package yandex

import (
	"bytes"
	"fmt"
	"mime/multipart"
	"net/textproto"
	"strings"
)

const (
	defaultContentType   = "text/cloud-config"
	shellContentType     = "text/x-shellscript"
	multipartContentType = "multipart/mixed"
)

const (
	cloudInitIPv6Config = `#!/usr/bin/env bash
dhclient -6 eth0
`
)

// MergeCloudUserMetaData allow merge some user-data sections
func MergeCloudUserMetaData(usersData ...string) (string, error) {
	buff := new(bytes.Buffer)
	data := multipart.NewWriter(buff)
	_, err := buff.WriteString(fmt.Sprintf("Content-Type: %s; boundary=\"%s\"\r\n", multipartContentType, data.Boundary()))
	if err != nil {
		return "", err
	}
	_, err = buff.WriteString("MIME-Version: 1.0\r\n\r\n")
	if err != nil {
		return "", err
	}

	for i, userData := range usersData {
		if len(userData) != 0 {
			w, err := data.CreatePart(textproto.MIMEHeader{
				"Content-Disposition": {fmt.Sprintf("attachment; filename=\"user-data-%d\"", i)},
				"Content-Type":        {detectContentType(userData)},
			})
			if err != nil {
				return "", err
			}
			_, err = w.Write([]byte(userData))
			if err != nil {
				return "", err
			}
		}
	}
	return buff.String(), nil
}

func detectContentType(content string) string {
	switch {
	case strings.HasPrefix(content, "#!"):
		return shellContentType
	case strings.HasPrefix(content, "#cloud-config"):
		return defaultContentType
	}

	return defaultContentType
}