Add tutorial for DropzoneJS. Stay tuned for two-parts article series on https://medium.com/@kataras and https://dev.to/@kataras

Former-commit-id: 2aac5c1f5a5b5a7039a7a5fad3312a49e9311ddd

_examples/tutorial/dropzonejs/src/main.go

@@ -0,0 +1,171 @@
+package main
+
+import (
+	"image/jpeg"
+	"image/png"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"github.com/kataras/iris"
+
+	"github.com/nfnt/resize"
+)
+
+// $ go get -u github.com/nfnt/resize
+
+const uploadsDir = "./public/uploads/"
+
+type uploadedFile struct {
+	// {name: "", size: } are the dropzone's only requirements.
+	Name string `json:"name"`
+	Size int64  `json:"size"`
+}
+
+type uploadedFiles struct {
+	dir   string
+	items []uploadedFile
+	mu    sync.RWMutex // slices are safe but RWMutex is a good practise for you.
+}
+
+func scanUploads(dir string) *uploadedFiles {
+
+	f := new(uploadedFiles)
+
+	lindex := dir[len(dir)-1]
+	if lindex != os.PathSeparator && lindex != '/' {
+		dir += string(os.PathSeparator)
+	}
+
+	// create directories if necessary
+	// and if, then return empty uploaded files; skipping the scan.
+	if err := os.MkdirAll(dir, os.FileMode(0666)); err != nil {
+		return f
+	}
+
+	// otherwise scan the given "dir" for files.
+	f.scan(dir)
+	return f
+}
+
+func (f *uploadedFiles) scan(dir string) {
+	f.dir = dir
+	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+
+		// if it's directory or a thumbnail we saved ealier, skip it.
+		if info.IsDir() || strings.HasPrefix(info.Name(), "thumbnail_") {
+			return nil
+		}
+
+		f.add(info.Name(), info.Size())
+		return nil
+	})
+}
+
+func (f *uploadedFiles) add(name string, size int64) uploadedFile {
+	f.mu.Lock()
+	uf := uploadedFile{
+		Name: name,
+		Size: size,
+	}
+	f.items = append(f.items, uf)
+	f.mu.Unlock()
+
+	return uf
+}
+
+func (f *uploadedFiles) createThumbnail(uf uploadedFile) {
+	file, err := os.Open(path.Join(f.dir, uf.Name))
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	name := strings.ToLower(uf.Name)
+
+	out, err := os.OpenFile(f.dir+"thumbnail_"+uf.Name,
+		os.O_WRONLY|os.O_CREATE, 0666)
+	if err != nil {
+		return
+	}
+	defer out.Close()
+
+	if strings.HasSuffix(name, ".jpg") {
+		// decode jpeg into image.Image
+		img, err := jpeg.Decode(file)
+		if err != nil {
+			return
+		}
+
+		// write new image to file
+		resized := resize.Thumbnail(180, 180, img, resize.Lanczos3)
+		jpeg.Encode(out, resized,
+			&jpeg.Options{Quality: jpeg.DefaultQuality})
+
+	} else if strings.HasSuffix(name, ".png") {
+		img, err := png.Decode(file)
+		if err != nil {
+			return
+		}
+
+		// write new image to file
+		resized := resize.Thumbnail(180, 180, img, resize.Lanczos3) // slower but better res
+		png.Encode(out, resized)
+	}
+	// and so on... you got the point, this code can be simplify, as a practise.
+
+}
+
+func main() {
+	app := iris.New()
+	app.RegisterView(iris.HTML("./views", ".html"))
+
+	app.StaticWeb("/public", "./public")
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.View("upload.html")
+	})
+
+	files := scanUploads(uploadsDir)
+
+	app.Get("/uploads", func(ctx iris.Context) {
+		ctx.JSON(files.items)
+	})
+
+	app.Post("/upload", iris.LimitRequestBodySize(10<<20), func(ctx iris.Context) {
+		// Get the file from the dropzone request
+		file, info, err := ctx.FormFile("file")
+		if err != nil {
+			ctx.StatusCode(iris.StatusInternalServerError)
+			ctx.Application().Logger().Warnf("Error while uploading: %v", err.Error())
+			return
+		}
+
+		defer file.Close()
+		fname := info.Filename
+
+		// Create a file with the same name
+		// assuming that you have a folder named 'uploads'
+		out, err := os.OpenFile(uploadsDir+fname,
+			os.O_WRONLY|os.O_CREATE, 0666)
+
+		if err != nil {
+			ctx.StatusCode(iris.StatusInternalServerError)
+			ctx.Application().Logger().Warnf("Error while preparing the new file: %v", err.Error())
+			return
+		}
+		defer out.Close()
+
+		io.Copy(out, file)
+
+		// optionally, add that file to the list in order to be visible when refresh.
+		uploadedFile := files.add(fname, info.Size)
+		go files.createThumbnail(uploadedFile)
+	})
+
+	// start the server at http://localhost:8080
+	app.Run(iris.Addr(":8080"))
+}