package anthropic

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
)

// flusherOf extracts the http.Flusher when the writer supports it.
func flusherOf(w http.ResponseWriter) http.Flusher {
	if f, ok := w.(http.Flusher); ok {
		return f
	}
	return nil
}

// writeEvent emits one Server-Sent Event in Anthropic's format:
// "event: <name>\ndata: <json>\n\n".
func writeEvent(w io.Writer, f http.Flusher, name string, data any) error {
	payload, err := json.Marshal(data)
	if err != nil {
		return err
	}
	if _, err := fmt.Fprintf(w, "event: %s\ndata: %s\n\n", name, payload); err != nil {
		return err
	}
	if f != nil {
		f.Flush()
	}
	return nil
}