Google MCP Router

import { createHash, randomBytes } from 'crypto';
export class GoogleOAuth {
    config;
    constructor(config) {
        this.config = config;
    }
    async initialize() {
    }
    generateAuthUrl() {
        const codeVerifier = this.generateCodeVerifier();
        const codeChallenge = this.generateCodeChallenge(codeVerifier);
        const state = this.generateState();
        const params = new URLSearchParams({
            client_id: this.config.clientId,
            redirect_uri: this.config.redirectUri,
            scope: this.config.scopes.join(' '),
            code_challenge: codeChallenge,
            code_challenge_method: 'S256',
            state,
            response_type: 'code'
        });
        const url = `https://accounts.google.com/o/oauth2/v2/auth?${params.toString()}`;
        return { url, codeVerifier, state };
    }
    async exchangeCodeForTokens(code, codeVerifier, state) {
        const response = await fetch('https://oauth2.googleapis.com/token', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
            },
            body: new URLSearchParams({
                client_id: this.config.clientId,
                client_secret: this.config.clientSecret,
                code,
                grant_type: 'authorization_code',
                redirect_uri: this.config.redirectUri,
                code_verifier: codeVerifier
            })
        });
        if (!response.ok) {
            throw new Error(`Token exchange failed: ${response.statusText}`);
        }
        return await response.json();
    }
    async refreshAccessToken(refreshToken) {
        const response = await fetch('https://oauth2.googleapis.com/token', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
            },
            body: new URLSearchParams({
                client_id: this.config.clientId,
                client_secret: this.config.clientSecret,
                refresh_token: refreshToken,
                grant_type: 'refresh_token'
            })
        });
        if (!response.ok) {
            throw new Error(`Token refresh failed: ${response.statusText}`);
        }
        return await response.json();
    }
    extractTokens(tokenSet) {
        if (!tokenSet.access_token) {
            throw new Error('No access token in token set');
        }
        if (!tokenSet.refresh_token) {
            throw new Error('No refresh token in token set');
        }
        return {
            access_token: tokenSet.access_token,
            refresh_token: tokenSet.refresh_token,
            expires_at: tokenSet.expires_at || Date.now() + 3600000, // Default 1 hour
            scope: tokenSet.scope || this.config.scopes.join(' ')
        };
    }
    isTokenExpired(tokens) {
        return Date.now() >= tokens.expires_at;
    }
    needsRefresh(tokens) {
        const bufferMs = 5 * 60 * 1000; // 5 minutes
        return Date.now() >= (tokens.expires_at - bufferMs);
    }
    generateCodeVerifier() {
        return randomBytes(32).toString('base64url');
    }
    generateCodeChallenge(verifier) {
        return createHash('sha256').update(verifier).digest('base64url');
    }
    generateState() {
        return randomBytes(16).toString('hex');
    }
}
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