[Vertex AI] Add Developer API encoding CountTokensRequest

FirebaseVertexAI/Sources/GenerateContentRequest.swift

@@ -18,12 +18,14 @@ import Foundation
 struct GenerateContentRequest: Sendable {
   /// Model name.
   let model: String
+
   let contents: [ModelContent]
   let generationConfig: GenerationConfig?
   let safetySettings: [SafetySetting]?
   let tools: [Tool]?
   let toolConfig: ToolConfig?
   let systemInstruction: ModelContent?
+
   let apiConfig: APIConfig
   let apiMethod: APIMethod
   let options: RequestOptions
@@ -32,13 +34,30 @@ struct GenerateContentRequest: Sendable {
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 extension GenerateContentRequest: Encodable {
   enum CodingKeys: String, CodingKey {
+    case model
     case contents
     case generationConfig
     case safetySettings
     case tools
     case toolConfig
     case systemInstruction
   }
+
+  func encode(to encoder: any Encoder) throws {
+    var container = encoder.container(keyedBy: CodingKeys.self)
+    // The model name only needs to be encoded when this `GenerateContentRequest` instance is used
+    // in a `CountTokensRequest` (calling `countTokens`). When calling `generateContent` or
+    // `generateContentStream`, the `model` field is populated in the backend from the `url`.
+    if apiMethod == .countTokens {
+      try container.encode(model, forKey: .model)
+    }
+    try container.encode(contents, forKey: .contents)
+    try container.encodeIfPresent(generationConfig, forKey: .generationConfig)
+    try container.encodeIfPresent(safetySettings, forKey: .safetySettings)
+    try container.encodeIfPresent(tools, forKey: .tools)
+    try container.encodeIfPresent(toolConfig, forKey: .toolConfig)
+    try container.encodeIfPresent(systemInstruction, forKey: .systemInstruction)
+  }
 }
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)

FirebaseVertexAI/Sources/GenerativeModel.swift

@@ -260,15 +260,31 @@ public final class GenerativeModel: Sendable {
   /// - Returns: The results of running the model's tokenizer on the input; contains
   /// ``CountTokensResponse/totalTokens``.
   public func countTokens(_ content: [ModelContent]) async throws -> CountTokensResponse {
-    let countTokensRequest = CountTokensRequest(
+    let requestContent = switch apiConfig.service {
+    case .vertexAI:
+      content
+    case .developer:
+      // The `role` defaults to "user" but is ignored in `countTokens`. However, it is erroneously
+      // erroneously counted towards the prompt and total token count when using the Developer API
+      // backend; set to `nil` to avoid token count discrepancies between `countTokens` and
+      // `generateContent` and the two backend APIs.
+      content.map { ModelContent(role: nil, parts: $0.parts) }
+    }
+
+    let generateContentRequest = GenerateContentRequest(
       model: modelResourceName,
-      contents: content,
-      systemInstruction: systemInstruction,
-      tools: tools,
+      contents: requestContent,
       generationConfig: generationConfig,
+      safetySettings: safetySettings,
+      tools: tools,
+      toolConfig: toolConfig,
+      systemInstruction: systemInstruction,
       apiConfig: apiConfig,
+      apiMethod: .countTokens,
       options: requestOptions
     )
+    let countTokensRequest = CountTokensRequest(generateContentRequest: generateContentRequest)
+
     return try await generativeAIService.loadRequest(request: countTokensRequest)
   }
 

FirebaseVertexAI/Sources/CountTokensRequest.swift → FirebaseVertexAI/Sources/Types/Internal/Requests/CountTokensRequest.swift

@@ -16,24 +16,21 @@ import Foundation
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 struct CountTokensRequest {
-  let model: String
-
-  let contents: [ModelContent]
-  let systemInstruction: ModelContent?
-  let tools: [Tool]?
-  let generationConfig: GenerationConfig?
-
-  let apiConfig: APIConfig
-  let options: RequestOptions
+  let generateContentRequest: GenerateContentRequest
 }
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 extension CountTokensRequest: GenerativeAIRequest {
   typealias Response = CountTokensResponse
 
+  var options: RequestOptions { generateContentRequest.options }
+
+  var apiConfig: APIConfig { generateContentRequest.apiConfig }
+
   var url: URL {
-    URL(string:
-      "\(apiConfig.service.endpoint.rawValue)/\(apiConfig.version.rawValue)/\(model):countTokens")!
+    let version = apiConfig.version.rawValue
+    let endpoint = apiConfig.service.endpoint.rawValue
+    return URL(string: "\(endpoint)/\(version)/\(generateContentRequest.model):countTokens")!
   }
 }
 
@@ -57,12 +54,42 @@ public struct CountTokensResponse {
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 extension CountTokensRequest: Encodable {
-  enum CodingKeys: CodingKey {
+  enum VertexCodingKeys: CodingKey {
     case contents
     case systemInstruction
     case tools
     case generationConfig
   }
+
+  enum DeveloperCodingKeys: CodingKey {
+    case generateContentRequest
+  }
+
+  func encode(to encoder: any Encoder) throws {
+    switch apiConfig.service {
+    case .vertexAI:
+      try encodeForVertexAI(to: encoder)
+    case .developer:
+      try encodeForDeveloper(to: encoder)
+    }
+  }
+
+  private func encodeForVertexAI(to encoder: any Encoder) throws {
+    var container = encoder.container(keyedBy: VertexCodingKeys.self)
+    try container.encode(generateContentRequest.contents, forKey: .contents)
+    try container.encodeIfPresent(
+      generateContentRequest.systemInstruction, forKey: .systemInstruction
+    )
+    try container.encodeIfPresent(generateContentRequest.tools, forKey: .tools)
+    try container.encodeIfPresent(
+      generateContentRequest.generationConfig, forKey: .generationConfig
+    )
+  }
+
+  private func encodeForDeveloper(to encoder: any Encoder) throws {
+    var container = encoder.container(keyedBy: DeveloperCodingKeys.self)
+    try container.encode(generateContentRequest, forKey: .generateContentRequest)
+  }
 }
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)

FirebaseVertexAI/Tests/TestApp/Sources/Constants.swift

@@ -21,5 +21,6 @@ public enum FirebaseAppNames {
 }
 
 public enum ModelNames {
+  public static let gemini2Flash = "gemini-2.0-flash-001"
   public static let gemini2FlashLite = "gemini-2.0-flash-lite-001"
 }

FirebaseVertexAI/Tests/TestApp/Tests/Integration/CountTokensIntegrationTests.swift

@@ -0,0 +1,122 @@
+// Copyright 2025 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 FirebaseAuth
+import FirebaseCore
+import FirebaseStorage
+import FirebaseVertexAI
+import Testing
+import VertexAITestApp
+
+@testable import struct FirebaseVertexAI.APIConfig
+
+@Suite(.serialized)
+struct CountTokensIntegrationTests {
+  let generationConfig = GenerationConfig(
+    temperature: 1.2,
+    topP: 0.95,
+    topK: 32,
+    candidateCount: 1,
+    maxOutputTokens: 8192,
+    presencePenalty: 1.5,
+    frequencyPenalty: 1.75,
+    stopSequences: ["cat", "dog", "bird"]
+  )
+  let safetySettings = [
+    SafetySetting(harmCategory: .harassment, threshold: .blockLowAndAbove),
+    SafetySetting(harmCategory: .hateSpeech, threshold: .blockLowAndAbove),
+    SafetySetting(harmCategory: .sexuallyExplicit, threshold: .blockLowAndAbove),
+    SafetySetting(harmCategory: .dangerousContent, threshold: .blockLowAndAbove),
+    SafetySetting(harmCategory: .civicIntegrity, threshold: .blockLowAndAbove),
+  ]
+  let systemInstruction = ModelContent(
+    role: "system",
+    parts: "You are a friendly and helpful assistant."
+  )
+
+  @Test(arguments: InstanceConfig.allConfigs)
+  func countTokens_text(_ config: InstanceConfig) async throws {
+    let prompt = "Why is the sky blue?"
+    let model = VertexAI.componentInstance(config).generativeModel(
+      modelName: ModelNames.gemini2Flash,
+      generationConfig: generationConfig,
+      safetySettings: safetySettings
+    )
+
+    let response = try await model.countTokens(prompt)
+
+    #expect(response.totalTokens == 6)
+    switch config.apiConfig.service {
+    case .vertexAI:
+      #expect(response.totalBillableCharacters == 16)
+    case .developer:
+      #expect(response.totalBillableCharacters == nil)
+    }
+    #expect(response.promptTokensDetails.count == 1)
+    let promptTokensDetails = try #require(response.promptTokensDetails.first)
+    #expect(promptTokensDetails.modality == .text)
+    #expect(promptTokensDetails.tokenCount == response.totalTokens)
+  }
+
+  @Test(arguments: [
+    InstanceConfig.vertexV1,
+    InstanceConfig.vertexV1Beta,
+    /* System instructions are not supported on the v1 Developer API. */
+    InstanceConfig.developerV1Beta,
+  ])
+  func countTokens_text_systemInstruction(_ config: InstanceConfig) async throws {
+    let model = VertexAI.componentInstance(config).generativeModel(
+      modelName: ModelNames.gemini2Flash,
+      generationConfig: generationConfig,
+      safetySettings: safetySettings,
+      systemInstruction: systemInstruction // Not supported on the v1 Developer API
+    )
+
+    let response = try await model.countTokens("What is your favourite colour?")
+
+    #expect(response.totalTokens == 14)
+    switch config.apiConfig.service {
+    case .vertexAI:
+      #expect(response.totalBillableCharacters == 61)
+    case .developer:
+      #expect(response.totalBillableCharacters == nil)
+    }
+    #expect(response.promptTokensDetails.count == 1)
+    let promptTokensDetails = try #require(response.promptTokensDetails.first)
+    #expect(promptTokensDetails.modality == .text)
+    #expect(promptTokensDetails.tokenCount == response.totalTokens)
+  }
+
+  @Test(arguments: [
+    /* System instructions are not supported on the v1 Developer API. */
+    InstanceConfig.developerV1,
+  ])
+  func countTokens_text_systemInstruction_unsupported(_ config: InstanceConfig) async throws {
+    let model = VertexAI.componentInstance(config).generativeModel(
+      modelName: ModelNames.gemini2Flash,
+      systemInstruction: systemInstruction // Not supported on the v1 Developer API
+    )
+
+    try await #require(
+      throws: BackendError.self,
+      """
+      If this test fails (i.e., `countTokens` succeeds), remove \(config) from this test and add it
+      to `countTokens_text_systemInstruction`.
+      """,
+      performing: {
+        try await model.countTokens("What is your favourite colour?")
+      }
+    )
+  }
+}

FirebaseVertexAI/Tests/TestApp/Tests/Integration/GenerateContentIntegrationTests.swift

@@ -19,29 +19,8 @@ import FirebaseVertexAI
 import Testing
 import VertexAITestApp
 
-@testable import struct FirebaseVertexAI.APIConfig
-
 @Suite(.serialized)
 struct GenerateContentIntegrationTests {
-  static let vertexV1Config =
-    InstanceConfig(apiConfig: APIConfig(service: .vertexAI, version: .v1))
-  static let vertexV1BetaConfig =
-    InstanceConfig(apiConfig: APIConfig(service: .vertexAI, version: .v1beta))
-  static let developerV1Config = InstanceConfig(
-    appName: FirebaseAppNames.spark,
-    apiConfig: APIConfig(
-      service: .developer(endpoint: .generativeLanguage), version: .v1
-    )
-  )
-  static let developerV1BetaConfig = InstanceConfig(
-    appName: FirebaseAppNames.spark,
-    apiConfig: APIConfig(
-      service: .developer(endpoint: .generativeLanguage), version: .v1beta
-    )
-  )
-  static let allConfigs =
-    [vertexV1Config, vertexV1BetaConfig, developerV1Config, developerV1BetaConfig]
-
   // Set temperature, topP and topK to lowest allowed values to make responses more deterministic.
   let generationConfig = GenerationConfig(temperature: 0.0, topP: 0.0, topK: 1)
   let safetySettings = [
@@ -67,7 +46,7 @@ struct GenerateContentIntegrationTests {
     storage = Storage.storage()
   }
 
-  @Test(arguments: allConfigs)
+  @Test(arguments: InstanceConfig.allConfigs)
   func generateContent(_ config: InstanceConfig) async throws {
     let model = VertexAI.componentInstance(config).generativeModel(
       modelName: ModelNames.gemini2FlashLite,
@@ -98,10 +77,10 @@ struct GenerateContentIntegrationTests {
   @Test(
     "Generate an enum and provide a system instruction",
     arguments: [
-      vertexV1Config,
-      vertexV1BetaConfig,
+      InstanceConfig.vertexV1,
+      InstanceConfig.vertexV1Beta,
       /* System instructions are not supported on the v1 Developer API. */
-      developerV1BetaConfig,
+      InstanceConfig.developerV1Beta,
     ]
   )
   func generateContentEnum(_ config: InstanceConfig) async throws {