on-disk structure of the forwarding
-// package has potentially been mangled.
-var ErrCorruptedFwdPkg = errors.New("fwding package db has been corrupted")
+	// FwdState is an enum used to describe the lifecycle of a FwdPkg.
+	FwdState = cstate.FwdState
+
+	// PkgFilter is used to compactly represent a particular subset of the
+	// Adds in a forwarding package.
+	PkgFilter = cstate.PkgFilter
 
-// FwdState is an enum used to describe the lifecycle of a FwdPkg.
-type FwdState byte
+	// FwdPkg records all adds, settles, and fails that were locked in as a
+	// result of the remote peer sending us a revocation.
+	FwdPkg = cstate.FwdPkg
+)
 
 const (
 	// FwdStateLockedIn is the starting state for all forwarding packages.
-	// Packages in this state have not yet committed to the exact set of
-	// Adds to forward to the switch.
-	FwdStateLockedIn FwdState = iota
+	FwdStateLockedIn = cstate.FwdStateLockedIn
 
 	// FwdStateProcessed marks the state in which all Adds have been
-	// locally processed and the forwarding decision to the switch has been
-	// persisted.
-	FwdStateProcessed
-
-	// FwdStateCompleted signals that all Adds have been acked, and that all
-	// settles and fails have been delivered to their sources. Packages in
-	// this state can be removed permanently.
-	FwdStateCompleted
+	// locally processed.
+	FwdStateProcessed = cstate.FwdStateProcessed
+
+	// FwdStateCompleted signals that all Adds have been acked, and that
+	// all settles and fails have been delivered to their sources.
+	FwdStateCompleted = cstate.FwdStateCompleted
 )
 
 var (
+	// NewPkgFilter initializes an empty PkgFilter supporting `count`
+	// elements.
+	NewPkgFilter = cstate.NewPkgFilter
+
+	// NewFwdPkg initializes a new forwarding package in FwdStateLockedIn.
+	NewFwdPkg = cstate.NewFwdPkg
+
+	// ErrCorruptedFwdPkg signals that the on-disk structure of the
+	// forwarding package has potentially been mangled.
+	ErrCorruptedFwdPkg = errors.New("fwding package db has been corrupted")
+
 	// fwdPackagesKey is the root-level bucket that all forwarding packages
 	// are written. This bucket is further subdivided based on the short
 	// channel ID of each channel.
@@ -109,234 +117,6 @@ var (
 	settleFailFilterKey = []byte("settle-fail-filter-key")
 )
 
-// PkgFilter is used to compactly represent a particular subset of the Adds in a
-// forwarding package. Each filter is represented as a simple, statically-sized
-// bitvector, where the elements are intended to be the indices of the Adds as
-// they are written in the FwdPkg.
-type PkgFilter struct {
-	count  uint16
-	filter []byte
-}
-
-// NewPkgFilter initializes an empty PkgFilter supporting `count` elements.
-func NewPkgFilter(count uint16) *PkgFilter {
-	// We add 7 to ensure that the integer division yields properly rounded
-	// values.
-	filterLen := (count + 7) / 8
-
-	return &PkgFilter{
-		count:  count,
-		filter: make([]byte, filterLen),
-	}
-}
-
-// Count returns the number of elements represented by this PkgFilter.
-func (f *PkgFilter) Count() uint16 {
-	return f.count
-}
-
-// Set marks the `i`-th element as included by this filter.
-// NOTE: It is assumed that i is always less than count.
-func (f *PkgFilter) Set(i uint16) {
-	byt := i / 8
-	bit := i % 8
-
-	// Set the i-th bit in the filter.
-	// TODO(conner): ignore if > count to prevent panic?
-	f.filter[byt] |= byte(1 << (7 - bit))
-}
-
-// Contains queries the filter for membership of index `i`.
-// NOTE: It is assumed that i is always less than count.
-func (f *PkgFilter) Contains(i uint16) bool {
-	byt := i / 8
-	bit := i % 8
-
-	// Read the i-th bit in the filter.
-	// TODO(conner): ignore if > count to prevent panic?
-	return f.filter[byt]&(1<<(7-bit)) != 0
-}
-
-// Equal checks two PkgFilters for equality.
-func (f *PkgFilter) Equal(f2 *PkgFilter) bool {
-	if f == f2 {
-		return true
-	}
-	if f.count != f2.count {
-		return false
-	}
-
-	return bytes.Equal(f.filter, f2.filter)
-}
-
-// IsFull returns true if every element in the filter has been Set, and false
-// otherwise.
-func (f *PkgFilter) IsFull() bool {
-	// Batch validate bytes that are fully used.
-	for i := uint16(0); i < f.count/8; i++ {
-		if f.filter[i] != 0xFF {
-			return false
-		}
-	}
-
-	// If the count is not a multiple of 8, check that the filter contains
-	// all remaining bits.
-	rem := f.count % 8
-	for idx := f.count - rem; idx < f.count; idx++ {
-		if !f.Contains(idx) {
-			return false
-		}
-	}
-
-	return true
-}
-
-// Size returns number of bytes produced when the PkgFilter is serialized.
-func (f *PkgFilter) Size() uint16 {
-	// 2 bytes for uint16 `count`, then round up number of bytes required to
-	// represent `count` bits.
-	return 2 + (f.count+7)/8
-}
-
-// Encode writes the filter to the provided io.Writer.
-func (f *PkgFilter) Encode(w io.Writer) error {
-	if err := binary.Write(w, binary.BigEndian, f.count); err != nil {
-		return err
-	}
-
-	_, err := w.Write(f.filter)
-
-	return err
-}
-
-// Decode reads the filter from the provided io.Reader.
-func (f *PkgFilter) Decode(r io.Reader) error {
-	if err := binary.Read(r, binary.BigEndian, &f.count); err != nil {
-		return err
-	}
-
-	f.filter = make([]byte, f.Size()-2)
-	_, err := io.ReadFull(r, f.filter)
-
-	return err
-}
-
-// String returns a human-readable string.
-func (f *PkgFilter) String() string {
-	return fmt.Sprintf("count=%v, filter=%v", f.count, f.filter)
-}
-
-// FwdPkg records all adds, settles, and fails that were locked in as a result
-// of the remote peer sending us a revocation. Each package is identified by
-// the short chanid and remote commitment height corresponding to the revocation
-// that locked in the HTLCs. For everything except a locally initiated payment,
-// settles and fails in a forwarding package must have a corresponding Add in
-// another package, and can be removed individually once the source link has
-// received the fail/settle.
-//
-// Adds cannot be removed, as we need to present the same batch of Adds to
-// properly handle replay protection. Instead, we use a PkgFilter to mark that
-// we have finished processing a particular Add. A FwdPkg should only be deleted
-// after the AckFilter is full and all settles and fails have been persistently
-// removed.
-type FwdPkg struct {
-	// Source identifies the channel that wrote this forwarding package.
-	Source lnwire.ShortChannelID
-
-	// Height is the height of the remote commitment chain that locked in
-	// this forwarding package.
-	Height uint64
-
-	// State signals the persistent condition of the package and directs how
-	// to reprocess the package in the event of failures.
-	State FwdState
-
-	// Adds contains all add messages which need to be processed and
-	// forwarded to the switch. Adds does not change over the life of a
-	// forwarding package.
-	Adds []LogUpdate
-
-	// FwdFilter is a filter containing the indices of all Adds that were
-	// forwarded to the switch.
-	//
-	// NOTE: This value signals when persisted to disk that the fwd package
-	// has been processed and garbage collection can happen. So it also
-	// has to be set for packages with no adds (empty packages or only
-	// settle/fail packages) so that they can be garbage collected as well.
-	FwdFilter *PkgFilter
-
-	// AckFilter is a filter containing the indices of all Adds for which
-	// the source has received a settle or fail and is reflected in the next
-	// commitment txn. A package should not be removed until IsFull()
-	// returns true.
-	AckFilter *PkgFilter
-
-	// SettleFails contains all settle and fail messages that should be
-	// forwarded to the switch.
-	SettleFails []LogUpdate
-
-	// SettleFailFilter is a filter containing the indices of all Settle or
-	// Fails originating in this package that have been received and locked
-	// into the incoming link's commitment state.
-	SettleFailFilter *PkgFilter
-}
-
-// NewFwdPkg initializes a new forwarding package in FwdStateLockedIn. This
-// should be used to create a package at the time we receive a revocation.
-func NewFwdPkg(source lnwire.ShortChannelID, height uint64,
-	addUpdates, settleFailUpdates []LogUpdate) *FwdPkg {
-
-	nAddUpdates := uint16(len(addUpdates))
-	nSettleFailUpdates := uint16(len(settleFailUpdates))
-
-	return &FwdPkg{
-		Source:           source,
-		Height:           height,
-		State:            FwdStateLockedIn,
-		Adds:             addUpdates,
-		FwdFilter:        NewPkgFilter(nAddUpdates),
-		AckFilter:        NewPkgFilter(nAddUpdates),
-		SettleFails:      settleFailUpdates,
-		SettleFailFilter: NewPkgFilter(nSettleFailUpdates),
-	}
-}
-
-// SourceRef is a convenience method that returns an AddRef to this forwarding
-// package for the index in the argument. It is the caller's responsibility
-// to ensure that the index is in bounds.
-func (f *FwdPkg) SourceRef(i uint16) AddRef {
-	return AddRef{
-		Height: f.Height,
-		Index:  i,
-	}
-}
-
-// DestRef is a convenience method that returns a SettleFailRef to this
-// forwarding package for the index in the argument. It is the caller's
-// responsibility to ensure that the index is in bounds.
-func (f *FwdPkg) DestRef(i uint16) SettleFailRef {
-	return SettleFailRef{
-		Source: f.Source,
-		Height: f.Height,
-		Index:  i,
-	}
-}
-
-// ID returns an unique identifier for this package, used to ensure that sphinx
-// replay processing of this batch is idempotent.
-func (f *FwdPkg) ID() []byte {
-	var id = make([]byte, 16)
-	byteOrder.PutUint64(id[:8], f.Source.ToUint64())
-	byteOrder.PutUint64(id[8:], f.Height)
-	return id
-}
-
-// String returns a human-readable description of the forwarding package.
-func (f *FwdPkg) String() string {
-	return fmt.Sprintf("%T(src=%v, height=%v, nadds=%v, nfailsettles=%v)",
-		f, f.Source, f.Height, len(f.Adds), len(f.SettleFails))
-}
-
 // SettleFailAcker is a generic interface providing the ability to acknowledge
 // settle/fail HTLCs stored in forwarding packages.
 type SettleFailAcker interface {
diff --git a/chanstate/forwarding.go b/chanstate/forwarding.go
index 9cc830f..49728fe 100644
--- a/chanstate/forwarding.go
+++ b/chanstate/forwarding.go
@@ -1,7 +1,9 @@
 package chanstate
 
 import (
+	"bytes"
 	"encoding/binary"
+	"fmt"
 	"io"
 
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -55,3 +57,252 @@ type SettleFailRef struct {
 	// NOTE: This index is static over the lifetime of a forwarding package.
 	Index uint16
 }
+
+// FwdState is an enum used to describe the lifecycle of a FwdPkg.
+type FwdState byte
+
+const (
+	// FwdStateLockedIn is the starting state for all forwarding packages.
+	// Packages in this state have not yet committed to the exact set of
+	// Adds to forward to the switch.
+	FwdStateLockedIn FwdState = iota
+
+	// FwdStateProcessed marks the state in which all Adds have been
+	// locally processed and the forwarding decision to the switch has been
+	// persisted.
+	FwdStateProcessed
+
+	// FwdStateCompleted signals that all Adds have been acked, and that all
+	// settles and fails have been delivered to their sources. Packages in
+	// this state can be removed permanently.
+	FwdStateCompleted
+)
+
+// PkgFilter is used to compactly represent a particular subset of the Adds in a
+// forwarding package. Each filter is represented as a simple, statically-sized
+// bitvector, where the elements are intended to be the indices of the Adds as
+// they are written in the FwdPkg.
+type PkgFilter struct {
+	count  uint16
+	filter []byte
+}
+
+// NewPkgFilter initializes an empty PkgFilter supporting `count` elements.
+func NewPkgFilter(count uint16) *PkgFilter {
+	// We add 7 to ensure that the integer division yields properly rounded
+	// values.
+	filterLen := (count + 7) / 8
+
+	return &PkgFilter{
+		count:  count,
+		filter: make([]byte, filterLen),
+	}
+}
+
+// Count returns the number of elements represented by this PkgFilter.
+func (f *PkgFilter) Count() uint16 {
+	return f.count
+}
+
+// Set marks the `i`-th element as included by this filter.
+// NOTE: It is assumed that i is always less than count.
+func (f *PkgFilter) Set(i uint16) {
+	byt := i / 8
+	bit := i % 8
+
+	// Set the i-th bit in the filter.
+	// TODO(conner): ignore if > count to prevent panic?
+	f.filter[byt] |= byte(1 << (7 - bit))
+}
+
+// Contains queries the filter for membership of index `i`.
+// NOTE: It is assumed that i is always less than count.
+func (f *PkgFilter) Contains(i uint16) bool {
+	byt := i / 8
+	bit := i % 8
+
+	// Read the i-th bit in the filter.
+	// TODO(conner): ignore if > count to prevent panic?
+	return f.filter[byt]&(1<<(7-bit)) != 0
+}
+
+// Equal checks two PkgFilters for equality.
+func (f *PkgFilter) Equal(f2 *PkgFilter) bool {
+	if f == f2 {
+		return true
+	}
+	if f.count != f2.count {
+		return false
+	}
+
+	return bytes.Equal(f.filter, f2.filter)
+}
+
+// IsFull returns true if every element in the filter has been Set, and false
+// otherwise.
+func (f *PkgFilter) IsFull() bool {
+	// Batch validate bytes that are fully used.
+	for i := uint16(0); i < f.count/8; i++ {
+		if f.filter[i] != 0xFF {
+			return false
+		}
+	}
+
+	// If the count is not a multiple of 8, check that the filter contains
+	// all remaining bits.
+	rem := f.count % 8
+	for idx := f.count - rem; idx < f.count; idx++ {
+		if !f.Contains(idx) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// Size returns number of bytes produced when the PkgFilter is serialized.
+func (f *PkgFilter) Size() uint16 {
+	// 2 bytes for uint16 `count`, then round up number of bytes required to
+	// represent `count` bits.
+	return 2 + (f.count+7)/8
+}
+
+// Encode writes the filter to the provided io.Writer.
+func (f *PkgFilter) Encode(w io.Writer) error {
+	if err := binary.Write(w, binary.BigEndian, f.count); err != nil {
+		return err
+	}
+
+	_, err := w.Write(f.filter)
+
+	return err
+}
+
+// Decode reads the filter from the provided io.Reader.
+func (f *PkgFilter) Decode(r io.Reader) error {
+	if err := binary.Read(r, binary.BigEndian, &f.count); err != nil {
+		return err
+	}
+
+	f.filter = make([]byte, f.Size()-2)
+	_, err := io.ReadFull(r, f.filter)
+
+	return err
+}
+
+// String returns a human-readable string.
+func (f *PkgFilter) String() string {
+	return fmt.Sprintf("count=%v, filter=%v", f.count, f.filter)
+}
+
+// FwdPkg records all adds, settles, and fails that were locked in as a result
+// of the remote peer sending us a revocation. Each package is identified by
+// the short chanid and remote commitment height corresponding to the revocation
+// that locked in the HTLCs. For everything except a locally initiated payment,
+// settles and fails in a forwarding package must have a corresponding Add in
+// another package, and can be removed individually once the source link has
+// received the fail/settle.
+//
+// Adds cannot be removed, as we need to present the same batch of Adds to
+// properly handle replay protection. Instead, we use a PkgFilter to mark that
+// we have finished processing a particular Add. A FwdPkg should only be deleted
+// after the AckFilter is full and all settles and fails have been persistently
+// removed.
+type FwdPkg struct {
+	// Source identifies the channel that wrote this forwarding package.
+	Source lnwire.ShortChannelID
+
+	// Height is the height of the remote commitment chain that locked in
+	// this forwarding package.
+	Height uint64
+
+	// State signals the persistent condition of the package and directs how
+	// to reprocess the package in the event of failures.
+	State FwdState
+
+	// Adds contains all add messages which need to be processed and
+	// forwarded to the switch. Adds does not change over the life of a
+	// forwarding package.
+	Adds []LogUpdate
+
+	// FwdFilter is a filter containing the indices of all Adds that were
+	// forwarded to the switch.
+	//
+	// NOTE: This value signals when persisted to disk that the fwd package
+	// has been processed and garbage collection can happen. So it also
+	// has to be set for packages with no adds (empty packages or only
+	// settle/fail packages) so that they can be garbage collected as well.
+	FwdFilter *PkgFilter
+
+	// AckFilter is a filter containing the indices of all Adds for which
+	// the source has received a settle or fail and is reflected in the next
+	// commitment txn. A package should not be removed until IsFull()
+	// returns true.
+	AckFilter *PkgFilter
+
+	// SettleFails contains all settle and fail messages that should be
+	// forwarded to the switch.
+	SettleFails []LogUpdate
+
+	// SettleFailFilter is a filter containing the indices of all Settle or
+	// Fails originating in this package that have been received and locked
+	// into the incoming link's commitment state.
+	SettleFailFilter *PkgFilter
+}
+
+// NewFwdPkg initializes a new forwarding package in FwdStateLockedIn. This
+// should be used to create a package at the time we receive a revocation.
+func NewFwdPkg(source lnwire.ShortChannelID, height uint64,
+	addUpdates, settleFailUpdates []LogUpdate) *FwdPkg {
+
+	nAddUpdates := uint16(len(addUpdates))
+	nSettleFailUpdates := uint16(len(settleFailUpdates))
+
+	return &FwdPkg{
+		Source:           source,
+		Height:           height,
+		State:            FwdStateLockedIn,
+		Adds:             addUpdates,
+		FwdFilter:        NewPkgFilter(nAddUpdates),
+		AckFilter:        NewPkgFilter(nAddUpdates),
+		SettleFails:      settleFailUpdates,
+		SettleFailFilter: NewPkgFilter(nSettleFailUpdates),
+	}
+}
+
+// SourceRef is a convenience method that returns an AddRef to this forwarding
+// package for the index in the argument. It is the caller's responsibility
+// to ensure that the index is in bounds.
+func (f *FwdPkg) SourceRef(i uint16) AddRef {
+	return AddRef{
+		Height: f.Height,
+		Index:  i,
+	}
+}
+
+// DestRef is a convenience method that returns a SettleFailRef to this
+// forwarding package for the index in the argument. It is the caller's
+// responsibility to ensure that the index is in bounds.
+func (f *FwdPkg) DestRef(i uint16) SettleFailRef {
+	return SettleFailRef{
+		Source: f.Source,
+		Height: f.Height,
+		Index:  i,
+	}
+}
+
+// ID returns an unique identifier for this package, used to ensure that sphinx
+// replay processing of this batch is idempotent.
+func (f *FwdPkg) ID() []byte {
+	var id = make([]byte, 16)
+	binary.BigEndian.PutUint64(id[:8], f.Source.ToUint64())
+	binary.BigEndian.PutUint64(id[8:], f.Height)
+
+	return id
+}
+
+// String returns a human-readable description of the forwarding package.
+func (f *FwdPkg) String() string {
+	return fmt.Sprintf("%T(src=%v, height=%v, nadds=%v, nfailsettles=%v)",
+		f, f.Source, f.Height, len(f.Adds), len(f.SettleFails))
+}