// This file is part of Moonfire NVR, a security camera digital video recorder.
// Copyright (C) 2018 Scott Lamb <slamb@slamb.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// In addition, as a special exception, the copyright holders give
// permission to link the code of portions of this program with the
// OpenSSL library under certain conditions as described in each
// individual source file, and distribute linked combinations including
// the two.
//
// You must obey the GNU General Public License in all respects for all
// of the code used other than OpenSSL. If you modify file(s) with this
// exception, you may extend this exception to your version of the
// file(s), but you are not obligated to do so. If you do not wish to do
// so, delete this exception statement from your version. If you delete
// this exception statement from all source files in the program, then
// also delete it here.
//
// 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, see <http://www.gnu.org/licenses/>.

syntax = "proto3";

// Metadata stored in sample file dirs as "<dir>/meta". This is checked
// against the metadata stored within the database to detect inconsistencies
// between the directory and database, including the following:
//
// * sample file directory's disk not being mounted.
// * mixing up mount points of two sample file directories belonging to the
//   same database.
// * directory renames not properly recorded in the database.
// * restoration of the database from backup but not the sample file
//   directory.
// * restoration of the sample file directory but not the database.
// * two sample file directory paths pointed at the same inode via symlinks
//   or non-canonical paths. (Note that flock(2) has a design flaw in which
//   multiple file descriptors can share a lock, so the current locking scheme
//   is not sufficient to detect this otherwise.)
// * database and sample file directories forked from the same version, opened
//   the same number of times, then crossed.
message DirMeta {
  // A uuid associated with the database, in binary form. dir_uuid is strictly
  // more powerful, but it improves diagnostics to know if the directory
  // belongs to the expected database at all or not.
  bytes db_uuid = 1;

  // A uuid associated with the directory itself.
  bytes dir_uuid = 2;

  // Corresponds to an entry in the `open` database table.
  message Open {
    uint32 id = 1;
    bytes uuid = 2;
  }

  // The last open that was known to be recorded in the database as completed.
  // Absent if this has never happened. Note this can backtrack in exactly one
  // scenario: when deleting the directory, after all associated files have
  // been deleted, last_complete_open can be moved to in_progress_open.
  Open last_complete_open = 3;

  // The last run which is in progress, if different from last_complete_open.
  // This may or may not have been recorded in the database, but it's
  // guaranteed that no data has yet been written by this open.
  Open in_progress_open = 4;
}