coreapi: FetchBlocks option

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

core/coreapi/coreapi.go

@@ -210,7 +210,9 @@ func (api *CoreAPI) WithOptions(opts ...options.ApiOption) (coreiface.CoreAPI, e
 		subApi.peerstore = nil
 		subApi.peerHost = nil
 		subApi.recordValidator = nil
+	}
 
+	if settings.Offline || !settings.FetchBlocks {
 		subApi.exchange = offlinexch.Exchange(subApi.blockstore)
 		subApi.blocks = bserv.New(subApi.blockstore, subApi.exchange)
 		subApi.dag = dag.NewDAGService(subApi.blocks)

core/coreapi/interface/options/global.go

 package options
 
 type ApiSettings struct {
-	Offline bool
+	Offline     bool
+	FetchBlocks bool
 }
 
 type ApiOption func(*ApiSettings) error
 
 func ApiOptions(opts ...ApiOption) (*ApiSettings, error) {
 	options := &ApiSettings{
-		Offline: false,
+		Offline:     false,
+		FetchBlocks: true,
 	}
 
 	return ApiOptionsTo(options, opts...)
@@ -34,3 +36,12 @@ func (apiOpts) Offline(offline bool) ApiOption {
 		return nil
 	}
 }
+
+// FetchBlocks when set to false prevents api from fetching blocks from the
+// network while allowing other services such as IPNS to still be online
+func (apiOpts) FetchBlocks(fetch bool) ApiOption {
+	return func(settings *ApiSettings) error {
+		settings.FetchBlocks = fetch
+		return nil
+	}
+}