package lib import ( "bufio" "io" "mime" "net/http" "os" "path/filepath" "github.com/emersion/go-message/mail" "github.com/pkg/errors" ) type Part struct { MimeType string Params map[string]string Body io.Reader } func NewPart(mimetype string, params map[string]string, body io.Reader) *Part { return &Part{ MimeType: mimetype, Params: params, Body: body, } } type Attachment interface { Name() string WriteTo(w *mail.Writer) error } type FileAttachment struct { path string } func NewFileAttachment(path string) *FileAttachment { return &FileAttachment{ path, } } func (fa *FileAttachment) Name() string { return fa.path } func (fa *FileAttachment) WriteTo(w *mail.Writer) error { f, err := os.Open(fa.path) if err != nil { return errors.Wrap(err, "os.Open") } defer f.Close() reader := bufio.NewReader(f) // if we have an extension, prefer that instead of trying to sniff the header. // That's generally more accurate than sniffing as lots of things are zip files // under the hood, e.g. most office file types ext := filepath.Ext(fa.path) var mimeString string if mimeString = mime.TypeByExtension(ext); mimeString != "" { // found it in the DB } else { // Sniff the mime type instead // http.DetectContentType only cares about the first 512 bytes head, err := reader.Peek(512) if err != nil && err != io.EOF { return errors.Wrap(err, "Peek") } mimeString = http.DetectContentType(head) } // mimeString can contain type and params (like text encoding), // so we need to break them apart before passing them to the headers mimeType, params, err := mime.ParseMediaType(mimeString) if err != nil { return errors.Wrap(err, "ParseMediaType") } filename := filepath.Base(fa.path) params["name"] = filename // set header fields ah := mail.AttachmentHeader{} ah.SetContentType(mimeType, params) // setting the filename auto sets the content disposition ah.SetFilename(filename) aw, err := w.CreateAttachment(ah) if err != nil { return errors.Wrap(err, "CreateAttachment") } defer aw.Close() if _, err := reader.WriteTo(aw); err != nil { return errors.Wrap(err, "reader.WriteTo") } return nil } type PartAttachment struct { part *Part name string } func NewPartAttachment(part *Part, name string) *PartAttachment { return &PartAttachment{ part, name, } } func (pa *PartAttachment) Name() string { return pa.name } func (pa *PartAttachment) WriteTo(w *mail.Writer) error { // set header fields ah := mail.AttachmentHeader{} ah.SetContentType(pa.part.MimeType, pa.part.Params) // setting the filename auto sets the content disposition ah.SetFilename(pa.Name()) aw, err := w.CreateAttachment(ah) if err != nil { return errors.Wrap(err, "CreateAttachment") } defer aw.Close() if _, err := io.Copy(aw, pa.part.Body); err != nil { return errors.Wrap(err, "io.Copy") } return nil }