maildir: move common maildir code out of worker

This change moves code that could be common to both notmuch and maildir
workers in worker/lib.

Signed-off-by: Julian Pidancet <julian.pidancet@oracle.com>
Acked-by: Robin Jarry <robin@jarry.cc>
Acked-by: Tim Culverhouse <tim@timculverhouse.com>

worker/lib/maildir.go

@@ -0,0 +1,153 @@
+package lib
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/emersion/go-maildir"
+)
+
+type MaildirStore struct {
+	root      string
+	maildirpp bool // whether to use Maildir++ directory layout
+}
+
+func NewMaildirStore(root string, maildirpp bool) (*MaildirStore, error) {
+	f, err := os.Open(root)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	s, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+	if !s.IsDir() {
+		return nil, fmt.Errorf("Given maildir '%s' not a directory", root)
+	}
+	return &MaildirStore{
+		root: root, maildirpp: maildirpp,
+	}, nil
+}
+
+// ListFolders returns a list of maildir folders in the container
+func (s *MaildirStore) ListFolders() ([]string, error) {
+	folders := []string{}
+	if s.maildirpp {
+		// In Maildir++ layout, INBOX is the root folder
+		folders = append(folders, "INBOX")
+	}
+	err := filepath.Walk(s.root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return fmt.Errorf("Invalid path '%s': error: %w", path, err)
+		}
+		if !info.IsDir() {
+			return nil
+		}
+
+		// Skip maildir's default directories
+		n := info.Name()
+		if n == "new" || n == "tmp" || n == "cur" {
+			return filepath.SkipDir
+		}
+
+		// Get the relative path from the parent directory
+		dirPath, err := filepath.Rel(s.root, path)
+		if err != nil {
+			return err
+		}
+
+		// Skip the parent directory
+		if dirPath == "." {
+			return nil
+		}
+
+		// Drop dirs that lack {new,tmp,cur} subdirs
+		for _, sub := range []string{"new", "tmp", "cur"} {
+			if _, err := os.Stat(filepath.Join(path, sub)); os.IsNotExist(err) {
+				return nil
+			}
+		}
+
+		if s.maildirpp {
+			// In Maildir++ layout, mailboxes are stored in a single directory
+			// and prefixed with a dot, and subfolders are separated by dots.
+			if !strings.HasPrefix(dirPath, ".") {
+				return filepath.SkipDir
+			}
+			dirPath = strings.TrimPrefix(dirPath, ".")
+			dirPath = strings.ReplaceAll(dirPath, ".", "/")
+			folders = append(folders, dirPath)
+
+			// Since all mailboxes are stored in a single directory, don't
+			// recurse into subdirectories
+			return filepath.SkipDir
+		}
+
+		folders = append(folders, dirPath)
+		return nil
+	})
+	return folders, err
+}
+
+// Folder returns a maildir.Dir with the specified name inside the Store
+func (s *MaildirStore) Dir(name string) maildir.Dir {
+	if s.maildirpp {
+		// Use Maildir++ layout
+		if name == "INBOX" {
+			return maildir.Dir(s.root)
+		}
+		return maildir.Dir(filepath.Join(s.root, "."+strings.ReplaceAll(name, "/", ".")))
+	}
+	return maildir.Dir(filepath.Join(s.root, name))
+}
+
+// uidReg matches filename encoded UIDs in maildirs synched with mbsync or
+// OfflineIMAP
+var uidReg = regexp.MustCompile(`,U=\d+`)
+
+func StripUIDFromMessageFilename(basename string) string {
+	return uidReg.ReplaceAllString(basename, "")
+}
+
+var MaildirToFlag = map[maildir.Flag]models.Flag{
+	maildir.FlagReplied: models.AnsweredFlag,
+	maildir.FlagSeen:    models.SeenFlag,
+	maildir.FlagTrashed: models.DeletedFlag,
+	maildir.FlagFlagged: models.FlaggedFlag,
+	// maildir.FlagDraft Flag = 'D'
+	// maildir.FlagPassed Flag = 'P'
+}
+
+var FlagToMaildir = map[models.Flag]maildir.Flag{
+	models.AnsweredFlag: maildir.FlagReplied,
+	models.SeenFlag:     maildir.FlagSeen,
+	models.DeletedFlag:  maildir.FlagTrashed,
+	models.FlaggedFlag:  maildir.FlagFlagged,
+	// maildir.FlagDraft Flag = 'D'
+	// maildir.FlagPassed Flag = 'P'
+}
+
+func FromMaildirFlags(maildirFlags []maildir.Flag) []models.Flag {
+	var flags []models.Flag
+	for _, maildirFlag := range maildirFlags {
+		if flag, ok := MaildirToFlag[maildirFlag]; ok {
+			flags = append(flags, flag)
+		}
+	}
+	return flags
+}
+
+func ToMaildirFlags(flags []models.Flag) []maildir.Flag {
+	var maildirFlags []maildir.Flag
+	for _, flag := range flags {
+		if maildirFlag, ok := FlagToMaildir[flag]; ok {
+			maildirFlags = append(maildirFlags, maildirFlag)
+		}
+	}
+	return maildirFlags
+}