add rpc call for latest header information

internal/hmyapi/blockchain.go

@@ -225,3 +225,9 @@ func doCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumb
 	}
 	return res, gas, failed, err
 }
+
+// LatestHeader returns the latest header information
+func (s *PublicBlockChainAPI) LatestHeader(ctx context.Context) *HeaderInformation {
+	header, _ := s.b.HeaderByNumber(context.Background(), rpc.LatestBlockNumber) // latest header should always be available
+	return newHeaderInformation(header)
+}

internal/hmyapi/types.go

@@ -6,7 +6,9 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
+	"github.com/harmony-one/harmony/block"
 	"github.com/harmony-one/harmony/core/types"
+	common2 "github.com/harmony-one/harmony/internal/common"
 )
 
 // RPCTransaction represents a transaction that will serialize to the RPC representation of a transaction
@@ -41,6 +43,28 @@ type RPCCXReceipt struct {
 	Amount      *hexutil.Big    `json:"value"`
 }
 
+// HeaderInformation represents the latest consensus information
+type HeaderInformation struct {
+	BlockHash   common.Hash `json:"blockHash"`
+	BlockNumber uint64      `json:"blockNumber"`
+	ShardID     uint32      `json:"shardID"`
+	Leader      string      `json:"leader"`
+	ViewID      uint64      `json:"viewID"`
+	Epoch       uint64      `json:"epoch"`
+}
+
+func newHeaderInformation(header *block.Header) *HeaderInformation {
+	result := &HeaderInformation{
+		BlockHash:   header.Hash(),
+		BlockNumber: header.Number().Uint64(),
+		ShardID:     header.ShardID(),
+		Leader:      common2.MustAddressToBech32(header.Coinbase()),
+		ViewID:      header.ViewID().Uint64(),
+		Epoch:       header.Epoch().Uint64(),
+	}
+	return result
+}
+
 // newRPCCXReceipt returns a CXReceipt that will serialize to the RPC representation
 func newRPCCXReceipt(cx *types.CXReceipt, blockHash common.Hash, blockNumber uint64) *RPCCXReceipt {
 	result := &RPCCXReceipt{