added config pkg

internal/config/config.go

@@ -0,0 +1,94 @@
+package config
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/BurntSushi/toml"
+	"github.com/caos/logging"
+	"github.com/ghodss/yaml"
+
+	"github.com/caos/zitadel/internal/errors"
+)
+
+type Reader interface {
+	Unmarshal(data []byte, o interface{}) error
+}
+
+type ValidatableConfiguration interface {
+	Validate() error
+}
+
+type ReaderFunc func(data []byte, o interface{}) error
+
+func (c ReaderFunc) Unmarshal(data []byte, o interface{}) error {
+	return c(data, o)
+}
+
+var (
+	JSONReader = ReaderFunc(json.Unmarshal)
+	TOMLReader = ReaderFunc(toml.Unmarshal)
+	YAMLReader = ReaderFunc(func(y []byte, o interface{}) error {
+		return yaml.Unmarshal(y, o)
+	})
+)
+
+// Read deserializes each config file to the target obj
+// using a Reader (depending on file extension)
+// env vars are replaced in the config file as well as the file path
+func Read(obj interface{}, configFiles ...string) error {
+	for _, cf := range configFiles {
+		configReader, err := configReaderForFile(cf)
+		if err != nil {
+			return err
+		}
+		if err := readConfigFile(configReader, cf, obj); err != nil {
+			return err
+		}
+	}
+
+	if validatable, ok := obj.(ValidatableConfiguration); ok {
+		if err := validatable.Validate(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func readConfigFile(configReader Reader, configFile string, obj interface{}) error {
+	configFile = os.ExpandEnv(configFile)
+
+	if _, err := os.Stat(configFile); err != nil {
+		logging.LogWithFields("CONFI-Hs93M", "file", configFile).WithError(err).Warn("config file does not exist")
+		return nil
+	}
+
+	configStr, err := ioutil.ReadFile(configFile)
+	if err != nil {
+		return errors.ThrowInternalf(err, "CONFI-nJk2a", "failed to read config file %s", configFile)
+	}
+
+	configStr = []byte(os.ExpandEnv(string(configStr)))
+
+	if err := configReader.Unmarshal(configStr, obj); err != nil {
+		return errors.ThrowInternalf(err, "CONFI-2Mc3c", "error parse config file %s", configFile)
+	}
+
+	return nil
+}
+
+func configReaderForFile(configFile string) (Reader, error) {
+	ext := filepath.Ext(configFile)
+	switch ext {
+	case ".yaml", ".yml":
+		return YAMLReader, nil
+	case ".json":
+		return JSONReader, nil
+	case ".toml":
+		return TOMLReader, nil
+	}
+	return nil, errors.ThrowUnimplementedf(nil, "file extension (%s) not supported", ext)
+}