") || strings.Contains(body, "
") ||
strings.Contains(body, "
") || strings.Contains(body, " 0 {
data = attachment.Data
fileName = attachment.Name
} else {
data, err = l.readAttachmentFile(attachment.Content)
if err != nil {
return err
}
fileName = filepath.Base(attachment.Content)
}
if attachment.Name != "" {
fileName = attachment.Name
}
// 检测 MIME 类型
mimeType := attachment.ContentType
if mimeType == "" {
mimeType = mime.TypeByExtension(filepath.Ext(fileName))
if mimeType == "" {
mimeType = "application/octet-stream"
}
}
buffer.WriteString(fmt.Sprintf("--%s\r\n", boundary))
buffer.WriteString("Content-Transfer-Encoding: base64\r\n")
buffer.WriteString(fmt.Sprintf("Content-Disposition: attachment; filename=%s\r\n", fileName))
buffer.WriteString(fmt.Sprintf("Content-Type: %s; name=%s\r\n\r\n", mimeType, fileName))
// base64编码
encoded := base64.StdEncoding.EncodeToString(data)
for i := 0; i < len(encoded); i += 76 {
end := i + 76
if end > len(encoded) {
end = len(encoded)
}
buffer.WriteString(encoded[i:end] + "\r\n")
}
return nil
}
// 写入内嵌图片
func (l *Smtp) writeInlineImage(buffer *bytes.Buffer, boundary string, attachment interfaces.Attachment, ctx context.Context) error {
var data []byte
var err error
var fileName string
// 获取数据
if len(attachment.Data) > 0 {
data = attachment.Data
fileName = attachment.Name
} else {
data, err = l.readAttachmentFile(attachment.Content)
if err != nil {
return err
}
fileName = filepath.Base(attachment.Content)
}
if attachment.Name != "" {
fileName = attachment.Name
}
// 检测 MIME 类型
mimeType := attachment.ContentType
if mimeType == "" {
mimeType = mime.TypeByExtension(filepath.Ext(fileName))
if mimeType == "" {
mimeType = "image/jpeg" // 默认图片类型
}
}
// 生成 Content-ID
cid := attachment.CID
if cid == "" {
cid = fmt.Sprintf("img_%d_%s", time.Now().UnixNano(), strings.ReplaceAll(fileName, ".", "_"))
}
buffer.WriteString(fmt.Sprintf("--%s\r\n", boundary))
buffer.WriteString("Content-Transfer-Encoding: base64\r\n")
buffer.WriteString(fmt.Sprintf("Content-Disposition: inline; filename=%s\r\n", fileName))
buffer.WriteString(fmt.Sprintf("Content-Type: %s; name=%s\r\n", mimeType, fileName))
buffer.WriteString(fmt.Sprintf("Content-ID: <%s>\r\n\r\n", cid))
// base64编码
encoded := base64.StdEncoding.EncodeToString(data)
for i := 0; i < len(encoded); i += 76 {
end := i + 76
if end > len(encoded) {
end = len(encoded)
}
buffer.WriteString(encoded[i:end] + "\r\n")
}
return nil
}
// 读取附件文件
func (l *Smtp) readAttachmentFile(fileName string) ([]byte, error) {
stat, err := os.Stat(fileName)
if err != nil {
return nil, fmt.Errorf("file stat failed: %w", err)
}
if stat.Size() > MaxAttachmentSize {
return nil, fmt.Errorf("attachment too large: %d bytes (max: %d)", stat.Size(), MaxAttachmentSize)
}
return os.ReadFile(fileName)
}
// 行包装器，用于base64编码时的换行
type lineWrapper struct {
w io.Writer
count int
}
func (lw *lineWrapper) Write(p []byte) (n int, err error) {
for i, b := range p {
if lw.count == 76 {
if _, err := lw.w.Write([]byte("\r\n")); err != nil {
return i, err
}
lw.count = 0
}
if _, err := lw.w.Write([]byte{b}); err != nil {
return i, err
}
lw.count++
}
return len(p), nil
}