From 99112e1cbd817dd7f7c5066e023129e521fd2a8b Mon Sep 17 00:00:00 2001
From: Helder Moreira <helder-moreira@users.noreply.github.com>
Date: Fri, 26 Feb 2021 15:50:22 +0000
Subject: [PATCH] init: add random chain-id generator (#797)

* init: add random chain-id generator

* Update types/chain_id.go

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Alessio Treglia <alessio@tendermint.com>
---
 client/config.go       | 20 ++++++++++++++++++++
 cmd/ethermintd/main.go |  6 ++++--
 types/chain_id.go      |  6 ++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/client/config.go b/client/config.go
index 1069e5c0..b374b0a0 100644
--- a/client/config.go
+++ b/client/config.go
@@ -61,3 +61,23 @@ func ValidateChainID(baseCmd *cobra.Command) *cobra.Command {
 	baseCmd.RunE = validateFn
 	return baseCmd
 }
+
+// GenerateChainID wraps a cobra command with a RunE function with base 10 integer chain-id random generation
+// when a chain-id is not provided.
+func GenerateChainID(baseCmd *cobra.Command) *cobra.Command {
+	// Copy base run command to be used after chain verification
+	baseRunE := baseCmd.RunE
+
+	// Function to replace command's RunE function
+	generateFn := func(cmd *cobra.Command, args []string) error {
+		chainID := viper.GetString(flags.FlagChainID)
+
+		if chainID == "" {
+			viper.Set(flags.FlagChainID, ethermint.GenerateRandomChainID())
+		}
+		return baseRunE(cmd, args)
+	}
+
+	baseCmd.RunE = generateFn
+	return baseCmd
+}
diff --git a/cmd/ethermintd/main.go b/cmd/ethermintd/main.go
index 506c22f8..e6715122 100644
--- a/cmd/ethermintd/main.go
+++ b/cmd/ethermintd/main.go
@@ -65,8 +65,10 @@ func main() {
 	}
 	// CLI commands to initialize the chain
 	rootCmd.AddCommand(
-		client.ValidateChainID(
-			genutilcli.InitCmd(ctx, cdc, app.ModuleBasics, app.DefaultNodeHome),
+		client.GenerateChainID(
+			client.ValidateChainID(
+				genutilcli.InitCmd(ctx, cdc, app.ModuleBasics, app.DefaultNodeHome),
+			),
 		),
 		genutilcli.CollectGenTxsCmd(ctx, cdc, auth.GenesisAccountIterator{}, app.DefaultNodeHome),
 		genutilcli.MigrateGenesisCmd(ctx, cdc),
diff --git a/types/chain_id.go b/types/chain_id.go
index 7bc316b1..1c54fbe2 100644
--- a/types/chain_id.go
+++ b/types/chain_id.go
@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+	tmrand "github.com/tendermint/tendermint/libs/rand"
 )
 
 var (
@@ -46,3 +47,8 @@ func ParseChainID(chainID string) (*big.Int, error) {
 
 	return chainIDInt, nil
 }
+
+// GenerateRandomChainID returns a random chain-id in the valid format.
+func GenerateRandomChainID() string {
+	return fmt.Sprintf("ethermint-%d", 10+tmrand.Intn(10000))
+}