Add Slack-Compatible webhook notification target

Signed-off-by: Knut Ahlers <knut@ahlers.me>

README.md

@@ -20,7 +20,7 @@ Usage of birthday-notifier:
       --fetch-interval duration       How often to fetch birthdays from CardDAV (default 1h0m0s)
       --log-level string              Log level (debug, info, warn, error, fatal) (default "info")
       --notify-days-in-advance ints   Send notification X days before birthday (default [1])
-      --notify-via string             How to send the notification (one of: log, pushover) (default "log")
+      --notify-via strings            How to send the notification (log, pushover, slack) (default [log])
       --version                       Prints current version and exits
       --webdav-base-url string        Webdav server to connect to
       --webdav-pass string            Password for the Webdav user
@@ -39,3 +39,8 @@ To adjust the notification text see the template in [`pkg/formatter/formatter.go
   - `PUSHOVER_API_TOKEN` - Token for the App you've created in the Pushover Dashboard
   - `PUSHOVER_USER_KEY` - Token for the User to send the notification to
   - `PUSHOVER_SOUND` - (Optional) Specify a sound to use
+- **`slack`** - Send notification through Slack(-compatible) webhook
+  - `SLACK_WEBHOOK` - Webhook URL (i.e. `https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX` or `https://discord.com/api/webhooks/00000/XXXXX/slack`)
+  - `SLACK_CHANNEL` - (Optional) Specify the channel to send to
+  - `SLACK_ICON_EMOJI` - (Optional) Emoji to use as user icon
+  - `SLACK_USERNAME` - (Optional) Overwrite the hooks username

main.go

@@ -21,7 +21,7 @@ var (
 		FetchInterval       time.Duration `flag:"fetch-interval" default:"1h" description:"How often to fetch birthdays from CardDAV"`
 		LogLevel            string        `flag:"log-level" default:"info" description:"Log level (debug, info, warn, error, fatal)"`
 		NotifyDaysInAdvance []int         `flag:"notify-days-in-advance" default:"1" description:"Send notification X days before birthday"`
-		NotifyVia           []string      `flag:"notify-via" default:"log" description:"How to send the notification (one of: log, pushover)"`
+		NotifyVia           []string      `flag:"notify-via" default:"log" description:"How to send the notification (log, pushover, slack)"`
 		WebdavBaseURL       string        `flag:"webdav-base-url" default:"" description:"Webdav server to connect to"`
 		WebdavPass          string        `flag:"webdav-pass" default:"" description:"Password for the Webdav user"`
 		WebdavPrincipal     string        `flag:"webdav-principal" default:"principals/users/%s" description:"Principal format to fetch the addressbooks for (%s will be replaced with the webdav-user)"`

notifier.go

@@ -4,6 +4,7 @@ import (
 	"git.luzifer.io/luzifer/birthday-notifier/pkg/notifier"
 	"git.luzifer.io/luzifer/birthday-notifier/pkg/notifier/log"
 	"git.luzifer.io/luzifer/birthday-notifier/pkg/notifier/pushover"
+	"git.luzifer.io/luzifer/birthday-notifier/pkg/notifier/slack"
 )
 
 func getNotifierByName(name string) notifier.Notifier {
@@ -14,6 +15,9 @@ func getNotifierByName(name string) notifier.Notifier {
 	case "pushover":
 		return pushover.Notifier{}
 
+	case "slack":
+		return slack.Notifier{}
+
 	default:
 		return nil
 	}

pkg/formatter/formatter.go

@@ -59,6 +59,22 @@ func FormatNotificationText(contact vcard.Card, when time.Time) (text string, er
 	return buf.String(), nil
 }
 
+// FormatNotificationTitle provides a title from the contacts formatted
+// name or from given and family name
+func FormatNotificationTitle(contact vcard.Card) (title string) {
+	for _, fn := range contact.FormattedNames() {
+		if fn.Value != "" {
+			title = fmt.Sprintf("%s (Birthday)", fn.Value)
+		}
+	}
+
+	if title == "" {
+		title = fmt.Sprintf("%s %s (Birthday)", contact.Name().GivenName, contact.Name().FamilyName)
+	}
+
+	return title
+}
+
 func getAge(t time.Time) int {
 	return dateutil.ProjectToNextBirthday(t).Year() - t.Year()
 }

pkg/notifier/pushover/pushover.go

@@ -43,20 +43,9 @@ func (Notifier) SendNotification(contact vcard.Card, when time.Time) error {
 		return fmt.Errorf("rendering text: %w", err)
 	}
 
-	var title string
-	for _, fn := range contact.FormattedNames() {
-		if fn.Value != "" {
-			title = fmt.Sprintf("%s (Birthday)", fn.Value)
-		}
-	}
-
-	if title == "" {
-		title = fmt.Sprintf("%s %s (Birthday)", contact.Name().GivenName, contact.Name().FamilyName)
-	}
-
 	message := &pushover.Message{
 		Message: text,
-		Title:   title,
+		Title:   formatter.FormatNotificationTitle(contact),
 		Sound:   os.Getenv("PUSHOVER_SOUND"),
 	}
 

pkg/notifier/slack/slack.go

@@ -0,0 +1,85 @@
+// Package slack provides a notifier to send birthday notifications
+// through a Slack(-compatible) WebHook
+package slack
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+
+	"git.luzifer.io/luzifer/birthday-notifier/pkg/formatter"
+	"git.luzifer.io/luzifer/birthday-notifier/pkg/notifier"
+	"github.com/emersion/go-vcard"
+	"github.com/sirupsen/logrus"
+)
+
+const webhookPostTimeout = 2 * time.Second
+
+type (
+	// Notifier implements the notifier interface
+	Notifier struct{}
+)
+
+var _ notifier.Notifier = Notifier{}
+
+// SendNotification implements the Notifier interface
+func (Notifier) SendNotification(contact vcard.Card, when time.Time) error {
+	if contact.Name() == nil {
+		return fmt.Errorf("contact has no name")
+	}
+
+	webhookURL := os.Getenv("SLACK_WEBHOOK")
+
+	if webhookURL == "" {
+		return fmt.Errorf("missing SLACK_WEBHOOK env variable")
+	}
+
+	text, err := formatter.FormatNotificationText(contact, when)
+	if err != nil {
+		return fmt.Errorf("rendering text: %w", err)
+	}
+
+	payload := new(bytes.Buffer)
+	if err = json.NewEncoder(payload).Encode(struct {
+		Channel   string `json:"channel,omitempty"`
+		IconEmoji string `json:"icon_emoji,omitempty"`
+		Text      string `json:"text"`
+		Username  string `json:"username,omitempty"`
+	}{
+		Channel:   os.Getenv("SLACK_CHANNEL"),
+		IconEmoji: os.Getenv("SLACK_ICON_EMOJI"),
+		Text:      text,
+		Username:  os.Getenv("SLACK_USERNAME"),
+	}); err != nil {
+		return fmt.Errorf("encoding hook payload: %w", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), webhookPostTimeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, payload)
+	if err != nil {
+		return fmt.Errorf("creating request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("executing request: %w", err)
+	}
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			logrus.WithError(err).Error("closing slack response body (leaked fd)")
+		}
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status %d", resp.StatusCode)
+	}
+
+	return nil
+}