# macltok

`macltok` is a compact Rust application backend built above `matrix-sdk` and
`matrix-sdk-ui`. It aims to provide the stateful behavior needed by a useful
Matrix client without depending on a GUI toolkit or inventing another protocol
SDK.

The crate currently provides

- typed commands, owned UI-safe events and bounded per-client transport
- Sliding Sync with normalized connection and room-list state
- independently retained live room timelines and backwards pagination
- text, emote, reply, edit, redaction, reaction, receipt and typing operations
- raw encrypted or unencrypted media acquisition with configurable byte limits
- encryption state, recovery-key import and SAS verification
- password login and session restoration with caller-owned encrypted SQLite or
  IndexedDB stores

Matrix room, event, user, device and transaction identifiers remain strongly
typed. A toolkit timeline identity covers local echoes without pretending they
already have remote event IDs.

## Consuming the engine

spawn `Engine::run`, drain the `EventStream` from its own task, and talk to the
engine through `ClientHandle`. every command answers once, awaited
(`handle.send_message(..).await?`) or as a `Pending` you can await later or
drop. a sent message answers when the sdk send queue has it, delivery shows up
as the timeline item's send state. reads like `rooms`, `members` and `media`
go straight to the sdk. the stream only carries state

some commands put an event on the stream before they answer. `Open`, `Close`,
`OpenThread`, `CloseThread`, `Resync`, `Paginate`, `Logout` and the
verification actions all do. the stream is bounded, so a task that drains it
and awaits one of those answers deadlocks once it fills. from the draining
task, `try_send` the command and drop the `Pending`, the events tell you how it
went

start a timeline from `TimelineReset`, then apply each `TimelineChanged` whole
with `TimelineDiff::try_apply_all`. snapshots are `imbl::Vector`s, re-exported
as `macltok::imbl`, so a copy costs nothing. when a batch doesn't fit none of it
lands. stop applying, call `resync`, and pick up from the next `TimelineReset`

with `sqlite` or `indexeddb`, a `SessionStore` holds one login's record and its
store. `EncryptedSessionStore` seals the record with the store's passphrase, in a
file you pick natively or an IndexedDB database beside the store in a browser.
logging in saves the first record and `Session::restore` loads it. on every
`SessionTokensChanged`, `save` a fresh `ClientHandle::session_record()` before
the next refresh, refresh tokens only work once

`Engine::run` resolves to a `Termination` saying why it stopped, and
`Termination::retain` says what to do about it. after `LoggedOut` or
`AccessRevoked` the record and the store are dead, `discard` them once the
client is dropped, since an open store won't go quietly. `SoftLoggedOut` wants
the store kept and a fresh login as the same device, or the e2ee keys go with
it. `soft_log_out` swaps the record for one naming that device, so a restart
gets `Restore::SoftLoggedOut` and `SoftLogout::password_login` rather than
nothing, and the login overwrites it with a live record. `ShutDown` and
`HandlesDropped` keep everything. an `Err` is a real failure and kills nothing.
one store directory per login, the sdk won't share a crypto store between
devices

## wasm

macltok builds for `wasm32-unknown-unknown`. the `indexeddb` feature gives you
`StoreConfig::indexeddb` in place of `StoreConfig::sqlite`, and asking for either
on the wrong target won't compile. `Engine::run` hands back a `LocalBoxFuture`
there, so spawn it with `wasm_bindgen_futures::spawn_local`

getrandom picks its browser backend from a cfg flag, and `.cargo/config.toml`
only reaches this crate's own builds. every cdylib that pulls macltok in needs
it too

```toml
[target.wasm32-unknown-unknown]
rustflags = ["--cfg", "getrandom_backend=\"wasm_js\""]
```

what's different in a browser

- a panic aborts the whole instance. natively a panicking command costs its
  caller an `Interrupted`, here it takes the engine and everything else with it
- `MediaUploadProgress` only ever reports completion, the sdk's wasm http path
  has no upload progress
- the sdk doesn't retry requests or time them out individually. sync still
  restarts itself with backoff, that part is ours
- two tabs or workers on one store each need `StoreConfig::with_lock_holder`
  with a name of their own, or they both think they hold the crypto store

## Dependency policy

UI frameworks, image decoders, application-directory discovery and logging
subscribers do not belong in this crate. SQLite remains optional through the
`sqlite` and `bundled-sqlite` features, IndexedDB through `indexeddb`. Media
decoding belongs to the consumer.

## Verification

```sh
nix develop --command cargo fmt -- --check
nix develop --command cargo test --all-targets
nix develop --command cargo test --all-targets --features sqlite
nix develop --command cargo clippy --all-targets -- -D warnings
nix develop --command cargo clippy --all-targets --features sqlite -- -D warnings
nix flake check
```