package messenger

import "net/textproto"

// Messenger is an interface for a generic messaging backend,
// for instance, e-mail, SMS etc.
type Messenger interface {
	Name() string

	Push(fromAddr string, toAddr []string, subject string, message []byte, atts []*Attachment) error
	Flush() error
}

// Attachment represents a file or blob attachment that can be
// sent along with a message by a Messenger.
type Attachment struct {
	Name    string
	Header  textproto.MIMEHeader
	Content []byte
}

// MakeAttachmentHeader is a helper function that returns a
// textproto.MIMEHeader tailored for attachments, primarily
// email. If no encoding is given, base64 is assumed.
func MakeAttachmentHeader(filename, encoding string) textproto.MIMEHeader {
	if encoding == "" {
		encoding = "base64"
	}
	h := textproto.MIMEHeader{}
	h.Set("Content-Disposition", "attachment; filename="+filename)
	h.Set("Content-Type", "application/json; name=\""+filename+"\"")
	h.Set("Content-Transfer-Encoding", encoding)
	return h
}