feat(cli): get balance for an account (#109)

* feat(cli): get the balance of an account in wei

- accept block height as quantity of tag (only "latest" supported for now)
- allow conversion of the output from wei to ether
- accept any compatible rpc endpoint

* test(cli): initial test suite for balance command

* docs(readme): updated with balance command

* refactor(cli): factory pattern

* refactor(cli): const flags and cobra stdout support

* fix(cli): fix output redirection and little refactoring

README.md

@@ -26,8 +26,9 @@ Ethkit comes equipped with the `ethkit` CLI providing:
   with scrypt wallet encryption support.
 - **Abigen** - generate Go code from an ABI artifact file to interact with or deploy a smart
   contract.
-- **Artifacts** - parse details from a Truffle artifact file from command line such as contract
-  bytecode or the json abi
+- **Artifacts** - parse details from a Truffle artifact file from the command line such as contract
+  bytecode or the JSON abi.
+- **Balance** - retrieve the balance of an account at any block height for any supported network via RPC.
 
 ## Install
 
@@ -42,8 +43,7 @@ Ethkit comes equipped with the `ethkit` CLI providing:
 ### wallet
 
 `wallet` handles encrypted Ethereum wallet creation and management in user-supplied keyfiles.
-It allows users to create a new Ethereum wallet, import an existing Ethereum wallet from a secret
-mnemonic or print an existing wallet's secret mnemonic.
+It allows users to create a new Ethereum wallet, import an existing Ethereum wallet from a secret mnemonic, or print an existing wallet's secret mnemonic.
 
 ```bash
 Usage:
@@ -92,6 +92,21 @@ Flags:
   -h, --help          help for artifacts
 ```
 
+### balance
+
+`balance` retrieves the balance of an account via RPC by a provided address at a predefined block height.
+
+```bash
+Usage:
+  ethkit balance [account] [flags]
+
+Flags:
+  -B, --block string     The block height to query at (default "latest")
+  -e, --ether            Format the balance in ether
+  -h, --help             help for balance
+  -r, --rpc-url string   The RPC endpoint to the blockchain node to interact with
+```
+
 ## Ethkit Go Development Library
 
 Ethkit is a very capable Ethereum development library for writing systems in Go that

cmd/ethkit/balance.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math/big"
+	"net/url"
+	"strconv"
+
+	"github.com/spf13/cobra"
+
+	"github.com/0xsequence/ethkit/ethrpc"
+	"github.com/0xsequence/ethkit/go-ethereum/common"
+	"github.com/0xsequence/ethkit/go-ethereum/params"
+)
+
+const (
+	flagBalanceBlock = "block"
+	flagBalanceEther = "ether"
+	flagBalanceRpcUrl = "rpc-url"
+)
+
+func init() {
+	rootCmd.AddCommand(NewBalanceCmd())
+}
+
+func NewBalanceCmd() *cobra.Command {
+	c := &balance{}
+	cmd := &cobra.Command{
+		Use:   "balance [account]",
+		Short: "Get the balance of an account",
+		Aliases: []string{"b"},
+		Args:  cobra.ExactArgs(1),
+		RunE:  c.Run,
+	}
+
+	cmd.Flags().StringP(flagBalanceBlock, "B", "latest", "The block height to query at")
+	cmd.Flags().BoolP(flagBalanceEther, "e", false, "Format the balance in ether")
+	cmd.Flags().StringP(flagBalanceRpcUrl, "r", "", "The RPC endpoint to the blockchain node to interact with")
+
+	return cmd
+}
+
+type balance struct {
+}
+
+func (c *balance) Run(cmd *cobra.Command, args []string) error {
+	fAccount := cmd.Flags().Args()[0]
+	fBlock, err := cmd.Flags().GetString(flagBalanceBlock)
+	if err != nil {
+		return err
+	}
+	fEther, err := cmd.Flags().GetBool(flagBalanceEther)
+	if err != nil {
+		return err
+	}
+	fRpc, err := cmd.Flags().GetString(flagBalanceRpcUrl)
+	if err != nil {
+		return err
+	}
+
+	if !common.IsHexAddress(fAccount) {
+		return errors.New("error: please provide a valid account address (e.g. 0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742)")
+	}
+
+	if _, err = url.ParseRequestURI(fRpc); err != nil {
+		return errors.New("error: please provide a valid rpc url (e.g. https://nodes.sequence.app/mainnet)")
+	}
+
+	provider, err := ethrpc.NewProvider(fRpc)
+	if err != nil {
+		return err
+	}
+
+	block, err := strconv.ParseUint(fBlock, 10, 64)
+	if err != nil {
+		// TODO: implement support for all tags: earliest, latest, pending, finalized, safe
+		if fBlock == "latest" {
+			bh, err := provider.BlockNumber(context.Background())
+			if err != nil {
+				return err
+			}
+			block = bh
+		} else {
+			return errors.New("error: invalid block height")
+		}
+	}
+
+	wei, err := provider.BalanceAt(context.Background(), common.HexToAddress(fAccount), big.NewInt(int64(block)))
+	if err != nil {
+		return err
+	}
+
+	if fEther {
+		bal := weiToEther(wei)
+		fmt.Fprintln(cmd.OutOrStdout(), bal, "ether")
+	} else {
+		fmt.Fprintln(cmd.OutOrStdout(), wei, "wei")
+	}
+
+	return nil
+}
+
+// https://github.com/ethereum/go-ethereum/issues/21221
+func weiToEther(wei *big.Int) *big.Float {
+	f := new(big.Float)
+	f.SetPrec(236) //  IEEE 754 octuple-precision binary floating-point format: binary256
+	f.SetMode(big.ToNearestEven)
+	fWei := new(big.Float)
+	fWei.SetPrec(236) //  IEEE 754 octuple-precision binary floating-point format: binary256
+	fWei.SetMode(big.ToNearestEven)
+
+	return f.Quo(fWei.SetInt(wei), big.NewFloat(params.Ether))
+}

cmd/ethkit/balance_test.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func execute(args string) (string, error) {
+	cmd := NewBalanceCmd()
+	actual := new(bytes.Buffer)
+	cmd.SetOut(actual)
+	cmd.SetErr(actual)
+	cmd.SetArgs(strings.Split(args, " "))
+	if err := cmd.Execute(); err != nil {
+		return "", err
+	}
+
+	return actual.String(), nil
+}
+
+func Test_BalanceCmd(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia")
+	assert.Nil(t, err)
+	assert.NotNil(t, res)
+}
+
+func Test_BalanceCmd_ValidWei(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia")
+	assert.Nil(t, err)
+	assert.Equal(t, res, fmt.Sprintln(strconv.Itoa(500_000_000_000_000_000), "wei"))
+}
+
+func Test_BalanceCmd_ValidEther(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia --ether")
+	assert.Nil(t, err)
+	assert.Equal(t, res, fmt.Sprintln(strconv.FormatFloat(0.5, 'f', -1, 64), "ether"))
+}
+
+func Test_BalanceCmd_InvalidAddress(t *testing.T) {
+	res, err := execute("0x1 --rpc-url https://nodes.sequence.app/sepolia")
+	assert.NotNil(t, err)
+	assert.Empty(t, res)
+	assert.Contains(t, err.Error(), "please provide a valid account address")
+}
+
+func Test_BalanceCmd_InvalidRPC(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url nodes.sequence.app/sepolia")
+	assert.NotNil(t, err)
+	assert.Empty(t, res)
+	assert.Contains(t, err.Error(), "please provide a valid rpc url")
+}
+
+func Test_BalanceCmd_NotExistingBlockHeigh(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia --block " + fmt.Sprint(math.MaxInt64))
+	assert.NotNil(t, err)
+	assert.Empty(t, res)
+	assert.Contains(t, err.Error(), "jsonrpc error -32000: header not found")
+}
+
+func Test_BalanceCmd_NotAValidStringBlockHeigh(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia --block something")
+	assert.NotNil(t, err)
+	assert.Empty(t, res)
+	assert.Contains(t, err.Error(), "invalid block height")
+}
+
+func Test_BalanceCmd_NotAValidNumberBlockHeigh(t *testing.T) {
+	res, err := execute("0x213a286A1AF3Ac010d4F2D66A52DeAf762dF7742 --rpc-url https://nodes.sequence.app/sepolia --block -100")
+	assert.NotNil(t, err)
+	assert.Empty(t, res)
+}