From 6c9d1864dd078233b03ae4e3616769d479cf0017 Mon Sep 17 00:00:00 2001
From: ZGaetano <zgaetano@wilddragon.net>
Date: Sat, 9 May 2026 16:32:03 -0400
Subject: [PATCH] feat(restream): extend ProcessHooks with OnInputStart for
 WHIP ingest input legs

---
 restream/restream.go | 85 +++++++++++++++++++++++++++++---------------
 1 file changed, 57 insertions(+), 28 deletions(-)

diff --git a/restream/restream.go b/restream/restream.go
index f844f6c..300e6d7 100644
--- a/restream/restream.go
+++ b/restream/restream.go
@@ -60,9 +60,11 @@ type Restreamer interface {
 
 // ProcessStartHook is invoked synchronously inside startProcess just
 // before FFmpeg is started. It receives a pointer to the task config;
-// returning a non-empty slice of ConfigIO appends those output legs to
-// cfg.Output and causes the FFmpeg command to be rebuilt before
-// Start(). Returning a non-nil error aborts the start.
+// returning a non-empty slice of ConfigIO causes the command to be
+// rebuilt before Start(). Returning a non-nil error aborts the start.
+//
+// For OnStart the returned ConfigIO slices are appended to cfg.Output.
+// For OnInputStart the returned ConfigIO slices are prepended to cfg.Input.
 //
 // Hooks run with the restream write lock held, so they must not call
 // back into the Restreamer interface (it would deadlock). They can,
@@ -76,9 +78,15 @@ type ProcessStopHook func(id string)
 
 // ProcessHooks bundles the lifecycle callbacks a sibling subsystem
 // (currently: app/webrtc) installs via SetHooks.
+//
+// OnStart returns ConfigIO entries appended to cfg.Output (WHEP RTP egress legs).
+// OnInputStart returns ConfigIO entries prepended to cfg.Input (WHIP RTP ingest legs).
+// OnStop and OnInputStop are called after FFmpeg stops.
 type ProcessHooks struct {
-	OnStart ProcessStartHook
-	OnStop  ProcessStopHook
+	OnStart      ProcessStartHook
+	OnStop       ProcessStopHook
+	OnInputStart ProcessStartHook // WHIP ingest: returned legs prepended to cfg.Input
+	OnInputStop  ProcessStopHook  // WHIP ingest: teardown notification
 }
 
 // Config is the required configuration for a new restreamer instance.
@@ -1098,10 +1106,24 @@ func (r *restream) startProcess(id string) error {
 
 	task.process.Order = "start"
 
-	// Invoke the per-process start hook (used by app/webrtc to append
-	// RTP output legs). If it returns ConfigIO entries, append them to
-	// the output list and rebuild the FFmpeg process with the new
-	// command before we start it.
+	// Invoke the per-process lifecycle hooks. OnInputStart returns
+	// ConfigIO entries prepended to cfg.Input (WHIP ingest legs);
+	// OnStart returns ConfigIO entries appended to cfg.Output (WHEP
+	// egress legs). Both rebuild the FFmpeg process if non-empty.
+	needsRebuild := false
+
+	if r.hooks.OnInputStart != nil {
+		inputExtras, err := r.hooks.OnInputStart(task.id, task.config)
+		if err != nil {
+			r.logger.WithField("id", task.id).WithError(err).Error().Log("WHIP input hook aborted process start")
+			return err
+		}
+		if len(inputExtras) > 0 {
+			task.config.Input = append(inputExtras, task.config.Input...)
+			needsRebuild = true
+		}
+	}
+
 	if r.hooks.OnStart != nil {
 		extras, err := r.hooks.OnStart(task.id, task.config)
 		if err != nil {
@@ -1110,27 +1132,31 @@ func (r *restream) startProcess(id string) error {
 		}
 		if len(extras) > 0 {
 			task.config.Output = append(task.config.Output, extras...)
-			task.command = task.config.CreateCommand()
-
-			newFFmpeg, ferr := r.ffmpeg.New(ffmpeg.ProcessConfig{
-				Reconnect:      task.config.Reconnect,
-				ReconnectDelay: time.Duration(task.config.ReconnectDelay) * time.Second,
-				StaleTimeout:   time.Duration(task.config.StaleTimeout) * time.Second,
-				LimitCPU:       task.config.LimitCPU,
-				LimitMemory:    task.config.LimitMemory,
-				LimitDuration:  time.Duration(task.config.LimitWaitFor) * time.Second,
-				Command:        task.command,
-				Parser:         task.parser,
-				Logger:         task.logger,
-			})
-			if ferr != nil {
-				r.logger.WithField("id", task.id).WithError(ferr).Error().Log("Failed to rebuild FFmpeg after start hook")
-				return ferr
-			}
-			task.ffmpeg = newFFmpeg
+			needsRebuild = true
 		}
 	}
 
+	if needsRebuild {
+		task.command = task.config.CreateCommand()
+
+		newFFmpeg, ferr := r.ffmpeg.New(ffmpeg.ProcessConfig{
+			Reconnect:      task.config.Reconnect,
+			ReconnectDelay: time.Duration(task.config.ReconnectDelay) * time.Second,
+			StaleTimeout:   time.Duration(task.config.StaleTimeout) * time.Second,
+			LimitCPU:       task.config.LimitCPU,
+			LimitMemory:    task.config.LimitMemory,
+			LimitDuration:  time.Duration(task.config.LimitWaitFor) * time.Second,
+			Command:        task.command,
+			Parser:         task.parser,
+			Logger:         task.logger,
+		})
+		if ferr != nil {
+			r.logger.WithField("id", task.id).WithError(ferr).Error().Log("Failed to rebuild FFmpeg after hooks")
+			return ferr
+		}
+		task.ffmpeg = newFFmpeg
+	}
+
 	task.ffmpeg.Start()
 
 	r.nProc++
@@ -1175,11 +1201,14 @@ func (r *restream) stopProcess(id string) error {
 	r.nProc--
 
 	// Notify subsystems (app/webrtc) that this process has been
-	// stopped so they can tear down any per-process state. Hook is
+	// stopped so they can tear down any per-process state. Hooks are
 	// best-effort: errors are the hook's problem to log.
 	if r.hooks.OnStop != nil {
 		r.hooks.OnStop(task.id)
 	}
+	if r.hooks.OnInputStop != nil {
+		r.hooks.OnInputStop(task.id)
+	}
 
 	return nil
 }