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// 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 flyscrape
import (
"errors"
"fmt"
"os"
"time"
"github.com/fsnotify/fsnotify"
)
var StopWatch = errors.New("stop watch")
func Watch(path string, fn func(string) error) error {
watcher, err := fsnotify.NewWatcher()
if err != nil {
return fmt.Errorf("creating file watcher: %w", err)
}
defer watcher.Close()
if err := watcher.Add(path); err != nil {
return fmt.Errorf("watching file %q: %w", path, err)
}
update := func() error {
data, err := os.ReadFile(path)
if err != nil {
return err
}
return fn(string(data))
}
if err := update(); errors.Is(err, StopWatch) {
return nil
}
for {
select {
case e, ok := <-watcher.Events:
if !ok {
return nil
}
if e.Has(fsnotify.Rename) {
time.Sleep(10 * time.Millisecond)
watcher.Remove(path)
watcher.Add(path)
}
if e.Has(fsnotify.Write) || e.Has(fsnotify.Rename) {
if err := update(); errors.Is(err, StopWatch) {
return nil
}
}
case err, ok := <-watcher.Errors:
if !ok {
return nil
}
if err != nil {
return fmt.Errorf("watcher: %w", err)
}
}
}
}
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