Photo implements one method per PhotoExif field

Photo now implements a mapped type with one method per PhotoExif field,
each taking exif()'s options and giving that field's type, so the
build's type check fails when PhotoExif has a field Photo has no method
for, whatever the test fixtures hold. The test comment and TODO.md say
so.

Model: opus-5-5

README.md

@@ -8,9 +8,9 @@ and downloads individual images while decrypting them on the way to disk.
 quak also includes a resilient backup command that downloads every file in the
 account into a deduplicated local directory tree, skipping files that already
 exist on disk and continuing past individual download failures instead of
-crashing. It decrypts and persists all three metadata layers (basic, private
+crashing. For each file it persists the basic metadata fields quak keeps (title,
-magic, public magic) per file, including camera info, GPS coordinates, captions,
+file type, creation and modification time, latitude, longitude, content hash),
-and any face/keyword labels the Ente clients have added. A helper subcommand can
+and the private and public magic metadata in full. A helper subcommand can
 detect and regenerate missing thumbnails, encrypting and uploading them back to
 the server.
 
@@ -51,7 +51,8 @@ const client = await Client.login({
 
 // Open a cache-backed library. On an empty cache this awaits one server
 // refresh; on an existing cache it returns immediately and refreshes in the
-// background every `refreshIntervalSeconds` (default 3).
+// background. Later refreshes start `refreshIntervalSeconds` (default 3) after
+// the previous one ends.
 const lib = await Library.open({ client });
 
 // Default reads answer synchronously from the local cache — no network.
@@ -62,7 +63,7 @@ for (const album of lib.albums.list()) {
     }
 }
 
-// Fresh reads await a server round-trip and answer with current state.
+// Fresh reads await a server round-trip, joining one already running.
 const { albums } = await lib.fresh();
 console.log(`${albums.list().length} albums as of now`);
 
@@ -84,7 +85,7 @@ enumeration/download calls) is exported too and documented under Design below.
 This repository adheres to the
 [Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
 standard: normalized scripts in `script/` are the entrypoints for the
-development workflow, and the Makefile targets are thin shims that call them.
+development workflow, and most Makefile targets are thin shims that call them.
 The scripts are POSIX sh (not bash) so they run in minimal containers such as
 alpine. We provide:
 
@@ -122,9 +123,9 @@ alpine. We provide:
 Linting and testing are phases of the `Dockerfile`. The `lint` phase copies the
 repo into a digest-pinned node image and runs eslint and `prettier --check .`;
 the `test` phase does the same with the suite. `script/lint` and `script/test`
-each build one phase with `docker build --no-cache --target <phase>`. There is
+each build one phase with `docker build --no-cache --target <phase>`. Neither
-no host lint or test path: docker is required, and that also works where the
+script runs the tools on the host: docker is required, and that also works where
-docker daemon is remote and bind mounts are impossible.
+the docker daemon is remote and bind mounts are impossible.
 
 The last stage of the `Dockerfile` compiles the package, and it copies a file
 from each phase, so it cannot be built unless lint and the tests pass. That is
@@ -170,16 +171,19 @@ local cache is reliable, and the UI is responsive on a five-year-old laptop.
 
 All work on quak is test-driven. No exceptions.
 
-1. Every change starts on a feature branch off `main`.
+1. Every change starts on a feature branch off `next`, and its pull request
+   targets `next`.
 2. The first commit on the branch is the test suite for what is being added or
    changed. Those tests must fail at that commit; the branch is red until the
    implementation lands.
 3. Subsequent commits add the implementation and any refactors needed to make
    the tests pass.
-4. A feature branch can only be merged into `main` when `make check` is green.
+4. A pull request can only be merged into `next` when `make check` is green.
-   `main` is always green. CI runs `script/cibuild`, which builds the
+   Once it has passed review, the repository manager squash-merges it into
-   `Dockerfile`: its `lint` and `test` phases, then the compile, so neither a
+   `next`. Only sneak merges `next` into `main`. `main` and `next` are always
-   red branch nor one that does not compile can pass CI.
+   green. CI runs `script/cibuild`, which builds the `Dockerfile`: its `lint`
+   and `test` phases, then the compile, so neither a red branch nor one that
+   does not compile can pass CI.
 5. Tests are the canonical API documentation for this library. Every test file
    is commented thoroughly enough that a reader who has never seen quak can
    learn how to use it from the tests alone. Comments explain why a behavior
@@ -197,7 +201,7 @@ All work on quak is test-driven. No exceptions.
    not the tests, and so not the full `make check`. This is deliberate so the
    TDD red-phase commit (failing tests, no implementation yet) can land. The
    `test` phase is part of the image build, which is what CI executes via
-   `script/cibuild`, so a red branch still cannot reach `main`.
+   `script/cibuild`, so a red branch still cannot reach `next`.
 
 ## Design
 
@@ -209,7 +213,7 @@ the CLI is for humans.
 ```
 quak/
     src/
-        crypto/         libsodium primitives (boxes, secretstreams, KDF, SRP)
+        crypto/         libsodium primitives (boxes, secretstreams, KDF, hash)
         api/            HTTP client (ApiClient class)
         auth/           login flow (SRP + email OTP + TOTP), key unwrap
         model/          decrypted Collection, File, Metadata types + decrypt fns
@@ -219,7 +223,8 @@ quak/
                         and search, request pools
         backup.ts       resilient full-account backup with dedup
         metadata-backup.ts
-                        backup-metadata: all decrypted metadata as JSON
+                        backup-metadata: the metadata quak keeps, as JSON
+        exif.ts         EXIF read from an image's bytes with exifreader
         mldata-fetch.ts fetch + decrypt per-file ML data
         filename.ts     safe file names from server metadata
         errors.ts       error types shared across layers
@@ -250,7 +255,9 @@ the repository root rather than `src/`, because `bin/` is compiled too and
 ### Cryptography
 
 All cryptography is done by `libsodium-wrappers-sumo` (the "sumo" build is
-required for `crypto_pwhash` / Argon2id). No hand-rolled crypto.
+required for `crypto_pwhash` / Argon2id), except the SRP handshake, which uses
+`fast-srp-hap`, and the MD5 checksum sent with a thumbnail upload, which uses
+Node's built-in `node:crypto`. No hand-rolled crypto.
 
 The key hierarchy, derived during login, is:
 
@@ -258,19 +265,23 @@ The key hierarchy, derived during login, is:
 2. Argon2id (`crypto_pwhash`) over the password and a server-issued `kekSalt`,
    with server-issued `memLimit` and `opsLimit`, produces a 32-byte Key
    Encryption Key (KEK).
-3. SRP login: a 16-byte SRP login subkey is derived from the KEK using
+3. SRP login: `crypto_kdf_derive_from_key` (BLAKE2b) derives a 32-byte subkey
-   `crypto_kdf_derive_from_key` (BLAKE2b) with subkey id 1 and context
+   from the KEK with subkey id 1 and context `loginctx`. Its first 16 bytes are
-   `loginctx`. That 16-byte value is the SRP password.
+   the SRP password.
-4. After SRP completes (or after email-OTP fallback), the server returns a blob
+4. When SRP completes, the server returns a blob of "key attributes" plus an
-   of "key attributes" plus an encrypted auth token.
+   encrypted auth token, or first asks for a second factor. quak answers a TOTP
+   request with the code (`POST /users/two-factor/verify`), after which the
+   server returns them, and cannot answer a passkey request. When the account
+   has email MFA on (`isEmailMFAEnabled`), an email OTP replaces SRP and the
+   server returns them after it.
 5. `crypto_secretbox_open_easy` over the encrypted master key with the KEK
    yields the 32-byte master key.
 6. `crypto_secretbox_open_easy` over the encrypted secret key with the master
    key yields the user's X25519 private key. The matching public key is
    delivered in cleartext.
 7. `crypto_box_seal_open` over the encrypted token with the user's keypair
-   yields the URL-safe base64 auth token used in `X-Auth-Token` for all
+   yields the auth token's bytes. Encoded as URL-safe base64 with padding, they
-   subsequent calls.
+   are the `X-Auth-Token` value for all subsequent calls.
 
 Per-collection keys are decrypted with `crypto_secretbox_open_easy` using the
 master key (for owned collections). Per-file keys are decrypted with
@@ -306,7 +317,8 @@ Endpoints used:
 - `POST /users/srp/create-session`: begin SRP handshake.
 - `POST /users/srp/verify-session`: complete SRP, receive 2FA challenge or the
   encrypted token plus key attributes.
-- `POST /users/ott` and `POST /users/verify-email`: email OTP fallback path.
+- `POST /users/ott` and `POST /users/verify-email`: email OTP, used instead of
+  SRP when the SRP attributes have `isEmailMFAEnabled` set.
 - `POST /users/two-factor/verify`: TOTP second factor.
 - `POST /users/logout`: end the calling token's session (`quak logout`).
 - `GET /collections/v2?sinceTime=<usec>`: list collections changed since
@@ -328,8 +340,9 @@ request is repeated only when repeating it could produce a different answer:
 - Every other 4xx: not retried. A 404 in particular is an answer, and
   `listMissingThumbnails` depends on getting it promptly and once.
 - Transport failures — a `fetch` rejection, `ECONNRESET`, `ETIMEDOUT`, a DNS or
-  TLS failure — and deadline aborts: retried. The errno is looked for in the
+  TLS failure — and deadline aborts: retried. Node's `fetch` rejects with a
-  error's `cause` chain, because that is where Node's `fetch` puts it.
+  plain `TypeError`, so every `TypeError` is retried. The errno is looked for in
+  the error's `cause` chain, because that is where Node's `fetch` puts it.
 - A truncated download: retried.
 - Anything else, including a secretstream authentication failure that is not
   truncation: not retried. The default answer is no. For a backup tool, retrying
@@ -395,10 +408,13 @@ because a socket reset after the response headers have arrived surfaces in the
 download layer rather than in `ApiClient`, and that is the common failure for
 multi-megabyte photos over a CDN. The secretstream pull state is not resumable
 and these endpoints have no Range support, so a retry starts the file over. The
-atomic write stays outside the retry, so a download that needed three attempts
+atomic write is part of the retried unit: each attempt writes its own temporary
-still performs exactly one write and one rename. `runBackup` and
+files, one for most files and two for a live photo (its image and its video),
-`runMetadataBackup` are unchanged: the retry sits below them, and a file that
+and removes them if it fails. Only the attempt that completes renames anything
-fails after exhausting it is still logged, counted, and stepped over.
+into place. The retry sits below `runBackup` and `runMetadataBackup`.
+`runBackup` logs, counts and steps over a file that still fails after its
+retries; `runMetadataBackup`, which downloads only with `--exif`, records the
+error in that file's JSON as `imageMetadataError` and goes on.
 
 One imprecision is deliberate and worth knowing about. When a body ends part-way
 through a secretstream chunk, Poly1305 fails and carries no framing signal, so a
@@ -422,10 +438,11 @@ base64-encoded keys) that the consumer can write to disk, a database, or
 whatever else fits their use case. `Client.fromJSON(snapshot)` restores a
 working client from that snapshot without re-authenticating; it checks every
 field and each key's length first, and throws an error naming the bad field.
-`client.logout()` clears the token and zeroes the key buffers in place; every
+`client.logout()` clears the token and zeroes the key buffers in place; after
-later call on that client throws. It does not contact the server, so the token
+it, every other method on that client throws. It does not contact the server, so
-stays valid there and in any saved snapshot; `await client.logoutOnServer()`
+the token stays valid there and in any saved snapshot;
-first ends the session on the server (`POST /users/logout`).
+`await client.logoutOnServer()` first ends the session on the server
+(`POST /users/logout`).
 
 The CLI stores the snapshot at the platform-appropriate data directory via
 `env-paths`: `~/Library/Application Support/quak/session.json` on macOS,
@@ -433,15 +450,17 @@ The CLI stores the snapshot at the platform-appropriate data directory via
 `0600`. The key material is stored in cleartext in the JSON; treat this file as
 you would treat the password itself. A missing file is reported as "not logged
 in"; a file that exists but is corrupt is reported as such, naming the bad
-field. Both exit with status 1.
+field. Both exit with status 1, except that `quak logout` with no file says
+there is no session and exits 0.
 
 `quak logout` ends the session on the server, so the token in `session.json`
 stops working even in a copy of the file, and then deletes the file. If the
 server call fails (or the file is corrupt), the file is still deleted, the
 command says the server session could not be ended, and it exits with status 1.
-It does not delete the cache: it prints the account's cache directory and says
+It does not delete the cache. When it knows the cache directory, from
-it still holds decrypted data (file keys in `metadata.json`, cached originals
+`--cache-dir` or from a session file it could read, it prints it and says it
-and thumbnails), for the user to delete if they want it gone.
+still holds decrypted data (file keys in `metadata.json`, cached originals and
+thumbnails), for the user to delete if they want it gone.
 
 ### CLI surface
 
@@ -455,19 +474,19 @@ quak files --collection <id> [--json]           list files in a collection
 quak get <fileID> [--out path] [--collection]             download and decrypt a file
 quak get-thumb <fileID> [--out] [--collection]            download and decrypt a thumbnail
 quak backup <dir> [--json]                                full incremental backup
-quak backup-metadata <dir> [--exif]             dump all decrypted metadata as JSON
+quak backup-metadata <dir> [--exif]                       dump the metadata quak keeps as JSON
 quak helper list-missing-thumbnails [--json]              find files with missing thumbnails
-quak helper fix-missing-thumbnails [--file ids] generate + upload missing thumbnails
+quak helper fix-missing-thumbnails [--file ids] [--json]  generate + upload missing thumbnails
 ```
 
-Every command runs on the same cache-backed library. The read commands —
+Every command except `login`, `whoami` and `logout` runs on the cache-backed
-`collections`, `files`, `get`, `get-thumb`, `backup-metadata`,
+library. The read commands — `collections`, `files`, `get`, `get-thumb`,
-`helper list-missing-thumbnails` and `helper fix-missing-thumbnails` — force a
+`backup-metadata`, `helper list-missing-thumbnails` and
-fresh server round-trip before they answer, so they report current account state
+`helper fix-missing-thumbnails` — force a fresh server round-trip before they
-rather than whatever the cache last held. If that round-trip fails, the command
+answer, so they report current account state rather than whatever the cache last
-prints the error on one line and exits 1. `--cache-dir` overrides where the
+held. If that round-trip fails, the command prints the error on one line and
-cache lives; without it each account gets its own directory under the per-user
+exits 1. `--cache-dir` overrides where the cache lives; without it each account
-cache path.
+gets its own directory under the per-user cache path.
 
 `get` and `get-thumb` resolve the file by ID directly, so `--collection` is
 accepted for backward compatibility but ignored. For a live photo, `get` writes
@@ -475,18 +494,25 @@ its image and its video, each named after the title with its own extension, as
 Ente's clients name them (`IMG_0001.heic` and `IMG_0001.mov`). With
 `--out PATH`, the image is written to `PATH` and the video beside it, with
 `PATH`'s name and the video's extension; a `PATH` with the video's extension is
-refused. `backup-metadata --exif` (alias `--all`) additionally downloads each
+refused. `backup-metadata --exif` (alias `--all`) additionally fetches each
-file to extract full EXIF/IPTC/XMP metadata. The listing and backup commands
+file's original through the cache and records, from it or a live photo's image,
-support `--json` for machine-readable output.
+its XMP metadata, its EXIF metadata and, for a JPEG, its dimensions. EXIF is
+read with [exifreader](https://github.com/mattiasw/ExifReader) from any image
+format it reads, JPEG, HEIC/HEIF, AVIF, PNG and WebP among them. The record's
+`exif` field is exifreader's EXIF tag output: each tag by name, with its
+`value`, `description` and `computed` value. An EXIF block exifreader finds but
+reads no tag from is recorded, base64, as `exifRaw`, with the reason in
+`exifError`. `collections`, `files`, `backup`, `helper list-missing-thumbnails`
+and `helper fix-missing-thumbnails` take `--json` for machine-readable output.
 
 `backup-metadata` fetches ML data in requests of up to 200 files. When a request
-still fails after its retries, the error is logged, each of its files is written
+fails, the error is logged, each of its files is written with the reason in an
-with the reason in an `mlDataError` field instead of `mlData`, and the dump goes
+`mlDataError` field instead of `mlData`, and the dump goes on. The exit code is
-on. The exit code is non-zero if any ML data request failed.
+non-zero if any ML data request failed.
 
-`helper fix-missing-thumbnails` regenerates thumbnails for baseline JPEG images
+`helper fix-missing-thumbnails` regenerates thumbnails for JPEG images only,
-only, because the bundled decoder (`jpeg-js`) decodes only JPEG. A non-JPEG
+because the bundled decoder (`jpeg-js`) decodes only JPEG. A non-JPEG image
-image (PNG, HEIC) or a video is reported as `skipped` (unsupported format), kept
+(PNG, HEIC) or a video is reported as `skipped` (unsupported format), kept
 distinct from a `failed` repair, and does not affect the exit code; a genuine
 failure still exits non-zero. The server accepts a new thumbnail only from the
 file's owner and only when it is no larger than the thumbnail size it records
@@ -505,7 +531,9 @@ the smallest does not.
     originals/
         <fileID>.<ext>          actual file content (one per unique file,
                                 two for a live photo: see below)
-        <fileID>.json           all decrypted metadata for that file
+        <fileID>.json           the file's basic metadata fields quak
+                                keeps, and its private and public magic
+                                metadata
         <fileID>.livephoto.json which of a live photo's two files is which
     collections/
         <name>/
@@ -550,7 +578,9 @@ the cache. An original the cache already held is copied from there instead. On
 subsequent runs, existing originals are skipped. If a download fails, the error
 is logged and the backup continues with the next file. The exit code is non-zero
 if any files failed. `quak backup` opens its library with the thumbnail and
-originals precache off, so it fetches only what the backup stores.
+originals precache off, so the only file content it fetches is the originals the
+backup stores. The library's ML data fetch still runs and fills the cache's
+`mldata/`.
 
 Each original is written to a temporary file in the same directory, synced to
 disk, and renamed into place, so an original is either complete or absent, even
@@ -567,8 +597,8 @@ temporary file's permissions, not those of the file it replaced.
 
 ## TODO
 
-- [x] Retry policy: no retry on 4xx, exponential backoff on 5xx and network
+- [x] Retry policy: no retry on 4xx (except `408` and `429`), exponential
-      errors
+      backoff on 5xx and network errors
 - [x] Update the API reference section below to match the current implementation
 - [x] `make docker` green
 - [x] Store live photos in a form a photo viewer can open
@@ -591,7 +621,8 @@ Future (desktop client, separate repo):
 The library's primary surface is the cache-backed `Library`; the lower-level
 `Client` sits underneath it and is covered by the Design sections above. The
 test suite is the canonical, executable documentation — `test/library/` and
-`test/client/usage.test.ts` walk every operation, and `yarn test` verifies them.
+`test/client/usage.test.ts` walk most operations, `test/cli/backup.test.ts`
+walks `lib.backup()`, and `yarn test` verifies them.
 
 ### Opening a library
 
@@ -605,15 +636,15 @@ background, so an unreachable server does not block opening.
 `LibraryOptions`:
 
 | Option                   | Default                                            | Meaning                                                               |
-| ------------------------ | --------------------------- | --------------------------------------------------------------------- |
+| ------------------------ | -------------------------------------------------- | --------------------------------------------------------------------- |
 | `client`                 | required                                           | the account client (a `Client`, or any `LibraryClient`)               |
-| `cacheDirectory`         | `<XDG cache>/quak/<userID>` | where `metadata.json` and the content cache live                      |
+| `cacheDirectory`         | `quak/<userID>` under the per-user cache directory | where `metadata.json` and the content cache live                      |
 | `downloadDirectory`      | none                                               | backup destination; an original already stored there counts as cached |
 | `refreshIntervalSeconds` | `3`                                                | background refresh cadence                                            |
 | `precacheThumbnails`     | `true`                                             | prefetch every thumbnail, newest first                                |
 | `precacheOriginals`      | `true`                                             | prefetch the favorites album and the latest-window originals          |
 | `precacheOriginalsDays`  | `7`                                                | length in days of that latest window                                  |
-| `cacheOriginalsMaxBytes` | 100 GiB                     | hard ceiling on the originals cache                                   |
+| `cacheOriginalsMaxBytes` | 100 GiB                                            | size limit on the originals cache; pinned originals can exceed it     |
 | `freeBelowBytes`         | 50 GiB                                             | free space to protect on the volume; the effective limit adapts down  |
 | `isOriginalPinned`       | none                                               | extra predicate for originals that must never be evicted              |
 | `pools`                  | fresh `RequestPools`                               | the bounded request pools (sets concurrency)                          |
@@ -635,17 +666,21 @@ can then be removed.
 ### Default reads vs. fresh reads
 
 Default reads — `lib.albums`, `lib.photos`, `lib.timeline` — answer
-synchronously from the last refreshed copy held in RAM and never touch the
+synchronously from the copy held in RAM and never touch the network. A refresh
-network. The background timer refreshes that copy every
+changes that copy only once all its server requests have succeeded, and the
-`refreshIntervalSeconds`, so a default read is immediate but may be up to one
+background timer starts the next refresh `refreshIntervalSeconds` after the
-interval stale.
+previous one ends. So a default read is immediate, but only as current as the
+last refresh whose requests all succeeded; right after opening an existing
+cache, it is the copy on disk.
 
-`await lib.fresh()` forces a refresh, waits for it to complete and persist, and
+`await lib.fresh()` waits for a refresh to complete and persist, and returns the
-returns the same `{ albums, photos, timeline }` namespaces — now guaranteed to
+same `{ albums, photos, timeline }` namespaces, which then reflect a completed
-reflect a completed server round-trip. Concurrent `fresh()` calls coalesce onto
+server round-trip. When a refresh is already running, background or not,
-one refresh, and a refresh that fails rejects the caller (default reads stay
+`fresh()` waits for that one, so its answer can come from requests made before
-silent and keep serving the last good copy). The CLI's read commands use fresh
+the call; only when none is running does it start one. A refresh that fails
-reads (issue https://git.eeqj.de/sneak/quak/issues/75).
+rejects the caller (default reads stay silent and keep serving the last good
+copy). The CLI's read commands use fresh reads (issue
+https://git.eeqj.de/sneak/quak/issues/75).
 
 ### Read surface
 
@@ -662,17 +697,50 @@ reads (issue https://git.eeqj.de/sneak/quak/issues/75).
   `includeArchived`; hidden photos are always excluded.
 
 An `Album` exposes its record fields and `album.photos.list()` → `Photo[]`
-(newest first). A `Photo` exposes its record fields, `photo.record()` →
+(newest first). A `Photo` exposes its record fields other than `thumbnailPath`
-`PhotoRecord`, and two content methods:
+and `originalPath`, and `photo.year`, the local-time year of `takenAt`, all as
+synchronous getters read from RAM; `photo.record()` → `PhotoRecord`. Two more
+synchronous getters look at the disk and never touch the network:
+
+- `photo.savePath` → `string | undefined` — where `lib.backup()` writes the
+  original, `originals/<fileID>.<ext>` under the `downloadDirectory` the library
+  was opened with, whether or not it is there yet: for a live photo already
+  stored, its image. For a live photo not yet stored, it carries the title's
+  extension, and the backup may store the image under a different one, found
+  inside the live photo. `undefined` when the library has no `downloadDirectory`
+  or no content source.
+- `photo.isLocal` → `boolean` — whether the whole original is at `savePath`.
+
+These async methods may download:
 
 - `await photo.original(opts?)` → `{ path, bytes, videoPath? }` — the
   full-resolution file. For a live photo, `path` and `bytes` are its image's and
   `videoPath` is its video.
 - `await photo.thumbnail(opts?)` → `{ path, bytes }`.
+- `await photo.content(opts?)` → `Uint8Array` — the original's bytes, read
+  through `original()`; for a live photo, its image's.
+- `await photo.exif(opts?)` → `PhotoExif` — `make`, `model`, `lensModel`,
+  `dateTimeOriginal`, `offsetTimeOriginal`, `exposureTime`, `fNumber`, `iso`,
+  `focalLength`, `orientation`, `gpsLatitude`, `gpsLongitude` and `gpsAltitude`,
+  each absent when the file lacks it. GPS values are signed decimal degrees and
+  metres. `dateTimeOriginal` is the camera's clock reading held in the `Date`'s
+  UTC fields; `offsetTimeOriginal`, when present, is that clock's offset from
+  UTC. EXIF is read from any image format exifreader reads (such as JPEG,
+  HEIC/HEIF, AVIF, PNG, WebP and TIFF), a live photo's image included. Any other
+  original gives `{}`, and a video gives `{}` without being downloaded.
+- `await photo.make(opts?)`, and likewise `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` → one field of `exif()` each, typed as in `PhotoExif`, or
+  `undefined` when the file lacks it. Each calls `exif()` with its `opts`, so
+  each call reads the original again.
 
-Both serve from the on-disk content cache when the bytes are present and
+They serve from the on-disk content cache when the bytes are present and
-otherwise fetch through the pools; `opts.onProgress` reports per-file progress.
+otherwise fetch through the pools; `original()`, `content()` and `exif()` also
-They throw when the library was opened without a content source.
+serve an original the backup has already stored. `opts.onProgress` reports
+per-file progress. They throw when the library was opened without a content
+source. An original that `content()` or `exif()` downloads lands in the cache,
+which does not make `isLocal` true; only `lib.backup()` does.
 
 Lower-level accessors that return decrypted model objects (which hold key
 material) are also available: `listCollections()`, `getCollection(id)`,
@@ -684,10 +752,12 @@ material) are also available: `listCollections()`, `getCollection(id)`,
 The GUI-facing records hold no key material and no binary, so they survive
 `structuredClone`/JSON across the Electron IPC boundary:
 
-- `PhotoRecord`: `fileID`, `albumIDs`, `title`, `takenAt` (milliseconds),
+- `PhotoRecord`: `fileID`, `albumIDs`, `title`, `takenAt` and `modifiedAt`
-  `fileType`, optional `caption` / `width` / `height` / `latitude` /
+  (milliseconds), `fileType`, optional `caption` / `width` / `height` /
-  `longitude`, `isArchived`, `isHidden`, and `thumbnailPath` / `originalPath`
+  `latitude` / `longitude`, optional `hash` (the content hash recorded at
-  once the bytes are cached (for a live photo, `originalPath` is its image).
+  upload; very old files have none), `isArchived`, `isHidden`, and
+  `thumbnailPath` / `originalPath` once the bytes are cached (for a live photo,
+  `originalPath` is its image).
 - `AlbumRecord`: `collectionID`, `name`, `type`, `isShared`, `updationTime`, and
   `fileIDs` (newest first).
 - `LibrarySnapshot`: `{ albums, photos, takenAt }`.
@@ -712,16 +782,16 @@ photos newest first). `lib.subscribe({ onChange })` delivers a `LibraryChange`
   `SimilarResult[]` (`{ fileID, score }`, cosine similarity, most similar first,
   default limit 20). quak bundles no text encoder, so `searchByEmbedding` takes
   a query vector the caller produced elsewhere.
-- `await lib.backup(opts?)` → `BackupResult`. It refreshes, fetches every
+- `await lib.backup(opts?)` → `BackupResult`. It waits for a refresh as
-  in-scope original not already in the backup (and, with `includeThumbnails`,
+  `fresh()` does, fetches every in-scope original not already in the backup
-  thumbnails) through the content cache, and rebuilds the on-disk backup tree
+  (and, with `includeThumbnails`, thumbnails) through the content cache, and
-  with a durable failure ledger. A fetched original is written straight into the
+  rebuilds the on-disk backup tree with a durable failure ledger. A fetched
-  backup's `originals/` and not into the cache, which then counts it as present;
+  original is written straight into the backup's `originals/` and not into the
-  one the cache already held is copied from there. `BackupOptions`:
+  cache, which then counts it as present; one the cache already held is copied
-  `downloadDirectory` (falls back to the one `open()` was given),
+  from there. `BackupOptions`: `downloadDirectory` (falls back to the one
-  `includeOriginals` (default `true`), `includeThumbnails` (default `false`),
+  `open()` was given), `includeOriginals` (default `true`), `includeThumbnails`
-  `onlyAlbumNames`, and `onProgress`. See Backup layout above for the tree it
+  (default `false`), `onlyAlbumNames`, and `onProgress`. See Backup layout above
-  writes.
+  for the tree it writes.
 
 ### Request pools
 
@@ -782,6 +852,7 @@ from a very old client, is stored unchecked.
 - `src/library/records.ts`: `PhotoRecord`, `AlbumRecord`, `LibrarySnapshot`,
   `LibraryChange`
 - `src/library/mlsearch.ts`: `MLDataAPI`, `SimilarResult`
+- `src/exif.ts`: `PhotoExif`
 - `src/library/pools.ts`: `RequestPools`, `RequestPoolsOptions`, `BoundedPool`
 - `src/backup.ts`: `BackupOptions`, `BackupResult`, `BackupError`
 - `src/client.ts`: `Client`, `LoginOptions`, `ClientSnapshot`
@@ -813,14 +884,15 @@ documents:
   `yarn.lock`. Never `git add -A`. Never force-push to main.
 
 - **The "Development workflow" section above.** All changes go on feature
-  branches. Tests are written first and committed in a failing state before the
+  branches off `next`, and every pull request targets `next`; only sneak merges
-  implementation. Tests are the canonical API documentation and must be
+  `next` into `main`. Tests are written first and committed in a failing state
-  commented thoroughly. `main` is always green.
+  before the implementation. Tests are the canonical API documentation and must
+  be commented thoroughly. `main` and `next` are always green.
 
 - **Required checks before every commit:** `make lint` must pass — that is
   eslint plus the prettier check, and it builds the `lint` phase of the
   `Dockerfile`, so it needs docker. The pre-commit hook enforces exactly that.
-  `make check` (which also runs the tests) must pass before merging to `main`.
+  `make check` (which also runs the tests) must pass before merging into `next`.
   `make fmt-check` is available for a host-side formatting check on its own, but
   it is not a separate requirement: `make lint` already covers it, and running
   both would check formatting twice. Never invoke eslint or prettier directly;

TODO.md

@@ -1,12 +1,15 @@
 # Workflow
 
-- branch (from `main`)
+- branch from `next`
 - do the work in Next Step
 - move Next Step to the top of Completed Steps
 - move the top item of Future Steps into Next Step
 - commit (`TODO.md` changes in the same commit as the work)
-- merge to `main` if the branch is not protected, otherwise open a PR
 - push
+- open a pull request that targets `next`
+- once the pull request has passed review, the repository manager squash-merges
+  it into `next`
+- only sneak merges `next` into `main`
 
 # Status
 
@@ -14,13 +17,81 @@ pre-1.0
 
 # Next Step
 
-None: every issue still open is done on `next` and waits for it to reach `main`.
+None: no implementation work is open. The cache design,
+https://git.eeqj.de/sneak/quak/issues/36, waits on sneak's review.
 
 Tagging and releases are decided by sneak alone, and happen only when he
 declares one.
 
 # Completed Steps
 
+- 2026-10-01: A `Photo` has one async method for each field of `exif()`, named
+  and typed as in `PhotoExif`: `make()`, `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` (issue 148). Each calls `exif()` and returns its one
+  field, or undefined when the file lacks it. `Photo` implements a type with one
+  method per `PhotoExif` field, so the build's type check fails when a field has
+  no method. A test checks, on the JPEG and the HEIC, that each method gives the
+  same value as `exif()`.
+
+- 2026-10-01: `photo.exif()` and `backup-metadata --exif` read EXIF from
+  HEIC/HEIF originals, a live photo's HEIC image included, as well as JPEG and
+  the other image formats `exifreader` reads (issue 145). `exifreader` replaces
+  `exif-reader` and the JPEG segment scan; `PhotoExif` is unchanged. The `exif`
+  field of `backup-metadata --exif` is now exifreader's tag output, and
+  `exifRaw` holds the whole EXIF block it could not read. The tests use a real
+  HEIC, `test/exif.heic`.
+
+- 2026-10-01: A `Photo` has `savePath`, `isLocal`, `content()`, `exif()`,
+  `modifiedAt`, `hash` and `year` (issue 141). `savePath` is where
+  `lib.backup()` writes the original under the library's download directory; for
+  a live photo not yet stored, it carries the title's extension, and the backup
+  may store the image under a different one. `isLocal` says whether the whole
+  original is there. Both look only at the disk. `content()` returns the
+  original's bytes and `exif()` the common EXIF fields of a JPEG; both may
+  download the original, and `exif()` downloads no video. `PhotoRecord` gains
+  `modifiedAt` and `hash`, and the JPEG EXIF scan moved to `src/exif.ts`.
+
+- 2026-09-29: The "Workflow" list at the top of this file now says to branch
+  from `next` and open a pull request that targets `next`, that the repository
+  manager squash-merges a reviewed pull request into `next`, and that only sneak
+  merges `next` into `main`, as the README does (issue 137).
+
+- 2026-09-29: The README's "Development workflow" and "For LLMs" sections now
+  say work branches from `next`, every pull request targets `next`, the
+  repository manager squash-merges reviewed pull requests into `next`, and only
+  sneak merges `next` into `main` (issue 135).
+
+- 2026-09-29: Brought the README and this file in line with `next` after the
+  milestone merge (issue 132). The Next Step says no implementation work is open
+  and the cache design (issue 36) waits on sneak's review. README corrections:
+  the Getting Started comments say when the library refreshes; most, not all,
+  Makefile targets call a script; `script/lint` and `script/test` have no host
+  path, though `yarn test` does; the SRP handshake uses `fast-srp-hap`, outside
+  `crypto/`, and a thumbnail upload's MD5 uses `node:crypto`; the SRP password
+  is the first 16 bytes of a 32-byte subkey; the key attributes and token come
+  after SRP, after the TOTP code SRP may ask for, or after the email OTP that
+  replaces SRP when the account has email MFA on, and quak cannot answer a
+  passkey; the auth token is sent as URL-safe base64 with padding; every
+  `TypeError` is retried; each download attempt writes its own temporary files,
+  two for a live photo, and only the attempt that completes renames them into
+  place; `runMetadataBackup` records a failed download in the file's JSON; a
+  second `client.logout()` does not throw; `quak logout` with no session exits
+  0, and names the cache directory only when it knows it; `login`, `whoami` and
+  `logout` open no library; `--exif` records XMP and, for a JPEG, EXIF, and no
+  IPTC; which commands take `--json`; a failed ML data request may not have been
+  retried; the thumbnail fixer is not limited to baseline JPEG; `quak backup`
+  still fetches ML data; a backup's JSON holds the basic metadata fields quak
+  keeps and the private and public magic metadata, not every decrypted field,
+  and the README no longer lists what the magic metadata holds; the default
+  cache directory is the per-user one, not an XDG path on macOS; pinned
+  originals can exceed `cacheOriginalsMaxBytes`; which tests cover which
+  operations; a default read is only as current as the last refresh whose
+  requests all succeeded; `fresh()` and `lib.backup()` join a refresh already
+  running; a `Photo` has no `thumbnailPath` or `originalPath`; and `408` and
+  `429` are retried.
+
 - 2026-09-28: Tested the live-photo writer's fsyncs (issue 130). A test checks
   that the image's and the video's temp files are fsynced before either is
   renamed into place, and the directory after both renames, as the `writeAtomic`

package.json

@@ -46,7 +46,7 @@
         "@inquirer/prompts": "8.5.2",
         "commander": "14.0.3",
         "env-paths": "4.0.0",
-        "exif-reader": "2.0.3",
+        "exifreader": "4.46.0",
         "fast-srp-hap": "2.0.4",
         "fflate": "0.8.3",
         "jpeg-js": "0.4.4",

src/exif.ts

@@ -0,0 +1,115 @@
+// EXIF in an original's bytes, read with exifreader, which reads it from JPEG,
+// HEIC/HEIF, AVIF, PNG, WebP and the other image formats it supports.
+// `backup-metadata --exif` records every EXIF tag it finds except the
+// thumbnail's; `Photo.exif()` returns the common fields picked from them here.
+
+import ExifReader, { type ExpandedTags } from "exifreader";
+
+// The EXIF tags in `bytes` (`exif`), the GPS position exifreader computes from
+// them (`gps`), and where the EXIF block lies in `bytes` (`metadataRange`).
+// Undefined when exifreader cannot read the file at all, such as a video. An
+// EXIF block it finds but reads no tag from comes back as an empty `exif`.
+// `exif` holds every tag except the thumbnail's; a tag exifreader has no name
+// for is keyed `undefined-<tag number>`. Each tag's `computed` holds its value
+// as a string or number, or as an array of them for a tag with several values,
+// such as `GPSLatitude`'s `[40, 26, 46]`. A fraction with a zero denominator
+// computes to null.
+export const readExifTags = (bytes: Uint8Array): ExpandedTags | undefined => {
+    try {
+        return ExifReader.loadView(
+            new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength),
+            {
+                expanded: true,
+                computed: true,
+                includeOffsets: true,
+                includeUnknown: true,
+                includeTags: { exif: true, gps: true },
+            },
+        );
+    } catch {
+        return undefined;
+    }
+};
+
+// The common EXIF fields of an original. Each is absent when the file lacks it.
+export interface PhotoExif {
+    make?: string;
+    model?: string;
+    lensModel?: string;
+    // When the photo was taken, by the camera's clock. EXIF writes this as text
+    // with no time zone, and it is read as if it were UTC: the Date's UTC
+    // fields are the clock reading, which is the moment it was taken only when
+    // the clock was set to UTC.
+    dateTimeOriginal?: Date;
+    // The camera clock's offset from UTC, such as "+02:00".
+    offsetTimeOriginal?: string;
+    // Seconds.
+    exposureTime?: number;
+    fNumber?: number;
+    iso?: number;
+    // Millimetres.
+    focalLength?: number;
+    // The EXIF orientation code, 1 to 8.
+    orientation?: number;
+    // Decimal degrees, negative south of the equator and west of Greenwich.
+    gpsLatitude?: number;
+    gpsLongitude?: number;
+    // Metres, negative below sea level.
+    gpsAltitude?: number;
+}
+
+// exifreader gives "<faulty value>" for a tag whose value lies outside the
+// file; that tag is left out like one the file lacks.
+const asString = (v: unknown): string | undefined =>
+    typeof v === "string" && v.length > 0 && v !== "<faulty value>"
+        ? v
+        : undefined;
+
+const asNumber = (v: unknown): number | undefined =>
+    typeof v === "number" && Number.isFinite(v) ? v : undefined;
+
+// EXIF writes a date and time as "2021:07:15 14:30:00". This is that reading
+// in a Date's UTC fields.
+const asDate = (v: unknown): Date | undefined => {
+    const m =
+        typeof v === "string"
+            ? /^(\d{4}):(\d{2}):(\d{2}) (\d{2}:\d{2}:\d{2})$/.exec(v)
+            : null;
+    if (!m) return undefined;
+    const date = new Date(`${m[1]}-${m[2]}-${m[3]}T${m[4]}Z`);
+    return Number.isNaN(date.getTime()) ? undefined : date;
+};
+
+// The common fields of an original's EXIF: `{}` when the file has no EXIF,
+// exifreader cannot read its EXIF, or it is not an image exifreader reads.
+export const readPhotoExif = (bytes: Uint8Array): PhotoExif => {
+    const tags = readExifTags(bytes);
+    const exif = tags?.exif;
+    const gps = tags?.gps;
+    const altitude = asNumber(exif?.GPSAltitude?.computed);
+    const fields: PhotoExif = {
+        make: asString(exif?.Make?.computed),
+        model: asString(exif?.Model?.computed),
+        lensModel: asString(exif?.LensModel?.computed),
+        dateTimeOriginal: asDate(exif?.DateTimeOriginal?.computed),
+        offsetTimeOriginal: asString(exif?.OffsetTimeOriginal?.computed),
+        exposureTime: asNumber(exif?.ExposureTime?.computed),
+        fNumber: asNumber(exif?.FNumber?.computed),
+        // Only when the tag holds a single number, as most cameras write it.
+        iso: asNumber(exif?.ISOSpeedRatings?.computed),
+        focalLength: asNumber(exif?.FocalLength?.computed),
+        orientation: asNumber(exif?.Orientation?.computed),
+        gpsLatitude: asNumber(gps?.Latitude),
+        gpsLongitude: asNumber(gps?.Longitude),
+        // A GPSAltitudeRef of 1 means the altitude is below sea level.
+        gpsAltitude:
+            altitude !== undefined && exif?.GPSAltitudeRef?.value === 1
+                ? -altitude
+                : altitude,
+    };
+    // Leave out what the file lacks, so a missing field is absent rather than
+    // present and undefined.
+    return Object.fromEntries(
+        Object.entries(fields).filter(([, v]) => v !== undefined),
+    ) as PhotoExif;
+};

src/index.ts

@@ -84,6 +84,7 @@ export type {
     LibrarySnapshot,
     LibraryChange,
 } from "./library/records.js";
+export type { PhotoExif } from "./exif.js";
 export { decryptCollection, decryptFile } from "./model/index.js";
 export { downloadFile, downloadThumbnail } from "./download/index.js";
 export type {

src/library/content.ts

@@ -108,6 +108,11 @@ export interface ContentOptions {
 export interface PhotoContent {
     original(fileID: number, opts?: ContentOptions): Promise<ContentResult>;
     thumbnail(fileID: number, opts?: ContentOptions): Promise<ContentResult>;
+    // Where a backup stores the original, whether or not it is there yet. For
+    // a live photo not yet stored, it carries the title's extension, and the
+    // backup may store the image under a different one.
+    savePath(fileID: number): string | undefined;
+    isLocal(fileID: number): boolean;
 }
 
 export interface EnsureResult {
@@ -435,6 +440,31 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
         return this.get(fileID, "thumbnail", "on-demand", opts?.onProgress);
     }
 
+    // Where a backup to the download directory stores the file's original,
+    // whether or not it is there yet: for a live photo already stored, its
+    // image. For a live photo not yet stored, it carries the title's
+    // extension, and the backup may store the image under a different one.
+    // Undefined with no download directory.
+    savePath(fileID: number): string | undefined {
+        const file = this.getFile(fileID);
+        if (this.downloadDirectory === undefined || file === undefined)
+            return undefined;
+        const dir = join(this.downloadDirectory, "originals");
+        return (
+            storedOriginal(dir, file)?.path ?? join(dir, nameInOriginals(file))
+        );
+    }
+
+    // Whether the whole original is in the download directory, as a backup
+    // stores it. A copy only in the cache does not count.
+    isLocal(fileID: number): boolean {
+        const file = this.getFile(fileID);
+        if (this.downloadDirectory === undefined || file === undefined)
+            return false;
+        const dir = join(this.downloadDirectory, "originals");
+        return storedOriginal(dir, file) !== undefined;
+    }
+
     // Get an original for a backup. One not present anywhere is written
     // straight to `destination` and recorded there, so no second copy lands
     // in the cache; one already present is returned where it is.

src/library/read.ts

@@ -11,11 +11,16 @@
 // access and, for an album, its photos. They are not sent across IPC — the
 // plain records are the serializable surface, and `record()` returns one.
 //
-// A `Photo` also fetches its own bytes: `original()` and `thumbnail()` go
+// A `Photo` also fetches its own bytes: `original()`, `thumbnail()`,
-// through the on-disk content cache (issue #46), the one place in this module
+// `content()`, `exif()` and the methods that each return one field of `exif()`
-// that is not synchronous and RAM-only. A library opened without a content
+// go through the on-disk content cache (issue #46), and are the one place in
-// source leaves that cache absent, and those two methods then throw.
+// this module that may touch the network. A library opened without a content
+// source leaves that cache absent, and those methods then throw. `savePath` and
+// `isLocal` look only at the disk.
 
+import { readFile } from "node:fs/promises";
+
+import { readPhotoExif, type PhotoExif } from "../exif.js";
 import type { CollectionType, FileType } from "../model/types.js";
 import type { ContentOptions, ContentResult, PhotoContent } from "./content.js";
 import type { AlbumRecord, PhotoRecord, DerivedRecords } from "./records.js";
@@ -30,12 +35,19 @@ const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
 const byNewestAlbum = (a: AlbumRecord, b: AlbumRecord): number =>
     b.updationTime - a.updationTime || b.collectionID - a.collectionID;
 
+// A method for each `PhotoExif` field, named after it, taking the options
+// `exif()` takes and giving that field. `Photo` implements it, so the build's
+// type check fails when `PhotoExif` has a field `Photo` has no method for.
+type PhotoExifMethods = {
+    [K in keyof PhotoExif]-?: (opts?: ContentOptions) => Promise<PhotoExif[K]>;
+};
+
 // A single photo. Field access mirrors `PhotoRecord`; `record()` returns the
 // underlying plain record for callers that need the IPC-safe value.
-export class Photo {
+export class Photo implements PhotoExifMethods {
     constructor(
         private readonly rec: PhotoRecord,
-        private readonly content?: PhotoContent,
+        private readonly cache?: PhotoContent,
     ) {}
 
     get fileID(): number {
@@ -50,6 +62,13 @@ export class Photo {
     get takenAt(): number {
         return this.rec.takenAt;
     }
+    get modifiedAt(): number {
+        return this.rec.modifiedAt;
+    }
+    // The local-time year of `takenAt`.
+    get year(): number {
+        return new Date(this.rec.takenAt).getFullYear();
+    }
     get fileType(): FileType {
         return this.rec.fileType;
     }
@@ -68,6 +87,9 @@ export class Photo {
     get longitude(): number | undefined {
         return this.rec.longitude;
     }
+    get hash(): string | undefined {
+        return this.rec.hash;
+    }
     get isArchived(): boolean {
         return this.rec.isArchived;
     }
@@ -75,6 +97,22 @@ export class Photo {
         return this.rec.isHidden;
     }
 
+    // Where `lib.backup()` stores the original in the library's download
+    // directory, whether or not it is there yet: for a live photo already
+    // stored, its image. For a live photo not yet stored, it carries the
+    // title's extension, and the backup may store the image under a different
+    // one. Undefined when the library has no download directory or no content
+    // cache.
+    get savePath(): string | undefined {
+        return this.cache?.savePath(this.rec.fileID);
+    }
+
+    // Whether the whole original is at `savePath`. A copy only in the cache
+    // does not count.
+    get isLocal(): boolean {
+        return this.cache?.isLocal(this.rec.fileID) ?? false;
+    }
+
     record(): PhotoRecord {
         return this.rec;
     }
@@ -84,21 +122,98 @@ export class Photo {
     // `videoPath`. Served from the cache (or the backup download directory)
     // when already present, otherwise fetched through the content pool.
     async original(opts?: ContentOptions): Promise<ContentResult> {
-        return this.contentOrThrow().original(this.rec.fileID, opts);
+        return this.cacheOrThrow().original(this.rec.fileID, opts);
     }
 
     // As `original`, for the thumbnail, through the thumbnail pool.
     async thumbnail(opts?: ContentOptions): Promise<ContentResult> {
-        return this.contentOrThrow().thumbnail(this.rec.fileID, opts);
+        return this.cacheOrThrow().thumbnail(this.rec.fileID, opts);
     }
 
-    private contentOrThrow(): PhotoContent {
+    // The original's bytes, read from where `original()` puts it. For a live
-        if (!this.content) {
+    // photo, its image's.
+    async content(opts?: ContentOptions): Promise<Uint8Array> {
+        const { path } = await this.original(opts);
+        return readFile(path);
+    }
+
+    // The common EXIF fields of the original, read from `content()`, so this
+    // may download it. EXIF is read from any image format exifreader reads,
+    // JPEG and HEIC/HEIF among them; any other file gives `{}`, and a video
+    // gives it without fetching anything. Like the other content methods, it
+    // throws when there is no content cache, video or not.
+    async exif(opts?: ContentOptions): Promise<PhotoExif> {
+        this.cacheOrThrow();
+        if (this.rec.fileType === "video") return {};
+        return readPhotoExif(await this.content(opts));
+    }
+
+    // One field of `exif()` each, named and typed as in `PhotoExif`, and
+    // undefined when the file lacks it. Each call runs `exif()`, which reads
+    // the original again.
+    async make(opts?: ContentOptions): Promise<PhotoExif["make"]> {
+        return (await this.exif(opts)).make;
+    }
+    async model(opts?: ContentOptions): Promise<PhotoExif["model"]> {
+        return (await this.exif(opts)).model;
+    }
+    async lensModel(opts?: ContentOptions): Promise<PhotoExif["lensModel"]> {
+        return (await this.exif(opts)).lensModel;
+    }
+    async dateTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["dateTimeOriginal"]> {
+        return (await this.exif(opts)).dateTimeOriginal;
+    }
+    async offsetTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["offsetTimeOriginal"]> {
+        return (await this.exif(opts)).offsetTimeOriginal;
+    }
+    async exposureTime(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["exposureTime"]> {
+        return (await this.exif(opts)).exposureTime;
+    }
+    async fNumber(opts?: ContentOptions): Promise<PhotoExif["fNumber"]> {
+        return (await this.exif(opts)).fNumber;
+    }
+    async iso(opts?: ContentOptions): Promise<PhotoExif["iso"]> {
+        return (await this.exif(opts)).iso;
+    }
+    async focalLength(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["focalLength"]> {
+        return (await this.exif(opts)).focalLength;
+    }
+    async orientation(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["orientation"]> {
+        return (await this.exif(opts)).orientation;
+    }
+    async gpsLatitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLatitude"]> {
+        return (await this.exif(opts)).gpsLatitude;
+    }
+    async gpsLongitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLongitude"]> {
+        return (await this.exif(opts)).gpsLongitude;
+    }
+    async gpsAltitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsAltitude"]> {
+        return (await this.exif(opts)).gpsAltitude;
+    }
+
+    private cacheOrThrow(): PhotoContent {
+        if (!this.cache) {
             throw new Error(
                 "Photo content requires a library opened with a content cache",
             );
         }
-        return this.content;
+        return this.cache;
     }
 }
 

src/library/records.ts

@@ -5,10 +5,11 @@
 // 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
+// Ente holds edited/basic times in microseconds; records expose `takenAt` and
-// milliseconds. The magic-metadata field names below are the ones the Ente
+// `modifiedAt` in milliseconds. The magic-metadata field names below are the
-// clients write, confirmed against the repo's own fixtures: `w`/`h` in
+// ones the Ente clients write, confirmed against the repo's own fixtures:
-// test/cli/metadata-backup.test.ts, `visibility` in test/library/store.test.ts.
+// `w`/`h` in test/cli/metadata-backup.test.ts, `visibility` in
+// test/library/store.test.ts.
 
 import type {
     Collection,
@@ -33,12 +34,17 @@ export interface PhotoRecord {
     // Milliseconds. `pubMagicMetadata.editedTime` when the user edited the
     // date, else basic-metadata `creationTime`.
     takenAt: number;
+    // Milliseconds. Basic-metadata `modificationTime`.
+    modifiedAt: number;
     fileType: FileType;
     caption?: string;
     width?: number;
     height?: number;
     latitude?: number;
     longitude?: number;
+    // The content hash the uploader recorded (`FileMetadata.hash`); files from
+    // very old clients have none.
+    hash?: string;
     isArchived: boolean;
     isHidden: boolean;
     // Local cache paths, set once a later phase caches the bytes; unset here.
@@ -125,6 +131,7 @@ const toPhotoRecord = (
         albumIDs,
         title: asString(pub.editedName) ?? rep.metadata.title,
         takenAt: microsToMillis(takenAtMicros),
+        modifiedAt: microsToMillis(rep.metadata.modificationTime),
         fileType: rep.metadata.fileType,
         isArchived: visibility === VISIBILITY_ARCHIVED,
         isHidden: visibility === VISIBILITY_HIDDEN,
@@ -140,6 +147,7 @@ const toPhotoRecord = (
         record.latitude = rep.metadata.latitude;
     if (rep.metadata.longitude !== undefined)
         record.longitude = rep.metadata.longitude;
+    if (rep.metadata.hash !== undefined) record.hash = rep.metadata.hash;
 
     return record;
 };

src/metadata-backup.ts

@@ -1,8 +1,8 @@
 import { mkdirSync, readFileSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import * as jpeg from "jpeg-js";
-import exifReader from "exif-reader";
 import type { Client } from "./client.js";
+import { readExifTags } from "./exif.js";
 import type { Library, Photo } from "./library/index.js";
 import { sanitizeFileName } from "./filename.js";
 import {
@@ -19,63 +19,10 @@ export interface MetadataBackupOptions {
     onProgress?: ProgressCallback;
 }
 
-// Find the raw EXIF APP1 segment in JPEG bytes. Returns `exif` (the segment
+// Extract dimensions, EXIF and XMP from a file's bytes. `exif` is the EXIF tags
-// data, starting at the "Exif\0\0" header) when there is one, nothing when the
+// exifreader returns, from any image format it reads. When it finds an EXIF
-// bytes are not a JPEG or carry no EXIF, and `error` when the segment layout is
+// block but reads no tag from it, the record keeps the block's bytes, base64,
-// malformed. Each segment length is checked against the bytes that remain and
+// in `exifRaw`, with the reason in `exifError`.
-// each step moves forward by at least 4 bytes, so the scan ends on any input.
-export const extractExifFromJpeg = (
-    buf: Uint8Array,
-): { exif?: Buffer; error?: string } => {
-    if (buf[0] !== 0xff || buf[1] !== 0xd8) return {};
-    let offset = 2;
-    while (offset < buf.length) {
-        if (offset + 2 > buf.length)
-            return { error: `truncated segment marker at byte ${offset}` };
-        if (buf[offset] !== 0xff)
-            return { error: `no segment marker at byte ${offset}` };
-        const marker = buf[offset + 1]!;
-        if (marker === 0xda) return {}; // start of scan, no more markers
-        if (offset + 4 > buf.length)
-            return { error: `truncated segment length at byte ${offset}` };
-        const len = (buf[offset + 2]! << 8) | buf[offset + 3]!;
-        // The length counts its own two bytes, so anything under 2 is invalid.
-        if (len < 2)
-            return {
-                error: `segment length ${len} at byte ${offset} is too small`,
-            };
-        if (offset + 2 + len > buf.length)
-            return {
-                error: `segment length ${len} at byte ${offset} runs past the end of the file`,
-            };
-        if (marker === 0xe1) {
-            // APP1 — check for "Exif\0\0" header. A length under 8 cannot hold
-            // the six-byte header, so the segment is not EXIF; below 6 the
-            // bytes compared would also lie past the segment.
-            if (
-                len >= 8 &&
-                buf[offset + 4] === 0x45 &&
-                buf[offset + 5] === 0x78 &&
-                buf[offset + 6] === 0x69 &&
-                buf[offset + 7] === 0x66
-            ) {
-                return {
-                    exif: Buffer.from(
-                        buf.buffer,
-                        buf.byteOffset + offset + 4,
-                        len - 2,
-                    ),
-                };
-            }
-        }
-        offset += 2 + len;
-    }
-    return { error: "file ends before the image data" };
-};
-
-// Extract dimensions, EXIF and XMP from a file's bytes. When the EXIF segment
-// is malformed or cannot be parsed, the record carries the reason in
-// `exifError`.
 export const extractImageMetadata = (
     fileBytes: Uint8Array,
 ): Record<string, unknown> | undefined => {
@@ -92,19 +39,21 @@ export const extractImageMetadata = (
         result.height = decoded.height;
     } catch {
         // Not every original is a JPEG (PNG, HEIC, video), so a failed decode
-        // is expected and only means no dimensions; a malformed JPEG is still
+        // is expected and only means no dimensions; unreadable EXIF is still
         // reported below through `exifError`.
     }
 
-    const { exif, error } = extractExifFromJpeg(fileBytes);
+    const tags = readExifTags(fileBytes);
-    if (error) result.exifError = error;
+    if (tags?.exif && Object.keys(tags.exif).length > 0) {
-    if (exif) {
+        result.exif = tags.exif;
-        try {
+    } else if (tags?.exif) {
-            result.exif = exifReader(exif);
+        const block = tags.metadataRange?.blocks.find((b) => b.type === "exif");
-        } catch (err) {
+        if (block) {
-            result.exifRaw = exif.toString("base64");
+            result.exifRaw = Buffer.from(
-            result.exifError = err instanceof Error ? err.message : String(err);
+                fileBytes.subarray(block.start, block.end),
+            ).toString("base64");
         }
+        result.exifError = "no tag could be read from the EXIF block";
     }
 
     // Extract XMP (look for "http://ns.adobe.com/xap" in the bytes)

test/cli/commands.test.ts

@@ -56,6 +56,7 @@ import type { ContentSource } from "../../src/library/content.js";
 import type { Collection, EnteFile } from "../../src/model/types.js";
 import { init, toBase64 } from "../../src/crypto/index.js";
 import { defaultCacheDirectory } from "../../src/library/index.js";
+import { HEIC_WITH_EXIF } from "../exif-heic.js";
 import {
     asLivePhoto,
     cdnSource,
@@ -653,6 +654,31 @@ describe("a live photo", () => {
             height: 4,
         });
     });
+
+    it("backup-metadata --exif records the EXIF of a HEIC image", async () => {
+        const dir = join(root, "dump");
+
+        expect(
+            await backupMetadataCommand(
+                context(await livePhotoClient(HEIC_WITH_EXIF)),
+                dir,
+                { exif: true },
+            ),
+        ).toBe(0);
+
+        const record = JSON.parse(
+            readFileSync(
+                join(dir, "collections", "1-Vacation", "300.json"),
+                "utf-8",
+            ),
+        );
+        expect(record.imageMetadata.exifError).toBeUndefined();
+        expect(record.imageMetadata.exif).toMatchObject({
+            Make: { value: ["Canon"] },
+            Model: { value: ["EOS R5"] },
+            DateTimeOriginal: { value: ["2021:07:15 14:30:00"] },
+        });
+    });
 });
 
 describe("backup", () => {

test/cli/metadata-exif.test.ts

@@ -1,21 +1,24 @@
 /**
- * Tests for the JPEG EXIF scan behind `quak backup-metadata --exif`.
+ * Tests for reading EXIF (`src/exif.ts`) and the image metadata
+ * `quak backup-metadata --exif` records.
  *
- * The originals come from users' libraries, so a truncated or corrupt JPEG
+ * The originals come from users' libraries, so a truncated or corrupt file
- * must neither hang the scan nor throw out of it, and a malformed file must be
+ * must neither hang the read nor throw out of it: `readPhotoExif` gives `{}`,
- * told apart from one that simply has no EXIF: the record carries the reason in
+ * and `backup-metadata` tells an EXIF block it cannot read apart from a file
- * `exifError`. Each input below is a short hand-built byte array.
+ * that simply has no EXIF, carrying the reason in `exifError`. Each JPEG below
+ * is a short hand-built byte array; the HEIC is a real file.
  */
 
 import { describe, expect, it } from "vitest";
-import {
+import { readPhotoExif } from "../../src/exif.js";
-    extractExifFromJpeg,
+import { extractImageMetadata } from "../../src/metadata-backup.js";
-    extractImageMetadata,
+import { HEIC_WITH_EXIF } from "../exif-heic.js";
-} from "../../src/metadata-backup.js";
 
 const SOI = [0xff, 0xd8]; // start of image
-const SOS = [0xff, 0xda, 0x00, 0x02]; // start of scan, where the scan stops
+const SOS = [0xff, 0xda, 0x00, 0x02]; // start of scan
 const EXIF_HEADER = [0x45, 0x78, 0x69, 0x66, 0x00, 0x00]; // "Exif\0\0"
+const APP0 = [0xff, 0xe0, 0x00, 0x04, 0x00, 0x00];
+const ZERO_LENGTH_APP0 = [0xff, 0xe0, 0x00, 0x00];
 
 // A big-endian TIFF block with one IFD entry: Orientation (0x0112), SHORT, 6.
 const TIFF_ORIENTATION_6 = [
@@ -24,6 +27,66 @@ const TIFF_ORIENTATION_6 = [
     0x00, 0x00,
 ];
 
+// A big-endian TIFF block holding Orientation 6 and DateTimeOriginal
+// "0000:00:00 00:00:00", which a camera with an unset clock writes.
+const TIFF_UNSET_DATE = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: two entries, then no next IFD.
+    ...[0x00, 0x02],
+    // Orientation (0x0112), SHORT, 6.
+    ...[0x01, 0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00],
+    // The Exif IFD's offset (0x8769), LONG, 38.
+    ...[0x87, 0x69, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x26],
+    ...[0x00, 0x00, 0x00, 0x00],
+    // The Exif IFD, at 38: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // DateTimeOriginal (0x9003), 20 ASCII bytes at 56.
+    ...[0x90, 0x03, 0x00, 0x02, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x38],
+    ...[0x00, 0x00, 0x00, 0x00],
+    ...new TextEncoder().encode("0000:00:00 00:00:00\0"), // at 56
+];
+
+// A big-endian TIFF block holding a GPSAltitude of 12.5 m and no
+// GPSAltitudeRef.
+const TIFF_ALTITUDE_WITHOUT_REF = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // The GPS IFD's offset (0x8825), LONG, 26.
+    ...[0x88, 0x25, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x1a],
+    ...[0x00, 0x00, 0x00, 0x00],
+    // The GPS IFD, at 26: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // GPSAltitude (0x0006), one RATIONAL at 44.
+    ...[0x00, 0x06, 0x00, 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x2c],
+    ...[0x00, 0x00, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x19, 0x00, 0x00, 0x00, 0x02], // 25/2, at 44
+];
+
+// A big-endian TIFF block holding Orientation 6 and a Make whose value lies
+// past the end of the file.
+const TIFF_MAKE_PAST_END = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: two entries, then no next IFD.
+    ...[0x00, 0x02],
+    // Make (0x010f), 6 ASCII bytes at 4096.
+    ...[0x01, 0x0f, 0x00, 0x02, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x10, 0x00],
+    // Orientation (0x0112), SHORT, 6.
+    ...[0x01, 0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x00],
+];
+
+// A big-endian TIFF block with one IFD entry that exifreader has no name for:
+// tag 0xc000 (49152), SHORT, 7.
+const TIFF_UNNAMED_TAG = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // Tag 0xc000, SHORT, 7.
+    ...[0xc0, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x07, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x00],
+];
+
 // An APP1 segment whose length field matches its data.
 const app1 = (data: number[]): number[] => {
     const len = data.length + 2;
@@ -33,74 +96,87 @@ const app1 = (data: number[]): number[] => {
 const bytes = (...parts: number[][]): Uint8Array =>
     new Uint8Array(parts.flat());
 
-describe("extractExifFromJpeg", () => {
+describe("readPhotoExif", () => {
-    it("returns the EXIF segment of a valid JPEG", () => {
+    it("reads the common fields of a valid JPEG", () => {
         const data = [...EXIF_HEADER, ...TIFF_ORIENTATION_6];
-        const scan = extractExifFromJpeg(bytes(SOI, app1(data), SOS));
+        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
-        expect(scan.error).toBeUndefined();
+            orientation: 6,
-        expect([...scan.exif!]).toEqual(data);
+        });
     });
 
-    it("returns nothing for a file that is not a JPEG", () => {
+    it("gives no dateTimeOriginal for a DateTimeOriginal of 0000:00:00 00:00:00", () => {
-        const png = bytes([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
+        const data = [...EXIF_HEADER, ...TIFF_UNSET_DATE];
-        expect(extractExifFromJpeg(png)).toEqual({});
+        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+            orientation: 6,
+        });
     });
 
-    it("returns nothing for a JPEG without EXIF", () => {
+    it("reads a GPSAltitude without GPSAltitudeRef as above sea level", () => {
-        const app0 = [0xff, 0xe0, 0x00, 0x04, 0x00, 0x00];
+        const data = [...EXIF_HEADER, ...TIFF_ALTITUDE_WITHOUT_REF];
-        expect(extractExifFromJpeg(bytes(SOI, app0, SOS))).toEqual({});
+        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+            gpsAltitude: 12.5,
+        });
     });
 
-    it("ignores an APP1 segment too short to hold the Exif header", () => {
+    it("gives no make for a Make whose value lies past the end of the file", () => {
-        // A length under 8 cannot hold the six-byte "Exif\0\0" header, so the
+        const data = [...EXIF_HEADER, ...TIFF_MAKE_PAST_END];
-        // segment is not EXIF. This one has length 7 and holds only "Exif\0",
+        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
-        // which the old code, lacking the length check, returned as EXIF.
+            orientation: 6,
-        const short = app1(EXIF_HEADER.slice(0, 5));
+        });
-        expect(extractExifFromJpeg(bytes(SOI, short, SOS))).toEqual({});
     });
 
-    it("accepts an APP1 segment of length 8 holding just the Exif header", () => {
+    it.each([
-        const scan = extractExifFromJpeg(bytes(SOI, app1(EXIF_HEADER), SOS));
+        [
-        expect(scan.error).toBeUndefined();
+            "a file that is not an image",
-        expect([...scan.exif!]).toEqual(EXIF_HEADER);
+            new TextEncoder().encode("just some text, not an image"),
-    });
+        ],
-
+        [
-    it("reports a JPEG truncated inside a segment header", () => {
+            "a PNG without EXIF",
-        const scan = extractExifFromJpeg(bytes(SOI, [0xff, 0xe1, 0x00]));
+            bytes([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
-        expect(scan.exif).toBeUndefined();
+        ],
-        expect(scan.error).toMatch(/truncated segment length/);
+        ["a JPEG without EXIF", bytes(SOI, APP0, SOS)],
-    });
+        // A length under 8 cannot hold the six-byte "Exif\0\0" header. This one
-
+        // has length 7 and holds only "Exif\0", so a read past its end would
-    it("reports a JPEG that ends before the image data", () => {
+        // take the next segment's bytes as EXIF.
-        const app0 = [0xff, 0xe0, 0x00, 0x04, 0x00, 0x00];
+        [
-        const scan = extractExifFromJpeg(bytes(SOI, app0));
+            "an APP1 segment too short to hold the Exif header",
-        expect(scan.error).toMatch(/ends before the image data/);
+            bytes(SOI, app1(EXIF_HEADER.slice(0, 5)), SOS),
-    });
+        ],
-
+        [
-    it("stops on a zero-length segment instead of looping", () => {
+            "an APP1 segment holding just the Exif header",
-        // A length of 0 would otherwise step the scan by 2 bytes at a time
+            bytes(SOI, app1(EXIF_HEADER), SOS),
-        // through the rest of the file, reading garbage as markers.
+        ],
-        const zero = [0xff, 0xe0, 0x00, 0x00];
+        [
-        const scan = extractExifFromJpeg(
+            "a JPEG truncated inside a segment header",
-            bytes(SOI, zero, zero, zero, zero, SOS),
+            bytes(SOI, [0xff, 0xe1, 0x00]),
-        );
+        ],
-        expect(scan.error).toMatch(/segment length 0 at byte 2 is too small/);
+        ["a JPEG that ends before the image data", bytes(SOI, APP0)],
-    });
+        // A length of 0 would step a scan by 2 bytes at a time through the
-
+        // rest of the file, reading garbage as markers.
-    it("stops on a segment length of 1", () => {
+        [
-        const scan = extractExifFromJpeg(
+            "a zero-length segment",
-            bytes(SOI, [0xff, 0xe0, 0x00, 0x01], SOS),
+            bytes(
-        );
+                SOI,
-        expect(scan.error).toMatch(/segment length 1 at byte 2 is too small/);
+                ZERO_LENGTH_APP0,
-    });
+                ZERO_LENGTH_APP0,
-
+                ZERO_LENGTH_APP0,
-    it("reports a segment length that runs past the end of the file", () => {
+                ZERO_LENGTH_APP0,
+                SOS,
+            ),
+        ],
+        ["a segment length of 1", bytes(SOI, [0xff, 0xe0, 0x00, 0x01], SOS)],
         // APP1 claims 0x4000 bytes but only the "Exif\0\0" header follows.
-        const scan = extractExifFromJpeg(
+        [
+            "a segment length that runs past the end of the file",
             bytes(SOI, [0xff, 0xe1, 0x40, 0x00], EXIF_HEADER),
-        );
+        ],
-        expect(scan.exif).toBeUndefined();
+        // "XX" where the TIFF byte order belongs.
-        expect(scan.error).toMatch(/runs past the end of the file/);
+        [
+            "an EXIF block that cannot be parsed",
+            bytes(SOI, app1([...EXIF_HEADER, 0x58, 0x58]), SOS),
+        ],
+    ])("returns no fields for %s", (_, input) => {
+        expect(readPhotoExif(input)).toStrictEqual({});
     });
 });
 
@@ -110,10 +186,30 @@ describe("extractImageMetadata", () => {
             bytes(SOI, app1([...EXIF_HEADER, ...TIFF_ORIENTATION_6]), SOS),
         );
         expect(meta?.exifError).toBeUndefined();
-        expect(meta?.exif).toMatchObject({ Image: { Orientation: 6 } });
+        expect(meta?.exif).toMatchObject({ Orientation: { value: 6 } });
     });
 
-    it("returns nothing for a file that is not a JPEG", () => {
+    it("parses EXIF from a HEIC", () => {
+        const meta = extractImageMetadata(HEIC_WITH_EXIF);
+        expect(meta?.exifError).toBeUndefined();
+        expect(meta?.exif).toMatchObject({
+            Make: { value: ["Canon"] },
+            Model: { value: ["EOS R5"] },
+            DateTimeOriginal: { value: ["2021:07:15 14:30:00"] },
+            Orientation: { value: 6 },
+            GPSLatitudeRef: { value: ["N"] },
+        });
+    });
+
+    it("keys a tag exifreader has no name for by its number", () => {
+        const meta = extractImageMetadata(
+            bytes(SOI, app1([...EXIF_HEADER, ...TIFF_UNNAMED_TAG]), SOS),
+        );
+        expect(meta?.exifError).toBeUndefined();
+        expect(meta?.exif).toMatchObject({ "undefined-49152": { value: 7 } });
+    });
+
+    it("returns nothing for a file that is not an image", () => {
         const text = new TextEncoder().encode("just some text, not an image");
         expect(extractImageMetadata(text)).toBeUndefined();
     });
@@ -123,14 +219,20 @@ describe("extractImageMetadata", () => {
             bytes(SOI, [0xff, 0xe1, 0x40, 0x00], EXIF_HEADER),
         );
         expect(meta?.exif).toBeUndefined();
-        expect(meta?.exifError).toMatch(/runs past the end of the file/);
+        expect(meta?.exifError).toBe(
+            "no tag could be read from the EXIF block",
+        );
     });
 
     it("keeps the raw bytes and the reason when EXIF cannot be parsed", () => {
-        const data = [...EXIF_HEADER, 0x58, 0x58];
+        // The raw bytes are the whole EXIF block as exifreader finds it: for a
-        const meta = extractImageMetadata(bytes(SOI, app1(data), SOS));
+        // JPEG, the APP1 segment, marker and length included.
+        const segment = app1([...EXIF_HEADER, 0x58, 0x58]);
+        const meta = extractImageMetadata(bytes(SOI, segment, SOS));
         expect(meta?.exif).toBeUndefined();
-        expect(meta?.exifRaw).toBe(Buffer.from(data).toString("base64"));
+        expect(meta?.exifRaw).toBe(Buffer.from(segment).toString("base64"));
-        expect(meta?.exifError).toEqual(expect.any(String));
+        expect(meta?.exifError).toBe(
+            "no tag could be read from the EXIF block",
+        );
     });
 });

test/exif-heic.ts

@@ -0,0 +1,27 @@
+/**
+ * `exif.heic`, beside this file: a real 64x64 HEIC whose EXIF holds the same
+ * values as the hand-built JPEG in `library/content-library.test.ts`, for the
+ * tests of `exif()` and `backup-metadata --exif`.
+ *
+ * It was made once, in a throwaway node:22-alpine container (Alpine 3.23.3),
+ * with libheif 1.23.0 and exiftool 13.55:
+ *
+ *     apk add libheif-tools exiftool imagemagick
+ *     magick -size 64x64 gradient:red-blue -depth 8 in.png
+ *     heif-enc -q 30 -o exif.heic in.png
+ *     exiftool -overwrite_original \
+ *         -Make=Canon -Model="EOS R5" -LensModel="RF50mm F1.8 STM" \
+ *         -DateTimeOriginal="2021:07:15 14:30:00" -OffsetTimeOriginal="+02:00" \
+ *         -ExposureTime=1/250 -FNumber=2.8 -ISO=400 -FocalLength=50 \
+ *         -Orientation#=6 \
+ *         -GPSLatitude="40 26 46" -GPSLatitudeRef=N \
+ *         -GPSLongitude="79 58 56" -GPSLongitudeRef=W \
+ *         -GPSAltitude=12.5 -GPSAltitudeRef#=1 \
+ *         exif.heic
+ */
+
+import { readFileSync } from "node:fs";
+
+export const HEIC_WITH_EXIF = new Uint8Array(
+    readFileSync(new URL("exif.heic", import.meta.url)),
+);

test/library/content-library.test.ts

@@ -6,7 +6,8 @@
  * `Photo` objects that fetch through it, `lib.thumbnails.ensure` drives it, and
  * a cached path shows up on the projected record. A library opened without a
  * content source leaves those methods throwing rather than silently doing
- * nothing.
+ * nothing. It also covers a `Photo`'s `savePath`, `isLocal`, `content()`,
+ * `exif()` and the methods that each return one field of `exif()`.
  */
 
 import { describe, it, expect, beforeEach, afterEach } from "vitest";
@@ -24,7 +25,16 @@ import { Library, type LibraryOptions } from "../../src/library/index.js";
 import type { ContentSource } from "../../src/library/content.js";
 import type { CollectionsPage, FilesPage } from "../../src/client.js";
 import type { Collection, EnteFile } from "../../src/model/types.js";
-import { asLivePhoto, cdnSource, livePhotoZip } from "../live-photo.js";
+import type { PhotoExif } from "../../src/exif.js";
+import { HEIC_WITH_EXIF } from "../exif-heic.js";
+import {
+    asLivePhoto,
+    cdnSource,
+    IMAGE,
+    livePhotoHash,
+    livePhotoZip,
+    VIDEO,
+} from "../live-photo.js";
 
 const USER_ID = 7;
 
@@ -70,14 +80,23 @@ class MockClient {
     }
 }
 
-// A content source that writes a marker file and counts thumbnail fetches.
+// A content source that writes `original` as every original and a marker file
-const stubSource = (): ContentSource & { thumbCalls: () => number } => {
+// as every thumbnail, and counts the fetches of each.
+const stubSource = (
+    original: string | Uint8Array = "orig-bytes",
+): ContentSource & {
+    originalCalls: () => number;
+    thumbCalls: () => number;
+} => {
+    let originalCalls = 0;
     let thumbCalls = 0;
     return {
+        originalCalls: () => originalCalls,
         thumbCalls: () => thumbCalls,
         original: async ({ destination }) => {
-            writeFileSync(destination, "orig-bytes");
+            originalCalls++;
-            return { bytesWritten: 10 };
+            writeFileSync(destination, original);
+            return { bytesWritten: original.length };
         },
         thumbnail: async ({ destination }) => {
             thumbCalls++;
@@ -211,3 +230,301 @@ describe("Library content wiring", () => {
         await lib.close();
     });
 });
+
+// Big-endian bytes for the hand-built JPEG below.
+const u16 = (n: number): number[] => [n >> 8, n & 0xff];
+const u32 = (n: number): number[] => [...u16(n >>> 16), ...u16(n & 0xffff)];
+const ascii = (s: string): number[] => [...new TextEncoder().encode(s), 0];
+const rational = (num: number, den: number): number[] => [
+    ...u32(num),
+    ...u32(den),
+];
+// One IFD entry: tag, type (1 BYTE, 2 ASCII, 3 SHORT, 4 LONG, 5 RATIONAL),
+// count, then the value when it fits in 4 bytes, else its offset.
+const entry = (
+    tag: number,
+    type: number,
+    count: number,
+    value: number[],
+): number[] => [...u16(tag), ...u16(type), ...u32(count), ...value];
+
+// The TIFF block of a JPEG's EXIF segment, holding every field `exif()` picks:
+// the camera in the first IFD, the exposure in the Exif IFD, and a GPS position
+// of 40°26'46" N, 79°58'56" W, 12.5 m below sea level. Offsets count from the
+// start of this block.
+const TIFF = [
+    ...[0x4d, 0x4d, 0x00, 0x2a], // big-endian TIFF
+    ...u32(8), // the first IFD's offset
+    // The first IFD, at 8: five entries, then no next IFD.
+    ...u16(5),
+    ...entry(0x010f, 2, 6, u32(74)), // Make
+    ...entry(0x0110, 2, 7, u32(80)), // Model
+    ...entry(0x0112, 3, 1, [...u16(6), 0, 0]), // Orientation
+    ...entry(0x8769, 4, 1, u32(88)), // the Exif IFD's offset
+    ...entry(0x8825, 4, 1, u32(246)), // the GPS IFD's offset
+    ...u32(0),
+    ...ascii("Canon"), // at 74
+    ...ascii("EOS R5"), // at 80
+    0, // a pad byte
+    // The Exif IFD, at 88: seven entries, then no next IFD.
+    ...u16(7),
+    ...entry(0x829a, 5, 1, u32(178)), // ExposureTime
+    ...entry(0x829d, 5, 1, u32(186)), // FNumber
+    ...entry(0x8827, 3, 1, [...u16(400), 0, 0]), // ISOSpeedRatings
+    ...entry(0x9003, 2, 20, u32(194)), // DateTimeOriginal
+    ...entry(0x9011, 2, 7, u32(214)), // OffsetTimeOriginal
+    ...entry(0x920a, 5, 1, u32(222)), // FocalLength
+    ...entry(0xa434, 2, 16, u32(230)), // LensModel
+    ...u32(0),
+    ...rational(1, 250), // at 178
+    ...rational(28, 10), // at 186
+    ...ascii("2021:07:15 14:30:00"), // at 194
+    ...ascii("+02:00"), // at 214
+    0, // a pad byte
+    ...rational(50, 1), // at 222
+    ...ascii("RF50mm F1.8 STM"), // at 230
+    // The GPS IFD, at 246: six entries, then no next IFD.
+    ...u16(6),
+    ...entry(0x0001, 2, 2, [...ascii("N"), 0, 0]), // GPSLatitudeRef
+    ...entry(0x0002, 5, 3, u32(324)), // GPSLatitude
+    ...entry(0x0003, 2, 2, [...ascii("W"), 0, 0]), // GPSLongitudeRef
+    ...entry(0x0004, 5, 3, u32(348)), // GPSLongitude
+    ...entry(0x0005, 1, 1, [1, 0, 0, 0]), // GPSAltitudeRef: below sea level
+    ...entry(0x0006, 5, 1, u32(372)), // GPSAltitude
+    ...u32(0),
+    ...[...rational(40, 1), ...rational(26, 1), ...rational(46, 1)], // at 324
+    ...[...rational(79, 1), ...rational(58, 1), ...rational(56, 1)], // at 348
+    ...rational(25, 2), // at 372
+];
+
+const JPEG_WITH_EXIF = new Uint8Array([
+    ...[0xff, 0xd8], // start of image
+    ...[0xff, 0xe1, ...u16(2 + 6 + TIFF.length)], // APP1 and its length
+    ...[...ascii("Exif"), 0], // "Exif\0\0"
+    ...TIFF,
+    ...[0xff, 0xda, 0x00, 0x02], // start of scan
+]);
+
+// A JPEG whose EXIF segment is laid out correctly but holds "XX" where the TIFF
+// byte order belongs, so exifreader cannot parse it.
+const JPEG_WITH_BAD_EXIF = new Uint8Array([
+    ...[0xff, 0xd8], // start of image
+    ...[0xff, 0xe1, ...u16(2 + 6 + 2)], // APP1 and its length
+    ...[...ascii("Exif"), 0], // "Exif\0\0"
+    ...[0x58, 0x58], // "XX"
+    ...[0xff, 0xda, 0x00, 0x02], // start of scan
+]);
+
+describe("Photo save path, local copy, content and EXIF", () => {
+    // The same account, with `files` in its album instead.
+    class FilesClient extends MockClient {
+        constructor(private readonly files: EnteFile[]) {
+            super();
+        }
+        override async filesSince(): Promise<FilesPage> {
+            return { files: this.files, deleted: [], cursor: 1 };
+        }
+    }
+
+    const open = (opts: Partial<LibraryOptions> = {}): Promise<Library> =>
+        Library.open({
+            client: new MockClient(),
+            cacheDirectory: join(root, "cache"),
+            downloadDirectory: join(root, "backup"),
+            contentSource: stubSource(),
+            refreshIntervalSeconds: 3600,
+            precacheThumbnails: false,
+            precacheOriginals: false,
+            ...opts,
+        });
+
+    it("names where a backup writes the original, which is local once the backup has written it", async () => {
+        const lib = await open();
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        const savePath = join(root, "backup", "originals", "1.jpg");
+        expect(photo.savePath).toBe(savePath);
+        expect(photo.isLocal).toBe(false);
+
+        await lib.backup();
+        expect(photo.savePath).toBe(savePath);
+        expect(existsSync(savePath)).toBe(true);
+        expect(photo.isLocal).toBe(true);
+        await lib.close();
+    });
+
+    it("returns the original's bytes, and a copy only in the cache is not local", async () => {
+        const lib = await open();
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(await photo.content()).toEqual(Buffer.from("orig-bytes"));
+        expect(existsSync(join(root, "cache", "originals", "1.jpg"))).toBe(
+            true,
+        );
+        expect(existsSync(photo.savePath!)).toBe(false);
+        expect(photo.isLocal).toBe(false);
+        await lib.close();
+    });
+
+    it("has no save path and is not local without a download directory", async () => {
+        const lib = await open({ downloadDirectory: undefined });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(photo.savePath).toBeUndefined();
+        expect(photo.isLocal).toBe(false);
+        await lib.close();
+    });
+
+    it("has no save path and is not local without a content source", async () => {
+        const lib = await open({ contentSource: undefined });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(photo.savePath).toBeUndefined();
+        expect(photo.isLocal).toBe(false);
+        await lib.close();
+    });
+
+    it("gives a live photo's image as its save path once a backup has stored it", async () => {
+        const { file: live, body } = await asLivePhoto(file(1, 1));
+        const lib = await open({
+            client: new FilesClient([live]),
+            contentSource: cdnSource(new Map([[1, body]])),
+        });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        const originals = join(root, "backup", "originals");
+        // Until then the name comes from the title, file-1.jpg; the backup
+        // stores the image with the extension found inside the live photo.
+        expect(photo.savePath).toBe(join(originals, "1.jpg"));
+
+        await lib.backup();
+        expect(photo.savePath).toBe(join(originals, "1.heic"));
+        expect(photo.isLocal).toBe(true);
+        expect(await photo.content()).toEqual(Buffer.from(IMAGE));
+        await lib.close();
+    });
+
+    it("reads the common EXIF fields of a JPEG original", async () => {
+        const lib = await open({ contentSource: stubSource(JPEG_WITH_EXIF) });
+        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({
+            make: "Canon",
+            model: "EOS R5",
+            lensModel: "RF50mm F1.8 STM",
+            // The camera's clock reading, held in the Date's UTC fields.
+            dateTimeOriginal: new Date(Date.UTC(2021, 6, 15, 14, 30)),
+            offsetTimeOriginal: "+02:00",
+            exposureTime: 1 / 250,
+            fNumber: 2.8,
+            iso: 400,
+            focalLength: 50,
+            orientation: 6,
+            gpsLatitude: 40 + 26 / 60 + 46 / 3600,
+            gpsLongitude: -(79 + 58 / 60 + 56 / 3600),
+            gpsAltitude: -12.5,
+        });
+        await lib.close();
+    });
+
+    // What exif() returns for HEIC_WITH_EXIF, and for JPEG_WITH_EXIF, which
+    // holds the same values.
+    const heicFields: PhotoExif = {
+        make: "Canon",
+        model: "EOS R5",
+        lensModel: "RF50mm F1.8 STM",
+        dateTimeOriginal: new Date(Date.UTC(2021, 6, 15, 14, 30)),
+        offsetTimeOriginal: "+02:00",
+        exposureTime: 1 / 250,
+        fNumber: 2.8,
+        iso: 400,
+        focalLength: 50,
+        orientation: 6,
+        gpsLatitude: 40 + 26 / 60 + 46 / 3600,
+        gpsLongitude: -(79 + 58 / 60 + 56 / 3600),
+        gpsAltitude: -12.5,
+    };
+
+    it("reads the same common EXIF fields from a HEIC original", async () => {
+        const lib = await open({ contentSource: stubSource(HEIC_WITH_EXIF) });
+        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual(
+            heicFields,
+        );
+        await lib.close();
+    });
+
+    it("reads the EXIF of a live photo whose image is a HEIC", async () => {
+        const { file: live, body } = await asLivePhoto(
+            file(1, 1),
+            livePhotoZip({ "image.heic": HEIC_WITH_EXIF, "video.mov": VIDEO }),
+            livePhotoHash(HEIC_WITH_EXIF, VIDEO),
+        );
+        const lib = await open({
+            client: new FilesClient([live]),
+            contentSource: cdnSource(new Map([[1, body]])),
+        });
+        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual(
+            heicFields,
+        );
+        await lib.close();
+    });
+
+    // The build's type check, not this test, makes sure `Photo` has a method
+    // for every `PhotoExif` field, whatever the fixtures hold: `Photo`
+    // implements a type with one method per field. This test checks that each
+    // method gives the same value as exif().
+    it.each([
+        ["JPEG", JPEG_WITH_EXIF],
+        ["HEIC", HEIC_WITH_EXIF],
+    ])(
+        "has a method for each field exif() returns, giving the same value, for a %s",
+        async (_, bytes) => {
+            const lib = await open({ contentSource: stubSource(bytes) });
+            const photo = lib.photos.byID({ fileID: 1 })!;
+            const exif = await photo.exif();
+            // The file holds every field, so every method is checked.
+            expect(exif).toStrictEqual(heicFields);
+            for (const [field, value] of Object.entries(exif)) {
+                expect(await photo[field as keyof PhotoExif]()).toStrictEqual(
+                    value,
+                );
+            }
+            await lib.close();
+        },
+    );
+
+    it("returns no EXIF fields for an original that is not an image", async () => {
+        const lib = await open();
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(await photo.exif()).toStrictEqual({});
+        expect(await photo.dateTimeOriginal()).toBeUndefined();
+        await lib.close();
+    });
+
+    it("returns no EXIF fields for a JPEG whose EXIF cannot be parsed", async () => {
+        const lib = await open({
+            contentSource: stubSource(JPEG_WITH_BAD_EXIF),
+        });
+        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({});
+        await lib.close();
+    });
+
+    it("throws from exif() on a video without a content source, as the other content methods do", async () => {
+        const video = file(1, 1);
+        video.metadata.fileType = "video";
+        const lib = await open({
+            client: new FilesClient([video]),
+            contentSource: undefined,
+        });
+        await expect(lib.photos.byID({ fileID: 1 })!.exif()).rejects.toThrow(
+            /content cache/i,
+        );
+        await lib.close();
+    });
+
+    it("returns no EXIF fields for a video, without fetching it", async () => {
+        const video = file(1, 1);
+        video.metadata.fileType = "video";
+        const source = stubSource(JPEG_WITH_EXIF);
+        const lib = await open({
+            client: new FilesClient([video]),
+            contentSource: source,
+        });
+        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({});
+        expect(source.originalCalls()).toBe(0);
+        await lib.close();
+    });
+});

test/library/read.test.ts

@@ -209,6 +209,29 @@ describe("lib.photos", () => {
         expect("key" in photo.record()).toBe(false);
     });
 
+    it("byID exposes modifiedAt, hash and the year taken", () => {
+        // Mid-July, so the year is 2021 in every time zone.
+        const takenAt = Date.UTC(2021, 6, 15, 12);
+        const records = deriveRecords(
+            [collection(1)],
+            [
+                file(1001, 1, {
+                    metadata: {
+                        title: "IMG.jpg",
+                        fileType: "image",
+                        creationTime: micros(takenAt),
+                        modificationTime: micros(1_700_000_123_456),
+                        hash: "aGFzaA==",
+                    },
+                }),
+            ],
+        );
+        const photo = apis(records).photos.byID({ fileID: 1001 })!;
+        expect(photo.modifiedAt).toBe(ms(1_700_000_123_456));
+        expect(photo.hash).toBe("aGFzaA==");
+        expect(photo.year).toBe(2021);
+    });
+
     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();

test/library/records.test.ts

@@ -159,6 +159,7 @@ describe("deriveRecords: photo mapping", () => {
         expect("width" in rec).toBe(false);
         expect("height" in rec).toBe(false);
         expect("latitude" in rec).toBe(false);
+        expect("hash" in rec).toBe(false);
     });
 
     it("reads archived and hidden from private magicMetadata.visibility", () => {

yarn.lock

@@ -702,6 +702,11 @@
     loupe "^3.1.2"
     tinyrainbow "^1.2.0"
 
+"@xmldom/xmldom@^0.9.10":
+  version "0.9.12"
+  resolved "https://registry.yarnpkg.com/@xmldom/xmldom/-/xmldom-0.9.12.tgz#1f84c07cb95ccf28202299f77b5fd7fc257151e8"
+  integrity sha512-5AXjrcMClTryPe9LgZrygpB1lj7s0S9E0+W+AHaVKAVyHanafK86iPSvG5xHVSp/jC+VH1UXu0TAEmY279xH7A==
+
 acorn-jsx@^5.3.2:
   version "5.3.2"
   resolved "https://registry.yarnpkg.com/acorn-jsx/-/acorn-jsx-5.3.2.tgz#7ed5bb55908b3b2f1bc55c6af1653bada7f07937"
@@ -1002,10 +1007,12 @@ esutils@^2.0.2:
   resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.3.tgz#74d2eb4de0b8da1293711910d50775b9b710ef64"
   integrity sha512-kVscqXk4OCp68SZ0dkgEKVi6/8ij300KBWTJq32P/dYeWTSwK41WyTxalN1eRmA5Z9UU/LX9D7FWSmV9SAYx6g==
 
-exif-reader@2.0.3:
+exifreader@4.46.0:
-  version "2.0.3"
+  version "4.46.0"
-  resolved "https://registry.yarnpkg.com/exif-reader/-/exif-reader-2.0.3.tgz#259997735080bc6bb959c37b32c60f004ec4391d"
+  resolved "https://registry.yarnpkg.com/exifreader/-/exifreader-4.46.0.tgz#b6216eae512997587c45114f972cc14ca979205f"
-  integrity sha512-zFbQvguwT9JkqyYhR7pjE1Yn8SagwaGLNRU0Oh14xFa1paSf5Gzxn4gxgk0XhnudI0UIqU+HgnBX93+nva592A==
+  integrity sha512-ksHTpjXKWzbckY+bYlGaomG0EobHJkaMWLg5OPbzlTPda04F2dfrDfYSz8iAPp/kXYUSQdINBVI6nCAjQ8PQ/Q==
+  optionalDependencies:
+    "@xmldom/xmldom" "^0.9.10"
 
 expect-type@^1.1.0:
   version "1.3.0"