1 files changed, 136 insertions, 0 deletions
diff --git a/lib/attachment.go b/lib/attachment.go
new file mode 100644
index 0000000..d7cbf3f
--- /dev/null
+++ b/lib/attachment.go
@@ -0,0 +1,136 @@
+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
+}