Embedding images in mail

3 files changed, 184 insertions, 27 deletions

diff --git a/internal/feed/feed.go b/internal/feed/feed.go
index ddc91ed..1a6ef97 100644
--- a/internal/feed/feed.go
+++ b/internal/feed/feed.go
@@ -23,11 +23,18 @@ type feedDescriptor struct {
 	Url  string
 }
 
+type feedImage struct {
+	image []byte
+	mime  string
+}
+
 type feeditem struct {
 	*gofeed.Feed
 	*gofeed.Item
+	Body       string
 	updateOnly bool
 	reasons    []string
+	images     []feedImage
 }
 
 // Creator returns the name of the creating author.
@@ -45,6 +52,16 @@ func (item *feeditem) addReason(reason string) {
 	}
 }
 
+func (item *feeditem) addImage(img []byte, mime string) int {
+	i := feedImage{img, mime}
+	item.images = append(item.images, i)
+	return len(item.images)
+}
+
+func (item *feeditem) clearImages() {
+	item.images = []feedImage{}
+}
+
 func (feed *Feed) descriptor() feedDescriptor {
 	return feedDescriptor{
 		Name: feed.Name,
diff --git a/internal/feed/mail.go b/internal/feed/mail.go
index 620b444..5f543e4 100644
--- a/internal/feed/mail.go
+++ b/internal/feed/mail.go
@@ -2,15 +2,22 @@ package feed
 
 import (
 	"bytes"
+	"encoding/base64"
 	"fmt"
 	"io"
+	"io/ioutil"
+	"mime"
+	"path"
 	"strings"
 	"time"
 
+	"github.com/PuerkitoBio/goquery"
+	"github.com/emersion/go-message"
 	"github.com/emersion/go-message/mail"
 
 	"github.com/Necoro/feed2imap-go/internal/feed/template"
 	"github.com/Necoro/feed2imap-go/pkg/config"
+	"github.com/Necoro/feed2imap-go/pkg/log"
 )
 
 func address(name, address string) []*mail.Address {
@@ -36,8 +43,9 @@ func writeHtml(writer io.Writer, item feeditem) error {
 	return template.Feed.Execute(writer, item)
 }
 
-func writeToBuffer(b *bytes.Buffer, feed *Feed, item feeditem, cfg *config.Config) error {
+func buildHeader(feed *Feed, item feeditem, cfg *config.Config) message.Header {
 	var h mail.Header
+	h.SetContentType("multipart/alternative", nil)
 	h.SetAddressList("From", fromAdress(feed, item, cfg))
 	h.SetAddressList("To", address(feed.Name, cfg.DefaultEmail))
 	h.Add("X-Feed2Imap-Version", config.Version())
@@ -62,39 +70,84 @@ func writeToBuffer(b *bytes.Buffer, feed *Feed, item feeditem, cfg *config.Confi
 		h.SetSubject(subject)
 	}
 
-	tw, err := mail.CreateInlineWriter(b, h)
+	return h.Header
+}
+
+func writeHtmlPart(w *message.Writer, item feeditem) error {
+	var ih message.Header
+	ih.SetContentType("text/html", map[string]string{"charset": "utf-8"})
+	ih.SetContentDisposition("inline", nil)
+	ih.Set("Content-Transfer-Encoding", "8bit")
+
+	partW, err := w.CreatePart(ih)
 	if err != nil {
 		return err
 	}
-	defer tw.Close()
+	defer partW.Close()
 
-	if false /* cfg.WithPartText() */ {
-		var th mail.InlineHeader
-		th.SetContentType("text/plain", map[string]string{"charset": "utf-8", "format": "flowed"})
+	if err = writeHtml(w, item); err != nil {
+		return fmt.Errorf("writing html part: %w", err)
+	}
 
-		w, err := tw.CreatePart(th)
-		if err != nil {
-			return err
-		}
-		defer w.Close()
+	return nil
+}
+
+func writeImagePart(w *message.Writer, img feedImage, cid string) error {
+	var ih message.Header
+	ih.SetContentType(img.mime, nil)
+	ih.SetContentDisposition("inline", nil)
+	ih.Set("Content-Transfer-Encoding", "base64")
+	ih.SetText("Content-ID", fmt.Sprintf("<%s>", cid))
+
+	imgW, err := w.CreatePart(ih)
+	if err != nil {
+		return err
+	}
+	defer imgW.Close()
 
-		_, _ = io.WriteString(w, "Who are you?")
+	if _, err = imgW.Write(img.image); err != nil {
+		return err
 	}
 
+	return nil
+}
+
+func writeToBuffer(b *bytes.Buffer, feed *Feed, item feeditem, cfg *config.Config) error {
+	h := buildHeader(feed, item, cfg)
+
+	writer, err := message.CreateWriter(b, h)
+	if err != nil {
+		return err
+	}
+	defer writer.Close()
+
 	if cfg.WithPartHtml() {
-		var th mail.InlineHeader
-		th.SetContentType("text/html", map[string]string{"charset": "utf-8"})
+		feed.buildBody(&item)
 
-		w, err := tw.CreatePart(th)
-		if err != nil {
+		var relWriter *message.Writer
+		if len(item.images) > 0 {
+			var rh message.Header
+			rh.SetContentType("multipart/related", map[string]string{"type": "text/html"})
+			if relWriter, err = writer.CreatePart(rh); err != nil {
+				return err
+			}
+			defer relWriter.Close()
+		} else {
+			relWriter = writer
+		}
+
+		if err = writeHtmlPart(relWriter, item); err != nil {
 			return err
 		}
 
-		if err = writeHtml(w, item); err != nil {
-			return fmt.Errorf("writing html part: %w", err)
+		for idx, img := range item.images {
+			cid := cidNr(idx + 1)
+			if err = writeImagePart(relWriter, img, cid); err != nil {
+				return err
+			}
 		}
 
-		w.Close()
+		item.clearImages() // safe memory
 	}
 
 	return nil
@@ -122,3 +175,96 @@ func (feed *Feed) ToMails(cfg *config.Config) ([]string, error) {
 	}
 	return mails, nil
 }
+
+func getImage(src string) ([]byte, string) {
+	resp, err := stdHTTPClient.Get(src)
+	if err != nil {
+		log.Errorf("Error fetching from '%s': %s", src, err)
+		return nil, ""
+	}
+	defer resp.Body.Close()
+
+	img, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		log.Errorf("Error reading body from '%s': %s", src, err)
+		return nil, ""
+	}
+
+	ext := path.Ext(src)
+	if ext == "" {
+		log.Warnf("Cannot determine extension from '%s', skipping.", src)
+		return nil, ""
+	}
+
+	mime := mime.TypeByExtension(ext)
+	return img, mime
+}
+
+func cidNr(idx int) string {
+	return fmt.Sprintf("cid_%d", idx)
+}
+
+func (feed *Feed) buildBody(item *feeditem) {
+	var body string
+	var comment string
+
+	if item.Item.Content != "" {
+		comment = "<!-- Content -->\n"
+		body = item.Item.Content
+	} else if item.Item.Description != "" {
+		comment = "<!-- Description -->\n"
+		body = item.Item.Description
+	}
+
+	if !feed.InclImages {
+		item.Body = comment + body
+		return
+	}
+
+	doc, err := goquery.NewDocumentFromReader(strings.NewReader(body))
+	if err != nil {
+		log.Debugf("Feed %s: Error while parsing html content: %s", feed.Name, err)
+		if body != "" {
+			item.Body = "<br />" + comment + body
+		}
+		return
+	}
+
+	doneAnything := true
+	nodes := doc.Find("img")
+	nodes.Each(func(i int, selection *goquery.Selection) {
+		const attr = "src"
+
+		src, ok := selection.Attr(attr)
+		if !ok {
+			return
+		}
+
+		img, mime := getImage(src)
+		if img == nil {
+			return
+		}
+
+		if feed.EmbedImages {
+			imgStr := "data:" + mime + ";base64," + base64.StdEncoding.EncodeToString(img)
+			selection.SetAttr(attr, imgStr)
+		} else {
+			idx := item.addImage(img, mime)
+			cid := "cid:" + cidNr(idx)
+			selection.SetAttr(attr, cid)
+		}
+		doneAnything = true
+	})
+
+	if doneAnything {
+		html, err := doc.Find("body").Html()
+		if err != nil {
+			item.clearImages()
+			log.Errorf("Error during rendering HTML, skipping.")
+		} else {
+			body = html
+		}
+	}
+
+	item.Body = comment + body
+}
diff --git a/internal/feed/template/feed.tpl.go b/internal/feed/template/feed.tpl.go
index 8aab9d7..0e09180 100644
--- a/internal/feed/template/feed.tpl.go
+++ b/internal/feed/template/feed.tpl.go
@@ -40,14 +40,8 @@ const feedTpl = `{{- /*gotype:github.com/Necoro/feed2imap-go/internal/feed.feedi
     </td>
   </tr>
 </table>
-{{with .Item.Content}}
-  <br /> <!-- originally: only if content and 'content !~ /\A\s*</m' -->
+{{with .Body}}
   {{html .}}
-{{else}}
-{{with .Item.Description}}
-  <br /> <!-- originally: only if content and 'content !~ /\A\s*</m' -->
-  {{html .}}
-{{end}}
 {{end}}
 {{with .Item.Enclosures}}
   <table border="1" width="100%" cellpadding="0" cellspacing="0" style="border-spacing: 0; ">
@@ -59,7 +53,7 @@ const feedTpl = `{{- /*gotype:github.com/Necoro/feed2imap-go/internal/feed.feedi
               <tr>
                 <td>
                   &nbsp;&nbsp;&nbsp;
-                  <a href={{.URL}}>{{.URL | lastUrlPart}}</a> ({{.Length | byteCount}}, {{.Type}})
+                  <a href={{.URL}}>{{.URL | lastUrlPart}}</a> ({{with .Length}}{{. | byteCount}}, {{end}}{{.Type}})
                 </td>
               </tr>
           {{end}}