1 files changed, 126 insertions, 0 deletions
diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..3c93d53
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,126 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"strings"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/rs/zerolog"
+	"github.com/spf13/pflag"
+	"github.com/spf13/viper"
+)
+
+type LoggerConfig struct {
+	Verbose bool   `mapstructure:"verbose"`
+	Format  string `mapstructure:"format"`
+}
+
+func (c *LoggerConfig) MarshalZerologObject(e *zerolog.Event) {
+	e.
+		Bool("verbose", c.Verbose).
+		Str("format", c.Format)
+}
+
+type SomethingConfig struct {
+	Value int `mapstructure:"value"`
+}
+
+func (c *SomethingConfig) MarshalZerologObject(event *zerolog.Event) {
+	event.
+		Int("value", c.Value)
+}
+
+type MainConfig struct {
+	Something SomethingConfig `mapstructure:"something"`
+	Logger    LoggerConfig    `mapstructure:"logger"`
+
+	configFile string
+}
+
+func (c *MainConfig) MarshalZerologObject(event *zerolog.Event) {
+	event.
+		Str("config-file", c.configFile).
+		Object("logger", &c.Logger).
+		Object("something", &c.Something)
+}
+
+func addLoggerOptions() {
+	pflag.Bool("verbose", false, "log at debug level")
+	viper.BindPFlag("logger.verbose", pflag.Lookup("verbose")) //nolint:errcheck
+	pflag.String("log-format", "json", "logging format (json, console)")
+	viper.BindPFlag("logger.format", pflag.Lookup("log-format")) //nolint:errcheck
+}
+
+func addSomethingOptions() {
+	pflag.Int("something-value", 123, "value used to do something")
+	viper.BindPFlag("something.value", pflag.Lookup("something-value")) //nolint:errcheck
+	viper.BindEnv("something.value", "SOMETHING_VALUE")                 //nolint:errcheck
+}
+
+func addConfigFromFile(configRelPath string) error {
+	mode := os.Getenv("RUN_MODE")
+	if mode == "" {
+		mode = "development"
+	}
+
+	viper.SetConfigName("example." + mode)
+
+	myName, err := os.Executable()
+	if err == nil && !strings.HasPrefix(configRelPath, "/") {
+		myDir := path.Dir(myName)
+		viper.AddConfigPath(path.Join(myDir, configRelPath))
+	} else {
+		viper.AddConfigPath(configRelPath)
+	}
+
+	err = viper.ReadInConfig()
+	if err != nil {
+		var notFound viper.ConfigFileNotFoundError
+		if !errors.As(err, &notFound) {
+			return fmt.Errorf("failed to read config file at %s: %w", viper.ConfigFileUsed(), err)
+		}
+	}
+
+	return nil
+}
+
+func loadConfigFromFile(path string) (MainConfig, error) {
+	pathFromEnv := os.Getenv("EXAMPLE_CONFIG")
+	if pathFromEnv != "" {
+		path = pathFromEnv
+	}
+
+	err := addConfigFromFile(path)
+	if err != nil {
+		return MainConfig{}, err
+	}
+
+	var config MainConfig
+
+	err = viper.Unmarshal(&config, viper.DecodeHook(
+		mapstructure.ComposeDecodeHookFunc(
+			mapstructure.StringToTimeDurationHookFunc(),
+			mapstructure.StringToIPHookFunc(),
+		),
+	))
+	if err != nil {
+		return MainConfig{}, fmt.Errorf("failed to parse options: %w", err)
+	}
+
+	config.configFile = viper.ConfigFileUsed()
+
+	return config, nil
+}
+
+func GetMainConfig(path string) (MainConfig, error) {
+	addLoggerOptions()
+	addSomethingOptions()
+
+	pflag.Parse()
+	viper.BindPFlags(pflag.CommandLine) //nolint:errcheck
+
+	return loadConfigFromFile(path)
+}