summaryrefslogtreecommitdiff
path: root/src/helsinki.at/rhrdtime/rhrdtime.go
blob: 692882b3ec1c54419d37c35bf44bb760b217d8db (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
//
//  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 (
  "fmt"
  "time"
  "math"
  "flag"
  "net/http"
  "encoding/json"

  "github.com/codegangsta/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)
}