quak/src/library/records.ts

// Plain records projected from the decrypted store, and the diff between two
// projections. These are the library's GUI-facing surface: they hold no key
// material and no binary, so they survive `structuredClone`/JSON across the
// Electron IPC boundary where methods and file keys cannot go (design #36,
// owner ruling 5). The decrypted `Collection`/`EnteFile` objects stay in RAM in
// the main process; the window only ever sees these records.
//
// Ente holds edited/basic times in microseconds; records expose `takenAt` in
// milliseconds. The magic-metadata field names below are the ones the Ente
// clients write, confirmed against the repo's own fixtures: `w`/`h` in
// test/cli/metadata-backup.test.ts, `visibility` in test/library/store.test.ts.

import type {
    Collection,
    CollectionType,
    EnteFile,
    FileType,
} from "../model/types.js";

// Ente private-magic-metadata visibility values.
const VISIBILITY_ARCHIVED = 1;
const VISIBILITY_HIDDEN = 2;

// A single photo, deduplicated across the collections it belongs to. No key,
// no binary: safe to send to a window.
export interface PhotoRecord {
    fileID: number;
    // Every collection this file is a member of, ascending.
    albumIDs: number[];
    // `pubMagicMetadata.editedName` when the user renamed the file, else the
    // basic-metadata title.
    title: string;
    // Milliseconds. `pubMagicMetadata.editedTime` when the user edited the
    // date, else basic-metadata `creationTime`.
    takenAt: number;
    fileType: FileType;
    caption?: string;
    width?: number;
    height?: number;
    latitude?: number;
    longitude?: number;
    isArchived: boolean;
    isHidden: boolean;
    // Local cache paths, set once a later phase caches the bytes; unset here.
    thumbnailPath?: string;
    originalPath?: string;
}

export interface AlbumRecord {
    collectionID: number;
    name: string;
    // `favorites` identifies the account's favorites album.
    type: CollectionType;
    isShared: boolean;
    updationTime: number;
    // The album's files, newest first.
    fileIDs: number[];
}

export interface LibrarySnapshot {
    albums: AlbumRecord[];
    photos: PhotoRecord[];
    // Wall-clock milliseconds when the snapshot was taken.
    takenAt: number;
}

export interface LibraryChange {
    // Full records for albums/photos added or changed by the refresh.
    albumsChanged: AlbumRecord[];
    photosChanged: PhotoRecord[];
    fileIDsRemoved: number[];
    albumIDsRemoved: number[];
    // Wall-clock milliseconds of the refresh that produced this change.
    refreshedAt: number;
}

// The by-id projection of the store at one moment; the source for both
// `snapshotFrom` (sorted arrays for the GUI) and `diffRecords` (change sets).
export interface DerivedRecords {
    albums: Map<number, AlbumRecord>;
    photos: Map<number, PhotoRecord>;
}

const asString = (v: unknown): string | undefined =>
    typeof v === "string" && v.length > 0 ? v : undefined;

const asNumber = (v: unknown): number | undefined =>
    typeof v === "number" && Number.isFinite(v) ? v : undefined;

const microsToMillis = (micros: number): number => Math.floor(micros / 1000);

// Newest first, with fileID as a stable tiebreak so equal-timed files order
// deterministically.
const byNewestPhoto = (a: PhotoRecord, b: PhotoRecord): number =>
    b.takenAt - a.takenAt || b.fileID - a.fileID;

// Build one PhotoRecord from every membership of a file. The memberships share
// the same underlying file, so metadata is read from a single representative
// (the most recently synced, lowest collection id to break ties); `albumIDs`
// gathers them all.
const toPhotoRecord = (
    fileID: number,
    memberships: EnteFile[],
): PhotoRecord => {
    const albumIDs = memberships
        .map((m) => m.collectionID)
        .sort((a, b) => a - b);
    const rep = memberships.reduce((best, m) =>
        m.updationTime > best.updationTime ||
        (m.updationTime === best.updationTime &&
            m.collectionID < best.collectionID)
            ? m
            : best,
    );

    const pub = rep.pubMagicMetadata ?? {};
    const priv = rep.magicMetadata ?? {};

    const takenAtMicros = asNumber(pub.editedTime) ?? rep.metadata.creationTime;
    const visibility = asNumber(priv.visibility);

    const record: PhotoRecord = {
        fileID,
        albumIDs,
        title: asString(pub.editedName) ?? rep.metadata.title,
        takenAt: microsToMillis(takenAtMicros),
        fileType: rep.metadata.fileType,
        isArchived: visibility === VISIBILITY_ARCHIVED,
        isHidden: visibility === VISIBILITY_HIDDEN,
    };

    const caption = asString(pub.caption);
    if (caption !== undefined) record.caption = caption;
    const width = asNumber(pub.w);
    if (width !== undefined) record.width = width;
    const height = asNumber(pub.h);
    if (height !== undefined) record.height = height;
    if (rep.metadata.latitude !== undefined)
        record.latitude = rep.metadata.latitude;
    if (rep.metadata.longitude !== undefined)
        record.longitude = rep.metadata.longitude;

    return record;
};

const toAlbumRecord = (
    collection: Collection,
    files: EnteFile[],
    takenAtByFile: Map<number, number>,
): AlbumRecord => {
    const fileIDs = files
        .filter((f) => f.collectionID === collection.id)
        .map((f) => f.id)
        .sort(
            (a, b) =>
                (takenAtByFile.get(b) ?? 0) - (takenAtByFile.get(a) ?? 0) ||
                b - a,
        );
    return {
        collectionID: collection.id,
        name: collection.name,
        type: collection.type,
        isShared: collection.isShared,
        updationTime: collection.updationTime,
        fileIDs,
    };
};

// Project the decrypted collections and file memberships into by-id records.
// `files` is every membership (a file appears once per collection it is in).
export const deriveRecords = (
    collections: Collection[],
    files: EnteFile[],
): DerivedRecords => {
    const byFileID = new Map<number, EnteFile[]>();
    for (const f of files) {
        const arr = byFileID.get(f.id);
        if (arr) arr.push(f);
        else byFileID.set(f.id, [f]);
    }

    const photos = new Map<number, PhotoRecord>();
    const takenAtByFile = new Map<number, number>();
    for (const [fileID, memberships] of byFileID) {
        const record = toPhotoRecord(fileID, memberships);
        photos.set(fileID, record);
        takenAtByFile.set(fileID, record.takenAt);
    }

    const albums = new Map<number, AlbumRecord>();
    for (const c of collections) {
        albums.set(c.id, toAlbumRecord(c, files, takenAtByFile));
    }

    return { albums, photos };
};

// Sorted, GUI-ready arrays: albums newest updated first, photos newest first.
export const snapshotFrom = (
    records: DerivedRecords,
    takenAt: number,
): LibrarySnapshot => ({
    albums: [...records.albums.values()].sort(
        (a, b) =>
            b.updationTime - a.updationTime || b.collectionID - a.collectionID,
    ),
    photos: [...records.photos.values()].sort(byNewestPhoto),
    takenAt,
});

// Records compare by value; they are plain and built with a fixed key order, so
// a serialized form is a sound equality key.
const same = (a: unknown, b: unknown): boolean =>
    JSON.stringify(a) === JSON.stringify(b);

const diffMap = <T>(
    prev: Map<number, T>,
    next: Map<number, T>,
): { changed: T[]; removed: number[] } => {
    const changed: T[] = [];
    for (const [id, record] of next) {
        const before = prev.get(id);
        if (before === undefined || !same(before, record)) changed.push(record);
    }
    const removed: number[] = [];
    for (const id of prev.keys()) if (!next.has(id)) removed.push(id);
    removed.sort((a, b) => a - b);
    return { changed, removed };
};

// The change between two projections, or undefined when nothing changed.
export const diffRecords = (
    prev: DerivedRecords,
    next: DerivedRecords,
    refreshedAt: number,
): LibraryChange | undefined => {
    const albums = diffMap(prev.albums, next.albums);
    const photos = diffMap(prev.photos, next.photos);
    if (
        albums.changed.length === 0 &&
        albums.removed.length === 0 &&
        photos.changed.length === 0 &&
        photos.removed.length === 0
    ) {
        return undefined;
    }
    return {
        albumsChanged: albums.changed,
        photosChanged: photos.changed,
        fileIDsRemoved: photos.removed,
        albumIDsRemoved: albums.removed,
        refreshedAt,
    };
};