Add Slack notifier component

pkg/notifier/slack.go

@@ -0,0 +1,102 @@
+package notifier
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+)
+
+// Slack holds the hook URL
+type Slack struct {
+	URL       string
+	Username  string
+	Channel   string
+	IconEmoji string
+}
+
+// SlackPayload holds the channel and attachments
+type SlackPayload struct {
+	Channel     string            `json:"channel"`
+	Username    string            `json:"username"`
+	IconUrl     string            `json:"icon_url"`
+	IconEmoji   string            `json:"icon_emoji"`
+	Text        string            `json:"text,omitempty"`
+	Attachments []SlackAttachment `json:"attachments,omitempty"`
+}
+
+// SlackAttachment holds the markdown message body
+type SlackAttachment struct {
+	Color      string   `json:"color"`
+	AuthorName string   `json:"author_name"`
+	Text       string   `json:"text"`
+	MrkdwnIn   []string `json:"mrkdwn_in"`
+}
+
+// NewSlack validates the Slack URL and returns a Slack object
+func NewSlack(hookURL string, username string, channel string) (*Slack, error) {
+	_, err := url.ParseRequestURI(hookURL)
+	if err != nil {
+		return nil, fmt.Errorf("invalid Slack hook URL %s", hookURL)
+	}
+
+	if username == "" {
+		return nil, errors.New("empty Slack username")
+	}
+
+	if channel == "" {
+		return nil, errors.New("empty Slack channel")
+	}
+
+	return &Slack{
+		Channel:   channel,
+		URL:       hookURL,
+		Username:  username,
+		IconEmoji: ":rocket:",
+	}, nil
+}
+
+// Post Slack message
+func (s *Slack) Post(workload string, namespace string, message string, warn bool) error {
+	payload := SlackPayload{
+		Channel:  s.Channel,
+		Username: s.Username,
+	}
+
+	color := "good"
+	if warn {
+		color = "danger"
+	}
+
+	a := SlackAttachment{
+		Color:      color,
+		AuthorName: fmt.Sprintf("%s.%s", workload, namespace),
+		Text:       message,
+		MrkdwnIn:   []string{"text"},
+	}
+
+	payload.Attachments = []SlackAttachment{a}
+
+	data, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("marshalling slack payload failed %v", err)
+	}
+
+	b := bytes.NewBuffer(data)
+
+	if res, err := http.Post(s.URL, "application/json", b); err != nil {
+		return fmt.Errorf("sending data to slack failed %v", err)
+	} else {
+		defer res.Body.Close()
+		statusCode := res.StatusCode
+		if statusCode != 200 {
+			body, _ := ioutil.ReadAll(res.Body)
+			return fmt.Errorf("sending data to slack failed %v", string(body))
+		}
+	}
+
+	return nil
+}