//------------------------------------------------------------------------------
// Getting and monitoring Elasticsearch indices and send the metrics into zabbix
//-------------------------------------------------------------------------------
// Author: Sergey Kalinin
// e-mail: svk@nuk-svk.ru
// website: https://nuk-svk.ru
// Git repos: https://git.nuk-svk.ru
//-------------------------------------------------------------------------------
// Require:
// github.com/adubkov/go-zabbix 
// github.com/elastic/go-elasticsearch
//-------------------------------------------------------------------------------
// ZABBIX_SERVER="zabbix"
// ZABBIX_PORT="10051"
// ZABBIX_HOST="elastic cluster"
// ELASTICSEARCH_URL="https://user:pass@elastic:9200"
//-------------------------------------------------------------------------------

package main

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/adubkov/go-zabbix"
	"github.com/elastic/go-elasticsearch/v7"
	"github.com/elastic/go-elasticsearch/v7/esapi"
)

type json_records struct {
	INDEX        string
	RECORD_COUNT int
}

// Определяем входит ли строка в slice
func StringContains(a []string, x string) bool {
	for _, n := range a {
		if x == n {
			return true
		}
	}
	return false
}

func EsSearch(index_name string, es_request_time_range int) int {
	var (
		r map[string]interface{}
	)
	request_time_range := "now-" + strconv.Itoa(es_request_time_range) + "h"

	cfg := elasticsearch.Config{
		// Addresses: []string{
		// 	"http://localhost:9200",
		// 	"http://localhost:9201",
		// },
		// Username: "foo",
		// Password: "bar",
		Transport: &http.Transport{
			MaxIdleConnsPerHost:   10,
			ResponseHeaderTimeout: 60 * time.Second,
			DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
			TLSClientConfig: &tls.Config{
				MaxVersion:         tls.VersionTLS11,
				InsecureSkipVerify: true,
			},
		},
	}

	es, err := elasticsearch.NewClient(cfg)
	if err != nil {
		log.Fatalf("Error creating the client: %s", err)
	}
	res, err := es.Info()
	if err != nil {
		log.Fatalf("Error getting response: %s", err)
	}
	defer res.Body.Close()
	// Check response status
	if res.IsError() {
		log.Fatalf("Error: %s", res.String())
	}
	var buf bytes.Buffer
	query := map[string]interface{}{
		"query": map[string]interface{}{
			"range": map[string]interface{}{
				"@timestamp": map[string]interface{}{
					// "gt": "now-1h",
					"gt": request_time_range,
				},
				// "match": map[string]interface{}{
				// 	"host": "10.250.1.212",
			},
		},
		"size": 1,
		"sort": map[string]interface{}{
			"@timestamp": map[string]interface{}{
				"order": "desc",
			},
		},
	}
	if err := json.NewEncoder(&buf).Encode(query); err != nil {
		log.Fatalf("Error encoding query: %s", err)
	}

	// Perform the search request.
	res, err = es.Search(
		es.Search.WithContext(context.Background()),
		es.Search.WithIndex(index_name+"*"),
		es.Search.WithBody(&buf),
		es.Search.WithTrackTotalHits(true),
		es.Search.WithPretty(),
	)
	if err != nil {
		log.Fatalf("Error getting response: %s", err)
	}
	defer res.Body.Close()

	if res.IsError() {
		var e map[string]interface{}
		if err := json.NewDecoder(res.Body).Decode(&e); err != nil {
			log.Fatalf("Error parsing the response body: %s", err)
		} else {
			// Print the response status and error information.
			log.Fatalf("[%s] %s: %s",
				res.Status(),
				e["error"].(map[string]interface{})["type"],
				e["error"].(map[string]interface{})["reason"],
			)
		}
	}

	if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
		log.Fatalf("Error parsing the response body: %s", err)
	}
	// Вывод статуса, количество выбранных записей и времени запроса
	hits := int(r["hits"].(map[string]interface{})["total"].(map[string]interface{})["value"].(float64))
	return hits
}

func EsIndexDiscover(es_index_list []string) string {
	result_discovery_json := string("{\"data\": [")

	for _, value := range es_index_list {
		// result_discovery_json = result_discovery_json + "{\"{#INDEX}\":\"" + value + "\",\"{#ITEM_TYPE}\":\"Records count\"" + "},"
		result_discovery_json = result_discovery_json + "{\"{#INDEX}\":\"" + value + "\"" + "},"
	}
	result_discovery_json = strings.TrimRight(result_discovery_json, ",") + "]}"
	// fmt.Println(result_discovery_json)
	return (result_discovery_json)
}

func EsIndexRecordsCount(es_index_list []string, es_request_time_range int) {
	// fmt.Println(es_request_time_range)
	result_index := make(map[int]json_records)
	j := int(0)
	for _, value := range es_index_list {
		result_index[j] = json_records{value, EsSearch(value, es_request_time_range)}
		j++
	}
	log.Println(result_index)
}

func EsClusterInfo(es *elasticsearch.Client) {
	var (
		r map[string]interface{}
	)
	// 1. Get cluster info
	res, err := es.Info()
	if err != nil {
		log.Fatalf("Error getting response: %s", err)
	}
	defer res.Body.Close()
	// Check response status
	if res.IsError() {
		log.Fatalf("Error: %s", res.String())
	}
	// Deserialize the response into a map.
	if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
		log.Fatalf("Error parsing the response body: %s", err)
	}
	// Print client and server version numbers.
	fmt.Printf("Client: %s\n", elasticsearch.Version)
	fmt.Printf("Client: %s\n", elasticsearch.Version)
	fmt.Printf("Server: %s\n", r["version"].(map[string]interface{})["number"])
}

func EsIndexFieldExists(es *elasticsearch.Client, index_name string, field_name string) bool {
	// Check if the filed exists into index
	var (
		fields_request map[string]interface{}
		fields         []string
		indices        []string
		field_exists   bool
	)
	fields = append(fields, field_name)
	indices = append(indices, index_name)

	req := esapi.FieldCapsRequest{
		// Index:  []string{},
		Index:  indices,
		Fields: fields,
	}

	res, err := req.Do(context.Background(), es)
	if err != nil {
		log.Fatalf("ERROR: %s", err)
	}
	if err := json.NewDecoder(res.Body).Decode(&fields_request); err != nil {
		log.Fatalf("->Error parsing the response body: %s", err)
	}

	for i, f := range fields_request {
		if i == "fields" {
			// if f.(map[string]interface{})[`@timestamp`] == nil {
			if f.(map[string]interface{})[field_name] == nil {
				field_exists = false
			} else {
				field_exists = true
			}
		}
	}
	return (field_exists)
}

func EsGetIndices(es *elasticsearch.Client) []string {
	//Get indices list
	var (
		index_request []map[string]interface{}
		es_index_list []string
	)
	req := esapi.CatIndicesRequest{
		// Index:  []string{},
		Format: "JSON",
		// ExpandWildcards,
	}

	res, err := req.Do(context.Background(), es)
	if err != nil {
		log.Fatalf("ERROR: %s", err)
	}

	if err := json.NewDecoder(res.Body).Decode(&index_request); err != nil {
		log.Fatalf("Error parsing the response body: %s", err)
	}
	for _, hit := range index_request {
		m := regexp.MustCompile("-[0-9]")
		// позиция вхождения регулярки в имени индекса
		i := m.FindStringIndex(hit["index"].(string))
		// наименование индекса
		index_name := hit["index"].(string)

		// Checking the @timestamp field exists
		if !EsIndexFieldExists(es, index_name, `@timestamp`) {
			continue
			// fmt.Println(EsIndexFieldExists(es, index_name))
		}

		// Итоговое наименование индекса
		var index_name_short string
		// Исключаем индексы от кибаны (.kibana-*) и обрезаем цифры (даты и версии)
		if !strings.HasPrefix(index_name, ".") {
			if i != nil {
				index_name_short = strings.TrimSpace(index_name[0:i[0]])
			} else {
				index_name_short = strings.TrimSpace(index_name)
			}
			if !StringContains(es_index_list, index_name_short) {
				es_index_list = append(es_index_list, index_name_short)
			}
		}
	}
	return (es_index_list)
}

func ZabbixSender(zabbix_host string, metric_name string, metric_value string) bool {
	var (
		metrics     []*zabbix.Metric
		zabbix_port int
		err         error
	)
	zabbix_server := os.Getenv("ZABBIX_SERVER")

	// Read and checkin zabbix server and port
	if zabbix_server == "" {
		log.Println("Login error: make sure environment variables `ZABBIX_SERVER` are defined")
		os.Exit(1)
	}
	if os.Getenv("ZABBIX_PORT") == "" {
		log.Println("Login error: make sure environment variables `ZABBIX_PORT` are defined")
		os.Exit(1)
	}
	if zabbix_port, err = strconv.Atoi(os.Getenv("ZABBIX_PORT")); err != nil {
		log.Println(zabbix_port, "Zabbix port value error")
	}

	metrics = append(metrics, zabbix.NewMetric(zabbix_host, metric_name, metric_value, time.Now().Unix()))
	metrics = append(metrics, zabbix.NewMetric(zabbix_host, "status", "OK"))

	// Create instance of Packet class
	packet := zabbix.NewPacket(metrics)
	// fmt.Println(zabbix_host, metric_name, metric_value, metrics)
	// Send packet to zabbix
	z := zabbix.NewSender(zabbix_server, zabbix_port)
	res, err := z.Send(packet)
	log.Println(string(res))
	return true
}

//---------------------------------------------------------------------------
func main() {
	var (
		operation             string
		es_index_name         string
		es_request_time_range int
		zabbix_send           bool
		// zabbix_port           int
	)

	flag.StringVar(&es_index_name, "indexname", "", "Elasticsearch index name pattern, (like \"filebeat\")")
	flag.IntVar(&es_request_time_range, "timerange", 6, "Elasticsearch time range for records count into hours")
	flag.BoolVar(&zabbix_send, "zabbix-send", false, "Send metrics or discovery data into zabbix")

	flag.StringVar(&operation, "operation", "es-cluster-info", "Opertation type, must be:\n\tes-cluster-info - ES Cluster information (version e.t.c)\n\tes-get-indices - geting all index\n\tes-indices-discover - getting es index pattern list\n\tes-records-count - getting the number of records for a time range for all index pattern\n\tes-index-records-count - getting records count for one index (used with -indexname option")

	flag.Parse()

	zabbix_host := os.Getenv("ZABBIX_HOST")
	if zabbix_host == "" {
		fmt.Println("Send error: make sure environment variables `ZABBIX_HOST`")
		os.Exit(1)
	}
	// if es_request_time_range > 24 {
	// 	log.Println("Error: Time range must be a number between 1 and 24")
	// 	os.Exit(1)
	// }

	cfg := elasticsearch.Config{
		Transport: &http.Transport{
			MaxIdleConnsPerHost:   10,
			ResponseHeaderTimeout: 30 * time.Second,
			DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
			TLSClientConfig: &tls.Config{
				MaxVersion:         tls.VersionTLS11,
				InsecureSkipVerify: true,
			},
		},
	}

	es, err := elasticsearch.NewClient(cfg)
	if err != nil {
		log.Fatalf("Error creating the client: %s", err)
	}
	// fmt.Println(operation)
	switch operation {
	case "es-cluster-info":
		EsClusterInfo(es)
	case "es-get-indices":
		// fmt.Println(operation)
		for _, index := range EsGetIndices(es) {
			fmt.Println(index)
		}
	case "es-indices-discover":
		result_discovery_json := EsIndexDiscover(EsGetIndices(es))
		// fmt.Println(zabbix_send)
		if zabbix_send == true {
			ZabbixSender(zabbix_host, "indices", result_discovery_json)
		}
		fmt.Println(result_discovery_json)
	case "es-records-count":
		// records count for all indices
		// EsIndexRecordsCount(EsGetIndices(es), es_request_time_range)
		result_index := make(map[int]json_records)
		j := int(0)
		for _, es_index_name := range EsGetIndices(es) {
			result := EsSearch(es_index_name, es_request_time_range)
			result_index[j] = json_records{es_index_name, result}
			log.Println("ES index name:", es_index_name, "; Query time period:", es_request_time_range, "; Records count:", result)
			if zabbix_send == true {
				ZabbixSender(zabbix_host, `indices.records_count[`+es_index_name+`]`, strconv.Itoa(result))
				ZabbixSender(zabbix_host, `indices.records_count_time_range[`+es_index_name+`]`, strconv.Itoa(es_request_time_range))
			}
			j++
		}
	case "es-index-records-count":
		// records count for one index
		result := EsSearch(es_index_name, es_request_time_range)
		if zabbix_send == true {
			ZabbixSender(zabbix_host, `indices.records_count[`+es_index_name+`]`, strconv.Itoa(result))
			ZabbixSender(zabbix_host, `indices.records_count_time_range[`+es_index_name+`]`, strconv.Itoa(es_request_time_range))
		}
		log.Println("ES index name:", es_index_name, "; Query time period:", es_request_time_range, "; Records count:", result)
	}
}