From f6614dd4350c5a04fc7ada68a60a75ccd5bf62ce Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Tue, 19 Nov 2019 19:46:32 -0800
Subject: [PATCH] channeldb: add new AbandonChannel method

---
 channeldb/db.go      | 48 +++++++++++++++++++++++++++++++++
 channeldb/db_test.go | 64 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)

diff --git a/channeldb/db.go b/channeldb/db.go
index a67ccd2f..e8a8e5af 100644
--- a/channeldb/db.go
+++ b/channeldb/db.go
@@ -1094,6 +1094,54 @@ func (d *DB) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr, error) {
 	return dedupedAddrs, nil
 }
 
+// AbandonChannel attempts to remove the target channel from the open channel
+// database. If the channel was already removed (has a closed channel entry),
+// then we'll return a nil error. Otherwise, we'll insert a new close summary
+// into the database.
+func (d *DB) AbandonChannel(chanPoint *wire.OutPoint, bestHeight uint32) error {
+	// With the chanPoint constructed, we'll attempt to find the target
+	// channel in the database. If we can't find the channel, then we'll
+	// return the error back to the caller.
+	dbChan, err := d.FetchChannel(*chanPoint)
+	switch {
+	// If the channel wasn't found, then it's possible that it was already
+	// abandoned from the database.
+	case err == ErrChannelNotFound:
+		_, closedErr := d.FetchClosedChannel(chanPoint)
+		if closedErr != nil {
+			return closedErr
+		}
+
+		// If the channel was already closed, then we don't return an
+		// error as we'd like fro this step to be repeatable.
+		return nil
+	case err != nil:
+		return err
+	}
+
+	// Now that we've found the channel, we'll populate a close summary for
+	// the channel, so we can store as much information for this abounded
+	// channel as possible. We also ensure that we set Pending to false, to
+	// indicate that this channel has been "fully" closed.
+	summary := &ChannelCloseSummary{
+		CloseType:               Abandoned,
+		ChanPoint:               *chanPoint,
+		ChainHash:               dbChan.ChainHash,
+		CloseHeight:             bestHeight,
+		RemotePub:               dbChan.IdentityPub,
+		Capacity:                dbChan.Capacity,
+		SettledBalance:          dbChan.LocalCommitment.LocalBalance.ToSatoshis(),
+		ShortChanID:             dbChan.ShortChanID(),
+		RemoteCurrentRevocation: dbChan.RemoteCurrentRevocation,
+		RemoteNextRevocation:    dbChan.RemoteNextRevocation,
+		LocalChanConfig:         dbChan.LocalChanCfg,
+	}
+
+	// Finally, we'll close the channel in the DB, and return back to the
+	// caller.
+	return dbChan.CloseChannel(summary)
+}
+
 // syncVersions function is used for safe db version synchronization. It
 // applies migration functions to the current database and recovers the
 // previous state of db if at least one error/panic appeared during migration.
diff --git a/channeldb/db_test.go b/channeldb/db_test.go
index 198f6e2b..4deffe98 100644
--- a/channeldb/db_test.go
+++ b/channeldb/db_test.go
@@ -469,3 +469,67 @@ func TestRestoreChannelShells(t *testing.T) {
 		t.Fatalf("only a single edge should be inserted: %v", err)
 	}
 }
+
+// TestAbandonChannel tests that the AbandonChannel method is able to properly
+// remove a channel from the database and add a close channel summary. If
+// called after a channel has already been removed, the method shouldn't return
+// an error.
+func TestAbandonChannel(t *testing.T) {
+	t.Parallel()
+
+	cdb, cleanUp, err := makeTestDB()
+	if err != nil {
+		t.Fatalf("unable to make test database: %v", err)
+	}
+	defer cleanUp()
+
+	// If we attempt to abandon the state of a channel that doesn't exist
+	// in the open or closed channel bucket, then we should receive an
+	// error.
+	err = cdb.AbandonChannel(&wire.OutPoint{}, 0)
+	if err == nil {
+		t.Fatalf("removing non-existent channel should have failed")
+	}
+
+	// We'll now create a new channel to abandon shortly.
+	chanState, err := createTestChannelState(cdb)
+	if err != nil {
+		t.Fatalf("unable to create channel state: %v", err)
+	}
+	addr := &net.TCPAddr{
+		IP:   net.ParseIP("127.0.0.1"),
+		Port: 18555,
+	}
+	err = chanState.SyncPending(addr, 10)
+	if err != nil {
+		t.Fatalf("unable to sync pending channel: %v", err)
+	}
+
+	// We should now be able to abandon the channel without any errors.
+	closeHeight := uint32(11)
+	err = cdb.AbandonChannel(&chanState.FundingOutpoint, closeHeight)
+	if err != nil {
+		t.Fatalf("unable to abandon channel: %v", err)
+	}
+
+	// At this point, the channel should no longer be found in the set of
+	// open channels.
+	_, err = cdb.FetchChannel(chanState.FundingOutpoint)
+	if err != ErrChannelNotFound {
+		t.Fatalf("channel should not have been found: %v", err)
+	}
+
+	// However we should be able to retrieve a close channel summary for
+	// the channel.
+	_, err = cdb.FetchClosedChannel(&chanState.FundingOutpoint)
+	if err != nil {
+		t.Fatalf("unable to fetch closed channel: %v", err)
+	}
+
+	// Finally, if we attempt to abandon the channel again, we should get a
+	// nil error as the channel has already been abandoned.
+	err = cdb.AbandonChannel(&chanState.FundingOutpoint, closeHeight)
+	if err != nil {
+		t.Fatalf("unable to abandon channel: %v", err)
+	}
+}