nikoksr/notify

package viber

import (
    "context"
    "fmt"

    vb "github.com/mileusna/viber"
)

type viberClient interface {
    SetWebhook(url string, eventTypes []string) (vb.WebhookResp, error)
    SendTextMessage(receiver, msg string) (uint64, error)
}

// Compile-time check to ensure that vb.Viber implements the viberClient interface.
var _ viberClient = new(vb.Viber)

// Viber struct holds necessary fields to communicate with Viber API.
type Viber struct {
    Client            viberClient
    SubscribedUserIDs []string
}

// New returns a new instance of Viber notification service.
func New(appKey, senderName, senderAvatar string) *Viber {
    return &Viber{
        Client:            vb.New(appKey, senderName, senderAvatar),
        SubscribedUserIDs: []string{},
    }
}

// AddReceivers receives subscribed user IDs then add them to internal receivers list.
func (v *Viber) AddReceivers(subscribedUserIDs ...string) {
    v.SubscribedUserIDs = append(v.SubscribedUserIDs, subscribedUserIDs...)
}

// SetWebhook receives a URL that will we used as a webhook URL for Viber.
func (v *Viber) SetWebhook(webhookURL string) error {
    _, err := v.Client.SetWebhook(webhookURL, []string{})
    return err
}

// Send takes a message subject and a message body and sends them to all previously set userIds.
func (v *Viber) Send(ctx context.Context, subject, message string) error {
    fullMessage := subject + "\n" + message // Treating subject as message title

    for _, subscribedUserID := range v.SubscribedUserIDs {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
            if _, err := v.Client.SendTextMessage(subscribedUserID, fullMessage); err != nil {
                return fmt.Errorf("send message to user %q: %w", subscribedUserID, err)
            }
        }
    }

    return nil
}