env.go

package env

import (
	"fmt"
	"net"
	"os"
	"reflect"
	"strconv"
	"strings"

	"github.com/joho/godotenv"
)

type Env struct {
	MinioAddress         string `env:"MINIO_ADDRESS" help:"The URL used to access MinIO."`
	MinioAccessKeyId     string `env:"MINIO_ACCESS_KEY_ID" help:"The ID of the access key used to connect to MinIO."`
	MinioUseSsl          bool   `env:"MINIO_USE_SSL" help:"Whether SSL should be used when connecting to MinIO."`
	MinioAccessKeySecret string `env:"MINO_ACCESS_KEY_SECRET" help:"The secret of the access key used to connect to minio."`
	SocketAddress        string `env:"SOCKET_ADDRESS" help:"The TCP address the server should listen at."`
}

func Parse(program string) Env {
	var (
		errors []fmt.Stringer
		result Env
		val    = reflect.ValueOf(&result).Elem()
		typ    = val.Type()
		prefix = strings.ToUpper(program) + "_"
	)

	err := godotenv.Load()
	if err != nil {
		errors = append(errors, LoadDotenvFailed{Err: err})
	}

	for i := 0; i < typ.NumField(); i++ {
		field := typ.Field(i)
		envTag := field.Tag.Get("env")
		fullEnvKey := prefix + envTag

		envValue, ok := os.LookupEnv(fullEnvKey)
		if !ok {
			errors = append(errors, MissingEnvVarError{Key: fullEnvKey})
			continue
		}
		if envValue == "" {
			errors = append(errors, EmptyEnvVarError{Key: fullEnvKey})
			continue
		}

		switch field.Type {
		case reflect.TypeOf((*net.TCPAddr)(nil)):
			addr, err := net.ResolveTCPAddr("tcp", envValue)
			if err != nil {
				errors = append(errors, InvalidAddressError{Key: fullEnvKey, Value: envValue, Err: err})
				continue
			}
			val.Field(i).Set(reflect.ValueOf(addr))
		case reflect.TypeOf(""):
			val.Field(i).Set(reflect.ValueOf(envValue))
		case reflect.TypeOf(true):
			boolean, err := strconv.ParseBool(envValue)
			if err != nil {
				errors = append(errors, InvalidBooleanError{Key: fullEnvKey, Value: envValue, Err: err})
				continue
			}
			val.Field(i).Set(reflect.ValueOf(boolean))
		default:
			errors = append(errors, UnsupportedTypeError{Field: field.Name, Type: field.Type.String()})
		}
	}

	if len(errors) > 0 {
		printHelp(program, Env{})
		fmt.Println()
		fmt.Println(Bold + "I faced an error parsing the following environment variables:\n" + Reset)
		for _, err := range errors {
			fmt.Println(err.String())
		}
		fmt.Println()
		os.Exit(1)
	}

	return result
}