fix: improves search by backfilling on first search (#3261)

internal/support/web/sse.go

@@ -0,0 +1,101 @@
+package support_web
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+type SSEWriter struct {
+	f http.Flusher
+	w http.ResponseWriter
+}
+
+type HasId interface {
+	MessageId() int64
+}
+
+func NewSSEWriter(ctx context.Context, w http.ResponseWriter) (*SSEWriter, error) {
+	f, ok := w.(http.Flusher)
+
+	if !ok {
+		return nil, http.ErrNotSupported
+	}
+
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-transform")
+	w.Header().Add("Cache-Control", "no-cache")
+	w.Header().Set("Connection", "keep-alive")
+	w.Header().Set("X-Accel-Buffering", "no")
+
+	sse := &SSEWriter{
+		f: f,
+		w: w,
+	}
+
+	return sse, nil
+}
+
+func (s *SSEWriter) Write(data []byte) (int, error) {
+	written, err := s.w.Write(data)
+	if err != nil {
+		return written, err
+	}
+
+	_, err = s.w.Write([]byte("\n\n"))
+	if err != nil {
+		return written, err
+	}
+
+	s.f.Flush()
+
+	return written, nil
+}
+
+func (s *SSEWriter) Ping() error {
+	_, err := s.Write([]byte(":ping "))
+	return err
+}
+
+func (s *SSEWriter) Message(data any) error {
+	encoded, err := json.Marshal(data)
+
+	if err != nil {
+		return err
+	}
+
+	buffer := bytes.Buffer{}
+
+	buffer.WriteString("data: ")
+	buffer.Write(encoded)
+	buffer.WriteString("\n")
+
+	if f, ok := data.(HasId); ok {
+		if f.MessageId() > 0 {
+			buffer.WriteString(fmt.Sprintf("id: %d\n", f.MessageId()))
+		}
+	}
+
+	_, err = buffer.WriteTo(s)
+	return err
+}
+
+func (s *SSEWriter) Event(event string, data any) error {
+	encoded, err := json.Marshal(data)
+
+	if err != nil {
+		return err
+	}
+
+	buffer := bytes.Buffer{}
+
+	buffer.WriteString("event: " + event + "\n")
+	buffer.WriteString("data: ")
+	buffer.Write(encoded)
+	buffer.WriteString("\n")
+
+	_, err = buffer.WriteTo(s)
+	return err
+}