feature/listening (#2)

* basic listening loop

* added doc block

* added node interface

client/client.go

@@ -8,8 +8,8 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/golang/protobuf/proto"
 	"github.com/pkg/errors"
+	"github.com/vacp2p/dasy/client/internal"
 	"github.com/vacp2p/dasy/protobuf"
-	mvds "github.com/vacp2p/mvds/node"
 	mvdsproto "github.com/vacp2p/mvds/protobuf"
 	"github.com/vacp2p/mvds/state"
 	"github.com/vacp2p/mvds/store"
@@ -23,7 +23,7 @@ type Peer state.PeerID
 
 // Client is the actual daisy client.
 type Client struct {
-	node  mvds.Node
+	node  internal.DataSyncNode
 	store store.MessageStore // @todo we probably need a different message store, not sure tho
 
 	identity *ecdsa.PrivateKey
@@ -61,6 +61,16 @@ func (c *Client) Post(chat Chat, body []byte) error {
 	return c.send(chat, protobuf.Message_POST, body)
 }
 
+// Listen listens for newly received messages and handles them appropriately.
+func (c *Client) Listen() {
+	sub := make(chan mvdsproto.Message)
+	c.node.Subscribe(sub)
+
+	for {
+		go c.onReceive(<- sub)
+	}
+}
+
 func (c *Client) send(chat Chat, t protobuf.Message_MessageType, body []byte) error {
 	lastMessage := c.lastMessages[chat]
 	msg := &protobuf.Message{
@@ -89,6 +99,8 @@ func (c *Client) send(chat Chat, t protobuf.Message_MessageType, body []byte) er
 	return nil
 }
 
+// onReceive handles lower level message receiving logic, such as requesting all previous message dependencies that we
+// may not have, as well as unmarshalling and storing the message.
 func (c *Client) onReceive(message mvdsproto.Message) {
 	var msg protobuf.Message
 	err := proto.Unmarshal(message.Body, &msg)

client/internal/node.go

@@ -0,0 +1,12 @@
+package internal
+
+import (
+	"github.com/vacp2p/mvds/protobuf"
+	"github.com/vacp2p/mvds/state"
+)
+
+type DataSyncNode interface {
+	AppendMessage(groupID state.GroupID, data []byte) (state.MessageID, error)
+	Subscribe(sub chan <-protobuf.Message)
+	RequestMessage(group state.GroupID, id state.MessageID) error
+}