added network-go project

network-go/watcher/watcher.go

@@ -0,0 +1,83 @@
+package watcher
+
+import (
+	"crypto/md5"
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+// FileWatcher periodically checks a file for changes using MD5 hash
+type FileWatcher struct {
+	path    string
+	period  time.Duration
+	lastHash string
+	onChange func()
+	stopCh  chan struct{}
+}
+
+// NewFileWatcher creates a new file watcher that polls the file at the given period
+func NewFileWatcher(path string, period time.Duration, onChange func()) *FileWatcher {
+	return &FileWatcher{
+		path:      path,
+		period:    period,
+		lastHash:  "",
+		onChange:  onChange,
+		stopCh:    make(chan struct{}),
+	}
+}
+
+// hashFile computes an MD5 hash of the file contents
+func (fw *FileWatcher) hashFile() (string, error) {
+	data, err := os.ReadFile(fw.path)
+	if err != nil {
+		return "", fmt.Errorf("failed to read file %s: %w", fw.path, err)
+	}
+	return fmt.Sprintf("%x", md5.Sum(data)), nil
+}
+
+// Start begins polling the file for changes in a goroutine
+func (fw *FileWatcher) Start() {
+	// Compute initial hash
+	hash, err := fw.hashFile()
+	if err != nil {
+		log.Printf("WATCHER: initial hash computation failed for %s: %v", fw.path, err)
+	} else {
+		fw.lastHash = hash
+	}
+
+	go func() {
+		ticker := time.NewTicker(fw.period)
+		defer ticker.Stop()
+
+		log.Printf("WATCHER: started watching %s every %s", fw.path, fw.period)
+
+		for {
+			select {
+			case <-fw.stopCh:
+				log.Printf("WATCHER: stopped watching %s", fw.path)
+				return
+			case <-ticker.C:
+				hash, err := fw.hashFile()
+				if err != nil {
+					log.Printf("WATCHER: failed to hash %s: %v", fw.path, err)
+					continue
+				}
+
+				if hash != fw.lastHash {
+					log.Printf("WATCHER: detected change in %s", fw.path)
+					fw.lastHash = hash
+					if fw.onChange != nil {
+						fw.onChange()
+					}
+				}
+			}
+		}
+	}()
+}
+
+// Stop signals the watcher goroutine to stop
+func (fw *FileWatcher) Stop() {
+	close(fw.stopCh)
+}