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backend.go
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/
backend.go
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package main
import (
"bytes"
"errors"
"fmt"
"log"
"os"
"sync"
"github.com/fsnotify/fsnotify"
)
type Backend struct {
Address string
ScoreUpdate chan struct{}
score int64
dir string
mutex sync.RWMutex
}
func NewBackend(address string, path string) Backend {
return Backend{
Address: address,
ScoreUpdate: make(chan struct{}),
score: 1,
dir: path,
mutex: sync.RWMutex{},
}
}
func (b *Backend) StopWatchingFilesystem() {
close(b.ScoreUpdate)
}
func (b *Backend) WatchFilesystem() error {
watcher, err := fsnotify.NewWatcher()
if err != nil {
return err
}
defer watcher.Close()
err = watcher.Add(b.dir + "/score")
if err != nil {
return err
}
for {
select {
case <-b.ScoreUpdate:
return nil
case _, ok := <-watcher.Events:
if !ok {
return nil
}
b.ScoreUpdate <- struct{}{}
case err, ok := <-watcher.Errors:
if !ok {
return nil
}
log.Println(err)
}
}
}
func (b *Backend) GetScore() int64 {
b.mutex.RLock()
defer b.mutex.RUnlock()
return b.score
}
func (b *Backend) UpdateScore() error {
buffer, err := os.ReadFile(b.dir + "/score")
if err != nil {
return errors.New(
fmt.Sprintf("error opening backend file: %s\n", err.Error()),
)
}
var score int64
fmt.Fscanf(bytes.NewReader(buffer), "%d", &score)
b.mutex.Lock()
defer b.mutex.Unlock()
if b.score != score {
log.Printf(
"backend %s score updated (%d -> %d)", b.Address, b.score, score,
)
}
b.score = score
return nil
}