Initial commit

watcher.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"log"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+)
+
+type Watcher struct {
+	w    *fsnotify.Watcher
+	g    *Generator
+	done chan struct{}
+}
+
+func NewWatcher(dir string, g *Generator) (*Watcher, error) {
+	w, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, err
+	}
+	if err := w.Add(dir); err != nil {
+		w.Close()
+		return nil, err
+	}
+	return &Watcher{w: w, g: g, done: make(chan struct{})}, nil
+}
+
+// Watch blocks, watching for changes and triggering rebuilds.
+// Rapid events (e.g. scp writing an image then its sidecar) are debounced
+// with a 500 ms window so only one rebuild fires per logical upload.
+func (w *Watcher) Watch() {
+	var timer *time.Timer
+	rebuild := func() {
+		if err := w.g.Build(); err != nil {
+			log.Printf("rebuild: %v", err)
+		}
+	}
+
+	for {
+		select {
+		case event, ok := <-w.w.Events:
+			if !ok {
+				return
+			}
+			if !isRelevant(event.Name) {
+				continue
+			}
+			if event.Has(fsnotify.Create) || event.Has(fsnotify.Write) || event.Has(fsnotify.Remove) {
+				if timer != nil {
+					timer.Stop()
+				}
+				timer = time.AfterFunc(500*time.Millisecond, rebuild)
+			}
+		case err, ok := <-w.w.Errors:
+			if !ok {
+				return
+			}
+			log.Printf("watcher: %v", err)
+		case <-w.done:
+			return
+		}
+	}
+}
+
+func (w *Watcher) Close() {
+	close(w.done)
+	w.w.Close()
+}
+
+func isRelevant(name string) bool {
+	ext := strings.ToLower(filepath.Ext(name))
+	return ext == ".jpg" || ext == ".jpeg" || ext == ".png" || ext == ".toml"
+}