add arrayReverse

Author: cherylEnkidu

Firestore/Swift/Source/ExpressionImplementation.swift

@@ -71,6 +71,10 @@ public extension Expression {
 
   // MARK: Array Operations
 
+  func arrayReverse() -> FunctionExpression {
+    return FunctionExpression("array_reverse", [self])
+  }
+
   func arrayConcat(_ arrays: [Expression]) -> FunctionExpression {
     return FunctionExpression("array_concat", [self] + arrays)
   }

Firestore/Swift/Source/SwiftAPI/Pipeline/Expressions/Expression.swift

@@ -187,6 +187,16 @@ public protocol Expression: Sendable {
 
   // --- Added Array Operations ---
 
+  /// Creates an expression that returns the `input` with elements in reverse order.
+  ///
+  /// ```swift
+  /// // Reverse the "tags" array.
+  /// Field("tags").arrayReverse()
+  /// ```
+  ///
+  /// - Returns: A new `FunctionExpression` representing the reversed array.
+  func arrayReverse() -> FunctionExpression
+
   /// Creates an expression that concatenates an array expression (from `self`) with one or more
   /// other array expressions.
   /// Assumes `self` and all parameters evaluate to arrays.

Firestore/Swift/Source/SwiftAPI/Pipeline/Expressions/FunctionExpressions/BooleanExpression.swift

@@ -52,7 +52,7 @@ public class BooleanExpression: FunctionExpression, @unchecked Sendable {
   /// ```
   ///
   /// - Returns: An `AggregateFunction` that performs the conditional count.
-  internal func countIf() -> AggregateFunction {
+  func countIf() -> AggregateFunction {
     return AggregateFunction("count_if", [self])
   }
 

Firestore/Swift/Tests/Integration/PipelineTests.swift

@@ -1761,6 +1761,32 @@ class PipelineIntegrationTests: FSTIntegrationTestCase {
     XCTAssertEqual(snapshot.results.count, 10)
   }
 
+  func testArrayReverseWorks() async throws {
+    let collRef = collectionRef(withDocuments: [
+      "doc1": ["tags": ["a", "b", "c"]],
+      "doc2": ["tags": [1, 2, 3]],
+      "doc3": ["tags": []],
+    ])
+    let db = collRef.firestore
+
+    let pipeline = db.pipeline()
+      .collection(collRef.path)
+      .select([
+        Field("tags").arrayReverse().as("reversedTags"),
+      ])
+      .sort([Field("reversedTags").ascending()])
+
+    let snapshot = try await pipeline.execute()
+
+    let expectedResults: [[String: Sendable]] = [
+      ["reversedTags": []],
+      ["reversedTags": [3, 2, 1]],
+      ["reversedTags": ["c", "b", "a"]],
+    ]
+
+    TestHelper.compare(pipelineSnapshot: snapshot, expected: expectedResults, enforceOrder: true)
+  }
+
   func testStrConcat() async throws {
     let collRef = collectionRef(withDocuments: bookDocs)
     let db = collRef.firestore