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//
// rhrdtime
//
// The Radio Helsinki Rivendell Time Websocket Server
//
//
// Copyright (C) 2015 Christian Pointner <equinox@helsinki.at>
//
// This file is part of rhrdtime.
//
// rhrdtime is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// rhrdtime is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with rhrdtime. If not, see <http://www.gnu.org/licenses/>.
//
package main
import (
"encoding/json"
"flag"
"fmt"
"math"
"net/http"
"time"
"github.com/go-martini/martini"
"github.com/gorilla/websocket"
"github.com/tuxychandru/pubsub"
)
type timeUpdate struct {
Timestamp int64 `json:"timestamp"`
TZOffset int `json:"tz_offset"`
Week uint8 `json:"week"`
}
func getTimeUpdate() []byte {
//
// This computes the current Rivendell Week based on the number
// of weeks since epoch.
//
// Explanation:
// epoch was at 01.01.1970 UTC which was a Thursday.
// Monday in that week is (s-from-epoch + 3*24*60*60) seconds ago.
// This needs to be adjusted by the timezone offset for Europe/Vienna
// which is of course not constant (damn you daylight savings time)
// Divide this by (7*24*60*60) and you get the number of
// weeks since the Monday in the week of epoch adjusted for timezone offsets.
// This week had week number 3 so add an offset of 2 and
// get the modulo of 4. This rounded down gives you the current week
// with 0 meaning Week 1. So add 1 to that number and you will get
// the current RD week.
//
loc, err := time.LoadLocation("Europe/Vienna")
if err != nil {
fmt.Println(err)
return []byte{'{', '}'}
}
now := time.Now().In(loc)
_, offset := now.Zone()
sEpoch := now.Unix() + int64(offset)
week := uint8(math.Floor(math.Mod((((float64(sEpoch)+259200)/604800)+2), 4)) + 1)
update := timeUpdate{now.Unix(), offset, week}
update_json, err := json.Marshal(update)
if err != nil {
fmt.Println(err)
return []byte{'{', '}'}
}
return update_json
}
func goTalkWithClient(w http.ResponseWriter, r *http.Request, ps *pubsub.PubSub) {
ws, err := websocket.Upgrade(w, r, nil, 1024, 1024)
if _, ok := err.(websocket.HandshakeError); ok {
http.Error(w, "Not a websocket handshake", 400)
return
} else if err != nil {
fmt.Println(err)
return
}
fmt.Println("Client connected", ws.RemoteAddr())
timeupdate_chan := ps.Sub("timeupdate")
defer ps.Unsub(timeupdate_chan, "timeupdate")
update_json := getTimeUpdate()
if err := ws.WriteMessage(websocket.TextMessage, update_json); err != nil {
return
}
for jsonupdate := range timeupdate_chan {
if err := ws.WriteMessage(websocket.TextMessage, jsonupdate.([]byte)); err != nil {
return
}
}
}
func RunMartini(ps *pubsub.PubSub, addr string) {
m := martini.Classic()
m.Get("/time", func(w http.ResponseWriter, r *http.Request) {
goTalkWithClient(w, r, ps)
})
m.RunOnAddr(addr)
}
func main() {
interval_s := flag.String("interval", "15s", "the interval between updates, default: '15s'")
addr_s := flag.String("addr", ":3000", "addr:port to listen on, default: ':3000'")
help := flag.Bool("help", false, "show usage")
flag.Parse()
if *help {
flag.Usage()
return
}
interval, err := time.ParseDuration(*interval_s)
if err != nil {
fmt.Println(err)
return
}
ps := pubsub.New(1)
ticker := time.NewTicker(interval)
go func() {
for _ = range ticker.C {
ps.Pub(getTimeUpdate(), "timeupdate")
}
}()
RunMartini(ps, *addr_s)
}
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