rpc: refactor rpc packages and backend to support cosmos namespace (#1070)

* rpc: refactor rpc packages and backend to support cosmos namespace

* changelog

* typo

rpc/namespaces/ethereum/net/api.go

@@ -0,0 +1,55 @@
+package net
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/cosmos/cosmos-sdk/client"
+	rpcclient "github.com/tendermint/tendermint/rpc/client"
+	ethermint "github.com/tharsis/ethermint/types"
+)
+
+// PublicAPI is the eth_ prefixed set of APIs in the Web3 JSON-RPC spec.
+type PublicAPI struct {
+	networkVersion uint64
+	tmClient       rpcclient.Client
+}
+
+// NewPublicAPI creates an instance of the public Net Web3 API.
+func NewPublicAPI(clientCtx client.Context) *PublicAPI {
+	// parse the chainID from a integer string
+	chainIDEpoch, err := ethermint.ParseChainID(clientCtx.ChainID)
+	if err != nil {
+		panic(err)
+	}
+
+	return &PublicAPI{
+		networkVersion: chainIDEpoch.Uint64(),
+		tmClient:       clientCtx.Client,
+	}
+}
+
+// Version returns the current ethereum protocol version.
+func (s *PublicAPI) Version() string {
+	return fmt.Sprintf("%d", s.networkVersion)
+}
+
+// Listening returns if client is actively listening for network connections.
+func (s *PublicAPI) Listening() bool {
+	ctx := context.Background()
+	netInfo, err := s.tmClient.NetInfo(ctx)
+	if err != nil {
+		return false
+	}
+	return netInfo.Listening
+}
+
+// PeerCount returns the number of peers currently connected to the client.
+func (s *PublicAPI) PeerCount() int {
+	ctx := context.Background()
+	netInfo, err := s.tmClient.NetInfo(ctx)
+	if err != nil {
+		return 0
+	}
+	return len(netInfo.Peers)
+}