# Local Storage

The app uses multiple storage mechanisms to persist data locally for offline access and performance.

## Storage Overview

```
┌─────────────────────────────────────────┐
│             Local Storage               │
├─────────────────────────────────────────┤
│                                         │
│  ┌─────────────┐    ┌─────────────┐    │
│  │   Key-Value │    │   Database  │    │
│  │    Store    │    │   (Isar)    │    │
│  └─────────────┘    └─────────────┘    │
│                                         │
│  ┌─────────────┐    ┌─────────────┐    │
│  │   Image     │    │   Secure    │    │
│  │   Cache     │    │   Storage   │    │
│  └─────────────┘    └─────────────┘    │
│                                         │
└─────────────────────────────────────────┘
```

## Key-Value Store

Simple key-value storage for settings and small data.

### Store Service

The Store service provides typed access to stored values:

```
// Get a value with default
value = Store.get(StoreKey.themeMode, "system")

// Get a value (nullable)
value = Store.tryGet(StoreKey.accessToken)

// Save a value
Store.put(StoreKey.themeMode, "dark")

// Delete a value
Store.delete(StoreKey.accessToken)
```

### Store Keys

| Key | Type | Description |
|-----|------|-------------|
| version | Integer | Store schema version |
| assetETag | String | Last sync ETag |
| currentUser | User | Logged in user object |
| deviceId | String | Unique device identifier |
| deviceIdHash | Integer | Hashed device ID |
| serverUrl | String | Server URL |
| serverEndpoint | String | API endpoint URL |
| accessToken | String | Authentication token |
| autoBackup | Boolean | Auto backup enabled |
| backgroundBackup | Boolean | Background backup enabled |
| backupRequireWifi | Boolean | Require WiFi for backup |
| backupRequireCharging | Boolean | Require charging for backup |
| backupTriggerDelay | Integer | Minutes before backup starts |
| backupFailedSince | DateTime | When backup started failing |

### User Settings Keys

| Key | Type | Default | Description |
|-----|------|---------|-------------|
| loadPreview | Boolean | true | Load preview images |
| loadOriginal | Boolean | false | Load full resolution |
| themeMode | String | "system" | light/dark/system |
| primaryColor | String | Default | Theme accent color |
| dynamicTheme | Boolean | false | Use dynamic colors |
| colorfulInterface | Boolean | true | Colorful UI elements |
| tilesPerRow | Integer | 4 | Grid columns |
| dynamicLayout | Boolean | false | Dynamic grid layout |
| groupAssetsBy | Integer | 0 | Grouping mode |
| storageIndicator | Boolean | true | Show storage indicator |
| loopVideo | Boolean | true | Loop video playback |
| autoPlayVideo | Boolean | true | Auto-play videos |
| enableHapticFeedback | Boolean | true | Haptic feedback |

### Cache Size Keys

| Key | Type | Default | Description |
|-----|------|---------|-------------|
| thumbnailCacheSize | Integer | 10000 | Max thumbnail cache entries |
| imageCacheSize | Integer | 350 | Max preview cache entries |
| albumThumbnailCacheSize | Integer | 200 | Max album thumbnail entries |

## Database (Isar)

Embedded NoSQL database for structured data.

### Collections

#### Assets Collection

Stores all asset metadata:

```
Assets:
- id: Auto-increment primary key
- remoteId: Indexed (unique hash)
- localId: Indexed (unique hash)
- ownerId + checksum: Composite unique index
- All asset properties
```

**Indexes:**
- `remoteId` - Fast lookup by server ID
- `localId` - Fast lookup by device ID
- `ownerId, checksum` - Composite unique constraint

#### Albums Collection

Stores album information:

```
Albums:
- id: Auto-increment primary key
- remoteId: Indexed
- name, dates, ownership info
- Links to assets and users
```

#### Backup Albums Collection

Tracks device albums selected for backup:

```
BackupAlbum:
- id: Device album ID (primary key)
- name: Album name
- selection: include/exclude/none
- lastBackup: Last backup timestamp
```

#### Duplicated Assets Collection

Tracks already-uploaded assets:

```
DuplicatedAsset:
- id: Device asset ID
- Prevents re-upload of same file
```

#### ETag Collection

Stores sync ETags for incremental updates:

```
ETag:
- id: User ID
- assetCount: Number of assets
- time: Last sync time
```

#### Device Asset Collections

Platform-specific asset tracking:

**Android:**
```
AndroidDeviceAsset:
- id: Asset ID
- hash: Content hash
```

**iOS:**
```
IOSDeviceAsset:
- id: Asset ID
- hash: Content hash
- modifiedTime: Modification timestamp
```

### Database Operations

**Read Operations:**
```
// Find asset by remote ID
asset = db.assets.where().remoteIdEqualTo(id).findFirst()

// Get all assets for user
assets = db.assets.filter().ownerIdEqualTo(userId).findAll()

// Get assets in date range
assets = db.assets.filter()
  .fileCreatedAtBetween(start, end)
  .findAll()
```

**Write Operations:**
```
// Insert/update asset
db.writeTxn(() => db.assets.put(asset))

// Delete by remote IDs
db.writeTxn(() => db.assets.deleteAllByRemoteId(ids))

// Batch insert
db.writeTxn(() => db.assets.putAll(assets))
```

## Image Cache

Caches downloaded images for performance.

### Cache Layers

```
┌─────────────────┐
│  Memory Cache   │ ← Hot images (limited size)
├─────────────────┤
│   Disk Cache    │ ← Persistent storage
└─────────────────┘
```

### Cache Types

| Type | Purpose | Default Size |
|------|---------|--------------|
| Thumbnail | Grid view thumbnails | 10,000 entries |
| Preview | Full-screen previews | 350 entries |
| Album Thumbnail | Album cover images | 200 entries |

### Cache Management

**Clear All Cache:**
- Remove all cached thumbnails
- Remove all cached previews
- Free up storage space

**Cache Invalidation:**
- By asset ID when asset is deleted
- By album ID when album changes
- Manual clear from settings

## Secure Storage

For sensitive data that needs encryption.

### Stored Securely

| Data | Usage |
|------|-------|
| Access Token | Authentication |
| SSL Client Certificate | mTLS authentication |
| SSL Certificate Password | Certificate decryption |
| Custom Headers | Proxy authentication |

### SSL Client Certificate Storage

```
SSLClientCertStoreVal:
- data: Certificate binary (base64 encoded)
- password: Certificate password

Operations:
- save(): Persist to secure storage
- load(): Retrieve from secure storage
- delete(): Remove from secure storage
```

## Storage Location

### Per-Platform Paths

**Android:**
- Database: `/data/data/{app}/databases/`
- Cache: `/data/data/{app}/cache/`
- Secure: Android Keystore

**iOS:**
- Database: `~/Library/Application Support/`
- Cache: `~/Library/Caches/`
- Secure: iOS Keychain

## Data Migration

When upgrading the app, data may need migration:

### Version Tracking
- Store version in `StoreKey.version`
- Compare with expected version
- Run migration steps if needed

### Migration Steps
1. Read current version
2. Apply migrations sequentially
3. Update version number
4. Verify data integrity

## Cleanup Operations

### Free Up Space

Remove local copies of backed-up assets:

**Settings:**
- `cleanupKeepFavorites`: Keep favorite assets
- `cleanupKeepMediaType`: Keep photos/videos/both
- `cleanupKeepAlbumIds`: Keep assets in specific albums
- `cleanupCutoffDaysAgo`: Only remove older than X days

### Clear Cache

Remove cached images without affecting synced data:
- Thumbnails
- Previews
- Album covers

### Full Reset

Remove all local data:
1. Clear database
2. Clear cache
3. Clear settings
4. Return to login screen

---

[Previous: API Reference](api-reference.md) | [Next: Settings](settings.md)