feat: Support for config file reading

Add support for configuration files as described in #49

Author: jellonek

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/cloudoperators/greenhouse v0.8.0
 	github.com/onsi/gomega v1.38.3
 	github.com/spf13/cobra v1.10.2
+	github.com/spf13/pflag v1.0.10
 	github.com/spf13/viper v1.21.0
 	k8s.io/apimachinery v0.35.0
 	k8s.io/client-go v0.35.0
@@ -65,7 +66,6 @@ require (
 	github.com/sagikazarmark/locafero v0.12.0 // indirect
 	github.com/spf13/afero v1.15.0 // indirect
 	github.com/spf13/cast v1.10.0 // indirect
-	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect

main.go

@@ -8,8 +8,10 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"path"
 	"syscall"
 
+	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
 
 	"github.com/cloudoperators/cloudctl/cmd"
@@ -18,15 +20,69 @@ import (
 )
 
 func main() {
+	var (
+		config string
+	)
+
+	// It is assmued there that $HOME is always set to correct value
+	home := os.Getenv("HOME")
+
 	// Optionally read environment variables, config files, etc.
 	viper.SetEnvPrefix("CLOUDCTL")
 	viper.AutomaticEnv()
 
+	viper.BindPFlags(pflag.CommandLine)
+
+	pflag.StringVarP(&config, "config", "c", "", "Path to configuration file")
+	pflag.Parse()
+
+	viper.SetConfigType("yaml")
+
+	if len(config) > 0 {
+		// First we are trying config provided as command line parameter.
+		viper.SetConfigFile(config)
+	} else {
+		// Then we are searching for ".cloudctl.yaml" in current or home directory
+		viper.AddConfigPath(".")
+		viper.AddConfigPath(home)
+		viper.SetConfigName(".cloudctl")
+	}
+
+	err := viper.ReadInConfig()
+	if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+		// If reading config in above described locations failed, we are looking for configuration
+		// in these locations:
+		//   ./cloudctl.yaml
+		//   $HOME/cloudclt.yaml
+		//   $XDG_CONFIG_HOME/cloudctl/cloudctl.yaml
+		//   $XDG_CONFIG_HOME/cloudctl.yaml
+		//   $HOME/.config/cloudctl/cloudctl.yaml
+		//   $HOME/.config/cloudctl.yaml
+		viper.SetConfigName("cloudctl")
+		if xdgConfig := os.Getenv("XDG_CONFIG_HOME"); len(xdgConfig) > 0 {
+			viper.AddConfigPath(path.Join(xdgConfig, "cloudctl"))
+			viper.AddConfigPath(xdgConfig)
+		} else {
+			viper.AddConfigPath(path.Join(home, ".config", "cloudctl"))
+			viper.AddConfigPath(path.Join(home, ".config"))
+		}
+		err = viper.ReadInConfig()
+		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+			err = nil
+		}
+	}
+
+	// Show error message and exit if config file was found but failed to read.
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
 	// Graceful cancellation on SIGINT/SIGTERM
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()
 
-	if err := cmd.Execute(ctx); err != nil {
+	if err = cmd.Execute(ctx); err != nil {
 		// Print errors to stderr
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)