Merge branch 'ft/decode-config'

Author: NgoKimPhu

config_decode.go

@@ -0,0 +1,98 @@
+package kutils
+
+import (
+	"encoding"
+	"reflect"
+	"time"
+
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/KyberNetwork/kutils/internal/json"
+)
+
+// StringUnmarshalHookFunc converts string values using json.Unmarshaler or encoding.TextUnmarshaler
+// if the destination type implements it.
+func StringUnmarshalHookFunc() mapstructure.DecodeHookFuncValue {
+	return func(f, t reflect.Value) (any, error) {
+		if f.Kind() != reflect.String {
+			return f.Interface(), nil
+		}
+		data := f.String()
+
+		var dest any
+		if t.Kind() == reflect.Pointer {
+			if t.IsNil() {
+				dest = reflect.New(t.Type().Elem()).Interface()
+			} else {
+				dest = t.Interface()
+			}
+		} else if t.CanAddr() {
+			dest = t.Addr().Interface()
+		} else {
+			dest = reflect.New(t.Type()).Interface()
+		}
+
+		switch dest := dest.(type) {
+		case encoding.TextUnmarshaler:
+			return dest, dest.UnmarshalText([]byte(data))
+		case json.Unmarshaler:
+			quoted, _ := json.Marshal(data)
+			return dest, dest.UnmarshalJSON(quoted)
+		}
+		return data, nil
+	}
+}
+
+// StringToTimeDurationHookFunc converts string to time.Duration. It also handles json.Number.
+func StringToTimeDurationHookFunc() mapstructure.DecodeHookFuncValue {
+	durationType := reflect.TypeOf(time.Duration(0))
+	return func(f, t reflect.Value) (any, error) {
+		if f.Kind() != reflect.String {
+			return f.Interface(), nil
+		}
+		if t.Type() != durationType {
+			return f.Interface(), nil
+		}
+
+		data := f.String()
+		if data == "" {
+			return time.Duration(0), nil
+		}
+
+		lastChar := data[len(data)-1]
+		if lastChar == '.' || '0' <= lastChar && lastChar <= '9' {
+			return Atoi[time.Duration](data)
+		}
+		return time.ParseDuration(data)
+	}
+}
+
+// ConfigDecodeHook converts string to time.Duration and string to string slice like viper does.
+// It also contains StringUnmarshalHookFunc to account for fields implementing Unmarshal interfaces.
+// We also need special handling of string in StringToTimeDurationHookFunc hook in order to
+// process json.Number produced by JSONUnmarshal which uses UseNumber option.
+var ConfigDecodeHook = mapstructure.ComposeDecodeHookFunc(
+	StringUnmarshalHookFunc(),
+	StringToTimeDurationHookFunc(),
+	mapstructure.StringToSliceHookFunc(","),
+)
+
+// DecodeConfig unmarshalls the raw config value bytes into the specified destination with custom logic hooks.
+// It uses JSONUnmarshal which enables UseNumber option for maintaining number precision
+// and mapstructure to make use of custom hooks including a hook for making use of custom text/json unmarshaler
+// and hooks for time and string slice conversion hooks (same as viper config).
+func DecodeConfig(data []byte, dest any) error {
+	var cfgMap any
+	if err := JSONUnmarshal(data, &cfgMap); err != nil {
+		return err
+	}
+	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+		Result:           dest,
+		WeaklyTypedInput: true,
+		DecodeHook:       ConfigDecodeHook,
+	})
+	if err != nil {
+		return err
+	}
+	return decoder.Decode(cfgMap)
+}