+/* From the set of tags on 'message' and the flag2tag table, compute a
+ * set of maildir-flag actions to be taken, (flags that should be
+ * either set or cleared).
+ *
+ * The result is returned as two talloced strings: to_set, and to_clear
+ */
+static void
+_get_maildir_flag_actions (notmuch_message_t *message,
+ char **to_set_ret,
+ char **to_clear_ret)
+{
+ char *to_set, *to_clear;
+ notmuch_tags_t *tags;
+ const char *tag;
+ unsigned i;
+
+ to_set = talloc_strdup (message, "");
+ to_clear = talloc_strdup (message, "");
+
+ /* First, find flags for all set tags. */
+ 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) {
+ if (flag2tag[i].inverse)
+ to_clear = talloc_asprintf_append (to_clear,
+ "%c",
+ flag2tag[i].flag);
+ else
+ to_set = talloc_asprintf_append (to_set,
+ "%c",
+ flag2tag[i].flag);
+ }
+ }
+ }
+
+ /* Then, find the flags for all tags not present. */
+ for (i = 0; i < ARRAY_SIZE (flag2tag); i++) {
+ if (flag2tag[i].inverse) {
+ if (strchr (to_clear, flag2tag[i].flag) == NULL)
+ to_set = talloc_asprintf_append (to_set, "%c", flag2tag[i].flag);
+ } else {
+ if (strchr (to_set, flag2tag[i].flag) == NULL)
+ to_clear = talloc_asprintf_append (to_clear, "%c", flag2tag[i].flag);
+ }
+ }
+
+ *to_set_ret = to_set;
+ *to_clear_ret = to_clear;
+}
+
+/* Given 'filename' and a set of maildir flags to set and to clear,
+ * compute the new maildir filename.
+ *
+ * If the existing filename is in the directory "new", the new
+ * filename will be in the directory "cur".
+ *
+ * After a sequence of ":2," in the filename, any subsequent
+ * single-character flags will be added or removed according to the
+ * characters in flags_to_set and flags_to_clear. Any existing flags
+ * not mentioned in either string will remain. The final list of flags
+ * will be in ASCII order.
+ *
+ * If the original flags seem invalid, (repeated characters or
+ * non-ASCII ordering of flags), this function will return NULL
+ * (meaning that renaming would not be safe and should not occur).