# Firestore Enterprise Native Mode on iOS

This guide walks you through using the Cloud Firestore SDK in your iOS app using
Swift.

# ⛔️ CRITICAL RULE: NO FirebaseFirestoreSwift ⛔️

UNDER NO CIRCUMSTANCES should you import, link against, or configure a project
to use `FirebaseFirestoreSwift`.

As of Firebase SDK v11+, all Swift-specific features (including `@DocumentID`,
`@ServerTimestamp`, and `Codable` support) have been fully merged into the main
`FirebaseFirestore` module.

- NEVER add `.external(name: "FirebaseFirestoreSwift")` or similar to SPM or
  Xcode configurations.
- NEVER write `import FirebaseFirestoreSwift` in any Swift file.
- ONLY use `import FirebaseFirestore`.

This is a zero-tolerance constraint. Using `FirebaseFirestoreSwift` is
fundamentally incorrect and unacceptable.

# ⛔️ CRITICAL RULE: NO INLINE INITIALIZATION ⛔️

NEVER write `let db = Firestore.firestore()` or `Firestore.firestore(database:)`
as an inline class or struct property if there is ANY chance the object is
instantiated before `FirebaseApp.configure()` executes in the app root.

- **FATAL CRASH:**
  `@Observable class DataManager { let db = Firestore.firestore() }` initialized
  as a `@State` in the App root.
- **SAFE PATTERN:** Initialize `Firestore.firestore()` lazily
  (`lazy var db = Firestore.firestore()`) OR explicitly initialize the manager
  *after* `FirebaseApp.configure()` finishes.

## 1. Import and Initialize

Ensure you have installed the `FirebaseFirestore` SDK. Use the
`xcode-project-setup` skill to automate adding the SPM dependency to the Xcode
project.

```swift
import FirebaseFirestore
```

Initialize an instance of Cloud Firestore. **CRITICAL**: Enterprise databases
require a custom database ID and cannot use the `(default)` instance.

```swift
// Replace "your-enterprise-database-id" with your actual database ID
let db = Firestore.firestore(database: "your-enterprise-database-id")
```

## 2. Type-Safe Data Models (Codable)

To leverage modern Swift data modeling, define your data as `Codable` structs.
The main `FirebaseFirestore` module automatically supports mapping these types.

```swift
struct User: Codable {
    @DocumentID var id: String?
    var firstName: String
    var lastName: String
    var born: Int
}
```

## 3. Basic CRUD Operations

The operations are identical to standard Firestore, but ensure you use the `db`
instance initialized with your Enterprise database ID.

### Writing Data (Modern Concurrency & Codable)

```swift
let user = User(firstName: "Ada", lastName: "Lovelace", born: 1815)

do {
    // Add a new document with a generated ID using Codable
    let ref = try db.collection("users").addDocument(from: user)
    print("Document added with ID: \(ref.documentID)")
} catch {
    print("Error adding document: \(error)")
}
```

### Reading Data (Modern Concurrency & Codable)

```swift
do {
    let querySnapshot = try await db.collection("users").getDocuments()
    
    // Map documents to the User struct automatically
    let users = querySnapshot.documents.compactMap { document in
        try? document.data(as: User.self)
    }
    
    for user in users {
        print("Found user: \(user.firstName) \(user.lastName)")
    }
} catch {
    print("Error getting documents: \(error)")
}
```

## 4. Pipeline Queries

Firestore Enterprise supports Pipeline operations for complex queries.

### Initialization

```swift
let pipeline = db.pipeline()
```

### Examples

```swift
// Return all documents across all collections in the database
let results = try await db.pipeline().database().execute()

// Filtered query
let results = try await db.pipeline()
    .collection("cities")
    .where(Field("name").equal(Constant("Toronto")))
    .execute()

// Compound query
let results = try await db.pipeline()
    .collection("books")
    .where(Field("rating").equal(5) && Field("published").lessThan(1900))
    .execute()
```

## 5. Realtime Listeners in SwiftUI (Lifecycle Best Practices)

When implementing Firestore realtime listeners (`addSnapshotListener`) within a
SwiftUI application, you **MUST** tie the listener lifecycle to the view's
identity using `.task(id:)`, NOT `.onDisappear`.

### ⛔️ UNSAFE PATTERN (.onDisappear)

Presenting a `.sheet` or `.fullScreenCover` can trigger the underlying view's
`onDisappear` method. If you stop your listener here, the feed will stop
updating while the sheet is open, and won't resume when it's dismissed.

### ✅ SAFE PATTERN (.task with deinit)

Because `addSnapshotListener` is a synchronous call, placing it inside a `.task`
means the task completes immediately. This breaks SwiftUI's automatic
cancellation mechanism.

To safely manage traditional Firebase listeners in SwiftUI, you must use
**`deinit`** to handle memory cleanup when the view is destroyed, and
**`.task(id:)`** to handle data identity changes while the view is active.

```swift
import SwiftUI
import FirebaseFirestore

@MainActor
@Observable 
final class DataManager {
    private var listenerHandle: ListenerRegistration?
    var data: [String] = []
    
    func startListening(for userId: String) {
        // 1. Clean up any existing listener to prevent duplicates if the ID changes
        stopListening()
        
        // 2. Start the regular listener and capture the handle
        // Note: Using the global default instance here, make sure to use your enterprise instance if applicable
        // For enterprise, you might need to pass the db instance or use a shared manager.
        listenerHandle = Firestore.firestore(database: "your-enterprise-database-id").collection("users").document(userId).addSnapshotListener { snapshot, error in
            // Handle updates
        }
    }
    
    func stopListening() {
        listenerHandle?.remove()
        listenerHandle = nil
    }
    
    // 3. Guarantee cleanup when the View is destroyed and this object is deallocated
    isolated deinit {
        stopListening()
    }
}
```