Add mbox viewer panes

backend/06-mbox.go

@@ -3,6 +3,9 @@ package backend
 import (
 	"bytes"
 	"fmt"
+	"io"
+	"mime"
+	"net/mail"
 	"os"
 	"path/filepath"
 	"strings"
@@ -71,8 +74,96 @@ type MboxEntry struct {
 
 // ReadMboxList parst die Kopfzeilen aller Mails einer mbox-Datei (fuer die
 // Nachrichtenliste). ReadMboxMessage liefert eine einzelne Mail als Rohtext.
-func ReadMboxList(path string) ([]MboxEntry, error)          { return nil, nil } // TODO Codex
-func ReadMboxMessage(path string, index int) ([]byte, error) { return nil, nil } // TODO Codex
+func ReadMboxList(path string) ([]MboxEntry, error) {
+	msgs, err := readMboxMessages(path)
+	if err != nil {
+		return nil, err
+	}
+	out := make([]MboxEntry, 0, len(msgs))
+	for i, raw := range msgs {
+		msg, err := mail.ReadMessage(bytes.NewReader(raw))
+		if err != nil {
+			out = append(out, MboxEntry{Index: i, From: "(unlesbar)", Subject: "Unlesbare Nachricht"})
+			continue
+		}
+		out = append(out, MboxEntry{
+			Index:   i,
+			From:    decodeHeader(msg.Header.Get("From")),
+			Subject: decodeHeader(msg.Header.Get("Subject")),
+			Date:    decodeHeader(msg.Header.Get("Date")),
+		})
+	}
+	return out, nil
+}
+
+func ReadMboxMessage(path string, index int) ([]byte, error) {
+	msgs, err := readMboxMessages(path)
+	if err != nil {
+		return nil, err
+	}
+	if index < 0 || index >= len(msgs) {
+		return nil, fmt.Errorf("message index out of range")
+	}
+	return msgs[index], nil
+}
+
+func readMboxMessages(path string) ([][]byte, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	b = bytes.ReplaceAll(b, []byte("\r\n"), []byte("\n"))
+	lines := bytes.Split(b, []byte("\n"))
+	var msgs [][]byte
+	var cur bytes.Buffer
+	inMsg := false
+	for _, line := range lines {
+		if bytes.HasPrefix(line, []byte("From ")) {
+			if inMsg && cur.Len() > 0 {
+				msgs = append(msgs, bytes.TrimRight(cur.Bytes(), "\n"))
+				cur.Reset()
+			}
+			inMsg = true
+			continue
+		}
+		if !inMsg {
+			continue
+		}
+		if bytes.HasPrefix(line, []byte(">From ")) {
+			line = line[1:]
+		}
+		_, _ = cur.Write(line)
+		_ = cur.WriteByte('\n')
+	}
+	if inMsg && cur.Len() > 0 {
+		msgs = append(msgs, bytes.TrimRight(cur.Bytes(), "\n"))
+	}
+	return msgs, nil
+}
+
+func decodeHeader(v string) string {
+	v = strings.TrimSpace(v)
+	if v == "" {
+		return ""
+	}
+	decoded, err := new(mime.WordDecoder).DecodeHeader(v)
+	if err != nil {
+		return v
+	}
+	return decoded
+}
+
+func messageBody(raw []byte) string {
+	msg, err := mail.ReadMessage(bytes.NewReader(raw))
+	if err != nil {
+		return string(raw)
+	}
+	body, err := io.ReadAll(msg.Body)
+	if err != nil {
+		return string(raw)
+	}
+	return string(body)
+}
 
 func safeMboxName(folder string) string {
 	folder = strings.TrimSpace(folder)