All files / packages/gemini-core/examples simple.ts

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import { randomUUID } from 'crypto';
import {
  Content,
  GenerateContentConfig,
  GenerateContentResponse,
} from '@google/genai';
import { AuthType, Config, GeminiChat, StreamEventType } from '../src';
 
/**
 * A helper function to extract the text content from a streaming response chunk.
 * The Gemini API streams responses, and this function helps aggregate the text.
 * @param response A GenerateContentResponse chunk from the stream.
 * @returns The text content of the chunk, or null if there is none.
 */
function getResponseText(response: GenerateContentResponse): string | null {
  Iif (response.candidates && response.candidates.length > 0) {
    const candidate = response.candidates[0];
 
    Iif (
      candidate.content &&
      candidate.content.parts &&
      candidate.content.parts.length > 0
    ) {
      return candidate.content.parts
        .filter((part: any) => part.text)
        .map((part: any) => part.text)
        .join('');
    }
  }
  return null;
}
 
async function main() {
  console.log('--- Gemini Chat API Example (with Google Login) ---');
 
  // 1. Set up for Google Login
  // For this example, we'll authenticate using your Google account.
  // The first time you run this, a browser window will open for you to log in.
  // Your credentials will be cached for future runs in `~/.gemini/`.
  console.log('✓ Using Google Login for authentication.');
 
  // 2. Create a Configuration Object
  // The Config object holds settings for the session. For this example,
  // we provide a few essential parameters.
  const config = new Config({
    sessionId: `session-${randomUUID()}`,
    model: 'gemini-2.5-pro', // A default model for the session
  });
  console.log('✓ Configuration created.');
 
  // 3. Authenticate and Prepare the API Client (ContentGenerator)
  // The GeminiChat class relies on a `ContentGenerator` instance being available
  // on the Config object to make API calls. `refreshAuth` sets this up.
  try {
    // This will trigger the OAuth2 flow in the browser on the first run.
    await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
  } catch (e) {
    console.error('Authentication failed:', e);
    return;
  }
  console.log('✓ Authenticated with your Google account.');
 
  // 4. Define System Instruction and Conversation History
  const systemInstruction =
    'You are a poetic assistant. All your responses must be in the form of a haiku.';
 
  const initialHistory: Content[] = [
    { role: 'user', parts: [{ text: 'What is the largest mammal?' }] },
    {
      role: 'model',
      parts: [
        {
          text: "Giant blue whale swims,\nOcean's gentle, massive king,\nLargest on the Earth.",
        },
      ],
    },
  ];
 
  const generationConfig: GenerateContentConfig = {
    systemInstruction,
    temperature: 0.7,
  };
  console.log('✓ System instruction and history prepared.');
 
  // 5. Instantiate GeminiChat
  // We provide the config, generation settings (with system instruction), and initial history.
  const chat = new GeminiChat(config, generationConfig, initialHistory);
  console.log('✓ GeminiChat instance created.');
 
  // 6. Send a New Message with History and System Instruction
  console.log('\nUser: How much does it weigh?');
  const responseStream = await chat.sendMessageStream(
    'gemini-2.5-pro', // You can specify a model here to override the config default for this call
    { message: 'How much does it weigh?' },
    `prompt-${randomUUID()}`,
  );
 
  // 7. Process and Display the Streaming Response
  let fullResponse = '';
  process.stdout.write('Gemini: ');
  for await (const chunk of responseStream) {
    // The stream yields events. We are interested in 'chunk' events which contain response data.
    Iif (chunk.type === StreamEventType.CHUNK && chunk.value) {
      const text = getResponseText(chunk.value);
      Iif (text) {
        process.stdout.write(text);
        fullResponse += text;
      }
    }
  }
  console.log(); // Newline after the stream ends
 
  // 8. Verify the updated history
  // The chat history now contains the full conversation, including the latest turn.
  console.log('\n--- Full Conversation History ---');
  console.log(JSON.stringify(chat.getHistory(), null, 2));
  console.log('--- End of Example ---');
}
 
main().catch(console.error);