attendi/README.md

# Attendi Sample App

A sample app that implements an audio recording flow in SwiftUI: start, pause, resume, or discard a recording while a 
timer tracks the elapsed time, then send the recording to be transcribed on device — and read the resulting text in a 
sheet.

## Context

This sample app was created for a technical interview for a senior Mobile (iOS + Android) engineer role at 
[Attendi](https://attendi.nl), a Dutch health-tech company that makes voice-driven reporting software for 
healthcare professionals, based on [a given set of requirements](README.pdf).

## Requirements

| Requirement | Version |
| --- | --- |
| Xcode | 26 or later |
| Swift | 6.3 |
| Platforms | iOS/macOS/visionOS 26 |

## Project structure

The project separates the app shell from the feature code, which lives in a local Swift package:

```
Attendi/
├── Attendi.xcodeproj
├── Apps/
│   └── Attendi/                         # The app target (thin shell)
│       ├── App/                         # The @main entry point
│       ├── Views/                       # The root view: hosts the feature, the locale picker, and the transcription sheet
│       ├── View Models/                 # The services, the supported locales, and the speech model preinstallation
│       ├── Catalogs/                    # The app's assets and localized strings
│       └── Resources/                   # The Info.plist, including the microphone usage description
└── Packages/
    └── Features/                        # Local Swift package with the feature code
        ├── Package.swift
        ├── Sources/
        │   └── Recording/               # The Recording feature target
        │       ├── Catalogs/            # The record, pause, and send icons; the localized strings
        │       ├── Models/              # Transcription, RecordingError
        │       ├── Protocols/           # Capturing, Transcribing
        │       ├── Services/            # AudioCapturing, AudioTranscribing, and their development dummies
        │       ├── Styles/              # RecordingButtonStyle
        │       ├── View Models/         # RecordingViewModel
        │       └── Views/               # RecordingView
        └── Tests/
            ├── Recording/               # The model and view model suites, with their mocks
            └── Features.xctestplan
```

The app target only depends on the `Features` package and renders its public `RecordingView` view; all recording logic 
and UI live in the package's `Recording` target.

## The Recording feature

### State machine

The flow is modeled as a state machine in `RecordingView.Model`, an `@Observable`, `@MainActor` view model:

| State | Meaning |
| --- | --- |
| `notRecording` | Idle; no recording in progress. |
| `recording` | A recording is in progress and the timer is ticking. |
| `paused` | The recording is paused; it can be resumed, discarded, or sent. |
| `processing` | The sent recording is being stopped and transcribed. |

The main button starts, pauses, and resumes a recording. While paused, two more buttons appear: discard throws the 
recording away, and send moves the flow into processing — stopping the capture and transcribing the audio — before 
returning to idle. The model owns every side effect of a transition (timer, capture, processing), so the state machine 
works the same whether it is driven by the view's buttons or by the unit tests.

The calls to the capturing service are serialized through a task chain: no matter how quickly the states change, 
`start`, `pause`, `resume`, and `stop` always reach the service in order. When the system interrupts the audio session 
mid-recording — a phone call or Siri, for example — the service emits an event and the model pauses exactly like a 
press of the main button would; the capture is never resumed without the user asking for it.

### Timer

The recording time is measured with a monotonic `ContinuousClock`: an anchor marks the start of the current recording 
stretch, and pausing folds the stretch into an accumulated duration, so scheduling latency never accumulates as drift. 
While recording, an async task republishes the measured time once per second. The view formats the count as `mm:ss` 
and animates digit changes with a numeric text content transition.

### Errors

Failures of either service are published by the model as a `RecordingError` and presented by the view in an alert: a 
denied microphone permission additionally offers to open the app's settings, and unavailable speech model assets are 
distinguished from an ordinary transcription failure. The underlying errors are logged through `OSLog` under the 
`Features.Recording` subsystem.

### Views

- **`RecordingView`** — the public entry point of the feature. It renders the timer label and the control buttons for 
     the model's current state, forwards every transcription to a closure given at initialization, and presents the 
     error alert. All controls carry localized accessibility labels matching their current action, and the timer 
     exposes its value to assistive technologies spelled out in full units.
- **`RecordingButtonStyle`** — a custom `ButtonStyle` used by the controls: the label sits on a padded, circular red 
     Liquid Glass background that reacts fluidly to presses, and dims while disabled. The label and its padding scale 
     with Dynamic Type via `@ScaledMetric`, and an `invertStyle` flag controls whether the label's color scheme is 
     inverted for contrast.

### Services

The actual recording work is abstracted behind two protocols, injected into `RecordingView` at initialization and 
attached to its view model:

- **`Capturing`** — captures the audio from a microphone, with throwing async `start`, `pause`, `resume`, and `stop` 
     methods; `stop` hands the captured audio over as a file URL, avoiding any in-memory copies. An `events` stream 
     (empty by default) lets a service report interruptions of the capture.
- **`Transcribing`** — a callable service that transcribes a recorded audio file into text for a given locale, 
     returning a `Transcription`.

The real backends used by the app are:

- **`AudioCapturing`** — records single-channel AAC into a temporary file through `AVAudioRecorder`, requesting the 
     microphone permission and managing the shared audio session on the platforms that require it, and emitting an 
     event when the system interrupts the session while recording.
- **`AudioTranscribing`** — transcribes entirely on device through `SpeechAnalyzer` with a `SpeechTranscriber` module, 
     in the closest supported equivalent of the requested locale, installing any missing speech model assets before 
     the analysis.

The internal `DummyCapturing` and `DummyTranscribing` fake the work for previews and default model values (the latter 
with a two-second delay and a dummy transcription); the unit tests inject configurable mocks, and other backends can 
be plugged in the same way without touching the feature's state machine.

## The app shell

`ContentView` hosts the feature inside a navigation stack and presents the transcribed text of every processed 
recording in a modal sheet — or a content-unavailable message when the transcription is empty. A toolbar menu picks 
the locale of the spoken language from the locales the transcriber supports, aligned at launch with the closest 
supported equivalent of the user's locale. Picking a locale preinstalls its speech model assets in the background, so 
the first transcription does not have to download them mid-processing; the app keeps a single asset locale reservation 
at a time, releasing stale ones, since the system only permits a limited number per app.

## Testing

The package is covered by Swift Testing suites: `RecordingViewModelTests.swift` groups the view model's behaviors with 
nested `@Suite` types (initial state, button presses, computed properties, timer, capturer, errors, interruptions, and 
processing), and `TranscriptionTests.swift` covers the `Transcription` model. The state-dependent behaviors are 
exercised with parameterized tests across all four states, driven through the model's public press handlers, and the 
service mocks record their invocations in call order.

Run the tests with the `Features` scheme in Xcode (`⌘U`), or from the command line:

```sh
xcodebuild test -scheme Features -destination 'platform=iOS'
```

## Localization

Both the app and the feature package localize their user-facing text through string catalogs (`Localizable.xcstrings`, 
currently English only): the app's catalog covers the navigation titles and the transcription sheet, and the package's 
catalog covers the error alert and the accessibility labels.

## Tooling

- **`.swift-format`** — configuration for Apple's `swift-format`, used by Xcode's built-in formatter (4-space 
     indentation, 200-column lines).