132 lines
3.8 KiB
Go
132 lines
3.8 KiB
Go
package parsemail
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import (
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"bytes"
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"crypto/sha256"
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"encoding/json"
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"errors"
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"fmt"
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"time"
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"git.pcux.cn/xuans/Smail/config"
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"git.pcux.cn/xuans/Smail/utils/context"
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"github.com/emersion/go-message"
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"github.com/emersion/go-message/mail"
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)
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// BuildIMAPBytes 为同一封存储邮件生成稳定的 MIME，确保分段读取与大小、结构一致。
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// 收件视图的密送信息由调用方过滤；此方法只用于 IMAP，不能用于 SMTP 投递。
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func (e *Email) BuildIMAPBytes(_ *context.Context) ([]byte, error) {
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if e == nil || e.From == nil || e.From.EmailAddress == "" {
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return nil, errors.New("invalid sender")
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}
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encoded, err := json.Marshal(e)
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if err != nil {
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return nil, err
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}
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digest := sha256.Sum256(encoded)
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boundary := fmt.Sprintf("smail_%x", digest[:16])
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var h mail.Header
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date, err := time.Parse(time.RFC3339, e.Date)
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if err != nil {
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date, err = time.ParseInLocation(time.DateTime, e.Date, time.Local)
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}
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if err != nil {
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// 历史异常日期不能使用当前时间，否则重复 FETCH 的字节内容会变化。
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date = time.Unix(0, 0).UTC()
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}
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h.SetDate(date)
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messageID := e.MsgID
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if messageID == "" {
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cfg := config.CurrentConfig()
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if cfg == nil || cfg.Domain == "" {
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return nil, errors.New("message id domain is not configured")
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}
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messageID = fmt.Sprintf("%d@%s", e.MessageId, cfg.Domain)
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}
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h.SetMessageID(messageID)
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h.SetSubject(e.Subject)
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sender := e.Sender
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if sender == nil {
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sender = e.From
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}
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for _, field := range []struct {
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name string
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users []*User
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}{
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{"From", []*User{e.From}}, {"Sender", []*User{sender}},
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{"To", e.To}, {"Cc", e.Cc}, {"Bcc", e.Bcc}, {"Reply-To", e.ReplyTo},
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} {
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if len(field.users) == 0 {
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continue
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}
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addresses := make([]*mail.Address, 0, len(field.users))
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for _, user := range field.users {
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if user == nil || user.EmailAddress == "" {
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return nil, errors.New("invalid recipient")
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}
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addresses = append(addresses, &mail.Address{Name: user.Name, Address: user.EmailAddress})
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}
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h.SetAddressList(field.name, addresses)
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}
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h.SetContentType("multipart/mixed", map[string]string{"boundary": boundary + "_mixed"})
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var output bytes.Buffer
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writer, err := message.CreateWriter(&output, h.Header)
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if err != nil {
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return nil, err
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}
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var alternative message.Header
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alternative.SetContentType("multipart/alternative", map[string]string{"boundary": boundary + "_alternative"})
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inline, err := writer.CreatePart(alternative)
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if err != nil {
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return nil, err
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}
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writePart := func(parent *message.Writer, header message.Header, content []byte) error {
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header.Set("Content-Transfer-Encoding", "base64")
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part, err := parent.CreatePart(header)
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if err != nil {
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return err
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}
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return writeMessagePart(part, content)
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}
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if len(e.Text) > 0 || len(e.HTML) == 0 {
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var header message.Header
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header.SetContentType("text/plain", map[string]string{"charset": "utf-8"})
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if err := writePart(inline, header, e.Text); err != nil {
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return nil, err
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}
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}
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if len(e.HTML) > 0 {
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var header message.Header
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header.SetContentType("text/html", map[string]string{"charset": "utf-8"})
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if err := writePart(inline, header, e.HTML); err != nil {
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return nil, err
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}
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}
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if err := inline.Close(); err != nil {
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return nil, err
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}
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for _, attachment := range e.Attachments {
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if attachment == nil {
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return nil, errors.New("nil attachment")
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}
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var header mail.AttachmentHeader
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contentType := attachment.ContentType
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if contentType == "" {
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contentType = "application/octet-stream"
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}
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header.Set("Content-Type", contentType)
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header.SetFilename(attachment.Filename)
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if attachment.ContentID != "" {
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header.Set("Content-ID", fmt.Sprintf("<%s>", attachment.ContentID))
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}
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if err := writePart(writer, header.Header, attachment.Content); err != nil {
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return nil, err
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}
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}
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if err := writer.Close(); err != nil {
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return nil, err
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}
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return output.Bytes(), nil
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}
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