config: add Save/Load options

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

config/config.go

@@ -20,25 +20,27 @@ var (
 
 // Config is an interface abstraction for dynamic configuration
 type Config interface {
+	// Name returns name of config
 	Name() string
 	// Init the config
 	Init(opts ...Option) error
 	// Options in the config
 	Options() Options
 	// Load config from sources
-	Load(context.Context) error
+	Load(context.Context, ...LoadOption) error
 	// Save config to sources
-	Save(context.Context) error
+	Save(context.Context, ...SaveOption) error
 	// Watch a value for changes
-	//	Watch(interface{}) (Watcher, error)
+	//Watch(context.Context) (Watcher, error)
+	// String returns config type name
 	String() string
 }
 
 // Watcher is the config watcher
-// type Watcher interface {
+type Watcher interface {
 	// Next() (, error)
-//	Stop() error
-// }
+	Stop() error
+}
 
 // Load loads config from config sources
 func Load(ctx context.Context, cs ...Config) error {

config/default.go

@@ -25,18 +25,27 @@ func (c *defaultConfig) Init(opts ...Option) error {
 	return nil
 }
 
-func (c *defaultConfig) Load(ctx context.Context) error {
+func (c *defaultConfig) Load(ctx context.Context, opts ...LoadOption) error {
 	for _, fn := range c.opts.BeforeLoad {
 		if err := fn(ctx, c); err != nil && !c.opts.AllowFail {
 			return err
 		}
 	}
 
+	options := NewLoadOptions(opts...)
+	mopts := []func(*mergo.Config){mergo.WithTypeCheck}
+	if options.Override {
+		mopts = append(mopts, mergo.WithOverride)
+	}
+	if options.Append {
+		mopts = append(mopts, mergo.WithAppendSlice)
+	}
+
 	src, err := rutil.Zero(c.opts.Struct)
 	if err == nil {
 		valueOf := reflect.ValueOf(src)
 		if err = c.fillValues(valueOf); err == nil {
-			err = mergo.Merge(c.opts.Struct, src, mergo.WithOverride, mergo.WithTypeCheck, mergo.WithAppendSlice)
+			err = mergo.Merge(c.opts.Struct, src, mopts...)
 		}
 	}
 
@@ -232,7 +241,7 @@ func (c *defaultConfig) fillValues(valueOf reflect.Value) error {
 	return nil
 }
 
-func (c *defaultConfig) Save(ctx context.Context) error {
+func (c *defaultConfig) Save(ctx context.Context, opts ...SaveOption) error {
 	for _, fn := range c.opts.BeforeSave {
 		if err := fn(ctx, c); err != nil && !c.opts.AllowFail {
 			return err

config/options.go

@@ -57,6 +57,52 @@ func NewOptions(opts ...Option) Options {
 	return options
 }
 
+// LoadOption function signature
+type LoadOption func(o *LoadOptions)
+
+// LoadOptions struct
+type LoadOptions struct {
+	Override bool
+	Append   bool
+}
+
+func NewLoadOptions(opts ...LoadOption) LoadOptions {
+	options := LoadOptions{}
+	for _, o := range opts {
+		o(&options)
+	}
+	return options
+}
+
+// LoadOverride override values when load
+func LoadOverride(b bool) LoadOption {
+	return func(o *LoadOptions) {
+		o.Override = b
+	}
+}
+
+// LoadAppend override values when load
+func LoadAppend(b bool) LoadOption {
+	return func(o *LoadOptions) {
+		o.Append = b
+	}
+}
+
+// SaveOption function signature
+type SaveOption func(o *SaveOptions)
+
+// SaveOptions struct
+type SaveOptions struct {
+}
+
+func NewSaveOptions(opts ...SaveOption) SaveOptions {
+	options := SaveOptions{}
+	for _, o := range opts {
+		o(&options)
+	}
+	return options
+}
+
 // AllowFail allows config source to fail
 func AllowFail(b bool) Option {
 	return func(o *Options) {