Add video picker and Discord video attachments.

The picker accepts one MP4 or WebM, the thread lightbox zooms photos, and Discord gets the video as a file on a follow-up message so photo embeds still render.

internal/events/bus.go

@@ -40,12 +40,14 @@ func newBus(buffer int, start bool) *Bus {
 // Publish enqueues ev. It never blocks the caller; a full buffer is dropped.
 func (b *Bus) Publish(_ context.Context, ev any) {
 	if b == nil {
+		CallRelease(ev)
 		return
 	}
 	select {
 	case b.ch <- ev:
 	default:
 		log.Printf("events: dropped %T", ev)
+		CallRelease(ev)
 	}
 }
 

internal/events/bus_test.go

@@ -102,3 +102,44 @@ func TestBusDropsWhenFull(t *testing.T) {
 	default:
 	}
 }
+
+func TestNopReleasesPostCreated(t *testing.T) {
+	t.Parallel()
+
+	released := false
+	Nop{}.Publish(context.Background(), PostCreated{Release: func() { released = true }})
+	if !released {
+		t.Fatal("Nop.Publish did not release held upload")
+	}
+}
+
+func TestBusDropReleasesPostCreated(t *testing.T) {
+	t.Parallel()
+
+	bus := newBus(1, false)
+	bus.Publish(context.Background(), "kept")
+	released := false
+	bus.Publish(context.Background(), PostCreated{Release: func() { released = true }})
+	if !released {
+		t.Fatal("dropped PostCreated did not release held upload")
+	}
+}
+
+func TestSubscribeReleasePostedToDiscord(t *testing.T) {
+	t.Parallel()
+
+	bus := New()
+	defer bus.Close()
+	SubscribeRelease(bus)
+
+	released := make(chan struct{})
+	bus.Publish(context.Background(), PostedToDiscord{
+		PostID:  "post-1",
+		Release: func() { close(released) },
+	})
+	select {
+	case <-released:
+	case <-time.After(time.Second):
+		t.Fatal("PostedToDiscord did not release")
+	}
+}

internal/events/event.go

@@ -1,14 +1,27 @@
 package events
 
 import (
+	"io"
 	"net/url"
 	"strings"
 )
 
-// Image is a public photo already attached to a site post.
+// Image is a public photo or video already attached to a site post.
 type Image struct {
 	URL         string
 	Description string
+	Kind        string
+}
+
+// Media is a local upload still held from the create request so Discord can
+// attach the bytes. Photos carry re-encoded Bytes; videos carry an open Body.
+type Media struct {
+	Name        string
+	ContentType string
+	Kind        string
+	Size        int64
+	Body        io.ReadCloser
+	Bytes       []byte
 }
 
 // PostEvent is a Discord-free snapshot of a site post after a successful write.
@@ -29,6 +42,8 @@ type PostEvent struct {
 // PostCreated is emitted after a successful site create.
 type PostCreated struct {
 	PostEvent
+	Media   []Media `json:"-"`
+	Release func()  `json:"-"`
 }
 
 // PostUpdated is emitted after a successful site edit.
@@ -36,6 +51,13 @@ type PostUpdated struct {
 	PostEvent
 }
 
+// PostedToDiscord is emitted after the Discord subscriber finishes with a
+// PostCreated (sent, skipped, or failed). Release deletes held upload files.
+type PostedToDiscord struct {
+	PostID  string
+	Release func() `json:"-"`
+}
+
 // Permalink builds /questions/{root}#post-{id}, prefixed by baseURL when set.
 func Permalink(baseURL, rootID, postID string) string {
 	path := "/questions/" + url.PathEscape(rootID) + "#post-" + url.PathEscape(postID)

internal/events/nop.go

@@ -5,5 +5,7 @@ import "context"
 // Nop is a Publisher used when nothing is subscribed.
 type Nop struct{}
 
-// Publish discards ev.
-func (Nop) Publish(context.Context, any) {}
+// Publish discards ev after releasing any held upload.
+func (Nop) Publish(_ context.Context, ev any) {
+	CallRelease(ev)
+}

internal/events/release.go

@@ -0,0 +1,41 @@
+package events
+
+import (
+	"context"
+	"sync"
+)
+
+// Once returns fn wrapped so it runs at most once.
+func Once(fn func()) func() {
+	if fn == nil {
+		return func() {}
+	}
+	var once sync.Once
+	return func() { once.Do(fn) }
+}
+
+// CallRelease runs Release on PostCreated or PostedToDiscord when set.
+func CallRelease(ev any) {
+	switch e := ev.(type) {
+	case PostCreated:
+		if e.Release != nil {
+			e.Release()
+		}
+	case PostedToDiscord:
+		if e.Release != nil {
+			e.Release()
+		}
+	}
+}
+
+// SubscribeRelease runs PostedToDiscord.Release on the worker.
+func SubscribeRelease(bus *Bus) {
+	if bus == nil {
+		return
+	}
+	bus.Subscribe(func(_ context.Context, ev any) {
+		if _, ok := ev.(PostedToDiscord); ok {
+			CallRelease(ev)
+		}
+	})
+}