import { AppServices } from './app-services';
import { NoopAnalyticsService } from './analytics/noop-analytics-service';
import { UmamiAnalyticsService } from './analytics/umami-analytics-service';
import { MemoryCacheService } from './cache/memory-cache-service';
import { GlitchtipErrorReportingService } from './errors/glitchtip-error-reporting-service';
import { NoopErrorReportingService } from './errors/noop-error-reporting-service';
import { NoopLoggerService } from './logging/noop-logger-service';
import { PinoLoggerService } from './logging/pino-logger-service';

/**
 * Singleton instance of AppServices.
 *
 * In Next.js, module singletons are per-process (server) and per-tab (client).
 * This is sufficient for a small service layer and provides better performance
 * than creating new instances on every request.
 *
 * @private
 */
let singleton: AppServices | undefined;

/**
 * Get the application services singleton.
 *
 * This function creates and caches the application services, including:
 * - Analytics service (Umami or no-op)
 * - Error reporting service (GlitchTip/Sentry or no-op)
 * - Cache service (in-memory)
 *
 * The services are configured based on environment variables:
 * - `NEXT_PUBLIC_UMAMI_WEBSITE_ID` - Enables Umami analytics
 * - `NEXT_PUBLIC_SENTRY_DSN` - Enables client-side error reporting
 * - `SENTRY_DSN` - Enables server-side error reporting
 *
 * @returns {AppServices} The application services singleton
 *
 * @example
 * ```typescript
 * // Get services in a client component
 * import { getAppServices } from '@/lib/services/create-services';
 *
 * const services = getAppServices();
 * services.analytics.track('button_click', { button_id: 'cta' });
 * ```
 *
 * @example
 * ```typescript
 * // Get services in a server component or API route
 * import { getAppServices } from '@/lib/services/create-services';
 *
 * const services = getAppServices();
 * await services.cache.set('key', 'value');
 * ```
 *
 * @example
 * ```typescript
 * // Automatic service selection based on environment
 * // If NEXT_PUBLIC_UMAMI_WEBSITE_ID is set:
 * //   services.analytics = UmamiAnalyticsService
 * // If not set:
 * //   services.analytics = NoopAnalyticsService (safe no-op)
 * ```
 *
 * @see {@link UmamiAnalyticsService} for analytics implementation
 * @see {@link NoopAnalyticsService} for no-op fallback
 * @see {@link GlitchtipErrorReportingService} for error reporting
 * @see {@link MemoryCacheService} for caching
 */
export function getAppServices(): AppServices {
  // Return cached instance if available
  if (singleton) return singleton;

  // Determine which services to enable based on environment variables
  const umamiEnabled = Boolean(process.env.NEXT_PUBLIC_UMAMI_WEBSITE_ID);
  const sentryClientEnabled = Boolean(process.env.NEXT_PUBLIC_SENTRY_DSN);
  const sentryServerEnabled = Boolean(process.env.SENTRY_DSN);

  // Create analytics service (Umami or no-op)
  const analytics = umamiEnabled
    ? new UmamiAnalyticsService({ enabled: true })
    : new NoopAnalyticsService();

  // Create error reporting service (GlitchTip/Sentry or no-op)
  // Server-side and client-side have separate DSNs
  const errors =
    typeof window === 'undefined'
      ? sentryServerEnabled
        ? new GlitchtipErrorReportingService({ enabled: true })
        : new NoopErrorReportingService()
      : sentryClientEnabled
        ? new GlitchtipErrorReportingService({ enabled: true })
        : new NoopErrorReportingService();

  // IMPORTANT: This module is imported by client components.
  // Do not import Node-only modules (like the `redis` client) here.
  // Use [`getServerAppServices()`](lib/services/create-services.server.ts:1) on the server.
  const cache = new MemoryCacheService();

  const logger =
    typeof window === 'undefined'
      ? new PinoLoggerService('server')
      : new NoopLoggerService();

  // Create and cache the singleton
  singleton = new AppServices(analytics, errors, cache, logger);
  return singleton;
}