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# Synced Tabs Component
## Implementation Overview
This crate implements an in-memory syncing engine for remote tabs.
## Directory structure
The relevant directories are as follows:
- `src`: The meat of the library. This contains cross-platform rust code that
implements the syncing of tabs.
- `ffi`: The Rust public FFI bindings. This is a (memory-unsafe, by necessity)
API that is exposed to Kotlin and Swift. It leverages the `ffi_support` crate
to avoid many issues and make it more safe than it otherwise would be.
It uses protocol buffers for marshalling data over the FFI.
- `android`: This contains android bindings to synced tabs, written in Kotlin. These
use JNA to call into to the code in `ffi`.
- `ios`: This contains the iOS binding to synced tabs, written in Swift. These use
Swift's native support for calling code written in C to call into the code in
`ffi`.
## Features
- Synchronization of the local and remote session states.
## Business Logic
### Storage
The storage is all done in memory for simplicity purposes. The host applications are free to persist the remote tabs list if it makes sense to them.
### Payload format
Every remote sync record is roughly a list of tabs with their URL history (think of the back button). There is one record for each client.
### Association with device IDs
Each remote tabs sync record is associated to a "client" using a `client_id` field, which is really a foreign-key to a `clients` collection record.
However, because we'd like to move away from the clients collection, which is why this crate associates these records with Firefox Accounts device ids.
Currently for platforms using the sync-manager provided in this repo, the `client_id` is really the Firefox Accounts device ID and all is well, however for older platforms it is a distinct ID, which is why we have to feed the `clients` collection to this Tabs Sync engine to associate the correct Firefox Account device id.
## Getting started
**Prerequisites**: Firefox account authentication is necessary to obtain the keys to decrypt synced tabs data. See the [android-components FxA Client readme](https://github.com/mozilla-mobile/android-components/blob/master/components/service/firefox-accounts/README.md) for details on how to implement on Android. For iOS, Firefox for iOS still implement the legacy oauth.
**Platform-specific details**:
- <TODO-ST> Android
- iOS: start with the [guide to consuming rust components on iOS](https://github.com/mozilla/application-services/blob/main/docs/howtos/consuming-rust-components-on-ios.md)
## API Documentation
- TODO
## Testing
<TODO-ST>
## Telemetry
<TODO-ST>
## Examples
<TODO-ST>