mtsatellite/cmd/mtwebmapper/players.go

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package main
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import (
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"bufio"
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"bytes"
"encoding/json"
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"html/template"
"log"
"math"
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"net/http"
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"os"
"sort"
"sync"
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"time"
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)
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const sleepInterval = time.Second * 5
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var geoJSONTmpl = template.Must(template.New("geojson").Parse(
`{ "type": "Feature",
"geometry": {
"type": "Point",
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"coordinates": [{{.Z}}, {{.X}}]
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},
"properties": {
"name": "{{.Name | html }}"
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}
}`))
type player struct {
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X float64 `json:"x"`
Y float64 `json:"y"`
Z float64 `json:"z"`
Name string `json:"name"`
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}
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type players struct {
fifo string
wsf *websocketForwarder
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pls []*player
mu sync.RWMutex
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}
func newPlayers(fifo string, wsf *websocketForwarder) *players {
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return &players{fifo: fifo, wsf: wsf, pls: []*player{}}
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}
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func (p *player) MarshalJSON() ([]byte, error) {
var buf bytes.Buffer
if err := geoJSONTmpl.Execute(&buf, p); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
func (p *player) same(o *player) bool {
return p.Name == o.Name &&
math.Abs(p.X-o.X) < 0.000001 &&
math.Abs(p.Y-o.Y) < 0.000001 &&
math.Abs(p.Z-o.Z) < 0.000001
}
type sortPlayersByName []*player
func (pls sortPlayersByName) Len() int {
return len(pls)
}
func (pls sortPlayersByName) Less(i, j int) bool {
return pls[i].Name < pls[j].Name
}
func (pls sortPlayersByName) Swap(i, j int) {
pls[i], pls[j] = pls[j], pls[i]
}
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func (ps *players) readFromFIFO() ([]*player, error) {
file, err := os.Open(ps.fifo)
if err != nil {
return nil, err
}
defer file.Close()
reader := bufio.NewReader(file)
decoder := json.NewDecoder(reader)
var pls []*player
if err = decoder.Decode(&pls); err != nil {
return nil, err
}
return pls, nil
}
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func samePlayers(a, b []*player) bool {
if len(a) != len(b) {
return false
}
for i, p := range a {
if !p.same(b[i]) {
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return false
}
}
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return true
}
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func (ps *players) run() {
for {
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pls, err := ps.readFromFIFO()
if err != nil {
//log.Printf("err: %s\n", err)
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time.Sleep(sleepInterval)
continue
}
if pls == nil {
//log.Println("no players")
continue
}
//log.Printf("%+q\n", pls)
sort.Sort(sortPlayersByName(pls))
var change bool
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ps.mu.Lock()
//log.Printf("%+q\n", pls)
//log.Printf("%+q\n", ps.pls)
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if change = !samePlayers(pls, ps.pls); change {
ps.pls = pls
}
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ps.mu.Unlock()
if change && ps.wsf != nil {
// TODO: Throttle this!
ps.wsf.BroadcastPlayers(pls)
}
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}
}
func (ps *players) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
rw.Header().Set("Content-Type", "application/json")
var pls []*player
ps.mu.RLock()
pls = ps.pls
ps.mu.RUnlock()
encoder := json.NewEncoder(rw)
if err := encoder.Encode(pls); err != nil {
log.Printf("error: sending JSON failed: %s\n", err)
}
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}