Streaming (#49)

Add new status and notification websocket streaming capabilities

internal/api/client/streaming/stream.go

@@ -0,0 +1,89 @@
+package streaming
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/gorilla/websocket"
+)
+
+// StreamGETHandler handles the creation of a new websocket streaming request.
+func (m *Module) StreamGETHandler(c *gin.Context) {
+	l := m.log.WithField("func", "StreamGETHandler")
+
+	streamType := c.Query(StreamQueryKey)
+	if streamType == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("no stream type provided under query key %s", StreamQueryKey)})
+		return
+	}
+
+	accessToken := c.Query(AccessTokenQueryKey)
+	if accessToken == "" {
+		c.JSON(http.StatusUnauthorized, gin.H{"error": fmt.Sprintf("no access token provided under query key %s", AccessTokenQueryKey)})
+		return
+	}
+
+	// make sure a valid token has been provided and obtain the associated account
+	account, err := m.processor.AuthorizeStreamingRequest(accessToken)
+	if err != nil {
+		c.JSON(http.StatusUnauthorized, gin.H{"error": "could not authorize with given token"})
+		return
+	}
+
+	// prepare to upgrade the connection to a websocket connection
+	upgrader := websocket.Upgrader{
+		ReadBufferSize:  1024,
+		WriteBufferSize: 1024,
+		CheckOrigin: func(r *http.Request) bool {
+			// we fully expect cors requests (via something like pinafore.social) so we should be lenient here
+			return true
+		},
+	}
+
+	// do the actual upgrade here
+	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
+	if err != nil {
+		l.Infof("error upgrading websocket connection: %s", err)
+		return
+	}
+	defer conn.Close() // whatever happens, when we leave this function we want to close the websocket connection
+
+	// inform the processor that we have a new connection and want a stream for it
+	stream, errWithCode := m.processor.OpenStreamForAccount(account, streamType)
+	if errWithCode != nil {
+		c.JSON(errWithCode.Code(), errWithCode.Safe())
+		return
+	}
+	defer close(stream.Hangup) // closing stream.Hangup indicates that we've finished with the connection (the client has gone), so we want to do this on exiting this handler
+
+	// spawn a new ticker for pinging the connection periodically
+	t := time.NewTicker(30 * time.Second)
+
+	// we want to stay in the sendloop as long as possible while the client is connected -- the only thing that should break the loop is if the client leaves or something else goes wrong
+sendLoop:
+	for {
+		select {
+		case m := <-stream.Messages:
+			// we've got a streaming message!!
+			l.Debug("received message from stream")
+			if err := conn.WriteJSON(m); err != nil {
+				l.Infof("error writing json to websocket connection: %s", err)
+				// if something is wrong we want to bail and drop the connection -- the client will create a new one
+				break sendLoop
+			}
+			l.Debug("wrote message into websocket connection")
+		case <-t.C:
+			l.Debug("received TICK from ticker")
+			if err := conn.WriteMessage(websocket.PingMessage, []byte(": ping")); err != nil {
+				l.Infof("error writing ping to websocket connection: %s", err)
+				// if something is wrong we want to bail and drop the connection -- the client will create a new one
+				break sendLoop
+			}
+			l.Debug("wrote ping message into websocket connection")
+		}
+	}
+
+	l.Debug("leaving StreamGETHandler")
+}