v1.0.0

infra/conf/loader.go

@@ -0,0 +1,83 @@
+package conf
+
+import (
+	"encoding/json"
+	"strings"
+)
+
+type ConfigCreator func() interface{}
+
+type ConfigCreatorCache map[string]ConfigCreator
+
+func (v ConfigCreatorCache) RegisterCreator(id string, creator ConfigCreator) error {
+	if _, found := v[id]; found {
+		return newError(id, " already registered.").AtError()
+	}
+
+	v[id] = creator
+	return nil
+}
+
+func (v ConfigCreatorCache) CreateConfig(id string) (interface{}, error) {
+	creator, found := v[id]
+	if !found {
+		return nil, newError("unknown config id: ", id)
+	}
+	return creator(), nil
+}
+
+type JSONConfigLoader struct {
+	cache     ConfigCreatorCache
+	idKey     string
+	configKey string
+}
+
+func NewJSONConfigLoader(cache ConfigCreatorCache, idKey string, configKey string) *JSONConfigLoader {
+	return &JSONConfigLoader{
+		idKey:     idKey,
+		configKey: configKey,
+		cache:     cache,
+	}
+}
+
+func (v *JSONConfigLoader) LoadWithID(raw []byte, id string) (interface{}, error) {
+	id = strings.ToLower(id)
+	config, err := v.cache.CreateConfig(id)
+	if err != nil {
+		return nil, err
+	}
+	if err := json.Unmarshal(raw, config); err != nil {
+		return nil, err
+	}
+	return config, nil
+}
+
+func (v *JSONConfigLoader) Load(raw []byte) (interface{}, string, error) {
+	var obj map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &obj); err != nil {
+		return nil, "", err
+	}
+	rawID, found := obj[v.idKey]
+	if !found {
+		return nil, "", newError(v.idKey, " not found in JSON context").AtError()
+	}
+	var id string
+	if err := json.Unmarshal(rawID, &id); err != nil {
+		return nil, "", err
+	}
+	rawConfig := json.RawMessage(raw)
+	if len(v.configKey) > 0 {
+		configValue, found := obj[v.configKey]
+		if found {
+			rawConfig = configValue
+		} else {
+			// Default to empty json object.
+			rawConfig = json.RawMessage([]byte("{}"))
+		}
+	}
+	config, err := v.LoadWithID([]byte(rawConfig), id)
+	if err != nil {
+		return nil, id, err
+	}
+	return config, id, nil
+}