Maildir synchronization

This patch allows bi-directional synchronization between maildir
flags and certain tags. The flag-to-tag mapping is defined by flag2tag
array.

The synchronization works this way:

1) Whenever notmuch new is executed, the following happens:
   o New messages are tagged with configured new_tags.
   o For new or renamed messages with maildir info present in the file
     name, the tags defined in flag2tag are either added or removed
     depending on the flags from the file name.

2) Whenever notmuch tag (or notmuch restore) is executed, a new set of
   flags based on the tags is constructed for every message and a new
   file name is prepared based on the old file name but with the new
   flags. If the flags differs and the old message was in 'new'
   directory then this is replaced with 'cur' in the new file name. If
   the new and old file names differ, the file is renamed and notmuch
   database is updated accordingly.

   The rename happens before the database is updated. In case of crash
   between rename and database update, the next run of notmuch new
   brings the database in sync with the mail store again.

1 files changed, 226 insertions, 0 deletions

diff --git a/lib/message.cc b/lib/message.cc
index bf9f1edb..1548076d 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -41,6 +41,24 @@ struct _notmuch_message {
     Xapian::Document doc;
 };
 
+#define ARRAY_SIZE(arr) (sizeof (arr) / sizeof (arr[0]))
+
+struct maildir_flag_tag {
+    char flag;
+    const char *tag;
+    bool inverse;
+};
+
+/* ASCII ordered table of Maildir flags and associated tags */
+struct maildir_flag_tag flag2tag[] = {
+    { 'D', "draft",   false},
+    { 'F', "flagged", false},
+    { 'P', "passed",  false},
+    { 'R', "replied", false},
+    { 'S', "unread",  true },
+    { 'T', "deleted", false},
+};
+
 /* We end up having to call the destructor explicitly because we had
  * to use "placement new" in order to initialize C++ objects within a
  * block that we allocated with talloc. So C++ is making talloc
@@ -593,15 +611,29 @@ _notmuch_message_set_date (notmuch_message_t *message,
 			    Xapian::sortable_serialise (time_value));
 }
 
+static notmuch_private_status_t
+_notmuch_message_tags_to_maildir (notmuch_message_t *message);
+
 /* Synchronize changes made to message->doc out into the database. */
 void
 _notmuch_message_sync (notmuch_message_t *message)
 {
     Xapian::WritableDatabase *db;
+    notmuch_private_status_t status;
 
     if (message->notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY)
 	return;
 
+    if (// todo_sync_enabled &&
+	!notmuch_message_get_flag(message, NOTMUCH_MESSAGE_FLAG_TAGS_INVALID)) {
+ 	status = _notmuch_message_tags_to_maildir (message);
+	if (status != NOTMUCH_PRIVATE_STATUS_SUCCESS) {
+	    fprintf (stderr, "Error: Cannot sync tags to maildir (%s)\n",
+		     notmuch_status_to_string ((notmuch_status_t)status));
+	    /* Exit to avoid unsynchronized mailstore. */
+	    exit(1);
+	}
+    }
     db = static_cast <Xapian::WritableDatabase *> (message->notmuch->xapian_db);
     db->replace_document (message->doc_id, message->doc);
 }
@@ -713,6 +745,44 @@ _notmuch_message_remove_term (notmuch_message_t *message,
     return NOTMUCH_PRIVATE_STATUS_SUCCESS;
 }
 
+/* Change the message filename stored in the database.
+ *
+ * This change will not be reflected in the database until the next
+ * call to _notmuch_message_sync.
+ */
+notmuch_private_status_t
+_notmuch_message_rename (notmuch_message_t *message,
+			 const char *new_filename)
+{
+    void *local = talloc_new (message);
+    char *direntry;
+    Xapian::PostingIterator i, end;
+    Xapian::Document document;
+    notmuch_private_status_t pstatus;
+    notmuch_status_t status;
+    const char *old_filename;
+
+    old_filename = notmuch_message_get_filename(message);
+    old_filename = talloc_reference(local, old_filename);
+    if (unlikely(!old_filename))
+	return NOTMUCH_PRIVATE_STATUS_OUT_OF_MEMORY;
+
+    status = _notmuch_message_add_filename (message, new_filename);
+    if (status)
+	return (notmuch_private_status_t)status;
+
+    status = _notmuch_database_filename_to_direntry (local, message->notmuch,
+						     old_filename, &direntry);
+    if (status)
+	return (notmuch_private_status_t)status;
+
+    pstatus = _notmuch_message_remove_term (message, "file-direntry", direntry);
+
+    talloc_free (local);
+
+    return pstatus;
+}
+
 notmuch_status_t
 notmuch_message_add_tag (notmuch_message_t *message, const char *tag)
 {
@@ -770,6 +840,162 @@ notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
 }
 
 notmuch_status_t
+notmuch_message_maildir_to_tags (notmuch_message_t *message, const char *filename)
+{
+    const char *flags, *p;
+    char f;
+    bool valid, unread;
+    unsigned i;
+    notmuch_status_t status;
+
+    flags = strstr (filename, ":2,");
+    if (!flags)
+	return NOTMUCH_STATUS_FILE_NOT_EMAIL;
+    flags += 3;
+
+    /*  Check that the letters are valid Maildir flags */
+    f = 0;
+    valid = true;
+    for (p=flags; valid && *p; p++) {
+	switch (*p) {
+	case 'P':
+	case 'R':
+	case 'S':
+	case 'T':
+	case 'D':
+	case 'F':
+	    if (*p > f) f=*p;
+	    else valid = false;
+	break;
+	default:
+	    valid = false;
+	}
+    }
+    if (!valid) {
+	fprintf (stderr, "Warning: Invalid maildir flags in filename %s\n", filename);
+	return NOTMUCH_STATUS_FILE_NOT_EMAIL;
+    }
+
+    status = notmuch_message_freeze (message);
+    if (status)
+	return status;
+    unread = true;
+    for (i = 0; i < ARRAY_SIZE(flag2tag); i++) {
+	if ((strchr (flags, flag2tag[i].flag) != NULL) ^ flag2tag[i].inverse) {
+	    status = notmuch_message_add_tag (message, flag2tag[i].tag);
+	} else {
+	    status = notmuch_message_remove_tag (message, flag2tag[i].tag);
+	}
+	if (status)
+	    return status;
+    }
+    status = notmuch_message_thaw (message);
+
+    /* From now on, we can synchronize the tags from the database to
+     * the mailstore. */
+    notmuch_message_set_flag (message, NOTMUCH_MESSAGE_FLAG_TAGS_INVALID, FALSE);
+    return status;
+}
+
+static void
+maildir_get_new_flags(notmuch_message_t *message, char *flags)
+{
+    notmuch_tags_t *tags;
+    const char *tag;
+    unsigned i;
+    char *p;
+
+    for (i = 0; i < ARRAY_SIZE(flag2tag); i++)
+	flags[i] = flag2tag[i].inverse ? flag2tag[i].flag : '\0';
+
+    for (tags = notmuch_message_get_tags (message);
+	 notmuch_tags_valid (tags);
+	 notmuch_tags_move_to_next (tags))
+    {
+	tag = notmuch_tags_get (tags);
+	for (i = 0; i < ARRAY_SIZE(flag2tag); i++) {
+	    if (strcmp(tag, flag2tag[i].tag) == 0)
+		flags[i] = flag2tag[i].inverse ? '\0' : flag2tag[i].flag;
+	}
+    }
+
+    p = flags;
+    for (i = 0; i < ARRAY_SIZE(flag2tag); i++) {
+	if (flags[i])
+	    *p++ = flags[i];
+    }
+    *p = '\0';
+}
+
+static char *
+maildir_get_subdir (char *filename)
+{
+    char *p, *subdir = NULL;
+
+    p = filename + strlen (filename) - 1;
+    while (p > filename + 3 && *p != '/')
+	p--;
+    if (*p == '/') {
+	subdir = p - 3;
+	if (subdir > filename && *(subdir - 1) != '/')
+	    subdir = NULL;
+    }
+    return subdir;
+}
+
+/* Rename the message file so that maildir flags corresponds to the
+ * tags and, if aplicable, move the message from new/ to cur/. */
+static notmuch_private_status_t
+_notmuch_message_tags_to_maildir (notmuch_message_t *message)
+{
+    char flags[ARRAY_SIZE(flag2tag)+1];
+    const char *filename, *p;
+    char *filename_new, *subdir = NULL;
+    int ret;
+
+    maildir_get_new_flags (message, flags);
+
+    filename = notmuch_message_get_filename (message);
+    /* TODO: Iterate over all file names. */
+    p = strstr(filename, ":2,");
+    if ((p && strcmp (p+3, flags) == 0) ||
+	(!p && flags[0] == '\0')) {
+	// Return if flags are not to be changed - this suppresses
+	// moving the message from new/ to cur/ during initial
+	// tagging.
+	return NOTMUCH_PRIVATE_STATUS_SUCCESS;
+    }
+    if (!p)
+	p = filename + strlen(filename);
+
+    filename_new = (char*)talloc_size(message, (p-filename) + 3 + sizeof(flags));
+    if (unlikely (filename_new == NULL))
+	return NOTMUCH_PRIVATE_STATUS_OUT_OF_MEMORY;
+    memcpy(filename_new, filename, p-filename);
+    filename_new[p-filename] = '\0';
+
+    /* If message is in new/ move it under cur/. */
+    subdir = maildir_get_subdir (filename_new);
+    if (subdir && memcmp (subdir, "new/", 4) == 0)
+	memcpy (subdir, "cur/", 4);
+
+    strcpy (filename_new+(p-filename), ":2,");
+    strcpy (filename_new+(p-filename)+3, flags);
+
+    if (strcmp (filename, filename_new) != 0) {
+	ret = rename (filename, filename_new);
+	if (ret == -1) {
+	    perror (talloc_asprintf (message, "rename of %s to %s failed",
+				     filename, filename_new));
+	    exit (1);
+	}
+	return _notmuch_message_rename (message, filename_new);
+	/* _notmuch_message_sync is our caller. Do not call it here. */
+    }
+    return NOTMUCH_PRIVATE_STATUS_SUCCESS;
+}
+
+notmuch_status_t
 notmuch_message_remove_all_tags (notmuch_message_t *message)
 {
     notmuch_private_status_t private_status;