Process image only on fs event on plugin folder

buildAndRun.sh

@@ -18,7 +18,7 @@ mv -f `find $pluginSrc -name '*.so'` plugins.available/
 
 # Compile main app
 
-docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.8 /bin/bash -c "go get golang.org/x/net/websocket && go build"
+docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.8 /bin/bash -c "go get golang.org/x/net/websocket && go get github.com/fsnotify/fsnotify && go build"
 
 # Run it
 

main.go

@@ -12,6 +12,7 @@ import (
 	"plugin"
 	"time"
 
+	"github.com/fsnotify/fsnotify"
 	"golang.org/x/net/websocket"
 )
 
@@ -77,25 +78,35 @@ func getPlugins(pluginDir string) (map[int][]*Transformer, error) {
 	return ret, nil
 }
 
-func handler(w http.ResponseWriter, r *http.Request) {
-	fi, _ := os.Open("lca.jpg")
-	i, _ := jpeg.Decode(fi)
+var processed image.Image
 
-	plugins, err := getPlugins(pluginDir)
-	if err != nil {
-		panic(err)
-	}
+func processImage(events <-chan fsnotify.Event) {
+	for {
+		fi, _ := os.Open("lca.jpg")
+		i, _ := jpeg.Decode(fi)
 
-	for _, p := range plugins[1] {
-		fmt.Println("Apply", p.name)
-		i = p.t(i)
-	}
-	for _, p := range plugins[0] {
-		fmt.Println("Apply", p.name)
-		i = p.t(i)
+		plugins, err := getPlugins(pluginDir)
+		if err != nil {
+			panic(err)
+		}
+
+		for _, p := range plugins[1] {
+			fmt.Println("Apply", p.name)
+			i = p.t(i)
+		}
+		for _, p := range plugins[0] {
+			fmt.Println("Apply", p.name)
+			i = p.t(i)
+		}
+		processed = i
+
+		// Wait for a change in folder
+		<-events
 	}
+}
 
-	jpeg.Encode(w, i, nil)
+func handler(w http.ResponseWriter, r *http.Request) {
+	jpeg.Encode(w, processed, nil)
 }
 
 func wsHandler(ws *websocket.Conn) {
@@ -110,6 +121,17 @@ var pluginDir string
 func main() {
 	pluginDir = os.Args[1]
 
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	go processImage(watcher.Events)
+	err = watcher.Add(pluginDir)
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	http.HandleFunc("/a.jpg", handler)
 	http.Handle("/ws", websocket.Handler(wsHandler))
 	http.ListenAndServe(":8080", nil)