feat: add node simplified config

go.mod

@@ -0,0 +1,3 @@
+module github.com/cartesi/rollups-node
+
+go 1.21.1

internal/cmd/print_config/main.go

@@ -0,0 +1,10 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+package main
+
+import "github.com/cartesi/rollups-node/internal/pkg/config"
+
+func main() {
+	config.PrintDocumentation()
+}

internal/pkg/config/config.go

@@ -0,0 +1,35 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+// This package loads the node config from enviroment variables
+package config
+
+import (
+	"fmt"
+	"os"
+)
+
+// Prefix to all enviroment variables
+const Prefix string = "CARTESI_"
+
+// Definition of config variables.
+// For each variable declared below, there should be a entry in meta.go.
+
+var PrintConfig bool
+var LogLevel string
+
+// Prints the documentation for each variable in Stdout
+func PrintDocumentation() {
+	genDocumentation(os.Stdout)
+}
+
+// Loads the config from the environment.
+// If PrintConfig is true, prints the config to Stdout.
+// This function calls os.Exit if there is an error.
+func Load() {
+	err := loadFromEnv(os.Stdout)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}

internal/pkg/config/meta.go

@@ -0,0 +1,78 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+package config
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"slices"
+)
+
+// Describes a config variable.
+// This is useful for automatically generating documentation.
+type MetaConfig struct {
+	key          string
+	description  string
+	defaultValue string
+	parse        func(string) error
+}
+
+func (c MetaConfig) getKey() string {
+	return Prefix + c.key
+}
+
+// Meta config for each config variable
+var configs []MetaConfig = []MetaConfig{
+	{
+		"PRINT_CONFIG",
+		"If 'true' prints the config variables as they are parsed.\n" +
+			"Can be 'true' or 'false'.",
+		"true",
+		func(value string) error {
+			var err error
+			PrintConfig, err = parseBool(value)
+			return err
+		},
+	},
+	{
+		"LOG_LEVEL",
+		"Sets the log level of the node, can be 'trace', 'info', or 'warning'.",
+		"info",
+		func(value string) error {
+			valid := []string{"trace", "info", "warning"}
+			if !slices.Contains(valid, value) {
+				return errors.New("invalid value")
+			}
+			LogLevel = value
+			return nil
+		},
+	},
+}
+
+func loadFromEnv(writer io.Writer) error {
+	for _, c := range configs {
+		value, exists := os.LookupEnv(c.getKey())
+		if !exists {
+			value = c.defaultValue
+		}
+		err := c.parse(value)
+		if err != nil {
+			msg := "failed to parse %v=%v because of %v"
+			return errors.New(fmt.Sprintf(msg, c.getKey(), value, err))
+		}
+		if PrintConfig {
+			fmt.Fprintf(writer, "%v=%v\n", c.getKey(), value)
+		}
+	}
+	return nil
+}
+
+func genDocumentation(writer io.Writer) {
+	for _, c := range configs {
+		msg := "## %v\n%v\nDefault value: '%v'\n\n"
+		fmt.Fprintf(writer, msg, c.getKey(), c.description, c.defaultValue)
+	}
+}

internal/pkg/config/util.go

@@ -0,0 +1,18 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+package config
+
+import "errors"
+
+// Reads a boolean value from the string
+func parseBool(value string) (bool, error) {
+	switch value {
+	case "true":
+		return true, nil
+	case "false":
+		return false, nil
+	default:
+		return false, errors.New("invalid value")
+	}
+}