import { Config } from './services/config.ts';
import { Database, MigrationService } from './services/storage/index.ts';
import { Logger } from './utils/logger.ts';

/** Application composition root. */
export class App {
    /**
     * Construct infrastructure and validate all routes before returning a runnable app.
     */
    static async create(): Promise<App> {
        const config = Config.fromEnv();
        const debug = new Logger('sync-server-v2');
        debug('config loaded: %O', config);

        // Persistence must be ready before routes accept traffic.
        const database = new Database({ path: config.database.path, debug });
        const migrations = new MigrationService(database, debug);
        await migrations.migrateToLatest();

        return new App(database);
    }

    private stopPromise: Promise<void> | undefined;

    constructor(private readonly database: Database) {}

    async start(): Promise<void> {}

    /** Stop transports before releasing the database they may still use. */
    async stop(): Promise<void> {
        this.stopPromise ??= this.database.destroy();
        await this.stopPromise;
    }
}

const app = await App.create();
let shuttingDown = false;

const shutdown = (signal: NodeJS.Signals): void => {
    if (shuttingDown) {
        return;
    }

    shuttingDown = true;
    void app.stop().catch((error) => {
        console.error('Graceful shutdown failed after ' + signal, error);
        process.exitCode = 1;
    });
};

process.once('SIGINT', (): void => shutdown('SIGINT'));
process.once('SIGTERM', (): void => shutdown('SIGTERM'));

try {
    await app.start();
} catch (error: unknown) {
    await app.stop();
    throw error;
}