# All files / src/di container.ts

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     /**
     * Dependency Injection Container
     *
     * Provides type-safe service registration and resolution with support for
     * singleton and transient lifetimes.
     *
     * ISMS Policy: SC-002 (Input Validation), AC-003 (Least Privilege)
     */

    export { TOKENS } from './tokens.js';
    export type { DIToken } from './tokens.js';

    import { TOKENS } from './tokens.js';
    import type { RateLimiter } from '../utils/rateLimiter.js';
    import { createStandardRateLimiter } from '../utils/rateLimiter.js';
    import { MetricsService } from '../services/MetricsService.js';
    import { auditLogger } from '../utils/auditLogger.js';
    import { HealthService } from '../services/HealthService.js';

    /**
     * Service lifetime options
     */
    type ServiceLifetime = 'singleton' | 'transient';

    /**
     * Service factory function type
     */
    type ServiceFactory<T> = (container: DIContainer) => T;

    /**
     * Service descriptor
     */
    interface ServiceDescriptor<T> {
      factory: ServiceFactory<T>;
      lifetime: ServiceLifetime;
      instance?: T;
    }

    /**
     * Dependency Injection Container
     * Cyclomatic complexity: 5
     */
    export class DIContainer {
      private readonly services = new Map<symbol, ServiceDescriptor<unknown>>();

      /**
       * Register a service with the container
       * Cyclomatic complexity: 1
       *
       * @param token - Service identifier token
       * @param factory - Factory function to create service instances
       * @param lifetime - Service lifetime ('singleton' or 'transient')
       *
       * @example
       * ```typescript
       * const ReportServiceToken = Symbol('ReportService');
       * container.register(
       *   ReportServiceToken,
       *   (c) => new ReportService(c.resolve(EPClientToken)),
       *   'singleton'
       * );
       * ```
       *
       * @since 0.8.0
       */
      register<T>(
        token: symbol,
        factory: ServiceFactory<T>,
        lifetime: ServiceLifetime = 'singleton'
      ): void {
        this.services.set(token, { factory, lifetime });
      }

      /**
       * Resolve a service from the container
       * Cyclomatic complexity: 4
       *
       * @param token - Service identifier token
       * @returns Resolved service instance
       * @throws {Error} If service is not registered
       *
       * @example
       * ```typescript
       * const reportService = container.resolve(ReportServiceToken);
       * ```
       *
       * @since 0.8.0
       */
      // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-parameters
      resolve<T>(token: symbol): T {
        const descriptor = this.services.get(token) as ServiceDescriptor<T> | undefined;

        if (descriptor === undefined) {
          throw new Error(`Service not registered: ${String(token)}`);
        }

        if (descriptor.lifetime === 'singleton' && descriptor.instance !== undefined) {
          return descriptor.instance;
        }

        const instance = descriptor.factory(this);

        if (descriptor.lifetime === 'singleton') {
          descriptor.instance = instance;
        }

        return instance;
      }

      /**
       * Check if a service is registered
       * Cyclomatic complexity: 1
       *
       * @param token - Service identifier token
       * @returns `true` if the token is registered, `false` otherwise
       *
       * @since 0.8.0
       */
      has(token: symbol): boolean {
        return this.services.has(token);
      }

      /**
       * Clear all registered services and cached instances.
       *
       * Useful for testing and cleanup between test suites.
       *
       * @example
       * ```typescript
       * afterEach(() => {
       *   container.clear();
       * });
       * ```
       *
       * @since 0.8.0
       */
      clear(): void {
        this.services.clear();
      }
    }

    /**
     * Create a pre-configured DI container with the standard MCP server services
     * registered as singletons.
     *
     * Registered services:
     * - `TOKENS.RateLimiter`   → {@link RateLimiter} (standard EP API configuration)
     * - `TOKENS.MetricsService` → {@link MetricsService}
     * - `TOKENS.AuditLogger`   → {@link AuditLogger} (global singleton)
     * - `TOKENS.HealthService` → {@link HealthService}
     *
     * @returns A fully configured {@link DIContainer} with all standard services registered
     *
     * @example
     * ```typescript
     * const container = createDefaultContainer();
     * const health = container.resolve<HealthService>(TOKENS.HealthService);
     * console.log(health.checkHealth());
     * ```
     *
     * @since 0.8.0
     */
    export function createDefaultContainer(): DIContainer {
      const container = new DIContainer();

      container.register(TOKENS.RateLimiter, () => createStandardRateLimiter());
      container.register(TOKENS.MetricsService, () => new MetricsService());
      container.register(TOKENS.AuditLogger, () => auditLogger);
      container.register(TOKENS.HealthService, (c) =>
        new HealthService(
          c.resolve<RateLimiter>(TOKENS.RateLimiter),
          c.resolve<MetricsService>(TOKENS.MetricsService)
        )
      );

      return container;
    }