Module backup

One file holding everything Aède knows, so that a disk failure costs a scan and not a year of listening.

Six independently versioned stores are nested whole: the mostly derived catalog (which also holds watched roots), costly byte-level conclusions, irreplaceable user statements, slowly re-fetchable external sources, and private account credentials, and parental policies/usage. Versions 1 and 2 carry no accounts; versions 1 through 3 carry no parental store. A version-1 envelope is still accepted: its embedded legacy conclusions are extracted into the fourth store before restoration.

A document of documents, and why that matters

The six are nested as they are, each keeping its own format_version and read back by its own from_json. Nothing here re-encodes a catalog, so a field added to the catalog tomorrow is in the backup tomorrow, with no second writer to forget it — the fault that would otherwise be discovered the day somebody restored one.

The consequence worth stating: each store is refused on its own. A backup written by an Aède whose catalog format has since moved still restores the notes and the fetched facts, because the catalog’s version check has nothing to say about user.json. A single check at the top would have thrown away irreplaceable data to protect the rebuildable catalog.

It stores, it never fetches or scans

Reading a backup produces documents; writing one consumes them. Nothing here touches the library, and — as everywhere in this program — nothing here touches an audio file.

Structs

Backup

Everything Aède knows, at one moment.

Enums

Part

One store inside a backup, and what this build can do with it.

Constants

BACKUP_FORMAT_VERSION

The version of the wrapper, which is not the version of what it wraps.

Functions

from_json

Reads back what to_json wrote.

read

Reads a backup from an ordinary local file, refusing blocking special files. A backup with credentials also requires a private, non-symlink source. The opened file’s identity and permissions are checked, and changes during reading are refused. Reading cannot grow past its inspected length.

to_json

The envelope, with the six documents nested unchanged.

write

Writes a backup through isolated temporary output and atomic replacement.