Initial commit

common/watcher/http.go

@@ -0,0 +1,75 @@
+package watcher
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+type HTTPWatcher struct {
+	hash         [32]byte
+	url          string
+	interval     uint
+	handler      EventHandler
+	errorHandler ErrorHandler
+	close        chan struct{}
+}
+
+func NewHTTPWatcher(url string, interval uint) *HTTPWatcher {
+	return &HTTPWatcher{
+		url:      url,
+		interval: interval,
+	}
+}
+
+func (w *HTTPWatcher) handle() error {
+	rsp, err := http.Get(w.url)
+	if err != nil {
+		return fmt.Errorf("request error: %w", err)
+	}
+	defer rsp.Body.Close()
+	b, err := io.ReadAll(rsp.Body)
+	if err != nil {
+		return fmt.Errorf("read body error: %w", err)
+	}
+	h := sha256.Sum256(b)
+	if bytes.Equal(w.hash[:], h[:]) {
+		return nil
+	}
+	w.hash = h
+	err = w.handler(w.url)
+	if err != nil {
+		return fmt.Errorf("handle error: %w", err)
+	}
+	return nil
+}
+
+func (w *HTTPWatcher) SetEventHandler(handler EventHandler) {
+	w.handler = handler
+}
+
+func (w *HTTPWatcher) SetErrorHandler(handler ErrorHandler) {
+	w.errorHandler = handler
+}
+
+func (w *HTTPWatcher) Watch() error {
+	go func() {
+		for range time.Tick(time.Duration(w.interval) * time.Second) {
+			select {
+			case <-w.close:
+				return
+			default:
+			}
+			w.errorHandler(w.handle())
+		}
+	}()
+	return nil
+}
+
+func (w *HTTPWatcher) Close() error {
+	close(w.close)
+	return nil
+}