import { ConfigService } from '@nestjs/config';
import { IntegrationStrategy, IntegrationResult } from '../integration.strategy';
export declare class GmailApiStrategy implements IntegrationStrategy {
    private readonly configService;
    constructor(configService: ConfigService);
    sendMessage(to: string | string[], message: string, config: any): Promise<IntegrationResult>;
    validateConfig(config: any): boolean;
    private setupOAuth2Client;
    refreshAccessToken(config: any): Promise<string>;
    validateConnection(config: any): Promise<boolean>;
    private buildSimpleEmail;
    private buildMultipartEmail;
}