multi: add labels to lnd native transactions

Follow up labelling of external transactions with labels for the
transaction types we create within lnd. Since these labels will live
a life of string matching, a version number and rigid format is added
so that string matching is less painful. We start out with channel ID,
where available, and a transaction "type". External labels, added in a
previous PR, are not updated to this new versioned label because they
are not lnd-initiated transactions. Label matching can check this case,
then check for a version number.

labels/labels.go

@@ -1,12 +1,24 @@
 // Package labels contains labels used to label transactions broadcast by lnd.
 // These labels are used across packages, so they are declared in a separate
 // package to avoid dependency issues.
+//
+// Labels for transactions broadcast by lnd have two set fields followed by an
+// optional set labelled data values, all separated by colons.
+// - Label version: an integer that indicates the version lnd used
+// - Label type: the type of transaction we are labelling
+// - {field name}-{value}: a named field followed by its value, these items are
+//   optional, and there may be more than field present.
+//
+// For version 0 we have the following optional data fields defined:
+// - shortchanid: the short channel ID that a transaction is associated with,
+//   with its value set to the uint64 short channel id.
 package labels
 
 import (
 	"fmt"
 
 	"github.com/btcsuite/btcwallet/wtxmgr"
+	"github.com/lightningnetwork/lnd/lnwire"
 )
 
 // External labels a transaction as user initiated via the api. This
@@ -31,3 +43,50 @@ func ValidateAPI(label string) (string, error) {
 
 	return label, nil
 }
+
+// LabelVersion versions our labels so they can be easily update to contain
+// new data while still easily string matched.
+type LabelVersion uint8
+
+// LabelVersionZero is the label version for labels that contain label type and
+// channel ID (where available).
+const LabelVersionZero LabelVersion = iota
+
+// LabelType indicates the type of label we are creating. It is a string rather
+// than an int for easy string matching and human-readability.
+type LabelType string
+
+const (
+	// LabelTypeChannelOpen is used to label channel opens.
+	LabelTypeChannelOpen LabelType = "openchannel"
+
+	// LabelTypeChannelClose is used to label channel closes.
+	LabelTypeChannelClose LabelType = "closechannel"
+
+	// LabelTypeJusticeTransaction is used to label justice transactions.
+	LabelTypeJusticeTransaction LabelType = "justicetx"
+
+	// LabelTypeSweepTransaction is used to label sweeps.
+	LabelTypeSweepTransaction LabelType = "sweep"
+)
+
+// LabelField is used to tag a value within a label.
+type LabelField string
+
+const (
+	// ShortChanID is used to tag short channel id values in our labels.
+	ShortChanID LabelField = "shortchanid"
+)
+
+// MakeLabel creates a label with the provided type and short channel id. If
+// our short channel ID is not known, we simply return version:label_type. If
+// we do have a short channel ID set, the label will also contain its value:
+// shortchanid-{int64 chan ID}.
+func MakeLabel(labelType LabelType, channelID *lnwire.ShortChannelID) string {
+	if channelID == nil {
+		return fmt.Sprintf("%v:%v", LabelVersionZero, labelType)
+	}
+
+	return fmt.Sprintf("%v:%v:%v-%v", LabelVersionZero, labelType,
+		ShortChanID, channelID.ToUint64())
+}