feat(chat): SSE writer + multipart upload endpoint with mime whitelist

internal/chat/sse.go

@@ -0,0 +1,83 @@
+package chat
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+
+	"github.com/go-chi/chi/v5"
+
+	"github.com/yan1h/agent-coding-workflow/internal/infra/errs"
+)
+
+// streamMessages implements GET /api/v1/conversations/{id}/stream.
+// It upgrades the connection to a Server-Sent Events stream and forwards
+// SSEEvents produced by MessageService.Stream until the channel closes or
+// the client disconnects.
+func (h *Handler) streamMessages(w http.ResponseWriter, r *http.Request) {
+	uid, err := h.userID(r)
+	if err != nil {
+		writeErr(w, r, err)
+		return
+	}
+	convID, err := parseUUID(chi.URLParam(r, "id"))
+	if err != nil {
+		writeErr(w, r, err)
+		return
+	}
+	var since int64
+	if s := r.URL.Query().Get("since"); s != "" {
+		since, _ = strconv.ParseInt(s, 10, 64)
+	}
+
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Connection", "keep-alive")
+	w.Header().Set("X-Accel-Buffering", "no")
+	w.WriteHeader(http.StatusOK)
+
+	ch, err := h.msgSvc.Stream(r.Context(), uid, convID, since)
+	if err != nil {
+		writeSSEError(w, flusher, err)
+		return
+	}
+	for {
+		select {
+		case <-r.Context().Done():
+			return
+		case ev, ok := <-ch:
+			if !ok {
+				return
+			}
+			writeSSE(w, flusher, ev)
+		}
+	}
+}
+
+// writeSSE writes a single SSE frame to w and flushes.
+func writeSSE(w http.ResponseWriter, f http.Flusher, ev SSEEvent) {
+	data, _ := json.Marshal(ev.Data)
+	fmt.Fprintf(w, "id: %d\nevent: %s\ndata: %s\n\n", ev.ID, ev.Event, data)
+	f.Flush()
+}
+
+// writeSSEError writes an error event to the SSE stream and flushes.
+func writeSSEError(w http.ResponseWriter, f http.Flusher, err error) {
+	code := errs.CodeInternal
+	msg := err.Error()
+	if ae, ok := errs.As(err); ok {
+		code = ae.Code
+		msg = ae.Message
+	}
+	payload := map[string]string{"code": string(code), "message": msg}
+	data, _ := json.Marshal(payload)
+	fmt.Fprintf(w, "event: error\ndata: %s\n\n", data)
+	f.Flush()
+}