How use Vertex AI in iOS Build

Unity Engine
,
1

Hi, I’m trying to create a virtual friend in Unity for iOS, where I use the Vertex AI model Gemini Flash for communication, but I can’t just use an API key for that communication; Vertex AI need OAuth 2.0 authentication. I tried code using the Google.Apis.Auth.OAuth2 library, but it seems to not work when building for iOS. Is there an alternative option?

using System;
using System.IO;
using System.Threading.Tasks;
using Google.Apis.Auth.OAuth2;
using UnityEngine;

public class GoogleCloudAuthHelper : MonoBehaviour
{
    public string apiKeyPath = "service-account";
    private GoogleCredential _credential;
    private string _accessToken;

    private async void Awake()
    {
        await InitializeCredential();
    }

    private async Task InitializeCredential()
    {
        try
        {
            Debug.Log($"Attempting to load service account JSON file from path: {apiKeyPath}");

            // Load the service-account.json file as a TextAsset from Resources
            string resourcePath = Path.GetFileNameWithoutExtension(apiKeyPath);
            TextAsset jsonKeyAsset = Resources.Load<TextAsset>(resourcePath);

            if (jsonKeyAsset == null)
            {
                throw new FileNotFoundException($"Service account JSON file not found at path: {resourcePath}");
            }

            Debug.Log("Service account JSON file loaded successfully.");

            // Create a memory stream from the TextAsset content
            using (var jsonKeyStream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(jsonKeyAsset.text)))
            {
                // Create Google Credential from the loaded JSON key
                _credential = GoogleCredential.FromStream(jsonKeyStream)
                    .CreateScoped(new[] { "https://www.googleapis.com/auth/cloud-platform" });
            }

            Debug.Log("Google Credential initialized successfully.");

            // Obtain the access token
            _accessToken = await GetAccessTokenAsync();
        }
        catch (Exception ex)
        {
            Debug.LogError($"Failed to initialize Google credentials: {ex.Message}");
        }
    }

    public async Task<string> GetAccessTokenAsync()
    {
        if (_credential == null)
        {
            Debug.LogError("Google Credential is not initialized.");
            return null;
        }

        if (_credential.UnderlyingCredential == null)
        {
            Debug.LogError("Underlying Credential is null.");
            return null;
        }

        try
        {
            // Get the access token from the underlying credential
            var tokenResponse = await _credential.UnderlyingCredential.GetAccessTokenForRequestAsync();
            Debug.Log("Access token obtained successfully.");
            return tokenResponse;
        }
        catch (Exception ex)
        {
            Debug.LogError($"Failed to obtain access token: {ex.Message}");
            throw;
        }
    }

    public GoogleCredential GetCredential()
    {
        if (_credential == null)
        {
            Debug.LogError("Google Credential is not initialized.");
        }
        return _credential;
    }

    public string GetStoredAccessToken()
    {
        return _accessToken;
    }
}