feat: added config implementation using viper

cmd/root.go

@@ -4,10 +4,13 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"strings"
 
 	logger "git.towk2.me/towk/makeshift/pkg/log"
 	"github.com/rs/zerolog/log"
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+	"github.com/spf13/viper"
 )
 
 var (
@@ -30,6 +33,9 @@ var rootCmd = cobra.Command{
 			log.Error().Err(err).Msg("failed to initialize logger")
 			os.Exit(1)
 		}
+
+		// You can bind cobra and viper in a few locations, but PersistencePreRunE on the root command works well
+		err = initializeConfig(cmd)
 	},
 	Run: func(cmd *cobra.Command, args []string) {
 		// try and set flags using env vars
@@ -127,3 +133,58 @@ func writeFiles(path string, body []byte) {
 		os.Exit(1)
 	}
 }
+
+// Bind each cobra flag to its associated viper configuration (config file and environment variable)
+func bindFlags(cmd *cobra.Command, v *viper.Viper) {
+	cmd.Flags().VisitAll(func(f *pflag.Flag) {
+		// Determine the naming convention of the flags when represented in the config file
+		configName := f.Name
+
+		// Apply the viper config value to the flag when the flag is not set and viper has a value
+		if !f.Changed && v.IsSet(configName) {
+			val := v.Get(configName)
+			cmd.Flags().Set(f.Name, fmt.Sprintf("%v", val))
+		}
+	})
+}
+
+func initializeConfig(cmd *cobra.Command) error {
+	v := viper.New()
+
+	// Set the base name of the config file, without the file extension.
+	v.SetConfigName("makeshift")
+
+	// Set as many paths as you like where viper should look for the
+	// config file. We are only looking in the current working directory.
+	v.AddConfigPath(".")
+
+	// Attempt to read the config file, gracefully ignoring errors
+	// caused by a config file not being found. Return an error
+	// if we cannot parse the config file.
+	if err := v.ReadInConfig(); err != nil {
+		// It's okay if there isn't a config file
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			return err
+		}
+	}
+
+	// When we bind flags to environment variables expect that the
+	// environment variables are prefixed, e.g. a flag like --number
+	// binds to an environment variable STING_NUMBER. This helps
+	// avoid conflicts.
+	v.SetEnvPrefix("MAKESHIFT")
+
+	// Environment variables can't have dashes in them, so bind them to their equivalent
+	// keys with underscores, e.g. --favorite-color to STING_FAVORITE_COLOR
+	v.SetEnvKeyReplacer(strings.NewReplacer("-", "_"))
+
+	// Bind to environment variables
+	// Works great for simple config names, but needs help for names
+	// like --favorite-color which we fix in the bindFlags function
+	v.AutomaticEnv()
+
+	// Bind the current command's flags to viper
+	bindFlags(cmd, v)
+
+	return nil
+}