Use preset mainnet and testnet genesis

Allow custom path by using a prefix as well

chain/public-configs/public-configs.go

@@ -0,0 +1,6 @@
+package publicconfigs
+
+const (
+	GenesisPathMainnet = "./chain/public-configs/genesis-mainnet.json"
+	GenesisPathTestnet = "./chain/public-configs/genesis-testnet.json"
+)

command/server/config/config.go

@@ -104,7 +104,7 @@ func DefaultConfig() *Config {
 	defaultNetworkConfig := network.DefaultConfig()
 
 	return &Config{
-		GenesisPath:    "./genesis.json",
+		GenesisPath:    "",
 		DataDir:        "",
 		BlockGasTarget: "0x5f5e100", // Special value signaling the parent gas limit should be applied
 		Network: &Network{

command/server/params.go

@@ -3,8 +3,10 @@ package server
 import (
 	"errors"
 	"net"
+	"strings"
 
 	"github.com/0xPolygon/polygon-edge/chain"
+	publicconfigs "github.com/0xPolygon/polygon-edge/chain/public-configs"
 	"github.com/0xPolygon/polygon-edge/command/server/config"
 	"github.com/0xPolygon/polygon-edge/network"
 	"github.com/0xPolygon/polygon-edge/secrets"
@@ -15,7 +17,7 @@ import (
 
 const (
 	configFlag                   = "config"
-	genesisPathFlag              = "chain"
+	genesisFlag                  = "chain"
 	dataDirFlag                  = "data-dir"
 	libp2pAddressFlag            = "libp2p"
 	prometheusAddressFlag        = "prometheus"
@@ -67,7 +69,8 @@ var (
 )
 
 var (
-	errInvalidNATAddress = errors.New("could not parse NAT IP address")
+	errInvalidNATAddress          = errors.New("could not parse NAT IP address")
+	errGenesisCustomPrexifMissing = errors.New("genesis path must start with 'custom:'")
 )
 
 type serverParams struct {
@@ -148,6 +151,25 @@ func (p *serverParams) setJSONLogFormat(jsonLogFormat bool) {
 	p.rawConfig.JSONLogFormat = jsonLogFormat
 }
 
+func (p *serverParams) setRawGenesisPath(genesisFlag string) error {
+	switch genesisFlag {
+	case "mainnet":
+		p.rawConfig.GenesisPath = publicconfigs.GenesisPathMainnet
+	case "testnet":
+		p.rawConfig.GenesisPath = publicconfigs.GenesisPathTestnet
+	default:
+		const customPrefix = "custom:"
+		if !strings.HasPrefix(genesisFlag, customPrefix) {
+			return errGenesisCustomPrexifMissing
+		} else {
+			actualPath := strings.TrimPrefix(genesisFlag, customPrefix)
+			p.rawConfig.GenesisPath = actualPath
+		}
+	}
+
+	return nil
+}
+
 func (p *serverParams) generateConfig() *server.Config {
 	return &server.Config{
 		Chain: p.genesisConfig,

command/server/server.go

@@ -48,9 +48,10 @@ func setFlags(cmd *cobra.Command) {
 
 	cmd.Flags().StringVar(
 		&params.rawConfig.GenesisPath,
-		genesisPathFlag,
+		genesisFlag,
 		defaultConfig.GenesisPath,
-		"the genesis file used for starting the chain",
+		"the genesis file used for starting the chain."+
+			`Can be "mainnet", "testnet" or "custom"<path_to_custom_genesis_file>"`,
 	)
 
 	cmd.Flags().StringVar(
@@ -301,6 +302,11 @@ func runPreRun(cmd *cobra.Command, _ []string) error {
 		}
 	}
 
+	// Before raw params are initialized, set the actual genesis path based on --chain flag
+	if err := params.setRawGenesisPath(params.rawConfig.GenesisPath); err != nil {
+		return err
+	}
+
 	if err := params.initRawParams(); err != nil {
 		return err
 	}