package upload

import (
	"bytes"
	"io"
	"mime/multipart"
	"net/http"
	"os"
	"path/filepath"
)

// NewRequest creates a new file upload HTTP request with optional extra params.
// Based on https://gist.github.com/mattetti/5914158
func NewRequest(url string, params map[string]string, paramName, path string) (*http.Request, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var body bytes.Buffer
	writer := multipart.NewWriter(&body)
	part, err := writer.CreateFormFile(paramName, filepath.Base(path))
	if err != nil {
		return nil, err
	}
	if _, err = io.Copy(part, file); err != nil {
		return nil, err
	}
	for k, v := range params {
		if err := writer.WriteField(k, v); err != nil {
			return nil, err
		}
	}
	if err := writer.Close(); err != nil {
		return nil, err
	}

	request, err := http.NewRequest("POST", url, &body)
	if err != nil {
		return nil, err
	}
	request.Header.Add("Content-Type", writer.FormDataContentType())
	return request, nil
}