+
+notmuch_status_t
+_notmuch_message_file_get_headers (notmuch_message_file_t *message_file,
+ const char **from_out,
+ const char **subject_out,
+ const char **to_out,
+ const char **date_out,
+ char **message_id_out)
+{
+ notmuch_status_t ret;
+ const char *header;
+ const char *from, *to, *subject, *date;
+ char *message_id = NULL;
+
+ /* Parse message up front to get better error status. */
+ ret = _notmuch_message_file_parse (message_file);
+ if (ret)
+ goto DONE;
+
+ /* Before we do any real work, (especially before doing a
+ * potential SHA-1 computation on the entire file's contents),
+ * let's make sure that what we're looking at looks like an
+ * actual email message.
+ */
+ from = _notmuch_message_file_get_header (message_file, "from");
+ subject = _notmuch_message_file_get_header (message_file, "subject");
+ to = _notmuch_message_file_get_header (message_file, "to");
+ date = _notmuch_message_file_get_header (message_file, "date");
+
+ if ((from == NULL || *from == '\0') &&
+ (subject == NULL || *subject == '\0') &&
+ (to == NULL || *to == '\0')) {
+ ret = NOTMUCH_STATUS_FILE_NOT_EMAIL;
+ goto DONE;
+ }
+
+ /* Now that we're sure it's mail, the first order of business
+ * is to find a message ID (or else create one ourselves).
+ */
+ header = _notmuch_message_file_get_header (message_file, "message-id");
+ if (header && *header != '\0') {
+ message_id = _notmuch_message_id_parse (message_file, header, NULL);
+
+ /* So the header value isn't RFC-compliant, but it's
+ * better than no message-id at all.
+ */
+ if (message_id == NULL)
+ message_id = talloc_strdup (message_file, header);
+ }
+
+ if (message_id == NULL ) {
+ /* No message-id at all, let's generate one by taking a
+ * hash over the file's contents.
+ */
+ char *sha1 = _notmuch_sha1_of_file (_notmuch_message_file_get_filename (message_file));
+
+ /* If that failed too, something is really wrong. Give up. */
+ if (sha1 == NULL) {
+ ret = NOTMUCH_STATUS_FILE_ERROR;
+ goto DONE;
+ }
+
+ message_id = talloc_asprintf (message_file, "notmuch-sha1-%s", sha1);
+ free (sha1);
+ }
+ DONE:
+ if (ret == NOTMUCH_STATUS_SUCCESS) {
+ if (from_out)
+ *from_out = from;
+ if (subject_out)
+ *subject_out = subject;
+ if (to_out)
+ *to_out = to;
+ if (date_out)
+ *date_out = date;
+ if (message_id_out)
+ *message_id_out = message_id;
+ }
+ return ret;
+}