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/*
* qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
* Copyright (C) 2026 Danilo M. <danix@danix.xyz>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "maildirname.h"
#include <QCoreApplication>
#include <QDateTime>
#include <QDir>
#include <QFileInfo>
#include <QHostInfo>
namespace MaildirName {
/// A fresh Maildir filename for a message being moved between folders,
/// preserving only its `:2,<flags>` suffix.
///
/// mbsync's manual is explicit about why this exists, under "the more
/// efficient default UID mapping scheme": "it is important that the MUA
/// renames files when moving them between Maildir folders", and "the general
/// expectation is that a completely new filename is generated as if the
/// message was new".
///
/// The `,U=<n>` infix mbsync writes is its per-folder IMAP UID. Carrying it
/// into another folder makes it a claim about a folder the file is no longer
/// in; moving a message out and back then reinserts a UID the server has
/// since reassigned, and mbsync refuses the folder with `Maildir error:
/// duplicate UID`. Measured on real mail, four collisions in one folder from
/// a single move-and-restore.
///
/// The FLAGS are kept, deliberately, and that is not a contradiction of
/// "as if the message was new". They record seen, flagged and replied, and
/// `maildir.synchronize_flags` is true, so notmuch reads them back as tags:
/// dropping them would mark every deleted message unread and lose Important
/// on the way to the trash. Only the unique part is regenerated.
QString fresh(const QString &oldName)
{
// The `:2,` suffix, when there is one. `info` is everything from the
// separator on, so an empty-flag `:2,` is preserved as faithfully as
// `:2,FS`.
QString info;
const int sep = oldName.indexOf(QStringLiteral(":2,"));
if (sep >= 0)
info = oldName.mid(sep);
// The conventional left-to-right unique part: time, a per-process counter,
// the pid, the host. The counter is what makes two messages moved in the
// same second distinct, which a timestamp alone does not guarantee.
static quint64 counter = 0;
const qint64 now = QDateTime::currentSecsSinceEpoch();
const QString host = QHostInfo::localHostName().isEmpty()
? QStringLiteral("localhost")
: QHostInfo::localHostName();
return QStringLiteral("%1.M%2P%3Q%4.%5%6")
.arg(now)
.arg(QDateTime::currentMSecsSinceEpoch() % 1000)
.arg(QCoreApplication::applicationPid())
.arg(++counter)
// A `/` or a `:` in a hostname would break the path or the flag
// separator. Neither is legal in a hostname, so this is belt and
// braces rather than a known case.
.arg(QString(host).replace(QLatin1Char('/'), QLatin1Char('_'))
.replace(QLatin1Char(':'), QLatin1Char('_')))
.arg(info);
}
QString resolveRenamed(const QString &path)
{
if (path.isEmpty())
return QString();
// The ordinary case, and the overwhelmingly common one: nothing was
// renamed. One stat, then out.
if (QFileInfo::exists(path))
return path;
const QFileInfo info(path);
const QString name = info.fileName();
// The unique part mbsync preserves. `<stem>:2,D` becomes
// `<stem>,U=5:2,D`, so the stem ends at whichever of `,` or `:` comes
// first. A name carrying neither is all stem.
int cut = name.size();
for (const QChar separator : { QLatin1Char(','), QLatin1Char(':') }) {
const int at = name.indexOf(separator);
if (at >= 0 && at < cut)
cut = at;
}
const QString stem = name.left(cut);
if (stem.isEmpty())
return QString();
// One directory, never a recursive walk: a rename keeps the file where it
// was, and a file that changed FOLDERS is a different question that only
// the message id can answer (see NotmuchWorker::moveMessages(), item 162).
const QDir dir(info.absolutePath());
if (!dir.exists())
return QString();
QString found;
const QFileInfoList entries =
dir.entryInfoList(QDir::Files | QDir::NoDotAndDotDot);
for (const QFileInfo &entry : entries) {
const QString candidate = entry.fileName();
// Anchored on the stem AND on what follows it, so `...Q2` cannot match
// `...Q23`: the next character must begin the infix or the flags.
if (!candidate.startsWith(stem))
continue;
const QString rest = candidate.mid(stem.size());
if (!rest.isEmpty() && !rest.startsWith(QLatin1Char(','))
&& !rest.startsWith(QLatin1Char(':'))) {
continue;
}
// Two files sharing a stem cannot happen in a correct Maildir. Refuse
// rather than guess: the caller reports "gone", which is honest, where
// a guess could open, move or delete the wrong message.
if (!found.isEmpty())
return QString();
found = entry.absoluteFilePath();
}
return found;
}
} // namespace MaildirName
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