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src
services
import { google } from "googleapis";
import { OAuth2Client } from "google-auth-library";
import * as fs from "fs";
import * as path from "path";
import { fileURLToPath } from "url";

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const TOKEN_PATH = path.join(__dirname, "../../credentials/google-token.json");
const CREDENTIALS_PATH = path.join(
  __dirname,
  "../../credentials/google-credentials.json"
);

export class GoogleAuthService {
  private static instance: GoogleAuthService;
  private oAuth2Client: OAuth2Client | null = null;
  private authUrl: string | null = null;

  private constructor() {}

  static getInstance(): GoogleAuthService {
    if (!GoogleAuthService.instance) {
      GoogleAuthService.instance = new GoogleAuthService();
    }
    return GoogleAuthService.instance;
  }

  async initialize(): Promise<void> {
    try {
      const credentials = JSON.parse(
        fs.readFileSync(CREDENTIALS_PATH, "utf-8")
      );
      const { client_secret, client_id, redirect_uris } = credentials.installed;

      this.oAuth2Client = new google.auth.OAuth2(
        client_id,
        client_secret,
        redirect_uris[0]
      );

      // Try to load existing token
      if (fs.existsSync(TOKEN_PATH)) {
        const token = JSON.parse(fs.readFileSync(TOKEN_PATH, "utf-8"));
        this.oAuth2Client.setCredentials(token);
      }
    } catch (error) {
      console.error("Error loading client secrets file:", error);
      throw error;
    }
  }

  async authenticate(): Promise<void> {
    if (!this.oAuth2Client) {
      throw new Error("OAuth2Client not initialized");
    }

    // If we already have a token, no need to authenticate
    if (fs.existsSync(TOKEN_PATH)) {
      return;
    }

    // Since we can't authenticate automatically in MCP context,
    // throw an error with instructions
    throw new Error(
      "Google authentication required. Please follow these steps:\n" +
        "1. Set up Google Cloud Project and enable required APIs\n" +
        "2. Create OAuth 2.0 credentials (Desktop Application type)\n" +
        "3. Download credentials and save as 'credentials/google-credentials.json'\n" +
        "4. Run the authentication helper script: 'npm run auth-google'\n" +
        "5. Restart the MCP server after authentication is complete"
    );
  }

  getAuth(): OAuth2Client {
    if (!this.oAuth2Client) {
      throw new Error("OAuth2Client not initialized");
    }
    return this.oAuth2Client;
  }

  async saveToken(token: any): Promise<void> {
    fs.writeFileSync(TOKEN_PATH, JSON.stringify(token));
    console.log("Token stored to", TOKEN_PATH);
  }
}