Load controller defaults from config

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

config.go

+package gosdn
+
+import (
+	"github.com/google/uuid"
+	"github.com/spf13/viper"
+)
+
+// Config represents the nucleus configuration
+type Config struct {
+	BasePndUUID        uuid.UUID
+	BaseSouthBoundType int32
+	BaseSouthBoundUUID uuid.UUID
+}
+
+func getUUIDFromViper(viperKey string) (uuid.UUID, error) {
+	UUIDAsString := viper.GetString(viperKey)
+	if UUIDAsString == "" {
+		newUUID := uuid.New()
+		viper.Set(viperKey, newUUID.String())
+		viper.WriteConfig()
+
+		return newUUID, nil
+	}
+
+	parsedUUID, err := uuid.Parse(UUIDAsString)
+	if err != nil {
+		return uuid.Nil, err
+	}
+
+	return parsedUUID, nil
+}
+
+// InitializeConfig loads the configuration
+func (c *Config) InitializeConfig() error {
+	var err error
+	basePNDUUIDKey := "basePNDUUID"
+	baseSouthBoundTypeKey := "baseSouthBoundType"
+	baseSouthBoundUUIDKey := "baseSouthBoundUUID"
+
+	basePNDUUID, err := getUUIDFromViper(basePNDUUIDKey)
+	if err != nil {
+		return err
+	}
+
+	c.BasePndUUID = basePNDUUID
+
+	baseSouthBoundUUID, err := getUUIDFromViper(baseSouthBoundUUIDKey)
+	if err != nil {
+		return err
+	}
+
+	c.BaseSouthBoundUUID = baseSouthBoundUUID
+
+	c.BaseSouthBoundType = viper.GetInt32("BaseSouthBoundType")
+	if c.BaseSouthBoundType != 0 {
+		viper.Set(baseSouthBoundTypeKey, 0)
+		viper.WriteConfig()
+	}
+
+	return nil
+}