# AI Implementation Guide

## How This App Was Architected & Built

This project was developed following strict senior-level iOS engineering standards, with guidance from AI assistants acting as Senior iOS Engineers specializing in SwiftUI and modern Apple frameworks.

---

## Guiding Principles (from AGENTS.md)

- **Protocol-Oriented Programming (POP) first**: All shared capabilities defined via protocols before concrete types
- **MVVM-lite**: Views are "dumb" — all logic lives in `@Observable` view models
- **Bedrock Design System**: Centralized design tokens, no magic numbers
- **Full accessibility**: Dynamic Type, VoiceOver labels/hints/traits/announcements
- **Modern Swift & SwiftUI**: Swift 6 concurrency, `@MainActor`, `foregroundStyle`, `clipShape(.rect)`, `NavigationStack`
- **Testable & reusable design**: Protocols enable mocking and future package extraction

---

## Architecture Overview

```
Shared/
├── DesignConstants.swift           → Uses Bedrock design tokens
├── BrandingConfig.swift            → App icon & launch screen config
├── Color+Extensions.swift          → Ring light color presets
├── Models/
│   ├── CameraFlashMode.swift       → Flash mode enum
│   ├── CameraHDRMode.swift         → HDR mode enum  
│   ├── PhotoQuality.swift          → Photo quality settings
│   └── CapturedPhoto.swift         → Photo data model
├── Protocols/
│   ├── RingLightConfigurable.swift → Border, color, brightness
│   ├── CaptureControlling.swift    → Timer, grid, zoom, capture
│   └── PremiumManaging.swift       → Subscription state
├── Premium/
│   └── PremiumManager.swift        → RevenueCat integration
├── Services/
│   └── PhotoLibraryService.swift   → Photo saving service
└── Storage/
    └── SyncedSettings.swift        → iCloud-synced settings

Features/
├── Camera/                         → Main camera UI
│   ├── ContentView.swift           → Screen coordinator
│   ├── Views/                      → UI components
│   └── GridOverlay.swift           → Rule of thirds
├── Settings/                       → Configuration
│   ├── SettingsView.swift          → Settings UI
│   └── SettingsViewModel.swift     → Settings logic + sync
└── Paywall/                        → Pro subscription flow
```

---

## Key Implementation Decisions

### 1. Ring Light Effect
- Achieved using `RingLightOverlay` view that creates a colored border around the camera preview
- Border width controlled via user setting (10-120pt range)
- Multiple preset colors with premium custom color picker
- Adjustable opacity/brightness (10%-100%)
- Enabled/disabled toggle for quick access

### 2. Camera System
- Uses **MijickCamera** framework for SwiftUI-native camera handling
- Supports front and back camera switching
- Pinch-to-zoom with smooth interpolation
- Flash modes: Off, On, Auto (with premium flash sync)
- HDR mode support (premium feature)
- Photo quality settings (medium free, high premium)

### 3. Capture Enhancements
- Self-timer with countdown (3s free, 5s/10s premium)
- Post-capture preview with share functionality
- Auto-save option to Photo Library
- Front flash using screen brightness
- **Camera Control button** (iPhone 16+): Full press captures, light press locks focus/exposure
- **Hardware shutter**: Volume buttons trigger capture via `VolumeButtonObserver`

### 4. Freemium Model
- Built with **RevenueCat** for subscription management
- `PremiumManager` wraps RevenueCat SDK
- `PremiumGate` utility for clean premium feature access
- Settings automatically fall back to free defaults when not premium

### 5. iCloud Sync
- Uses **Bedrock's CloudSyncManager** for settings synchronization
- `SyncedSettings` model contains all user preferences
- Debounced saves for slider values (300ms delay)
- Real-time sync status display in Settings
- Available to all users (not a premium feature)

### 6. Branding System
- Uses **Bedrock's Branding** module for launch screen and app icon
- `BrandingConfig.swift` defines app-specific colors and symbols
- `LaunchBackground.colorset` matches launch screen primary color
- Animated launch with configurable duration and pattern style
- Icon generator available in DEBUG builds

---

## Camera Control Button Integration

### Overview

The app supports the **Camera Control** button on iPhone 16+ via `AVCaptureEventInteraction` (iOS 17.2+).

### Files Involved

| File | Purpose |
|------|---------|
| `Shared/Protocols/CaptureEventHandling.swift` | Protocol defining hardware capture event handling |
| `Features/Camera/Views/CaptureEventInteraction.swift` | `AVCaptureEventInteraction` wrapper and SwiftUI integration |
| `Features/Camera/Views/VolumeButtonObserver.swift` | Volume button capture support (legacy) |

### Supported Hardware Events

| Event | Hardware | Action |
|-------|----------|--------|
| **Primary (full press)** | Camera Control, Action Button | Capture photo |
| **Secondary (light press)** | Camera Control | Lock focus/exposure |
| **Volume buttons** | All iPhones | Capture photo |

### Implementation Details

```swift
// CaptureEventInteractionView is added to the camera ZStack
CaptureEventInteractionView(
    onCapture: { performCapture() },
    onFocusLock: { locked in handleFocusLock(locked) }
)

// The interaction uses AVCaptureEventInteraction (iOS 17.2+)
AVCaptureEventInteraction(
    primaryEventHandler: { phase in /* capture on .ended */ },
    secondaryEventHandler: { phase in /* focus lock on .began/.ended */ }
)
```

### Device Compatibility

- **iPhone 16+**: Full Camera Control button support (press + light press)
- **iPhone 15 Pro+**: Action button support (when configured for camera)
- **All iPhones**: Volume button shutter via `VolumeButtonObserver`

---

## Premium Feature Implementation

### How Premium Gating Works

The app uses a centralized `PremiumGate` utility for consistent premium feature handling:

```swift
// In SettingsViewModel
var isMirrorFlipped: Bool {
    get { PremiumGate.get(cloudSync.data.isMirrorFlipped, default: false, isPremium: isPremiumUnlocked) }
    set { 
        guard PremiumGate.canSet(isPremium: isPremiumUnlocked) else { return }
        updateSettings { $0.isMirrorFlipped = newValue } 
    }
}
```

### Premium Features List

| Feature | Free Value | Premium Value |
|---------|-----------|---------------|
| Ring light colors | Pure White, Warm Cream | All presets + custom |
| Timer options | Off, 3s | Off, 3s, 5s, 10s |
| Photo quality | Medium | Medium, High |
| HDR mode | Off | Off, On, Auto |
| True mirror | Off | Configurable |
| Skin smoothing | Off | Configurable |
| Flash sync | Off | Configurable |
| Center stage | Off | Configurable |

---

## Settings & Persistence

### SyncedSettings Model

All user preferences are stored in a single `SyncedSettings` struct that syncs via iCloud:

- Ring light: size, color ID, custom color RGB, opacity, enabled
- Camera: position, flash mode, HDR mode, photo quality
- Display: mirror flip, skin smoothing, grid visible
- Capture: timer, capture mode, auto-save
- Premium features: flash sync, center stage

### Debounced Saves

Slider values (ring size, opacity) use debounced saving to prevent excessive iCloud writes:

```swift
private func debouncedSave(key: String, action: @escaping () -> Void) {
    debounceTask?.cancel()
    debounceTask = Task {
        try? await Task.sleep(for: .milliseconds(300))
        guard !Task.isCancelled else { return }
        action()
    }
}
```

---

## Branding Implementation

### Files Involved

1. **BrandingConfig.swift** - Defines app icon and launch screen configurations
2. **LaunchBackground.colorset** - Asset catalog color matching primary brand color
3. **SelfieCamApp.swift** - Wraps ContentView with AppLaunchView

### Color Scheme

```swift
extension Color {
    enum Branding {
        static let primary = Color(red: 0.85, green: 0.25, blue: 0.45)   // Vibrant magenta
        static let secondary = Color(red: 0.45, green: 0.12, blue: 0.35) // Deep purple
        static let accent = Color.white
    }
}
```

### Launch Screen Configuration

```swift
static let selfieCam = LaunchScreenConfig(
    title: "SELFIE CAM",
    tagline: "Look Your Best",
    iconSymbols: ["camera.fill", "sparkles"],
    cornerSymbol: "sparkle",
    patternStyle: .radial,
    // ... colors and sizing
)
```

---

## Development Workflow

### Adding a New Feature

1. **Define the protocol** (if shared behavior)
2. **Add to SyncedSettings** (if needs persistence)
3. **Implement in SettingsViewModel** (with premium gating if applicable)
4. **Add UI in SettingsView**
5. **Update documentation** (README, this file)

### Adding a Premium Feature

1. Add setting to `SyncedSettings` with appropriate default
2. Use `PremiumGate.get()` for the getter with free default
3. Use `PremiumGate.canSet()` guard for the setter
4. Add premium indicator (crown icon) in UI
5. Wire up paywall trigger for non-premium users

### Testing Premium Features

Set environment variable in scheme:
- **Name:** `ENABLE_DEBUG_PREMIUM`
- **Value:** `1`

---

## Reusability & Extraction

The codebase is structured for future extraction into reusable packages:

| Potential Package | Contents |
|-------------------|----------|
| **SelfieCameraKit** | Camera views, capture logic, preview components |
| **RingLightKit** | Ring light overlay, color presets, configuration |
| **PremiumKit** | Premium manager, gating utilities, paywall |
| **SyncedSettingsKit** | CloudSyncManager, settings model pattern |

---

## Key Dependencies

| Dependency | Purpose | Integration |
|------------|---------|-------------|
| **Bedrock** | Design system, branding, cloud sync | Local Swift package |
| **MijickCamera** | Camera capture and preview | SPM dependency |
| **RevenueCat** | Subscription management | SPM dependency |

---

## Code Quality Standards

- **No magic numbers**: All values from Design constants
- **Full accessibility**: Every interactive element has VoiceOver support
- **Protocol-first**: Shared behavior defined via protocols
- **Separation of concerns**: Views are dumb, ViewModels contain logic
- **Modern APIs**: Swift 6, async/await, @Observable
- **Documentation**: Code comments, README, implementation guides

---

## Known Issues / TODO

### Camera Control Button Light Press - NOT WORKING

**Status:** ❌ Broken - Needs Investigation

The Camera Control button (iPhone 16+) **full press works** for photo capture, but the **light press (secondary action) does NOT work**. 

Testing revealed that the "secondary" events in logs were actually triggered by **volume button**, not Camera Control light press. The volume button works because `onCameraCaptureEvent` handles all hardware capture buttons.

#### What Works:
- ✅ Camera Control full press → triggers photo capture
- ✅ Volume up/down → triggers secondary event (focus lock)

#### What Doesn't Work:
- ❌ Camera Control light press → no event received at all
- ❌ Camera Control swipe gestures (zoom) → Apple-exclusive API

#### User Action Required - Check Accessibility Settings:

**Settings > Accessibility > Camera Control**:
- Ensure **Camera Control** is enabled
- Ensure **Light-Press** is turned ON
- Adjust **Light-Press Force** if needed
- Check **Double Light-Press Speed**

These system settings may affect third-party apps differently than Apple Camera.

#### Investigation Areas:

1. **Accessibility settings may block third-party light press**
   - User reports light press works in Apple Camera but not SelfieCam
   - System may require explicit light-press enablement per-app

2. **MijickCamera session configuration**
   - The third-party camera framework may interfere with light press detection
   - MijickCamera manages its own AVCaptureSession - may conflict
   - Try testing with raw AVCaptureSession to isolate the issue

3. **`onCameraCaptureEvent` secondaryAction limitations**
   - The `secondaryAction` closure receives volume button events correctly
   - Camera Control light press may use different event pathway
   - Apple may internally route light press to their Camera app exclusively

4. **Light press may require AVCapturePhotoOutput configuration**
   - Secondary events might need specific photo output settings
   - Check if `AVCapturePhotoSettings` has light-press related properties

5. **Possible Apple restriction (most likely)**
   - Light press and swipe gestures appear restricted to first-party apps
   - Similar to swipe-to-zoom which is Apple-exclusive
   - No public API documentation confirms light press availability

---

## Future Enhancements

Potential areas for expansion:

- [ ] Real-time filters (beauty, color grading)
- [ ] Gesture-based capture (smile detection)
- [ ] Widget for quick camera access
- [ ] Apple Watch remote trigger
- [ ] Export presets (aspect ratios, watermarks)
- [ ] Social sharing integrations
- [ ] Camera Control button swipe-to-zoom (if Apple makes API public)

---

This architecture demonstrates production-quality SwiftUI development while delivering a polished, competitive user experience.