main.go

package main

import (
	"crypto/md5"
	"fmt"
	"io"
	"mime/multipart"
	"strconv"
	"strings"
	"time"

	"github.com/kataras/iris/v12"
)

func main() {
	app := newApp()
	// start the server at http://localhost:8080 with post limit at 32 MB.
	app.Listen(":8080", iris.WithPostMaxMemory(32<<20 /* same as 32 * iris.MB */))
}

func newApp() *iris.Application {
	app := iris.New()
	app.RegisterView(iris.HTML("./templates", ".html"))

	// Serve the upload_form.html to the client.
	app.Get("/upload", func(ctx iris.Context) {
		// create a token (optionally).

		now := time.Now().Unix()
		h := md5.New()
		io.WriteString(h, strconv.FormatInt(now, 10))
		token := fmt.Sprintf("%x", h.Sum(nil))

		// render the form with the token for any use you'd like.
		if err := ctx.View("upload_form.html", token); err != nil {
			ctx.HTML("<h3>%s</h3>", err.Error())
			return
		}
	})

	// Handle the post request from the upload_form.html to the server.
	app.Post("/upload", func(ctx iris.Context) {
		//
		// UploadFormFiles
		// uploads any number of incoming files ("multiple" property on the form input).
		//

		// second argument is optional,
		// it can be used to change a file's name based on the request,
		// at this example we will showcase how to use it
		// by prefixing the uploaded file with the current user's ip.
		ctx.UploadFormFiles("./uploads", beforeSave)
	})

	app.Post("/upload_manual", func(ctx iris.Context) {
		// Get the max post value size passed via iris.WithPostMaxMemory.
		maxSize := ctx.Application().ConfigurationReadOnly().GetPostMaxMemory()

		err := ctx.Request().ParseMultipartForm(maxSize)
		if err != nil {
			ctx.StopWithError(iris.StatusInternalServerError, err)
			return
		}

		form := ctx.Request().MultipartForm

		files := form.File["files[]"]
		failures := 0
		for _, file := range files {
			_, err = ctx.SaveFormFile(file, "./uploads/"+file.Filename)
			if err != nil {
				failures++
				ctx.Writef("failed to upload: %s\n", file.Filename)
			}
		}
		ctx.Writef("%d files uploaded", len(files)-failures)
	})

	return app
}

func beforeSave(ctx iris.Context, file *multipart.FileHeader) bool {
	ip := ctx.RemoteAddr()
	// make sure you format the ip in a way
	// that can be used for a file name (simple case):
	ip = strings.ReplaceAll(ip, ".", "_")
	ip = strings.ReplaceAll(ip, ":", "_")

	// you can use the time.Now, to prefix or suffix the files
	// based on the current time as well, as an exercise.
	// i.e unixTime :=	time.Now().Unix()
	// prefix the Filename with the $IP-
	// no need for more actions, internal uploader will use this
	// name to save the file into the "./uploads" folder.
	if ip == "" {
		return true // don't change the file but continue saving it.
	}

	file.Filename = ip + "-" + file.Filename
	return true
}