package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"mime/multipart"
	"net/http"
	"os"
)

//post a file to a url
func postFileForm(filename string, targetURL string, formFieldName string) (strJSON string, err error) {
	bodyBuf := &bytes.Buffer{}
	bodyWriter := multipart.NewWriter(bodyBuf)

	// this step is very important
	fileWriter, err := bodyWriter.CreateFormFile(formFieldName, filename)
	if err != nil {
		fmt.Println(err)
		return "", err
	}

	// open file handle
	fh, err := os.Open(filename)
	if err != nil {
		fmt.Println(err)
		return "", err
	}

	//iocopy
	_, err = io.Copy(fileWriter, fh)
	if err != nil {
		return "", err
	}

	contentType := bodyWriter.FormDataContentType()
	bodyWriter.Close()

	resp, err := http.Post(targetURL, contentType, bodyBuf)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	r, err := ioutil.ReadAll(resp.Body)
	strJSON = string(r)
	if err != nil {
		return "", err
	}
	fmt.Println(resp.Status)
	fmt.Println(string(strJSON))
	return strJSON, nil
}