### Install Dependencies

Source: https://github.com/googleapis/nodejs-firestore/blob/main/dev/CONTRIBUTING.md

Run this command to install all necessary project dependencies before running tests or making code changes.

```bash
npm install
```

--------------------------------

### Install the Firestore client library

Source: https://github.com/googleapis/nodejs-firestore/blob/main/README.md

Use npm to install the Firestore package in your Node.js project.

```bash
npm install @google-cloud/firestore
```

--------------------------------

### GET /document/get

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Retrieves the document snapshot for the current reference.

```APIDOC
## GET /document/get

### Description
Fetches the document snapshot from Firestore.

### Method
GET

### Response
#### Success Response (200)
- **DocumentSnapshot** (Object) - The snapshot containing the document data.
```

--------------------------------

### Perform CRUD operations with Firestore

Source: https://github.com/googleapis/nodejs-firestore/blob/main/README.md

Demonstrates initializing the Firestore client and performing set, update, get, and delete operations on a document.

```javascript
const {Firestore} = require('@google-cloud/firestore');

// Create a new client
const firestore = new Firestore();

async function quickstart() {
  // Obtain a document reference.
  const document = firestore.doc('posts/intro-to-firestore');

  // Enter new data into the document.
  await document.set({
    title: 'Welcome to Firestore',
    body: 'Hello World',
  });
  console.log('Entered new data into the document');

  // Update an existing document.
  await document.update({
    body: 'My first Firestore app',
  });
  console.log('Updated an existing document');

  // Read the document.
  const doc = await document.get();
  console.log('Read the document');

  // Delete the document.
  await document.delete();
  console.log('Deleted the document');
}
quickstart();
```

--------------------------------

### Perform Document Operations (Set, Get, Update, Delete)

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Manage documents using set(), get(), update(), and delete() methods. Use FieldValue for server timestamps, increments, array unions, and deletions. Supports merge options and preconditions.

```javascript
const {Firestore, FieldValue} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function documentOperations() {
  // Get a document reference
  const docRef = firestore.doc('users/user123');

  // Create or overwrite a document with set()
  await docRef.set({
    name: 'Alice',
    email: 'alice@example.com',
    createdAt: FieldValue.serverTimestamp(),
    tags: ['developer', 'admin']
  });

  // Merge data into existing document (doesn't overwrite entire doc)
  await docRef.set({
    lastLogin: FieldValue.serverTimestamp()
  }, { merge: true });

  // Merge only specific fields
  await docRef.set({
    name: 'Alice Smith',
    status: 'active'
  }, { mergeFields: ['name'] }); // Only 'name' is updated

  // Read a document
  const snapshot = await docRef.get();
  if (snapshot.exists) {
    console.log('Document data:', snapshot.data());
    console.log('Name field:', snapshot.get('name'));
    console.log('Created at:', snapshot.createTime.toDate());
  }

  // Update specific fields (document must exist)
  await docRef.update({
    'profile.bio': 'Software engineer',  // Nested field
    loginCount: FieldValue.increment(1),
    tags: FieldValue.arrayUnion('premium'),
    oldField: FieldValue.delete()
  });

  // Update with precondition
  await docRef.update({status: 'inactive'}, {
    lastUpdateTime: snapshot.updateTime
  });

  // Delete a document
  await docRef.delete();

  // Delete with precondition (only if document exists)
  await docRef.delete({ exists: true });
}
```

--------------------------------

### GET /transaction/get

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Retrieves a document or query result within the transaction.

```APIDOC
## GET /transaction/get

### Description
Retrieves a document snapshot or query snapshot within the transaction.

### Method
GET

### Parameters
#### Query Parameters
- **query/documentRef** (Query/DocumentReference) - Required - The query or document reference to fetch.
```

--------------------------------

### Timestamp Function

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Function to get the current server timestamp.

```APIDOC
## Timestamp Function

### Description
Returns the current server timestamp.

### Method
- `currentTimestamp(): FunctionExpression`
```

--------------------------------

### Array Access and Manipulation

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Functions for accessing, reversing, and getting the length of arrays.

```APIDOC
## arrayFirst

### Description
Gets the first element of an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayFirst(arrayExpression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayFirstN

### Description
Gets the first N elements of an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayFirstN(fieldName: string, n: number | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayGet

### Description
Gets an element from an array at a specific index.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayGet(arrayField: string, index: number | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayIndexOf

### Description
Finds the index of the first occurrence of a value in an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayIndexOf(fieldName: string, search: unknown | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayIndexOfAll

### Description
Finds the indices of all occurrences of a value in an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayIndexOfAll(fieldName: string, search: unknown | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayLast

### Description
Gets the last element of an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayLast(fieldName: string | arrayExpression: Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayLastIndexOf

### Description
Finds the index of the last occurrence of a value in an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayLastIndexOf(fieldName: string, search: unknown | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayLastN

### Description
Gets the last N elements of an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayLastN(fieldName: string, n: number | Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayLength

### Description
Gets the length of an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayLength(fieldName: string | array: Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```

## arrayReverse

### Description
Reverses the order of elements in an array.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "arrayReverse(fieldName: string | arrayExpression: Expression)"
}
```

### Response
#### Success Response (200)
- **FunctionExpression** (object) - A function expression representing the operation.

#### Response Example
```json
{
  "example": "FunctionExpression"
}
```
```

--------------------------------

### Run Sample Integration Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/CONTRIBUTING.md

Execute sample integration tests for the project.

```bash
# Run sample integration tests.
        npm run samples-test
```

--------------------------------

### Run Sample Integration Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/dev/CONTRIBUTING.md

Run integration tests that specifically target the sample code provided within the repository.

```bash
# Run sample integration tests.
npm run samples-test
```

--------------------------------

### GET /document/listCollections

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Lists all subcollections associated with this document reference.

```APIDOC
## GET /document/listCollections

### Description
Retrieves a list of all subcollections under this document.

### Method
GET

### Response
#### Success Response (200)
- **Array<CollectionReference>** (Array) - A list of subcollection references.
```

--------------------------------

### Implement Pagination with Query Cursors

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Uses startAt, startAfter, and endBefore methods to paginate through large datasets efficiently, including using document snapshots as cursors.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function paginationWithCursors() {
  const citiesRef = firestore.collection('cities');

  // Start at a specific field value
  const fromBoston = await citiesRef
    .orderBy('name')
    .startAt('Boston')
    .limit(10)
    .get();

  // Start after a specific field value
  const afterBoston = await citiesRef
    .orderBy('name')
    .startAfter('Boston')
    .limit(10)
    .get();

  // End before/at specific values
  const beforeMiami = await citiesRef
    .orderBy('name')
    .endBefore('Miami')
    .get();

  // Paginate using document snapshots (most reliable method)
  const firstPage = await citiesRef
    .orderBy('population', 'desc')
    .limit(25)
    .get();

  // Get cursor for next page
  const lastDoc = firstPage.docs[firstPage.docs.length - 1];

  // Fetch next page starting after the last document
  const secondPage = await citiesRef
    .orderBy('population', 'desc')
    .startAfter(lastDoc)
    .limit(25)
    .get();

  // Multiple orderBy fields with corresponding cursor values
  const multiFieldCursor = await citiesRef
    .orderBy('state')
    .orderBy('population', 'desc')
    .startAt('California', 1000000)
    .limit(10)
    .get();
}
```

--------------------------------

### Execute a Firestore Pipeline query

Source: https://github.com/googleapis/nodejs-firestore/blob/main/README.md

Demonstrates how to initialize a Firestore client, add documents to a collection, and execute a pipeline query that filters, sorts, and transforms data.

```javascript
const {Firestore} = require('@google-cloud/firestore');

// Require/import Pipelines from '@google-cloud/firestore/pipelines'
const {field} = require('@google-cloud/firestore/pipelines');

// Create a new client
const firestore = new Firestore({
  projectId: 'firestore-sdk-nightly',
  databaseId: 'enterprise'
});

async function pipelinesQuickstart() {
  // Obtain a collection reference.
  const collection = firestore.collection('books');

  // Enter new documents into the document.
  await collection.add({
    "title": "Whispers of the Cobalt Sea",
    "price": 12.99,
    "author": "Elara Vance",
    "yearPublished": 2023
  });
  await collection.add({
    "title": "The Antigravity Cat's Guide to Napping",
    "price": 24.50,
    "author": "Mittens the IV",
    "yearPublished": 2026
  });
  console.log('Entered new documents into the collection.');

  // Define a Pipeline query that selects books published this century,
  // orders them by price, and computes a discounted price (20% off).
  const pipeline = firestore.pipeline().collection('books')
      .where(field('yearPublished').greaterThanOrEqual(2000))
      .sort(field('price').ascending())
      .select('title', 'author', field('price').multiply(0.8).as('discountedPrice'));

  // Execute the pipeline
  const pipelineSnapshot = await pipeline.execute();
  console.log('Executed the Pipeline.');

  console.log('Results:');
  pipelineSnapshot.results.forEach(pipelineResult=> {
    console.log(pipelineResult.data());
  });
}
pipelinesQuickstart();
```

--------------------------------

### Run Unit Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/CONTRIBUTING.md

Execute unit tests for the project.

```bash
# Run unit tests.
        npm test
```

--------------------------------

### Firestore Client Initialization

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Initializes a new Firestore client instance with optional settings.

```APIDOC
## Firestore Client Constructor

### Description
Initializes a new Firestore client instance. Optional settings can be provided to configure the client.

### Method
Constructor

### Parameters
#### Request Body
- **settings** (firestore.Settings) - Optional - Configuration settings for the Firestore client.
```

--------------------------------

### Get Buffered Operations Count

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Retrieves the number of operations currently buffered by the BulkWriter. This is an internal method.

```typescript
_getBufferedOperationsCount(): number;
```

--------------------------------

### Initialize Firestore Client

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Initialize the Firestore client using Application Default Credentials or explicit configuration with project ID and key file.

```javascript
const {Firestore} = require('@google-cloud/firestore');

// Using Application Default Credentials
const firestore = new Firestore();
```

```javascript
// With explicit configuration
const firestoreWithConfig = new Firestore({
  projectId: 'your-project-id',
  keyFilename: '/path/to/service-account.json',
  databaseId: 'my-database', // Optional: for named databases
  preferRest: true,          // Optional: use HTTP/1.1 REST transport
  ignoreUndefinedProperties: true, // Optional: skip undefined values
  useBigInt: true            // Optional: use BigInt for integers
});
```

--------------------------------

### Run System Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/CONTRIBUTING.md

Execute all system tests for the project.

```bash
# Run all system tests.
        npm run system-test
```

--------------------------------

### Query.explain

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Executes the query and returns the query plan and execution statistics.

```APIDOC
## explain

### Description
Executes the query and returns the query plan and execution statistics.

### Parameters
#### Request Body
- **options** (firestore.ExplainOptions) - Optional - Configuration options for the explain operation.

### Response
#### Success Response (200)
- **result** (Promise<ExplainResults<QuerySnapshot>>) - The query plan and execution results.
```

--------------------------------

### Run System Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/dev/CONTRIBUTING.md

Execute comprehensive system tests to ensure the library functions correctly within a complete environment.

```bash
# Run all system tests.
npm run system-test
```

--------------------------------

### Run Unit Tests

Source: https://github.com/googleapis/nodejs-firestore/blob/main/dev/CONTRIBUTING.md

Execute unit tests to verify the correctness of individual code components.

```bash
# Run unit tests.
npm test
```

--------------------------------

### Create Firestore Bundle

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Packages query results and documents into a bundle for offline use. Add named queries and individual documents to the bundle before building and saving it.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const fs = require('fs');

const firestore = new Firestore();

async function createBundle() {
  // Create a bundle with a unique ID
  const bundle = firestore.bundle('my-app-bundle');

  // Add a named query
  const topProductsQuery = firestore
    .collection('products')
    .orderBy('sales', 'desc')
    .limit(50);
  const topProductsSnapshot = await topProductsQuery.get();
  bundle.add('top-products', topProductsSnapshot);

  // Add individual documents
  const featuredDoc = await firestore.doc('featured/current').get();
  bundle.add(featuredDoc);

  // Add another query
  const categoriesSnapshot = await firestore.collection('categories').get();
  bundle.add('all-categories', categoriesSnapshot);

  // Build the bundle (returns a Buffer)
  const bundleBuffer = bundle.build();

  // Save to file or serve via HTTP
  fs.writeFileSync('app-bundle.txt', bundleBuffer);

  // Or send as HTTP response
  // res.set('Content-Type', 'application/octet-stream');
  // res.send(bundleBuffer);

  console.log(`Bundle created: ${bundleBuffer.length} bytes`);
}
```

--------------------------------

### Perform Collection Operations (Add and List Documents)

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Add documents with auto-generated IDs using add(), list documents with listDocuments(), and access subcollections. Also shows listing root and subcollections.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function collectionOperations() {
  const usersRef = firestore.collection('users');

  // Add a document with auto-generated ID
  const newDocRef = await usersRef.add({
    name: 'Bob',
    email: 'bob@example.com',
    createdAt: new Date()
  });
  console.log('Added document with ID:', newDocRef.id);

  // Get a specific document in the collection
  const userDoc = usersRef.doc('specific-user-id');

  // List all documents (including missing documents with subcollections)
  const documentRefs = await usersRef.listDocuments();
  for (const docRef of documentRefs) {
    const doc = await docRef.get();
    console.log(doc.id, doc.exists ? doc.data() : 'missing');
  }

  // Access subcollection
  const postsRef = firestore.collection('users/user123/posts');

  // List root collections
  const collections = await firestore.listCollections();
  collections.forEach(col => console.log('Collection:', col.id));

  // List subcollections of a document
  const docRef = firestore.doc('users/user123');
  const subcollections = await docRef.listCollections();
  subcollections.forEach(col => console.log('Subcollection:', col.id));
}
```

--------------------------------

### Create a Document

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Creates a new document with the specified data at the given document reference. This operation is asynchronous and returns a Promise resolving to a WriteResult.

```typescript
create<AppModelType, DbModelType extends firestore.DocumentData>(documentRef: firestore.DocumentReference<AppModelType, DbModelType>, data: firestore.WithFieldValue<AppModelType>): Promise<WriteResult>;
```

--------------------------------

### Lint and Fix Code

Source: https://github.com/googleapis/nodejs-firestore/blob/main/CONTRIBUTING.md

Run the linter and attempt to automatically fix any style issues.

```bash
# Lint (and maybe fix) any changes:

        npm run fix
```

--------------------------------

### Create Document

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Creates a new document with the provided data. This operation is atomic and will only succeed if the document does not already exist.

```APIDOC
## POST /documents/{collectionId}/{documentId}

### Description
Creates a new document with the provided data. This operation is atomic and will only succeed if the document does not already exist.

### Method
POST

### Endpoint
/documents/{collectionId}/{documentId}

### Parameters
#### Path Parameters
- **collectionId** (string) - Required - The ID of the collection to create the document in.
- **documentId** (string) - Required - The ID of the document to create.

#### Request Body
- **data** (object) - Required - The data to write to the document.

### Request Example
```json
{
  "data": {
    "field1": "value1",
    "field2": 123
  }
}
```

### Response
#### Success Response (200)
- **writeTime** (Timestamp) - The time at which the write was committed.

#### Response Example
```json
{
  "writeTime": "2023-10-27T10:00:00Z"
}
```
```

--------------------------------

### Perform Simple Queries with Filters, Sorting, and Pagination

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Demonstrates basic Firestore query operations including equality checks, array membership, range comparisons, ordering, and limiting results.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function simpleQueries() {
  const usersRef = firestore.collection('users');

  // Simple equality query
  const activeUsers = await usersRef
    .where('status', '==', 'active')
    .get();

  // Comparison operators: <, <=, ==, !=, >=, >
  const recentUsers = await usersRef
    .where('createdAt', '>', new Date('2024-01-01'))
    .get();

  // Array contains
  const admins = await usersRef
    .where('roles', 'array-contains', 'admin')
    .get();

  // Array contains any (OR for array membership)
  const staffOrAdmin = await usersRef
    .where('roles', 'array-contains-any', ['staff', 'admin'])
    .get();

  // In query (field equals any value in list)
  const specificStatuses = await usersRef
    .where('status', 'in', ['active', 'pending'])
    .get();

  // Not in query
  const notDeleted = await usersRef
    .where('status', 'not-in', ['deleted', 'banned'])
    .get();

  // Order and limit
  const topUsers = await usersRef
    .orderBy('score', 'desc')
    .limit(10)
    .get();

  // Get last N results (requires orderBy)
  const bottomUsers = await usersRef
    .orderBy('score', 'asc')
    .limitToLast(5)
    .get();

  // Pagination with offset
  const page2 = await usersRef
    .orderBy('name')
    .offset(20)
    .limit(10)
    .get();

  // Process results
  topUsers.forEach(doc => {
    console.log(doc.id, doc.data());
  });
  console.log('Total results:', topUsers.size);
  console.log('Empty?', topUsers.empty);
}
```

--------------------------------

### PlanSummary Class

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Represents a summary of a query plan.

```APIDOC
## PlanSummary Class

### Description
Represents a summary of a query plan.

### Constructor
(Undocumented)
```

--------------------------------

### Utility Functions

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Utility functions for setting logging and handling timestamps.

```APIDOC
## setLogFunction

### Description
Sets a custom function for logging messages.

### Method
`setLogFunction(logger: ((msg: string) => void) | null): void`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
None

#### Response Example
None
```

```APIDOC
## Timestamp

### Description
Represents a point in time.

### Method
`constructor(seconds: number, nanoseconds: number)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### POST /transaction/create

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Creates a new document in the transaction.

```APIDOC
## POST /transaction/create

### Description
Creates a new document within the current transaction context.

### Method
POST

### Parameters
#### Request Body
- **documentRef** (firestore.DocumentReference) - Required - The reference to the document to create.
- **data** (firestore.WithFieldValue) - Required - The data to write to the document.
```

--------------------------------

### Expression Functions

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

A collection of beta functions for creating expressions, including comparisons, conditional logic, and data manipulation.

```APIDOC
## Expression Functions

### Comparison Functions
- **greaterThan(left, right)**: Creates a greater-than expression.
- **greaterThanOrEqual(left, right)**: Creates a greater-than-or-equal expression.

### Conditional Functions
- **ifAbsent(ifExpr, elseExpr)**: Returns the else expression if the if expression is absent.
- **ifError(tryExpr, catchExpr)**: Handles errors within expressions.

### Utility Functions
- **isAbsent(value)**: Checks if a value is absent.
- **isError(value)**: Checks if an expression resulted in an error.
- **isType(fieldName, type)**: Checks if a field matches a specific type.
- **join(array, delimiter)**: Joins an array field or expression with a delimiter.
- **last(expression)**: Aggregate function to get the last value.
- **length_2(expression)**: Function to get the length of a field or expression.
```

--------------------------------

### ExplainResults Class

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Contains the results of an explained query, including both the metrics and the query snapshot.

```APIDOC
## ExplainResults<T>

### Description
Encapsulates the metrics and the resulting snapshot from an explained Firestore query.

### Properties
- **metrics** (ExplainMetrics) - The metrics collected during query execution.
- **snapshot** (T | null) - The query snapshot result.
```

--------------------------------

### WriteBatch API

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Provides methods to create and manage batched write operations.

```APIDOC
## WriteBatch API

### Description
Returns a `WriteBatch` object that can be used to perform atomic writes.

### Method
batch()

### Endpoint
N/A (Instance method)

### Response
#### Success Response (200)
- **WriteBatch** - An object representing a batch of writes.
```

--------------------------------

### Configure Logging and Handle gRPC Errors

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Use setLogFunction to toggle SDK logging and switch statements to handle specific gRPC error codes during document operations.

```javascript
const {Firestore, setLogFunction, GrpcStatus} = require('@google-cloud/firestore');

// Enable logging
setLogFunction((msg) => {
  console.log(`[Firestore] ${msg}`);
});

// Disable logging
setLogFunction(null);

const firestore = new Firestore();

async function errorHandling() {
  try {
    await firestore.doc('users/user123').get();
  } catch (error) {
    // Check gRPC status codes
    switch (error.code) {
      case GrpcStatus.NOT_FOUND:
        console.log('Document not found');
        break;
      case GrpcStatus.PERMISSION_DENIED:
        console.log('Access denied - check security rules');
        break;
      case GrpcStatus.UNAVAILABLE:
        console.log('Service unavailable - retry later');
        break;
      case GrpcStatus.DEADLINE_EXCEEDED:
        console.log('Request timed out');
        break;
      case GrpcStatus.RESOURCE_EXHAUSTED:
        console.log('Quota exceeded - implement backoff');
        break;
      default:
        console.log('Unknown error:', error.message);
    }
  }

  // Graceful shutdown
  process.on('SIGTERM', async () => {
    console.log('Shutting down...');
    await firestore.terminate();
    process.exit(0);
  });
}
```

--------------------------------

### Perform high-throughput parallel writes with BulkWriter

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Use BulkWriter for efficient data migrations and bulk updates. It supports automatic batching, custom throttling, and granular error handling.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function bulkWriterExample() {
  // Create a BulkWriter with custom throttling
  const bulkWriter = firestore.bulkWriter({
    throttling: {
      initialOpsPerSecond: 500,
      maxOpsPerSecond: 1000
    }
  });

  // Track successes and failures
  bulkWriter.onWriteResult((documentRef, result) => {
    console.log(`Wrote ${documentRef.path} at ${result.writeTime.toDate()}`);
  });

  bulkWriter.onWriteError((error) => {
    if (error.failedAttempts < 3) {
      console.log(`Retrying ${error.documentRef.path}...`);
      return true;  // Retry the operation
    }
    console.error(`Failed to write ${error.documentRef.path}:`, error.message);
    return false;   // Don't retry
  });

  // Queue write operations (don't await individual operations)
  for (let i = 0; i < 10000; i++) {
    const docRef = firestore.collection('items').doc(`item${i}`);

    bulkWriter.create(docRef, {
      index: i,
      value: Math.random()
    }).then(result => {
      // Optional: handle individual success
    }).catch(error => {
      // Optional: handle individual failure
    });
  }

  // Flush pending writes (optional - useful for checkpoints)
  await bulkWriter.flush();

  // Close and wait for all operations to complete
  await bulkWriter.close();
  console.log('All writes completed');
}
```

--------------------------------

### Set Document

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Sets data to a document. If the document does not exist, it will be created. If the document exists, its contents will be overwritten unless merge options are provided.

```APIDOC
## POST /documents/{collectionId}/{documentId}

### Description
Sets data to a document. If the document does not exist, it will be created. If the document exists, its contents will be overwritten unless merge options are provided.

### Method
POST

### Endpoint
/documents/{collectionId}/{documentId}

### Parameters
#### Path Parameters
- **collectionId** (string) - Required - The ID of the collection containing the document.
- **documentId** (string) - Required - The ID of the document to set.

#### Request Body
- **data** (object) - Required - The data to write to the document.
- **options** (object) - Optional - Options for the set operation.
  - **merge** (boolean) - If true, only update the fields specified in the data, merging with existing fields.
  - **mergeFields** (array) - An array of field paths to merge.

### Request Example
```json
{
  "data": {
    "field1": "value1",
    "field2": 123
  },
  "options": {
    "merge": true
  }
}
```

### Response
#### Success Response (200)
- **writeTime** (Timestamp) - The time at which the write was committed.

#### Response Example
```json
{
  "writeTime": "2023-10-27T10:00:00Z"
}
```
```

--------------------------------

### PipelineSource Class

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Provides methods to create and manage Firestore pipelines.

```APIDOC
## PipelineSource Class

### Description
Provides methods to create and manage Firestore pipelines.

### Constructor
`constructor(db: Firestore)`

### Methods
- **collection(collection: string | firestore.CollectionReference): Pipeline**
  Starts a pipeline from a collection reference.
- **collection(options: firestore.Pipelines.CollectionStageOptions): Pipeline**
  Starts a pipeline from a collection reference with options.
- **collectionGroup(collectionId: string): Pipeline**
  Starts a pipeline from a collection group.
- **collectionGroup(options: firestore.Pipelines.CollectionGroupStageOptions): Pipeline**
  Starts a pipeline from a collection group with options.
- **createFrom(query: firestore.VectorQuery): Pipeline**
  Creates a pipeline from a vector query.
- **createFrom(query: firestore.Query): Pipeline**
  Creates a pipeline from a query.
- **database(): Pipeline**
  Starts a pipeline from the database root.
- **database(options: firestore.Pipelines.DatabaseStageOptions): Pipeline**
  Starts a pipeline from the database root with options.
- **documents(docs: Array<string | DocumentReference>): Pipeline**
  Starts a pipeline from a list of document references.
- **documents(options: firestore.Pipelines.DocumentsStageOptions): Pipeline**
  Starts a pipeline from a list of document references with options.
- **_validateReference(reference: firestore.CollectionReference | firestore.DocumentReference): reference is CollectionReference | DocumentReference**
  Validates a reference to be a CollectionReference or DocumentReference.
```

--------------------------------

### Query Methods

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Methods for constructing and executing Firestore queries.

```APIDOC
## select(...fieldPaths)

### Description
Creates and returns a new Query that only returns the specified fields.

### Parameters
#### Path Parameters
- **fieldPaths** (Array<string | FieldPath>) - Required - The fields to include in the result.

## startAfter(...fieldValuesOrDocumentSnapshot)

### Description
Creates and returns a new Query that starts after the provided document or field values.

### Parameters
#### Path Parameters
- **fieldValuesOrDocumentSnapshot** (Array<unknown>) - Required - The values or snapshot to start after.

## startAt(...fieldValuesOrDocumentSnapshot)

### Description
Creates and returns a new Query that starts at the provided document or field values.

### Parameters
#### Path Parameters
- **fieldValuesOrDocumentSnapshot** (Array<unknown>) - Required - The values or snapshot to start at.

## stream()

### Description
Executes the query and returns a readable stream of the results.

### Response
- **NodeJS.ReadableStream** - A stream of document results.

## where(fieldPath, opStr, value)

### Description
Creates and returns a new Query with an additional filter.

### Parameters
#### Path Parameters
- **fieldPath** (string | FieldPath) - Required - The field to filter by.
- **opStr** (firestore.WhereFilterOp) - Required - The comparison operator.
- **value** (unknown) - Required - The value to compare against.

## withConverter(converter)

### Description
Applies a custom data converter to the query.

### Parameters
#### Path Parameters
- **converter** (firestore.FirestoreDataConverter | null) - Required - The converter to apply.
```

--------------------------------

### Ordering and Aggregation Functions

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Functions for defining order and performing average aggregations.

```APIDOC
## ascending

### Description
Defines an ascending order for a field or expression.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "ascending(expr: Expression | fieldName: string)"
}
```

### Response
#### Success Response (200)
- **Ordering** (object) - An object representing the ascending order.

#### Response Example
```json
{
  "example": "Ordering"
}
```

## average

### Description
Calculates the average of values.

### Method
function

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "average(expression: Expression | fieldName: string)"
}
```

### Response
#### Success Response (200)
- **AggregateFunction** (object) - An object representing the average aggregation.

#### Response Example
```json
{
  "example": "AggregateFunction"
}
```
```

--------------------------------

### Listen to Document and Query Changes with onSnapshot

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Use `onSnapshot` to receive real-time updates for a single document or query results. Remember to unsubscribe from listeners when they are no longer needed to prevent memory leaks.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

function realtimeListeners() {
  // Listen to a single document
  const userRef = firestore.doc('users/user123');
  const unsubscribeDoc = userRef.onSnapshot(
    (snapshot) => {
      if (snapshot.exists) {
        console.log('User data:', snapshot.data());
      } else {
        console.log('User deleted');
      }
    },
    (error) => {
      console.error('Listener error:', error);
    }
  );

  // Listen to a query
  const activeUsersQuery = firestore
    .collection('users')
    .where('status', '==', 'online');

  const unsubscribeQuery = activeUsersQuery.onSnapshot(
    (snapshot) => {
      console.log(`${snapshot.size} users online`);

      // Track changes since last snapshot
      snapshot.docChanges().forEach(change => {
        if (change.type === 'added') {
          console.log('User came online:', change.doc.id);
        }
        if (change.type === 'modified') {
          console.log('User updated:', change.doc.id);
        }
        if (change.type === 'removed') {
          console.log('User went offline:', change.doc.id);
        }
      });
    },
    (error) => {
      console.error('Query listener error:', error);
    }
  );

  // Unsubscribe when done (important to prevent memory leaks)
  // unsubscribeDoc();
  // unsubscribeQuery();
}
```

--------------------------------

### Explain Firestore Query

Source: https://context7.com/googleapis/nodejs-firestore/llms.txt

Analyzes Firestore query execution plans with or without statistics. Use 'analyze: true' for detailed execution metrics and result counts.

```javascript
const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

async function queryExplain() {
  const query = firestore
    .collection('users')
    .where('status', '==', 'active')
    .where('age', '>=', 18)
    .orderBy('age')
    .limit(100);

  // Get query plan without executing
  const planOnly = await query.explain();
  console.log('Query plan:', planOnly.planSummary);

  // Get plan with execution statistics
  const withStats = await query.explain({ analyze: true });
  console.log('Plan:', withStats.planSummary);
  console.log('Execution stats:', withStats.executionStats);
  console.log('Results:', withStats.snapshot?.size);

  // Stream results with explain metrics
  const stream = query.explainStream({ analyze: true });
  stream.on('data', (data) => {
    if (data.document) {
      console.log('Document:', data.document.id);
    }
    if (data.metrics) {
      console.log('Metrics:', data.metrics);
    }
  });
}
```

--------------------------------

### ExplainMetrics Class

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Provides metrics regarding the execution of a Firestore query, including plan summaries and execution statistics.

```APIDOC
## ExplainMetrics

### Description
Represents the metrics associated with a Firestore query execution plan.

### Properties
- **executionStats** (ExecutionStats | null) - Statistics regarding the query execution duration and operations.
- **planSummary** (PlanSummary) - A summary of the query execution plan.
```

--------------------------------

### QueryPartition

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Represents a partition of a query, used for paginating query results.

```APIDOC
## QueryPartition

### Description
Represents a partition of a Firestore query. This class is typically used internally for paginating query results, especially when dealing with large datasets.

### Properties
- **endBefore** (unknown[] | undefined) - The cursor indicating the end of the partition (exclusive).
- **startAt** (unknown[] | undefined) - The cursor indicating the start of the partition (inclusive).

### Methods
- **toQuery()** (Query) - Converts this query partition back into a `Query` object.

### Example
```typescript
// This class is usually managed internally by Firestore SDK for pagination.
// Example of how it might be conceptually used:
// const queryPartition = new QueryPartition(firestore, 'myCollection', converter, startAtCursor, endBeforeCursor);
// const query = queryPartition.toQuery();
```
```

--------------------------------

### POST /document/set

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Writes data to the document reference, either overwriting or merging with existing data.

```APIDOC
## POST /document/set

### Description
Sets data on the document. If the document does not exist, it will be created.

### Method
POST

### Parameters
#### Request Body
- **data** (Object) - Required - The data to write to the document.
- **options** (Object) - Optional - Configuration options such as merge.
```

--------------------------------

### VectorQueryOptions Interface

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Defines the options for configuring a vector query.

```APIDOC
## VectorQueryOptions Interface

### Description
Options used to configure a vector search query.

### Fields

- **distanceMeasure** (string) - Required - The distance measure to use ('EUCLIDEAN', 'COSINE', 'DOT_PRODUCT').
- **distanceResultField** (string | firestore.FieldPath) - Optional - The field to store the calculated distance in.
- **distanceThreshold** (number) - Optional - The threshold for the distance measure.
- **limit** (number) - Required - The maximum number of results to return.
- **queryVector** (firestore.VectorValue | Array<number>) - Required - The vector to query with.
- **vectorField** (string | firestore.FieldPath) - Required - The field containing the vectors to search against.
```

--------------------------------

### Pipeline Class Methods

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Methods for constructing and executing Firestore aggregation pipelines.

```APIDOC
## Pipeline Class

### Description
The Pipeline class allows for the construction of complex data aggregation and transformation pipelines in Firestore.

### Methods
- **addFields**(field: Selectable, ...additionalFields: Selectable[]): Pipeline
- **aggregate**(accumulator: AliasedAggregate, ...additionalAccumulators: AliasedAggregate[]): Pipeline
- **distinct**(group: string | Selectable, ...additionalGroups: Array<string | Selectable>): Pipeline
- **execute**(pipelineExecuteOptions?: PipelineExecuteOptions): Promise<PipelineSnapshot>
- **findNearest**(options: FindNearestStageOptions): Pipeline
- **limit**(limit: number): Pipeline
- **offset**(offset: number): Pipeline
- **removeFields**(fieldValue: Field | string, ...additionalFields: Array<Field | string>): Pipeline
- **replaceWith**(expr: Expression | string): Pipeline
- **sample**(documents: number): Pipeline
- **select**(selection: Selectable | string, ...additionalSelections: Array<Selectable | string>): Pipeline
```

--------------------------------

### PipelineSnapshot Class

Source: https://github.com/googleapis/nodejs-firestore/blob/main/api-report/firestore.api.md

Represents a snapshot of a pipeline's execution, including results and execution time.

```APIDOC
## PipelineSnapshot Class

### Description
Represents a snapshot of a pipeline's execution, including results and execution time.

### Constructor
`constructor(pipeline: Pipeline, results: PipelineResult[], executionTime?: Timestamp, explainStats?: ExplainStats)`

### Properties
- **executionTime** (Timestamp) - The time the pipeline execution finished.
- **explainStats** (ExplainStats | undefined) - Optional statistics from the explain plan.
- **pipeline** (Pipeline) - The pipeline object.
- **results** (PipelineResult[]) - An array of results from the pipeline execution.
```