fix: chat accepts posts

internal/handler/chat.go

@@ -36,6 +36,8 @@ func writeChatError(w http.ResponseWriter, err error) {
 		response.Error(w, http.StatusNotFound, "conversation not found")
 	case errors.Is(err, service.ErrAvatarUnset):
 		response.Error(w, http.StatusNotFound, err.Error())
+	case errors.Is(err, service.ErrChatBadEntity):
+		response.Error(w, http.StatusBadRequest, err.Error())
 	case errors.Is(err, service.ErrChatBadQuote):
 		response.Error(w, http.StatusBadRequest, err.Error())
 	case errors.Is(err, service.ErrChatBadAvatarKey):
@@ -190,8 +192,11 @@ type sendReq struct {
 	Attachments []mediaReq `json:"attachments"`
 	// quote is a passage shared from the library. `path` must be app-relative;
 	// the service refuses anything that could navigate off-site.
-	Quote     *quoteReq `json:"quote"`
-	ReplyToID *string   `json:"reply_to_id"`
+	Quote *quoteReq `json:"quote"`
+	// entity shares something else in the app — a post — as a card. Only the
+	// reference; the BFF resolves the contents and re-checks visibility.
+	Entity    *entityReq `json:"entity"`
+	ReplyToID *string    `json:"reply_to_id"`
 	// forward_from_id is deliberately NOT accepted yet: forwarding lands with
 	// its own "can the caller see the source?" check in a later phase, and
 	// accepting an unvalidated message reference in the meantime would let a
@@ -221,12 +226,17 @@ func (h *ChatHandler) Send(w http.ResponseWriter, r *http.Request) {
 			Path: req.Quote.Path, Title: req.Quote.Title, Text: req.Quote.Text,
 		}
 	}
+	var entity *service.EntityAttachment
+	if req.Entity != nil {
+		entity = &service.EntityAttachment{Type: req.Entity.Type, ID: req.Entity.ID}
+	}
 	msg, err := h.svc.Send(r.Context(), userID, convID, service.SendRequest{
 		Body:        req.Body,
 		ClientMsgID: req.ClientMsgID,
 		ReplyToID:   req.ReplyToID,
 		PreviewURL:  req.PreviewURL,
 		Quote:       quote,
+		Entity:      entity,
 		Attachments: media,
 	})
 	if err != nil {
@@ -566,6 +576,11 @@ func (h *ChatHandler) UpdateGroup(w http.ResponseWriter, r *http.Request) {
 	response.NoContent(w)
 }
 
+type entityReq struct {
+	Type string `json:"type"`
+	ID   string `json:"id"`
+}
+
 type quoteReq struct {
 	Path  string `json:"path"`
 	Title string `json:"title"`