From 07f820ed4d0ef6dce342ea7847315d8ca7ea5608 Mon Sep 17 00:00:00 2001
From: pk910 <philipp@pk910.de>
Date: Sat, 30 Mar 2024 07:28:28 +0100
Subject: [PATCH] event stream fixes

---
 rpc/eventstream/eventstream.go | 57 +++++++++++++++++++++++++---------
 1 file changed, 43 insertions(+), 14 deletions(-)

diff --git a/rpc/eventstream/eventstream.go b/rpc/eventstream/eventstream.go
index 1ebbb864..1fd2342d 100644
--- a/rpc/eventstream/eventstream.go
+++ b/rpc/eventstream/eventstream.go
@@ -18,7 +18,7 @@ import (
 type Stream struct {
 	c           *http.Client
 	req         *http.Request
-	lastEventId string
+	lastEventID string
 	retry       time.Duration
 	// Events emits the events received by the stream
 	Events chan StreamEvent
@@ -59,27 +59,28 @@ func (e SubscriptionError) Error() string {
 
 // Subscribe to the Events emitted from the specified url.
 // If lastEventId is non-empty it will be sent to the server in case it can replay missed events.
-func Subscribe(url, lastEventId string) (*Stream, error) {
-	req, err := http.NewRequest("GET", url, nil)
+func Subscribe(url, lastEventID string) (*Stream, error) {
+	req, err := http.NewRequest("GET", url, http.NoBody)
 	if err != nil {
 		return nil, err
 	}
-	return SubscribeWithRequest(lastEventId, req)
+
+	return SubscribeWithRequest(lastEventID, req)
 }
 
 // SubscribeWithRequest will take an http.Request to setup the stream, allowing custom headers
 // to be specified, authentication to be configured, etc.
-func SubscribeWithRequest(lastEventId string, request *http.Request) (*Stream, error) {
-	return SubscribeWith(lastEventId, http.DefaultClient, request)
+func SubscribeWithRequest(lastEventID string, request *http.Request) (*Stream, error) {
+	return SubscribeWith(lastEventID, http.DefaultClient, request)
 }
 
 // SubscribeWith takes a http client and request providing customization over both headers and
 // control over the http client settings (timeouts, tls, etc)
-func SubscribeWith(lastEventId string, client *http.Client, request *http.Request) (*Stream, error) {
+func SubscribeWith(lastEventID string, client *http.Client, request *http.Request) (*Stream, error) {
 	stream := &Stream{
 		c:           client,
 		req:         request,
-		lastEventId: lastEventId,
+		lastEventID: lastEventID,
 		retry:       time.Millisecond * 3000,
 		Events:      make(chan StreamEvent),
 		Errors:      make(chan error, 10),
@@ -91,7 +92,9 @@ func SubscribeWith(lastEventId string, client *http.Client, request *http.Reques
 	if err != nil {
 		return nil, err
 	}
+
 	go stream.stream(r)
+
 	return stream, nil
 }
 
@@ -100,6 +103,7 @@ func (stream *Stream) Close() {
 	go func() {
 		stream.closeMutex.Lock()
 		defer stream.closeMutex.Unlock()
+
 		if stream.isClosed {
 			return
 		}
@@ -116,24 +120,30 @@ func checkRedirect(req *http.Request, via []*http.Request) error {
 	if len(via) >= 10 {
 		return errors.New("stopped after 10 redirects")
 	}
+
 	for k, vv := range via[0].Header {
 		for _, v := range vv {
 			req.Header.Add(k, v)
 		}
 	}
+
 	return nil
 }
 
 func (stream *Stream) connect() (r io.ReadCloser, err error) {
 	var resp *http.Response
+
 	stream.req.Header.Set("Cache-Control", "no-cache")
 	stream.req.Header.Set("Accept", "text/event-stream")
-	if len(stream.lastEventId) > 0 {
-		stream.req.Header.Set("Last-Event-ID", stream.lastEventId)
+
+	if stream.lastEventID != "" {
+		stream.req.Header.Set("Last-Event-ID", stream.lastEventID)
 	}
+
 	if resp, err = stream.c.Do(stream.req); err != nil {
 		return
 	}
+
 	if resp.StatusCode != 200 {
 		message, _ := io.ReadAll(resp.Body)
 		err = SubscriptionError{
@@ -141,7 +151,9 @@ func (stream *Stream) connect() (r io.ReadCloser, err error) {
 			Message: string(message),
 		}
 	}
+
 	r = resp.Body
+
 	return
 }
 
@@ -162,39 +174,53 @@ func (stream *Stream) receiveEvents(r io.ReadCloser) {
 
 	for {
 		ev, err := dec.Decode()
+
 		stream.closeMutex.Lock()
 		if stream.isClosed {
 			stream.closeMutex.Unlock()
 			return
 		}
+
 		if err != nil {
 			stream.Errors <- err
 			stream.closeMutex.Unlock()
+
 			return
 		}
-		stream.closeMutex.Unlock()
 
-		pub := ev.(StreamEvent)
+		pub, ok := ev.(StreamEvent)
+		if !ok {
+			stream.closeMutex.Unlock()
+			continue
+		}
+
 		if pub.Retry() > 0 {
 			stream.retry = time.Duration(pub.Retry()) * time.Millisecond
 		}
-		if len(pub.Id()) > 0 {
-			stream.lastEventId = pub.Id()
+
+		if pub.Id() != "" {
+			stream.lastEventID = pub.Id()
 		}
+
 		stream.Events <- pub
+		stream.closeMutex.Unlock()
 	}
 }
 
 func (stream *Stream) retryRestartStream() {
 	backoff := stream.retry
+
 	for {
 		if stream.Logger != nil {
 			stream.Logger.Printf("Reconnecting in %0.4f secs\n", backoff.Seconds())
 		}
+
 		time.Sleep(backoff)
+
 		if stream.isClosed {
 			return
 		}
+
 		// NOTE: because of the defer we're opening the new connection
 		// before closing the old one. Shouldn't be a problem in practice,
 		// but something to be aware of.
@@ -203,10 +229,13 @@ func (stream *Stream) retryRestartStream() {
 			go stream.stream(r)
 			return
 		}
+
 		if stream.isClosed {
 			return
 		}
+
 		stream.Errors <- err
+
 		backoff = 10 * time.Second
 	}
 }