[Vertex AI] Add POC for initializing function declarations from JSON

FirebaseVertexAI/Sources/FunctionCalling.swift

@@ -19,7 +19,7 @@ import Foundation
 /// This `FunctionDeclaration` is a representation of a block of code that can be used as a ``Tool``
 /// by the model and executed by the client.
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-public struct FunctionDeclaration {
+public struct FunctionDeclaration: Equatable {
   /// The name of the function.
   let name: String
 
@@ -48,6 +48,22 @@ public struct FunctionDeclaration {
       nullable: false
     )
   }
+
+  /// Constructs a new `FunctionDeclaration`.
+  ///
+  /// - Parameters:
+  ///   - jsonString: A string representing a function declaration in JSON format; see the [REST
+  ///   documentation]( https://cloud.google.com/vertex-ai/generative-ai/docs/reference/rest/v1/Tool#FunctionDeclaration)
+  ///   for details.
+  public init(jsonString: String) throws {
+    guard let jsonData = jsonString.data(using: .utf8) else {
+      throw DecodingError.dataCorrupted(DecodingError.Context(
+        codingPath: [],
+        debugDescription: "Could not parse JSON string as UTF8."
+      ))
+    }
+    self = try JSONDecoder().decode(Self.self, from: jsonData)
+  }
 }
 
 /// A helper tool that the model may use when generating responses.
@@ -146,7 +162,7 @@ public struct ToolConfig {
 // MARK: - Codable Conformance
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-extension FunctionDeclaration: Encodable {
+extension FunctionDeclaration: Codable {
   enum CodingKeys: String, CodingKey {
     case name
     case description

FirebaseVertexAI/Sources/Types/Internal/DataType.swift

@@ -37,4 +37,4 @@ enum DataType: String {
 
 // MARK: - Codable Conformance
 
-extension DataType: Encodable {}
+extension DataType: Codable {}

FirebaseVertexAI/Sources/Types/Public/Schema.swift

@@ -19,7 +19,7 @@ import Foundation
 /// These types can be objects, but also primitives and arrays. Represents a select subset of an
 /// [OpenAPI 3.0 schema object](https://spec.openapis.org/oas/v3.0.3#schema).
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-public class Schema {
+public final class Schema {
   /// Modifiers describing the expected format of a string `Schema`.
   @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
   public struct StringFormat: EncodableProtoEnum {
@@ -319,7 +319,7 @@ public class Schema {
 // MARK: - Codable Conformance
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-extension Schema: Encodable {
+extension Schema: Codable {
   enum CodingKeys: String, CodingKey {
     case dataType = "type"
     case format
@@ -331,3 +331,15 @@ extension Schema: Encodable {
     case requiredProperties = "required"
   }
 }
+
+// MARK: - Equatable Conformance
+
+@available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
+extension Schema: Equatable {
+  public static func == (lhs: Schema, rhs: Schema) -> Bool {
+    return lhs.dataType == rhs.dataType && lhs.format == rhs.format
+      && lhs.description == rhs.description && lhs.nullable == rhs.nullable
+      && lhs.enumValues == rhs.enumValues && lhs.items == rhs.items
+      && lhs.properties == rhs.properties && lhs.requiredProperties == rhs.requiredProperties
+  }
+}

FirebaseVertexAI/Tests/Unit/Types/FunctionDeclarationTests.swift

@@ -0,0 +1,48 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import FirebaseVertexAI
+import XCTest
+
+@available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
+final class FunctionDeclarationTests: XCTestCase {
+  func testFunctionDeclaration_jsonString() throws {
+    let json = """
+    {
+      "name": "getWeather",
+      "description": "gets the weather for a requested city",
+      "parameters": {
+        "type": "OBJECT",
+        "properties": {
+          "city": {
+            "type": "STRING",
+            "nullable": false
+          }
+        },
+        "nullable": false,
+        "required": ["city"]
+      }
+    }
+    """
+    let expectedFunctionDeclaration = FunctionDeclaration(
+      name: "getWeather",
+      description: "gets the weather for a requested city",
+      parameters: ["city": .string()]
+    )
+
+    let functionDeclaration = try FunctionDeclaration(jsonString: json)
+
+    XCTAssertEqual(functionDeclaration, expectedFunctionDeclaration)
+  }
+}