// This file is part of Moonfire NVR, a security camera network video recorder.
// Copyright (C) 2018 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
// SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.';

// Protobuf portion of the Moonfire NVR schema. In general Moonfire's schema
// uses a SQLite3 database with some fields in JSON representation. The protobuf
// stuff is just high-cardinality things that must be compact, e.g. permissions
// that can be stuffed into every user session.

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, such as those described in
// `design/schema.md`.
//
// As of schema version 4, the overall file format is as follows: a
// varint-encoded length, followed by a serialized `DirMeta` message, followed
// by NUL bytes padding to a total length of 512 bytes. This message never
// exceeds that length.
//
// The goal of this format is to allow atomically rewriting a meta file
// in-place. I hope that on modern OSs and hardware, a single-sector
// rewrite is atomic, though POSIX frustratingly doesn't seem to guarantee
// this. There's some discussion of that here:
// <https://stackoverflow.com/a/2068608/23584>. At worst, there's a short
// window during which the meta file can be corrupted. As the file's purpose
// is to check for inconsistencies, it can be reconstructed if you assume no
// inconsistency exists.
//
// Schema version 3 wrote a serialized DirMeta message with no length or
// padding, and renamed new meta files over the top of old. This scheme
// requires extra space while opening the directory. If the filesystem is
// completely full, it requires freeing space manually, an undocumented and
// error-prone administrator procedure.
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;
}

// Permissions to perform actions. See description in design/api.md.
//
// This protobuf form is stored in user and session rows.
message Permissions {
  bool view_video = 1;
  bool read_camera_configs = 2;
  bool update_signals = 3;
  bool admin_users = 4;
}
