golang to get zabbix graph by itemid

zabbix_client.go

// Copyright (C) 2018 郑欣 <zhngxin@aliyun.com>

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//  Author: 郑欣 <zhngxin@aliyun.com>

/*
This Package provides a simple client to download graph from zabbix by itemID to jpg image file.

Usage:
    client = zabbix.New("http://127.0.0.1/zabbix","Admin","password")
    client.SaveImage("73723","")
    client.SaveImage("73723","~/Pictures/temp.jpg")
*/
package zabbix

import (
	"../../../settings"
	"../../constatns"
	"fmt"
	"io"
	"net/http"
	"net/http/cookiejar"
	"os"
	"path/filepath"
	"time"
)

var(
  BaseDir string
)
func init(){
  BaseDir, _ = os.Getwd()
}

func getTimeStr() string {
	timeDelta, _ := time.ParseDuration("-3h")
	stime := time.Now().Add(timeDelta)
	timeStr := stime.Format("20060102150405")
	return timeStr
}

type Client struct {
	client   *http.Client
	username string
	password string
	url      string
}

func New(url, username, password string) *Client {
	jar, _ := cookiejar.New(nil)
	client := &http.Client{
		Timeout: constatns.HttpRequestTimeOut,
		Jar:     jar,
	}
	return &Client{
		client:   client,
		username: username,
		password: password,
		url:      url,
	}
}

func (client *Client) indexUrl() string {
	return fmt.Sprintf("%s/index.php", client.url)
}

func (client *Client) login() error {
	req, err := http.NewRequest("GET", client.indexUrl(), nil)
	if err != nil {
		fmt.Println(err)
		return err
	}
	urlQuery := req.URL.Query()
	urlQuery.Add("request", "charts.php?ddreset=1")
	urlQuery.Add("name", client.username)
	urlQuery.Add("password", client.password)
	urlQuery.Add("autologin", "1")
	urlQuery.Add("enter", "Sign in")
	req.URL.RawQuery = urlQuery.Encode()
	req.Header.Set("User-Agent", "Mozilla/5.0 (X11; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0")
	req.Header.Set("Referer", client.indexUrl())
	res, err := client.client.Do(req)
	if err != nil {
		return err
	}
	defer res.Body.Close()
	return nil
}

func (client *Client) SaveImage(itemid, fileName string) (string, error) {
	req, err := http.NewRequest("GET", client.url+"/chart.php", nil)
	if err != nil {
		return "", fmt.Errorf("ZabbixClient:SaveImage:GenerateUrl:%v", err)
	}
	err = client.login()
	if err != nil {
		return "", fmt.Errorf("ZabbixClient:SaveImage:GetCookies:%v", err)

	}
	urlQuery := req.URL.Query()
	urlQuery.Add("itemids", itemid)
	urlQuery.Add("period", "7200")
	urlQuery.Add("width", "600")
	timeStr := getTimeStr()
	urlQuery.Add("time", timeStr)
	req.URL.RawQuery = urlQuery.Encode()
	res, err := client.client.Do(req)
	if err != nil {
		return "", fmt.Errorf("ZabbixClient:SaveImage:RequestImage:%v", err)
	}
	defer res.Body.Close()
	if fileName == "" {
		fileName = filepath.Join(BaseDir, "tmp", timeStr+".jpg")
	}

	out, err := os.Create(fileName)
	if err != nil {
		return fileName, fmt.Errorf("ZabbixClient:SaveImage:CreateImage:%v", err)
	}
	defer out.Close()

	_, err = io.Copy(out, res.Body)
	if err != nil {
		return fileName, fmt.Errorf("ZabbixClient:SaveImage:SaveImage:%v", err)
	}
	return fileName, nil
}