Method chatPostMessage

backend/plugin/webhook/slack/app.go:200–244

https://api.slack.com/methods/chat.postMessage

(ctx context.Context, channelID string, webhookContext webhook.Context)

// https://api.slack.com/methods/chat.postMessage
func (p *provider) chatPostMessage(ctx context.Context, channelID string, webhookContext webhook.Context) error {
	msg := BuildMessage(webhookContext)
	attachmentsJSON, err := json.Marshal(msg.Attachments)
	if err != nil {
		return errors.Wrapf(err, "failed to marshal attachments")
	}

	data := url.Values{}
	data.Set("channel", channelID)
	if msg.Text != "" {
		data.Set("text", msg.Text)
	}
	data.Set("attachments", string(attachmentsJSON))

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, "https://slack.com/api/chat.postMessage", strings.NewReader(data.Encode()))
	if err != nil {
		return errors.Wrapf(err, "failed to new request")
	}
	req.Header.Add("Authorization", "Bearer "+p.token)
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := p.c.Do(req)
	if err != nil {
		return errors.Wrapf(err, "failed to send request")
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return errors.Errorf("received non-200 status code %d", resp.StatusCode)
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return errors.Wrapf(err, "failed to read body")
	}
	var res chatPostMessageResponse
	if err := json.Unmarshal(body, &res); err != nil {
		return errors.Wrapf(err, "failed to unmarshal")
	}
	if !res.OK {
		return errors.Errorf("failed to post message, error: %v", res.Error)
	}

	return nil
}