Add JSON unmarshal for subkey inspect (#98)

* Revert "Add ExtrinsicSignatureV5 (#68)"

This reverts commit 461cf42.

* Add JSON unmarshal for subkey inspect

Author: mikiquantum

README.md

@@ -13,6 +13,11 @@ This client is modelled after [polkadot-js/api](https://github.com/polkadot-js/a
 
 This package is feature complete, but it is relatively new and might still contain bugs. We advice to use it with caution in production. It comes without any warranties, please refer to LICENCE for details.
 
+## Requirements
+Substrate Key Management requires `subkey` to be present in your PATH: https://substrate.dev/docs/en/knowledgebase/integrate/subkey
+
+The `subkey` recommended version: https://github.com/paritytech/substrate/releases/tag/v2.0.0-rc6 
+
 ## Documentation & Usage Examples
 
 Please refer to https://godoc.org/github.com/centrifuge/go-substrate-rpc-client

signature/signature.go

@@ -18,10 +18,10 @@ package signature
 
 import (
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
 	"os"
 	"os/exec"
-	"regexp"
 	"strings"
 
 	"golang.org/x/crypto/blake2b"
@@ -38,9 +38,14 @@ type KeyringPair struct {
 	PublicKey []byte
 }
 
-var rePubKey = regexp.MustCompile(`Public key \(hex\): 0x([a-f0-9]*)\n`)
-var reAddressOld = regexp.MustCompile(`Address \(SS58\): ([a-zA-Z0-9]*)\n`)
-var reAddressNew = regexp.MustCompile(`SS58 Address:\s+([a-zA-Z0-9]*)\n`)
+// InspectKeyInfo type is used as target from `subkey` inspect JSON output
+type InspectKeyInfo struct {
+	AccountID    string `json:"accountId"`
+	PublicKey    string `json:"publicKey"`
+	SecretPhrase string `json:"secretPhrase"`
+	SecretSeed   string `json:"secretSeed"`
+	SS58Address  string `json:"ss58Address"`
+}
 
 // KeyringPairFromSecret creates KeyPair based on seed/phrase and network
 // Leave network empty for default behavior
@@ -49,7 +54,7 @@ func KeyringPairFromSecret(seedOrPhrase, network string) (KeyringPair, error) {
 	if network != "" {
 		args = []string{"--network", network}
 	}
-	args = append([]string{"inspect", seedOrPhrase}, args...)
+	args = append([]string{"inspect", "--output-type", "Json", seedOrPhrase}, args...)
 
 	// use "subkey" command for creation of public key and address
 	cmd := exec.Command(subkeyCmd, args...)
@@ -64,29 +69,21 @@ func KeyringPairFromSecret(seedOrPhrase, network string) (KeyringPair, error) {
 		return KeyringPair{}, fmt.Errorf("failed to generate keyring pair from secret: invalid phrase/URI given")
 	}
 
-	// find the pub key
-	resPk := rePubKey.FindStringSubmatch(string(out))
-	if len(resPk) != 2 {
-		return KeyringPair{}, fmt.Errorf("failed to generate keyring pair from secret, pubkey not found in output: %v", resPk)
-	}
-	pk, err := hex.DecodeString(resPk[1])
+	var keyInfo InspectKeyInfo
+	err = json.Unmarshal(out, &keyInfo)
 	if err != nil {
-		return KeyringPair{}, fmt.Errorf("failed to generate keyring pair from secret, could not hex decode pubkey: %v",
-			resPk[1])
+		return KeyringPair{}, fmt.Errorf("failed to deserialize key info JSON output: %v", err.Error())
 	}
 
-	// find the address
-	addr := reAddressNew.FindStringSubmatch(string(out))
-	if len(addr) != 2 {
-		addr = reAddressOld.FindStringSubmatch(string(out))
-	}
-	if len(addr) != 2 {
-		return KeyringPair{}, fmt.Errorf("failed to generate keyring pair from secret, address not found in output: %v", addr)
+	pk, err := hex.DecodeString(strings.Replace(keyInfo.PublicKey, "0x", "", 1))
+	if err != nil {
+		return KeyringPair{}, fmt.Errorf("failed to generate keyring pair from secret, could not hex decode pubkey: "+
+			"%v with error: %v", keyInfo.PublicKey, err.Error())
 	}
 
 	return KeyringPair{
 		URI:       seedOrPhrase,
-		Address:   addr[1],
+		Address:   keyInfo.SS58Address,
 		PublicKey: pk,
 	}, nil
 }