ntfy-alertmanager/main.go

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"git.xenrox.net/~xenrox/go-log"
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

type receiver struct {
	logger *log.Logger
}

type payload struct {
	Status            string                 `json:"status"`
	Alerts            []alert                `json:"alerts"`
	GroupLabels       map[string]interface{} `json:"groupLabels"`
	CommonLabels      map[string]interface{} `json:"commonLabels"`
	CommonAnnotations map[string]interface{} `json:"commonAnnotations"`
}

type alert struct {
	Status      string                 `json:"status"`
	Labels      map[string]interface{} `json:"labels"`
	Annotations map[string]interface{} `json:"annotations"`
}

func (rcv *receiver) handleWebhooks(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()

	var event payload
	if err := json.NewDecoder(r.Body).Decode(&event); err != nil {
		rcv.logger.Error(err)
		return
	}

	count := len(event.Alerts)
	title := fmt.Sprintf("[%s", strings.ToUpper(event.Status))
	if event.Status == "firing" {
		title = fmt.Sprintf("%s:%d", title, count)
	}

	title += "]"
	for _, value := range event.GroupLabels {
		title = fmt.Sprintf("%s %s", title, value)
	}

	var body string
	c := cases.Title(language.English)

	for _, alert := range event.Alerts {
		alertBody := fmt.Sprintf("%s\nLabels:\n", c.String(alert.Status))
		for key, value := range alert.Labels {
			alertBody = fmt.Sprintf("%s%s = %s\n", alertBody, key, value)
		}

		alertBody += "Annotations:\n"
		for key, value := range alert.Annotations {
			alertBody = fmt.Sprintf("%s%s = %s\n", alertBody, key, value)
		}

		alertBody += "\n"

		body += alertBody
	}

	client := &http.Client{Timeout: time.Second * 3}
	url := "https://ntfy.sh/alertmanager_test"
	req, err := http.NewRequest(http.MethodPost, url, strings.NewReader(body))
	if err != nil {
		rcv.logger.Error(err)
	}

	req.Header.Set("X-Title", title)
	resp, err := client.Do(req)
	if err != nil {
		rcv.logger.Error(err)
	}

	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		rcv.logger.Error("ntfy: received status code %d", resp.StatusCode)
	}
}

func main() {
	logger := log.NewDefaultLogger()

	receiver := &receiver{logger: logger}

	http.HandleFunc("/", receiver.handleWebhooks)
	logger.Fatal(http.ListenAndServe("127.0.0.1:8080", nil))
}