/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package sse

import (
	"bytes"
	"fmt"
	"net/http"
	"strconv"
	"time"
)

// ServeHTTP serves new connections with events for a given stream ...
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	flusher, err := w.(http.Flusher)
	if !err {
		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")

	for k, v := range s.Headers {
		w.Header().Set(k, v)
	}

	// Get the StreamID from the URL
	streamID := r.URL.Query().Get("stream")
	if streamID == "" {
		http.Error(w, "Please specify a stream!", http.StatusInternalServerError)
		return
	}

	stream := s.getStream(streamID)

	if stream == nil {
		if !s.AutoStream {
			http.Error(w, "Stream not found!", http.StatusInternalServerError)
			return
		}

		stream = s.CreateStream(streamID)
	}

	eventid := 0
	if id := r.Header.Get("Last-Event-ID"); id != "" {
		var err error
		eventid, err = strconv.Atoi(id)
		if err != nil {
			http.Error(w, "Last-Event-ID must be a number!", http.StatusBadRequest)
			return
		}
	}

	// Create the stream subscriber
	sub := stream.addSubscriber(eventid, r.URL)

	go func() {
		<-r.Context().Done()

		sub.close()

		if s.AutoStream && !s.AutoReplay && stream.getSubscriberCount() == 0 {
			s.RemoveStream(streamID)
		}
	}()

	w.WriteHeader(http.StatusOK)
	flusher.Flush()

	// Push events to client
	for ev := range sub.connection {
		// If the data buffer is an empty string abort.
		if len(ev.Data) == 0 && len(ev.Comment) == 0 {
			break
		}

		// if the event has expired, dont send it
		if s.EventTTL != 0 && time.Now().After(ev.timestamp.Add(s.EventTTL)) {
			continue
		}

		if len(ev.Data) > 0 {
			fmt.Fprintf(w, "id: %s\n", ev.ID)

			if s.SplitData {
				sd := bytes.Split(ev.Data, []byte("\n"))
				for i := range sd {
					fmt.Fprintf(w, "data: %s\n", sd[i])
				}
			} else {
				if bytes.HasPrefix(ev.Data, []byte(":")) {
					fmt.Fprintf(w, "%s\n", ev.Data)
				} else {
					fmt.Fprintf(w, "data: %s\n", ev.Data)
				}
			}

			if len(ev.Event) > 0 {
				fmt.Fprintf(w, "event: %s\n", ev.Event)
			}

			if len(ev.Retry) > 0 {
				fmt.Fprintf(w, "retry: %s\n", ev.Retry)
			}
		}

		if len(ev.Comment) > 0 {
			fmt.Fprintf(w, ": %s\n", ev.Comment)
		}

		fmt.Fprint(w, "\n")

		flusher.Flush()
	}
}