Fetch, store, and index per-file ML data and CLIP embeddings (closes #49)

Ente's "magic" search data (face detections + CLIP embeddings) is now
fetched, decrypted, and cached under cacheDirectory/mldata/, never in
metadata.json.

A new mldata-fetch module holds the /files/data/fetch (type mldata)
decrypt+gunzip, reused by both the metadata backup and the library.
MLDataStore writes one payload file per fileID by rename (present means
complete) and maintains a derived index: clip.json (fileIDs in order +
embedding length) and clip.f32 (embeddings packed as one Float32Array,
loaded in a single read). The index is rebuilt from the payloads when
missing or structurally inconsistent with the files present, and appended
to as payloads arrive; fetched.json records each file's fetch-time
updationTime for refetch decisions.

After each refresh the library fetches, through the #45 metadata pool, the
ML data for every known file absent from mldata/ or whose updationTime
advanced, reporting via onProgress (operation fetchMLData) and status().
RAM holds only the id list and Float32Array; payloads are read on demand.

Model: opus-4-8

src/index.ts

@@ -36,11 +36,19 @@ export {
 export {
     Library,
     DEFAULT_REFRESH_INTERVAL_SECONDS,
+    Album,
+    Photo,
     type LibraryClient,
     type LibraryOptions,
     type LibraryStatus,
     type RefreshEvent,
     type RefreshProgressCallback,
+    type AlbumsAPI,
+    type PhotosAPI,
+    type TimelineAPI,
+    type PhotoFilter,
+    type TimelineGroup,
+    type GroupBy,
 } from "./library/index.js";
 export type {
     AlbumRecord,

src/library/index.ts

@@ -33,6 +33,25 @@ import {
     type LibrarySnapshot,
     type LibraryChange,
 } from "./records.js";
+import {
+    makeAlbumsAPI,
+    makePhotosAPI,
+    makeTimelineAPI,
+    type AlbumsAPI,
+    type PhotosAPI,
+    type TimelineAPI,
+} from "./read.js";
+
+export {
+    Album,
+    Photo,
+    type AlbumsAPI,
+    type PhotosAPI,
+    type TimelineAPI,
+    type PhotoFilter,
+    type TimelineGroup,
+    type GroupBy,
+} from "./read.js";
 import type { CollectionsPage, FilesPage } from "../client.js";
 import { MLDATA_BATCH_SIZE, type MLData } from "../mldata-fetch.js";
 import type { Collection, EnteFile } from "../model/types.js";
@@ -113,6 +132,13 @@ export class Library {
     readonly cacheDirectory: string;
     readonly downloadDirectory?: string;
 
+    // The in-process read surface (issue #44). Each namespace answers
+    // synchronously from the live record projection; no read touches the
+    // network.
+    readonly albums: AlbumsAPI;
+    readonly photos: PhotosAPI;
+    readonly timeline: TimelineAPI;
+
     private readonly client: LibraryClient;
     private readonly store: MetadataStore;
     private readonly userID: number;
@@ -164,6 +190,13 @@ export class Library {
         this.pools = args.pools;
         this.mldata = args.mldata;
         this.lastRecords = this.deriveNow();
+
+        // The read namespaces derive fresh from the store on each call, so they
+        // always reflect the latest refresh.
+        const derive = (): DerivedRecords => this.deriveNow();
+        this.albums = makeAlbumsAPI(derive);
+        this.photos = makePhotosAPI(derive);
+        this.timeline = makeTimelineAPI(derive);
     }
 
     // Load the cache and start the refresh loop. With an empty cache the first

src/library/read.ts

@@ -0,0 +1,344 @@
+// The in-process read surface over the local cache (issue #44).
+//
+// A CLI or an in-process script reads albums, photos, and a grouped timeline
+// through `lib.albums`, `lib.photos`, and `lib.timeline`. Every call is
+// answered synchronously from the same plain-record projection the GUI reads
+// (`deriveRecords`, issue #43); nothing here touches the network. Every method
+// takes a single named-argument object.
+//
+// The `Album` and `Photo` classes are thin, in-process-only wrappers over
+// those records: a caller that holds an object reference gets typed field
+// access and, for an album, its photos. They are not sent across IPC — the
+// plain records are the serializable surface, and `record()` returns one.
+// Content-fetch methods (`Photo.original` / `thumbnail`) belong to a later
+// unit; this surface is read-only.
+
+import type { CollectionType, FileType } from "../model/types.js";
+import type { AlbumRecord, PhotoRecord, DerivedRecords } from "./records.js";
+
+// Newest first, with fileID as a stable tiebreak so equal-timed files order
+// deterministically — the same order the record projection uses.
+const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
+    b.takenAt - a.takenAt || b.fileID - a.fileID;
+
+// Albums newest updated first, collection id breaking ties. This is the order
+// `albums.list` returns and the order `byName` resolves a name collision in.
+const byNewestAlbum = (a: AlbumRecord, b: AlbumRecord): number =>
+    b.updationTime - a.updationTime || b.collectionID - a.collectionID;
+
+// A single photo. Field access mirrors `PhotoRecord`; `record()` returns the
+// underlying plain record for callers that need the IPC-safe value.
+export class Photo {
+    constructor(private readonly rec: PhotoRecord) {}
+
+    get fileID(): number {
+        return this.rec.fileID;
+    }
+    get albumIDs(): number[] {
+        return this.rec.albumIDs;
+    }
+    get title(): string {
+        return this.rec.title;
+    }
+    get takenAt(): number {
+        return this.rec.takenAt;
+    }
+    get fileType(): FileType {
+        return this.rec.fileType;
+    }
+    get caption(): string | undefined {
+        return this.rec.caption;
+    }
+    get width(): number | undefined {
+        return this.rec.width;
+    }
+    get height(): number | undefined {
+        return this.rec.height;
+    }
+    get latitude(): number | undefined {
+        return this.rec.latitude;
+    }
+    get longitude(): number | undefined {
+        return this.rec.longitude;
+    }
+    get isArchived(): boolean {
+        return this.rec.isArchived;
+    }
+    get isHidden(): boolean {
+        return this.rec.isHidden;
+    }
+
+    record(): PhotoRecord {
+        return this.rec;
+    }
+}
+
+// A single album. `photos.list()` returns the album's photos as wrappers,
+// newest first (the record already stores `fileIDs` in that order).
+export class Album {
+    constructor(
+        private readonly rec: AlbumRecord,
+        private readonly records: DerivedRecords,
+    ) {}
+
+    get collectionID(): number {
+        return this.rec.collectionID;
+    }
+    get name(): string {
+        return this.rec.name;
+    }
+    get type(): CollectionType {
+        return this.rec.type;
+    }
+    get isShared(): boolean {
+        return this.rec.isShared;
+    }
+    get updationTime(): number {
+        return this.rec.updationTime;
+    }
+    get fileIDs(): number[] {
+        return this.rec.fileIDs;
+    }
+
+    get photos(): { list: () => Photo[] } {
+        return { list: (): Photo[] => this.listPhotos() };
+    }
+
+    record(): AlbumRecord {
+        return this.rec;
+    }
+
+    private listPhotos(): Photo[] {
+        const out: Photo[] = [];
+        for (const id of this.rec.fileIDs) {
+            const p = this.records.photos.get(id);
+            if (p) out.push(new Photo(p));
+        }
+        return out;
+    }
+}
+
+export interface AlbumsAPI {
+    list(): Album[];
+    byName(args: { albumName: string }): Album | undefined;
+    byID(args: { collectionID: number }): Album | undefined;
+}
+
+export interface PhotosAPI {
+    byID(args: { fileID: number }): Photo | undefined;
+    // Plain records for the requested ids, in the order requested, each id at
+    // most once, unknown ids dropped.
+    records(args: { fileIDs: number[] }): PhotoRecord[];
+}
+
+export type GroupBy = "day" | "week" | "month";
+
+// A filter over the timeline. All fields are optional and combine with AND.
+// Hidden photos are never included, regardless of this filter.
+export interface PhotoFilter {
+    // Keep only photos that belong to this album.
+    albumID?: number;
+    // Case-insensitive substring of the title, caption, or any album name the
+    // photo belongs to.
+    text?: string;
+    // Keep only photos of one of these types.
+    fileTypes?: FileType[];
+    // `true` keeps only geotagged photos; `false` keeps only those without a
+    // location; omitted places no constraint.
+    hasLocation?: boolean;
+    // Archived photos are excluded unless this is `true`. Defaults to `false`.
+    includeArchived?: boolean;
+}
+
+export interface TimelineGroup {
+    // The period's identity: `YYYY-MM-DD` for day, `YYYY-Www` (ISO 8601 week,
+    // e.g. `2025-W32`) for week, and `YYYY-MM` for month.
+    key: string;
+    // Local-time milliseconds at the start of the period.
+    startsAt: number;
+    // The period's files, newest first, each file once.
+    fileIDs: number[];
+}
+
+export interface TimelineAPI {
+    groups(args: { groupBy: GroupBy; filter?: PhotoFilter }): TimelineGroup[];
+}
+
+export const makeAlbumsAPI = (derive: () => DerivedRecords): AlbumsAPI => ({
+    list: (): Album[] => {
+        const records = derive();
+        return [...records.albums.values()]
+            .sort(byNewestAlbum)
+            .map((rec) => new Album(rec, records));
+    },
+    byID: ({ collectionID }): Album | undefined => {
+        const records = derive();
+        const rec = records.albums.get(collectionID);
+        return rec ? new Album(rec, records) : undefined;
+    },
+    byName: ({ albumName }): Album | undefined => {
+        const records = derive();
+        // Names are not unique in Ente; resolve a collision deterministically
+        // to the newest-updated album, matching `list` order.
+        const match = [...records.albums.values()]
+            .sort(byNewestAlbum)
+            .find((rec) => rec.name === albumName);
+        return match ? new Album(match, records) : undefined;
+    },
+});
+
+export const makePhotosAPI = (derive: () => DerivedRecords): PhotosAPI => ({
+    byID: ({ fileID }): Photo | undefined => {
+        const rec = derive().photos.get(fileID);
+        return rec ? new Photo(rec) : undefined;
+    },
+    records: ({ fileIDs }): PhotoRecord[] => {
+        const { photos } = derive();
+        const seen = new Set<number>();
+        const out: PhotoRecord[] = [];
+        for (const id of fileIDs) {
+            if (seen.has(id)) continue;
+            const rec = photos.get(id);
+            if (rec) {
+                out.push(rec);
+                seen.add(id);
+            }
+        }
+        return out;
+    },
+});
+
+export const makeTimelineAPI = (derive: () => DerivedRecords): TimelineAPI => ({
+    groups: ({ groupBy, filter }): TimelineGroup[] => {
+        const records = derive();
+        return groupPhotos(filterPhotos(records, filter), groupBy);
+    },
+});
+
+// Apply a `PhotoFilter` to the projection. Hidden photos are always dropped;
+// archived photos are dropped unless `includeArchived` asks for them.
+const filterPhotos = (
+    records: DerivedRecords,
+    filter?: PhotoFilter,
+): PhotoRecord[] => {
+    const f = filter ?? {};
+    const includeArchived = f.includeArchived ?? false;
+    const needle = f.text?.toLowerCase();
+    const out: PhotoRecord[] = [];
+    for (const rec of records.photos.values()) {
+        if (rec.isHidden) continue;
+        if (rec.isArchived && !includeArchived) continue;
+        if (f.albumID !== undefined && !rec.albumIDs.includes(f.albumID))
+            continue;
+        if (f.fileTypes !== undefined && !f.fileTypes.includes(rec.fileType))
+            continue;
+        if (f.hasLocation !== undefined) {
+            const has =
+                rec.latitude !== undefined && rec.longitude !== undefined;
+            if (has !== f.hasLocation) continue;
+        }
+        if (needle !== undefined && !matchesText(rec, needle, records))
+            continue;
+        out.push(rec);
+    }
+    return out;
+};
+
+const matchesText = (
+    rec: PhotoRecord,
+    needle: string,
+    records: DerivedRecords,
+): boolean => {
+    if (rec.title.toLowerCase().includes(needle)) return true;
+    if (rec.caption !== undefined && rec.caption.toLowerCase().includes(needle))
+        return true;
+    for (const id of rec.albumIDs) {
+        const album = records.albums.get(id);
+        if (album && album.name.toLowerCase().includes(needle)) return true;
+    }
+    return false;
+};
+
+// Bucket photos into periods, groups newest first, members newest first.
+const groupPhotos = (
+    photos: PhotoRecord[],
+    groupBy: GroupBy,
+): TimelineGroup[] => {
+    const buckets = new Map<
+        string,
+        { startsAt: number; recs: PhotoRecord[] }
+    >();
+    for (const rec of photos) {
+        const { key, startsAt } = periodOf(rec.takenAt, groupBy);
+        const bucket = buckets.get(key);
+        if (bucket) bucket.recs.push(rec);
+        else buckets.set(key, { startsAt, recs: [rec] });
+    }
+    const groups: TimelineGroup[] = [];
+    for (const [key, bucket] of buckets) {
+        bucket.recs.sort(byNewest);
+        groups.push({
+            key,
+            startsAt: bucket.startsAt,
+            fileIDs: bucket.recs.map((r) => r.fileID),
+        });
+    }
+    groups.sort((a, b) => b.startsAt - a.startsAt);
+    return groups;
+};
+
+const pad = (n: number): string => String(n).padStart(2, "0");
+
+const dateKey = (d: Date): string =>
+    `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
+
+const WEEK_MS = 7 * 24 * 60 * 60 * 1000;
+
+// The ISO 8601 week key `YYYY-Www` for the week starting at the given Monday.
+// The week-year is the year of that week's Thursday, so it can differ from the
+// calendar year at the January/December boundary (e.g. 2024-12-30 is 2025-W01).
+const isoWeekKey = (monday: Date): string => {
+    const thursday = new Date(
+        monday.getFullYear(),
+        monday.getMonth(),
+        monday.getDate() + 3,
+    );
+    const isoYear = thursday.getFullYear();
+    // Thursday of ISO week 1 is the Thursday of the week containing January 4.
+    const jan4 = new Date(isoYear, 0, 4);
+    const week1Thursday = new Date(
+        isoYear,
+        0,
+        4 + 3 - ((jan4.getDay() + 6) % 7),
+    );
+    const week =
+        1 +
+        Math.round((thursday.getTime() - week1Thursday.getTime()) / WEEK_MS);
+    return `${isoYear}-W${pad(week)}`;
+};
+
+// The period a millisecond instant falls in, in local time. Weeks start on
+// Monday. `Date` normalizes out-of-range day arguments, so the week's Monday
+// is correct across month and year boundaries.
+const periodOf = (
+    takenAt: number,
+    groupBy: GroupBy,
+): { key: string; startsAt: number } => {
+    const d = new Date(takenAt);
+    const year = d.getFullYear();
+    const month = d.getMonth();
+    const day = d.getDate();
+
+    if (groupBy === "month") {
+        const start = new Date(year, month, 1);
+        return { key: `${year}-${pad(month + 1)}`, startsAt: start.getTime() };
+    }
+    if (groupBy === "week") {
+        // getDay(): 0=Sunday..6=Saturday; shift so Monday is the week start.
+        const fromMonday = (d.getDay() + 6) % 7;
+        const start = new Date(year, month, day - fromMonday);
+        return { key: isoWeekKey(start), startsAt: start.getTime() };
+    }
+    const start = new Date(year, month, day);
+    return { key: dateKey(start), startsAt: start.getTime() };
+};

test/library/mldata.test.ts

@@ -321,8 +321,13 @@ describe("Library ML-data fetch on refresh", () => {
             refreshIntervalSeconds: FAST_INTERVAL,
         });
         try {
+            // Wait on `lastMLFetchAt`, set only once the pass has persisted the
+            // index and payloads — not on the in-RAM counts, which advance
+            // before `storeFetched` writes to disk, so the reopen below reads
+            // the committed index rather than racing the write.
             await vi.waitFor(
                 () => {
+                    expect(lib.status().lastMLFetchAt).toBeGreaterThan(0);
                     expect(lib.status().mlIndexed).toBe(2);
                     expect(lib.status().mlStored).toBe(2);
                 },
@@ -369,10 +374,13 @@ describe("Library ML-data fetch on refresh", () => {
             refreshIntervalSeconds: FAST_INTERVAL,
         });
         try {
-            await vi.waitFor(() => expect(lib.status().mlIndexed).toBe(1), {
-                timeout: 2000,
-                interval: 5,
-            });
+            // Wait on `lastMLFetchAt`, set only after the first pass has
+            // persisted, not on `mlIndexed`, which is bumped in RAM before the
+            // write lands.
+            await vi.waitFor(
+                () => expect(lib.status().lastMLFetchAt).toBeGreaterThan(0),
+                { timeout: 2000, interval: 5 },
+            );
             const callsBefore = client.mlFetchCalls.length;
 
             // The file changes on the server (updationTime advances) with a new
@@ -389,20 +397,27 @@ describe("Library ML-data fetch on refresh", () => {
                 cursor: 190,
             });
 
+            // Poll the persisted index itself, not the fetch-call log: a call
+            // is recorded the instant the mock is entered, but `storeFetched`
+            // rewrites `clip.f32` only after it resolves, so an earlier reopen
+            // would read the pre-refetch vector. Reopening reads only committed
+            // (atomically renamed) files, so this sees the new embedding once —
+            // and only once — the store has written it.
             await vi.waitFor(
-                () => {
-                    expect(client.mlFetchCalls.length).toBeGreaterThan(
-                        callsBefore,
-                    );
-                    expect(client.mlFetchCalls.flat()).toContain(1001);
-                },
-                { timeout: 2000, interval: 5 },
-            );
-
+                async () => {
                     const reopened = await MLDataStore.open(
                         join(cacheDirectory, "mldata"),
                     );
-            expect([...reopened.getIndex().embeddings]).toEqual([9, 9, 9]);
+                    expect([...reopened.getIndex().embeddings]).toEqual([
+                        9, 9, 9,
+                    ]);
+                },
+                { timeout: 2000, interval: 20 },
+            );
+
+            // The refetch really went back to the server for 1001.
+            expect(client.mlFetchCalls.length).toBeGreaterThan(callsBefore);
+            expect(client.mlFetchCalls.flat()).toContain(1001);
         } finally {
             lib.close();
         }

test/library/read.test.ts

@@ -0,0 +1,537 @@
+/**
+ * Tests for the in-process read surface (issue #44).
+ *
+ * Phase 1 (#43) projected the decrypted store into plain `AlbumRecord` /
+ * `PhotoRecord` values. This phase adds the read API a CLI or in-process script
+ * uses, all served from RAM with no network:
+ *
+ *  - `lib.albums`  — `list` / `byName` / `byID`, returning thin `Album` wrappers.
+ *  - `lib.photos`  — `byID` (a `Photo` wrapper) and `records` (plain records).
+ *  - `lib.timeline.groups` — photos bucketed by local day / week / month.
+ *
+ * Every call takes a single named-argument object; there are no positional
+ * arguments. The wrapper classes are for in-process callers only (they hold
+ * object identity, not JSON); the plain records remain the IPC-safe surface.
+ * Content-fetch methods (`Photo.original` / `thumbnail`) are a later unit and
+ * deliberately absent here — this surface is read-only.
+ *
+ * The detailed cases drive the API factories directly over a hand-built
+ * projection (`deriveRecords`), which keeps them free of disk and timers. A
+ * final section opens a real `Library` to prove the namespaces are wired to the
+ * live store and that a read never touches the client.
+ */
+
+import { describe, it, expect, beforeAll, afterAll } from "vitest";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import {
+    deriveRecords,
+    type DerivedRecords,
+} from "../../src/library/records.js";
+import {
+    Album,
+    Photo,
+    makeAlbumsAPI,
+    makePhotosAPI,
+    makeTimelineAPI,
+    type TimelineGroup,
+} from "../../src/library/read.js";
+import { Library } from "../../src/library/index.js";
+import { MetadataStore } from "../../src/library/store.js";
+import type { CollectionsPage, FilesPage } from "../../src/client.js";
+import type { Collection, EnteFile } from "../../src/model/types.js";
+
+const OWNER = 42;
+
+// Ente stores times in microseconds; records expose milliseconds. These
+// helpers keep the fixtures readable: `ms(...)` picks an epoch-millisecond
+// instant, `micros(...)` is what the fixture stores so the derived record's
+// `takenAt` comes back as the same millisecond value.
+const ms = (epochMillis: number): number => epochMillis;
+const micros = (epochMillis: number): number => epochMillis * 1000;
+
+const collection = (
+    id: number,
+    opts: Partial<Collection> = {},
+): Collection => ({
+    id,
+    ownerID: OWNER,
+    key: new Uint8Array([id & 0xff, 1, 2, 3]),
+    name: `album-${id}`,
+    type: "album",
+    updationTime: micros(1_700_000_000_000),
+    isShared: false,
+    ...opts,
+});
+
+const file = (
+    id: number,
+    collectionID: number,
+    opts: Partial<EnteFile> & {
+        creationTime?: number;
+        title?: string;
+        fileType?: EnteFile["metadata"]["fileType"];
+        latitude?: number;
+        longitude?: number;
+    } = {},
+): EnteFile => {
+    const { creationTime, title, fileType, latitude, longitude, ...rest } =
+        opts;
+    const metadata: EnteFile["metadata"] = {
+        title: title ?? `file-${id}.jpg`,
+        fileType: fileType ?? "image",
+        creationTime: creationTime ?? micros(1_700_000_000_000),
+        modificationTime: micros(1_700_000_000_000),
+    };
+    if (latitude !== undefined) metadata.latitude = latitude;
+    if (longitude !== undefined) metadata.longitude = longitude;
+    return {
+        id,
+        collectionID,
+        ownerID: OWNER,
+        key: new Uint8Array([id & 0xff, 9, 8, 7]),
+        metadata,
+        file: { decryptionHeader: "aGVhZGVy" },
+        thumbnail: { decryptionHeader: "dGh1bWI=" },
+        updationTime: micros(1_700_000_000_000),
+        ...rest,
+    };
+};
+
+// Build the three API objects over one fixed projection, the way `Library`
+// wires them over its live store.
+const apis = (records: DerivedRecords) => {
+    const derive = () => records;
+    return {
+        albums: makeAlbumsAPI(derive),
+        photos: makePhotosAPI(derive),
+        timeline: makeTimelineAPI(derive),
+    };
+};
+
+// Every file id present across all timeline groups, in group-then-member order.
+const allFileIDs = (groups: TimelineGroup[]): number[] =>
+    groups.flatMap((g) => g.fileIDs);
+
+describe("lib.albums", () => {
+    it("lists albums as Album wrappers, newest updated first", () => {
+        const records = deriveRecords(
+            [
+                collection(1, { updationTime: micros(1_700_000_000_000) }),
+                collection(2, { updationTime: micros(1_705_000_000_000) }),
+            ],
+            [file(10, 1), file(20, 2)],
+        );
+        const albums = apis(records).albums.list();
+        expect(albums.every((a) => a instanceof Album)).toBe(true);
+        // Collection 2 updated later, so it sorts ahead of collection 1.
+        expect(albums.map((a) => a.collectionID)).toEqual([2, 1]);
+    });
+
+    it("exposes album fields and its photos newest first", () => {
+        const records = deriveRecords(
+            [
+                collection(7, {
+                    name: "Trip",
+                    type: "favorites",
+                    isShared: true,
+                }),
+            ],
+            [
+                file(1, 7, { creationTime: micros(1_600_000_000_000) }),
+                file(2, 7, { creationTime: micros(1_800_000_000_000) }),
+                file(3, 7, { creationTime: micros(1_700_000_000_000) }),
+            ],
+        );
+        const album = apis(records).albums.byID({ collectionID: 7 })!;
+        expect(album.name).toBe("Trip");
+        expect(album.type).toBe("favorites");
+        expect(album.isShared).toBe(true);
+        expect(album.fileIDs).toEqual([2, 3, 1]);
+
+        const photos = album.photos.list();
+        expect(photos.every((p) => p instanceof Photo)).toBe(true);
+        expect(photos.map((p) => p.fileID)).toEqual([2, 3, 1]);
+
+        // record() hands back the plain, JSON-safe projection.
+        expect("key" in album.record()).toBe(false);
+    });
+
+    it("finds an album by exact name and returns undefined when absent", () => {
+        const records = deriveRecords(
+            [
+                collection(1, { name: "Berlin" }),
+                collection(2, { name: "Paris" }),
+            ],
+            [file(10, 1), file(20, 2)],
+        );
+        const { albums } = apis(records);
+        expect(albums.byName({ albumName: "Paris" })?.collectionID).toBe(2);
+        expect(albums.byName({ albumName: "paris" })).toBeUndefined();
+        expect(albums.byName({ albumName: "Nowhere" })).toBeUndefined();
+    });
+
+    it("returns undefined for an unknown collection id", () => {
+        const records = deriveRecords([collection(1)], [file(10, 1)]);
+        expect(
+            apis(records).albums.byID({ collectionID: 999 }),
+        ).toBeUndefined();
+    });
+});
+
+describe("lib.photos", () => {
+    it("byID returns a Photo wrapper carrying the mapped fields", () => {
+        const records = deriveRecords(
+            [collection(1)],
+            [
+                file(1001, 1, {
+                    title: "IMG.jpg",
+                    fileType: "video",
+                    creationTime: micros(1_699_000_000_000),
+                    latitude: 52.52,
+                    longitude: 13.405,
+                    pubMagicMetadata: { caption: "at the lake" },
+                }),
+            ],
+        );
+        const photo = apis(records).photos.byID({ fileID: 1001 })!;
+        expect(photo).toBeInstanceOf(Photo);
+        expect(photo.title).toBe("IMG.jpg");
+        expect(photo.fileType).toBe("video");
+        expect(photo.takenAt).toBe(ms(1_699_000_000_000));
+        expect(photo.caption).toBe("at the lake");
+        expect(photo.latitude).toBeCloseTo(52.52);
+        expect(photo.isArchived).toBe(false);
+        expect(photo.isHidden).toBe(false);
+        // The wrapper hands back the plain record, IPC-safe.
+        expect("key" in photo.record()).toBe(false);
+    });
+
+    it("byID returns undefined for an unknown file id", () => {
+        const records = deriveRecords([collection(1)], [file(1, 1)]);
+        expect(apis(records).photos.byID({ fileID: 999 })).toBeUndefined();
+    });
+
+    it("records() returns plain records in requested order, deduped, skipping unknowns", () => {
+        const records = deriveRecords(
+            [collection(1)],
+            [file(1, 1), file(2, 1), file(3, 1)],
+        );
+        const out = apis(records).photos.records({
+            fileIDs: [3, 1, 3, 999, 2],
+        });
+        // Requested order preserved; the repeated 3 appears once; 999 is dropped.
+        expect(out.map((r) => r.fileID)).toEqual([3, 1, 2]);
+        // Plain records, not wrappers, and JSON round-trips whole.
+        expect(out[0]).not.toBeInstanceOf(Photo);
+        expect(JSON.parse(JSON.stringify(out[0]))).toEqual(out[0]);
+    });
+
+    it("emits one record for a file even when it belongs to several albums", () => {
+        // File 1001 is a member of collections 1 and 2.
+        const records = deriveRecords(
+            [collection(1), collection(2)],
+            [file(1001, 1), file(1001, 2)],
+        );
+        const out = apis(records).photos.records({ fileIDs: [1001, 1001] });
+        expect(out).toHaveLength(1);
+        expect(out[0]!.albumIDs).toEqual([1, 2]);
+    });
+});
+
+describe("lib.timeline grouping", () => {
+    // Group keys and `startsAt` are computed in local time. Pinning the zone to
+    // UTC makes the expected values exact and lets the fixtures use `Date.UTC`.
+    const savedTZ = process.env.TZ;
+    beforeAll(() => {
+        process.env.TZ = "UTC";
+    });
+    afterAll(() => {
+        if (savedTZ === undefined) delete process.env.TZ;
+        else process.env.TZ = savedTZ;
+    });
+
+    it("buckets by local day, newest group and newest member first", () => {
+        const records = deriveRecords(
+            [collection(1)],
+            [
+                file(1, 1, { creationTime: micros(Date.UTC(2024, 0, 15, 9)) }),
+                file(2, 1, { creationTime: micros(Date.UTC(2024, 0, 15, 18)) }),
+                file(3, 1, { creationTime: micros(Date.UTC(2024, 0, 16, 12)) }),
+                file(4, 1, { creationTime: micros(Date.UTC(2024, 1, 1, 12)) }),
+            ],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "day" });
+        expect(groups.map((g) => g.key)).toEqual([
+            "2024-02-01",
+            "2024-01-16",
+            "2024-01-15",
+        ]);
+        // Group start is local midnight of the day.
+        expect(groups[2]!.startsAt).toBe(Date.UTC(2024, 0, 15));
+        // Within the 2024-01-15 group, the later photo (id 2) is first.
+        expect(groups[2]!.fileIDs).toEqual([2, 1]);
+    });
+
+    it("buckets by week with weeks starting on Monday", () => {
+        // 2024-01-15 is a Monday; the week runs through Sunday 2024-01-21.
+        const records = deriveRecords(
+            [collection(1)],
+            [
+                file(1, 1, { creationTime: micros(Date.UTC(2024, 0, 15, 12)) }), // Mon
+                file(2, 1, { creationTime: micros(Date.UTC(2024, 0, 17, 12)) }), // Wed
+                file(3, 1, { creationTime: micros(Date.UTC(2024, 0, 21, 12)) }), // Sun
+                file(4, 1, { creationTime: micros(Date.UTC(2024, 0, 22, 12)) }), // next Mon
+            ],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "week" });
+        // ISO week keys: 2024-01-15 is in 2024-W03, the next Monday in 2024-W04.
+        expect(groups.map((g) => g.key)).toEqual(["2024-W04", "2024-W03"]);
+        const first = groups.find((g) => g.key === "2024-W03")!;
+        expect(first.startsAt).toBe(Date.UTC(2024, 0, 15));
+        // The Sunday belongs to the Monday-started week, not the next one.
+        expect(first.fileIDs.sort((a, b) => a - b)).toEqual([1, 2, 3]);
+    });
+
+    it("assigns a Sunday to the preceding Monday's week across a month boundary", () => {
+        // 2024-01-14 is a Sunday; its week started Monday 2024-01-08.
+        const records = deriveRecords(
+            [collection(1)],
+            [file(1, 1, { creationTime: micros(Date.UTC(2024, 0, 14, 12)) })],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "week" });
+        expect(groups.map((g) => g.key)).toEqual(["2024-W02"]);
+        expect(groups[0]!.startsAt).toBe(Date.UTC(2024, 0, 8));
+    });
+
+    it("buckets by month", () => {
+        const records = deriveRecords(
+            [collection(1)],
+            [
+                file(1, 1, { creationTime: micros(Date.UTC(2024, 0, 3, 12)) }),
+                file(2, 1, { creationTime: micros(Date.UTC(2024, 0, 28, 12)) }),
+                file(3, 1, { creationTime: micros(Date.UTC(2024, 1, 9, 12)) }),
+            ],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "month" });
+        expect(groups.map((g) => g.key)).toEqual(["2024-02", "2024-01"]);
+        expect(groups[1]!.startsAt).toBe(Date.UTC(2024, 0, 1));
+        expect(groups[1]!.fileIDs).toEqual([2, 1]);
+    });
+
+    it("lists each file once even when it belongs to several albums", () => {
+        // File 1001 is in collections 1 and 2 but must appear once in a group.
+        const records = deriveRecords(
+            [collection(1), collection(2)],
+            [
+                file(1001, 1, {
+                    creationTime: micros(Date.UTC(2024, 0, 15, 12)),
+                }),
+                file(1001, 2, {
+                    creationTime: micros(Date.UTC(2024, 0, 15, 12)),
+                }),
+            ],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "day" });
+        expect(allFileIDs(groups)).toEqual([1001]);
+    });
+});
+
+describe("lib.timeline uses local time, not UTC", () => {
+    const savedTZ = process.env.TZ;
+    afterAll(() => {
+        if (savedTZ === undefined) delete process.env.TZ;
+        else process.env.TZ = savedTZ;
+    });
+
+    it("buckets by the viewer's local day", () => {
+        // Kolkata is UTC+5:30 with no DST. An instant at 2024-01-14T20:00Z is
+        // 2024-01-15 01:30 local, so it belongs to the local day 2024-01-15.
+        process.env.TZ = "Asia/Kolkata";
+        const records = deriveRecords(
+            [collection(1)],
+            [file(1, 1, { creationTime: micros(Date.UTC(2024, 0, 14, 20)) })],
+        );
+        const groups = apis(records).timeline.groups({ groupBy: "day" });
+        expect(groups[0]!.key).toBe("2024-01-15");
+        // Local midnight of 2024-01-15, which is 2024-01-14T18:30Z.
+        expect(groups[0]!.startsAt).toBe(new Date(2024, 0, 15).getTime());
+        expect(groups[0]!.startsAt).toBe(Date.UTC(2024, 0, 14, 18, 30));
+    });
+});
+
+describe("PhotoFilter", () => {
+    // A fixture spanning albums, file types, geotags, captions, and the two
+    // visibility states, all on the same local day so grouping is incidental.
+    const day = (h: number): number => micros(Date.UTC(2024, 2, 4, h));
+    const records = (): DerivedRecords =>
+        deriveRecords(
+            [
+                collection(1, { name: "Holidays" }),
+                collection(2, { name: "Work" }),
+            ],
+            [
+                file(1, 1, {
+                    title: "Beach sunset",
+                    creationTime: day(1),
+                    latitude: 1,
+                    longitude: 2,
+                }),
+                file(2, 1, {
+                    title: "clip.mov",
+                    fileType: "video",
+                    creationTime: day(2),
+                }),
+                file(3, 2, {
+                    title: "invoice scan",
+                    creationTime: day(3),
+                    pubMagicMetadata: { caption: "SUNSET colours" },
+                }),
+                file(4, 2, {
+                    title: "archived note",
+                    creationTime: day(4),
+                    magicMetadata: { visibility: 1 },
+                }),
+                file(5, 2, {
+                    title: "secret",
+                    creationTime: day(5),
+                    magicMetadata: { visibility: 2 },
+                }),
+            ],
+        );
+
+    const idsWith = (
+        filter: Parameters<
+            ReturnType<typeof apis>["timeline"]["groups"]
+        >[0]["filter"],
+    ): number[] =>
+        allFileIDs(
+            apis(records()).timeline.groups({ groupBy: "day", filter }),
+        ).sort((a, b) => a - b);
+
+    it("never includes hidden photos and excludes archived by default", () => {
+        // No filter: hidden (5) always gone, archived (4) gone unless asked for.
+        expect(idsWith(undefined)).toEqual([1, 2, 3]);
+    });
+
+    it("includes archived photos when includeArchived is set, hidden still never", () => {
+        expect(idsWith({ includeArchived: true })).toEqual([1, 2, 3, 4]);
+    });
+
+    it("filters by album membership", () => {
+        expect(idsWith({ albumID: 1 })).toEqual([1, 2]);
+        expect(idsWith({ albumID: 2 })).toEqual([3]);
+    });
+
+    it("filters by file type", () => {
+        expect(idsWith({ fileTypes: ["video"] })).toEqual([2]);
+        expect(idsWith({ fileTypes: ["image", "video"] })).toEqual([1, 2, 3]);
+    });
+
+    it("filters by presence or absence of location", () => {
+        expect(idsWith({ hasLocation: true })).toEqual([1]);
+        expect(idsWith({ hasLocation: false })).toEqual([2, 3]);
+    });
+
+    it("matches text case-insensitively against title, caption, and album name", () => {
+        // Title match (case-insensitive): "Beach sunset".
+        expect(idsWith({ text: "SUNSET" })).toEqual([1, 3]);
+        // Caption-only match: file 3's caption is "SUNSET colours".
+        expect(idsWith({ text: "colours" })).toEqual([3]);
+        // Album-name match: everything in "Holidays".
+        expect(idsWith({ text: "holiday" })).toEqual([1, 2]);
+    });
+
+    it("combines filters", () => {
+        // Images in album 1 with a location: only file 1.
+        expect(
+            idsWith({ albumID: 1, fileTypes: ["image"], hasLocation: true }),
+        ).toEqual([1]);
+    });
+});
+
+/**
+ * A minimal mock `Client`, enough for `Library.open` to run its refresh loop.
+ * The queues are empty, so the background refresh over a seeded cache changes
+ * nothing; the counters prove that a read never calls the client.
+ */
+class MockClient {
+    userID = OWNER;
+    collectionsCalls = 0;
+    filesCalls = 0;
+
+    whoami(): { email: string; userID: number } {
+        return { email: "user@example.com", userID: this.userID };
+    }
+    async collectionsSince(args: {
+        sinceTime: number;
+    }): Promise<CollectionsPage> {
+        this.collectionsCalls++;
+        return { collections: [], deleted: [], cursor: args.sinceTime };
+    }
+    async filesSince(args: {
+        collectionID: number;
+        collectionKey: Uint8Array;
+        sinceTime: number;
+    }): Promise<FilesPage> {
+        this.filesCalls++;
+        return { files: [], deleted: [], cursor: args.sinceTime };
+    }
+}
+
+describe("Library exposes the read surface over its live store", () => {
+    let dir: string;
+
+    beforeAll(() => {
+        dir = mkdtempSync(join(tmpdir(), "quak-read-"));
+    });
+    afterAll(() => {
+        rmSync(dir, { recursive: true, force: true });
+    });
+
+    it("serves albums, photos, and timeline from RAM without calling the client", async () => {
+        const cacheDirectory = join(dir, "cache");
+        const path = join(cacheDirectory, "metadata.json");
+
+        // Seed a cache as a prior run left it, so open() serves it at once.
+        const seed = await MetadataStore.load(path);
+        seed.userID = OWNER;
+        seed.collectionsSinceTime = 100;
+        seed.putCollection(collection(1, { name: "Seeded" }));
+        seed.putFile(
+            file(1001, 1, { creationTime: micros(Date.UTC(2024, 5, 1, 12)) }),
+        );
+        await seed.save();
+
+        const client = new MockClient();
+        // A long interval keeps the background timer from firing during the test.
+        const lib = await Library.open({
+            client,
+            cacheDirectory,
+            refreshIntervalSeconds: 3600,
+        });
+        try {
+            const collectionsBefore = client.collectionsCalls;
+            const filesBefore = client.filesCalls;
+
+            expect(lib.albums.list().map((a) => a.name)).toEqual(["Seeded"]);
+            expect(
+                lib.albums.byName({ albumName: "Seeded" })?.collectionID,
+            ).toBe(1);
+            expect(lib.photos.byID({ fileID: 1001 })?.fileID).toBe(1001);
+            expect(
+                lib.photos.records({ fileIDs: [1001] }).map((r) => r.fileID),
+            ).toEqual([1001]);
+            const groups = lib.timeline.groups({ groupBy: "month" });
+            expect(allFileIDs(groups)).toEqual([1001]);
+
+            // Reads are answered from RAM: no read called the client.
+            expect(client.collectionsCalls).toBe(collectionsBefore);
+            expect(client.filesCalls).toBe(filesBefore);
+        } finally {
+            lib.close();
+        }
+    });
+});