From dccef4c8bf28f2c92fa5c82e5f677864fad0a35a Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Fri, 26 Apr 2019 17:20:36 -0700
Subject: [PATCH] watchtower/wtdb/codec: import channeldb code for extension

---
 watchtower/wtdb/codec.go | 143 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 watchtower/wtdb/codec.go

diff --git a/watchtower/wtdb/codec.go b/watchtower/wtdb/codec.go
new file mode 100644
index 000000000..2fd30196f
--- /dev/null
+++ b/watchtower/wtdb/codec.go
@@ -0,0 +1,143 @@
+package wtdb
+
+import (
+	"io"
+
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/watchtower/blob"
+	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
+)
+
+// UnknownElementType is an alias for channeldb.UnknownElementType.
+type UnknownElementType = channeldb.UnknownElementType
+
+// ReadElement deserializes a single element from the provided io.Reader.
+func ReadElement(r io.Reader, element interface{}) error {
+	err := channeldb.ReadElement(r, element)
+	switch {
+
+	// Known to channeldb codec.
+	case err == nil:
+		return nil
+
+	// Fail if error is not UnknownElementType.
+	case err != nil:
+		if _, ok := err.(UnknownElementType); !ok {
+			return err
+		}
+	}
+
+	// Process any wtdb-specific extensions to the codec.
+	switch e := element.(type) {
+
+	case *SessionID:
+		if _, err := io.ReadFull(r, e[:]); err != nil {
+			return err
+		}
+
+	case *BreachHint:
+		if _, err := io.ReadFull(r, e[:]); err != nil {
+			return err
+		}
+
+	case *wtpolicy.Policy:
+		var (
+			blobType     uint16
+			sweepFeeRate uint64
+		)
+		err := channeldb.ReadElements(r,
+			&blobType,
+			&e.MaxUpdates,
+			&e.RewardBase,
+			&e.RewardRate,
+			&sweepFeeRate,
+		)
+		if err != nil {
+			return err
+		}
+
+		e.BlobType = blob.Type(blobType)
+		e.SweepFeeRate = lnwallet.SatPerKWeight(sweepFeeRate)
+
+	// Type is still unknown to wtdb extensions, fail.
+	default:
+		return channeldb.NewUnknownElementType(
+			"ReadElement", element,
+		)
+	}
+
+	return nil
+}
+
+// WriteElement serializes a single element into the provided io.Writer.
+func WriteElement(w io.Writer, element interface{}) error {
+	err := channeldb.WriteElement(w, element)
+	switch {
+
+	// Known to channeldb codec.
+	case err == nil:
+		return nil
+
+	// Fail if error is not UnknownElementType.
+	case err != nil:
+		if _, ok := err.(UnknownElementType); !ok {
+			return err
+		}
+	}
+
+	// Process any wtdb-specific extensions to the codec.
+	switch e := element.(type) {
+
+	case SessionID:
+		if _, err := w.Write(e[:]); err != nil {
+			return err
+		}
+
+	case BreachHint:
+		if _, err := w.Write(e[:]); err != nil {
+			return err
+		}
+
+	case wtpolicy.Policy:
+		return channeldb.WriteElements(w,
+			uint16(e.BlobType),
+			e.MaxUpdates,
+			e.RewardBase,
+			e.RewardRate,
+			uint64(e.SweepFeeRate),
+		)
+
+	// Type is still unknown to wtdb extensions, fail.
+	default:
+		return channeldb.NewUnknownElementType(
+			"WriteElement", element,
+		)
+	}
+
+	return nil
+}
+
+// WriteElements serializes a variadic list of elements into the given
+// io.Writer.
+func WriteElements(w io.Writer, elements ...interface{}) error {
+	for _, element := range elements {
+		if err := WriteElement(w, element); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// ReadElements deserializes the provided io.Reader into a variadic list of
+// target elements.
+func ReadElements(r io.Reader, elements ...interface{}) error {
+	for _, element := range elements {
+		if err := ReadElement(r, element); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}