[feature] Generate default config file, if file is missing

Author: g3force

internal/app/config/config.go

@@ -3,7 +3,9 @@ package config
 import (
 	"github.com/pkg/errors"
 	"gopkg.in/yaml.v2"
+	"io/ioutil"
 	"os"
+	"path/filepath"
 	"time"
 )
 
@@ -103,20 +105,34 @@ func LoadControllerConfig(fileName string) (config Controller, err error) {
 	if err != nil {
 		return
 	}
-
-	b, err := readAll(f)
+	b, err := ioutil.ReadAll(f)
 	if err != nil {
 		return
 	}
 
 	err = yaml.Unmarshal(b, &config)
 	if err != nil {
-		err = errors.Errorf("Could not unmarshal config file %v. %v", fileName, err)
+		err = errors.Wrapf(err, "Could not unmarshal config file %v. %v", fileName)
 	}
 
 	return
 }
 
+func (c *Controller) WriteTo(fileName string) (err error) {
+	b, err := yaml.Marshal(c)
+	if err != nil {
+		err = errors.Wrapf(err, "Could not marshal config %v", c)
+		return
+	}
+	err = os.MkdirAll(filepath.Dir(fileName), 0755)
+	if err != nil {
+		err = errors.Wrapf(err, "Could not create directly for config file: %v", fileName)
+		return
+	}
+	err = ioutil.WriteFile(fileName, b, 0600)
+	return
+}
+
 // DefaultControllerConfig creates a config with default values
 func DefaultControllerConfig() (c Controller) {
 	c.Network.PublishAddress = "224.5.23.1:10003"
@@ -180,15 +196,3 @@ func DefaultControllerConfig() (c Controller) {
 
 	return
 }
-
-func readAll(f *os.File) ([]byte, error) {
-	b := make([]byte, 10000)
-	n, err := f.Read(b)
-	if err != nil {
-		return []byte{}, errors.Errorf("Can not read config files: %v", err)
-	}
-	if n == len(b) {
-		return []byte{}, errors.New("Buffer size for reading config file is too small")
-	}
-	return b[:n], nil
-}

internal/app/controller/controller.go

@@ -202,6 +202,12 @@ func loadConfig() config.Controller {
 	cfg, err := config.LoadControllerConfig(configFileName)
 	if err != nil {
 		log.Printf("Could not load config: %v", err)
+		err = cfg.WriteTo(configFileName)
+		if err != nil {
+			log.Printf("Failed to write a default config file to %v: %v", configFileName, err)
+		} else {
+			log.Println("New default config has been written to ", configFileName)
+		}
 	}
 	return cfg
 }