nikoksr/notify

package sendgrid

import (
    "context"
    "errors"
    "fmt"
    "net/http"

    "github.com/sendgrid/sendgrid-go"
    "github.com/sendgrid/sendgrid-go/helpers/mail"
)

// SendGrid struct holds necessary data to communicate with the SendGrid API.
type SendGrid struct {
    client            *sendgrid.Client
    senderAddress     string
    senderName        string
    receiverAddresses []string
}

// New returns a new instance of a SendGrid notification service.
// You will need a SendGrid API key.
// See https://sendgrid.com/docs/for-developers/sending-email/api-getting-started/
func New(apiKey, senderAddress, senderName string) *SendGrid {
    return &SendGrid{
        client:            sendgrid.NewSendClient(apiKey),
        senderAddress:     senderAddress,
        senderName:        senderName,
        receiverAddresses: []string{},
    }
}

// AddReceivers takes email addresses and adds them to the internal address list. The Send method will send
// a given message to all those addresses.
func (s *SendGrid) AddReceivers(addresses ...string) {
    s.receiverAddresses = append(s.receiverAddresses, addresses...)
}

// Send takes a message subject and a message body and sends them to all previously set chats. Message body supports
// html as markup language.
func (s SendGrid) Send(ctx context.Context, subject, message string) error {
    from := mail.NewEmail(s.senderName, s.senderAddress)
    content := mail.NewContent("text/html", message)

    // Create a new personalization instance to be able to add multiple receiver addresses.
    personalization := mail.NewPersonalization()
    personalization.Subject = subject

    for _, receiverAddress := range s.receiverAddresses {
        personalization.AddTos(mail.NewEmail(receiverAddress, receiverAddress))
    }

    mailMessage := mail.NewV3Mail()
    mailMessage.AddPersonalizations(personalization)
    mailMessage.AddContent(content)
    mailMessage.SetFrom(from)

    select {
    case <-ctx.Done():
        return ctx.Err()
    default:
        resp, err := s.client.Send(mailMessage)
        if err != nil {
            return fmt.Errorf("send message: %w", err)
        }

        if resp.StatusCode != http.StatusAccepted {
            return errors.New("the SendGrid endpoint did not accept the message")
        }
    }

    return nil
}