chain: add IsCurrent method to chain.Interface

IsCurrent allows us to determine if the chain backend considers itself
"current" with the chain.

chain/bitcoind_client.go

@@ -174,6 +174,20 @@ func (c *BitcoindClient) GetBlockHeaderVerbose(
 	return c.chainConn.client.GetBlockHeaderVerbose(hash)
 }
 
+// IsCurrent returns whether the chain backend considers its view of the network
+// as "current".
+func (c *BitcoindClient) IsCurrent() bool {
+	bestHash, _, err := c.GetBestBlock()
+	if err != nil {
+		return false
+	}
+	bestHeader, err := c.GetBlockHeader(bestHash)
+	if err != nil {
+		return false
+	}
+	return bestHeader.Timestamp.After(time.Now().Add(-isCurrentDelta))
+}
+
 // GetRawTransactionVerbose returns a transaction from the tx hash.
 func (c *BitcoindClient) GetRawTransactionVerbose(
 	hash *chainhash.Hash) (*btcjson.TxRawResult, error) {

chain/interface.go

@@ -10,6 +10,11 @@ import (
 	"github.com/btcsuite/btcwallet/wtxmgr"
 )
 
+// isCurrentDelta is the delta duration we'll use from the present time to
+// determine if a backend is considered "current", i.e. synced to the tip of
+// the chain.
+const isCurrentDelta = 2 * time.Hour
+
 // BackEnds returns a list of the available back ends.
 // TODO: Refactor each into a driver and use dynamic registration.
 func BackEnds() []string {
@@ -31,6 +36,7 @@ type Interface interface {
 	GetBlock(*chainhash.Hash) (*wire.MsgBlock, error)
 	GetBlockHash(int64) (*chainhash.Hash, error)
 	GetBlockHeader(*chainhash.Hash) (*wire.BlockHeader, error)
+	IsCurrent() bool
 	FilterBlocks(*FilterBlocksRequest) (*FilterBlocksResponse, error)
 	BlockStamp() (*waddrmgr.BlockStamp, error)
 	SendRawTransaction(*wire.MsgTx, bool) (*chainhash.Hash, error)

chain/neutrino.go

@@ -157,6 +157,12 @@ func (s *NeutrinoClient) GetBlockHeader(
 	return s.CS.GetBlockHeader(blockHash)
 }
 
+// IsCurrent returns whether the chain backend considers its view of the network
+// as "current".
+func (s *NeutrinoClient) IsCurrent() bool {
+	return s.CS.IsCurrent()
+}
+
 // SendRawTransaction replicates the RPC client's SendRawTransaction command.
 func (s *NeutrinoClient) SendRawTransaction(tx *wire.MsgTx, allowHighFees bool) (
 	*chainhash.Hash, error) {

chain/rpc.go

@@ -140,6 +140,20 @@ func (c *RPCClient) Stop() {
 	c.quitMtx.Unlock()
 }
 
+// IsCurrent returns whether the chain backend considers its view of the network
+// as "current".
+func (c *RPCClient) IsCurrent() bool {
+	bestHash, _, err := c.GetBestBlock()
+	if err != nil {
+		return false
+	}
+	bestHeader, err := c.GetBlockHeader(bestHash)
+	if err != nil {
+		return false
+	}
+	return bestHeader.Timestamp.After(time.Now().Add(-isCurrentDelta))
+}
+
 // Rescan wraps the normal Rescan command with an additional paramter that
 // allows us to map an oupoint to the address in the chain that it pays to.
 // This is useful when using BIP 158 filters as they include the prev pkScript

wallet/mock.go

@@ -41,6 +41,10 @@ func (m *mockChainClient) GetBlockHeader(*chainhash.Hash) (*wire.BlockHeader,
 	return nil, nil
 }
 
+func (m *mockChainClient) IsCurrent() bool {
+	return false
+}
+
 func (m *mockChainClient) FilterBlocks(*chain.FilterBlocksRequest) (
 	*chain.FilterBlocksResponse, error) {
 	return nil, nil