lnrpc+rpcserver: add ConfirmationsUntilActive and ConfirmationHeight

Introduce ConfirmationsUntilActive and ConfirmationHeight in
PendingChannelsResponse_PendingChannel. ConfirmationsUntilActive indicates
the remaining confirmations needed for the channel to become active. If the
funding transaction is unconfirmed, ConfirmationsUntilActive defaults to the
total required confirmations (NumConfsRequired). ConfirmationHeight records
the block height at which the funding transaction was first confirmed; if
unconfirmed, it will be 0.

Signed-off-by: Nishant Bansal <nishant.bansal.282003@gmail.com>

rpcserver.go

@@ -3889,6 +3889,37 @@ type (
 	waitingCloseChannels []*lnrpc.PendingChannelsResponse_WaitingCloseChannel
 )
 
+// calcRemainingConfs calculates how many more confirmations are needed for a
+// pending channel to be fully confirmed. It takes into account:
+// 1. The current blockchain height
+// 2. The block height at which the funding transaction was first confirmed
+// 3. The total number of confirmations required for the channel.
+func calcRemainingConfs(pendingChan *channeldb.OpenChannel,
+	currentHeight uint32) uint32 {
+
+	// If the funding transaction hasn't been confirmed yet,
+	// we need all the required confirmations.
+	if pendingChan.ConfirmationHeight == 0 {
+		return uint32(pendingChan.NumConfsRequired)
+	}
+
+	// Calculate the target height at which the channel will be fully
+	// confirmed. The -1 is because the confirmation height of the first
+	// confirmation has to be taken into account.
+	targetConfirmationHeight := pendingChan.ConfirmationHeight +
+		uint32(pendingChan.NumConfsRequired) - 1
+
+	// In case the current height is already past the target, return 0. This
+	// should never happen because the channel should already be moved from
+	// pending to open state but we handle this case in case of timing
+	// issues.
+	if currentHeight >= targetConfirmationHeight {
+		return 0
+	}
+
+	return targetConfirmationHeight - currentHeight
+}
+
 // fetchPendingOpenChannels queries the database for a list of channels that
 // have pending open state. The returned result is used in the response of the
 // PendingChannels RPC.
@@ -3948,6 +3979,15 @@ func (r *rpcServer) fetchPendingOpenChannels() (pendingOpenChannels, error) {
 			pendingChan.BroadcastHeight()
 		fundingExpiryBlocks := int32(maxFundingHeight) - currentHeight
 
+		// Calculate remainingConfs, the number of blocks left until the
+		// funding transaction reaches the required confirmation height.
+		//
+		// ZeroConf channels are marked OPEN immediately upon creation,
+		// so they never enter the "pending" state.
+		remainingConfs := calcRemainingConfs(
+			pendingChan, uint32(currentHeight),
+		)
+
 		customChanBytes, err := encodeCustomChanData(pendingChan)
 		if err != nil {
 			return nil, fmt.Errorf("unable to encode open chan "+
@@ -3969,11 +4009,14 @@ func (r *rpcServer) fetchPendingOpenChannels() (pendingOpenChannels, error) {
 				Memo:                 string(pendingChan.Memo),
 				CustomChannelData:    customChanBytes,
 			},
-			CommitWeight:        commitWeight,
-			CommitFee:           int64(localCommitment.CommitFee),
-			FeePerKw:            int64(localCommitment.FeePerKw),
-			FundingExpiryBlocks: fundingExpiryBlocks,
-			// TODO(roasbeef): need to track confirmation height
+			CommitWeight: commitWeight,
+			CommitFee:    int64(localCommitment.CommitFee),
+			FeePerKw: int64(localCommitment.
+				FeePerKw),
+			FundingExpiryBlocks:      fundingExpiryBlocks,
+			ConfirmationsUntilActive: remainingConfs,
+			ConfirmationHeight: pendingChan.
+				ConfirmationHeight,
 		}
 	}