import type { FastMCP } from 'fastmcp';

/**
 * Server lifecycle management utilities
 */

export interface ServerLifecycleHooks {
  onStart?: (server: FastMCP) => Promise<void>;
  onStop?: (server: FastMCP) => Promise<void>;
  onError?: (error: Error, server: FastMCP) => Promise<void>;
}

/**
 * Manages the lifecycle of an MCP server with proper startup/shutdown handling
 */
export class ServerLifecycleManager {
  private server: FastMCP;
  private hooks: ServerLifecycleHooks;
  private isRunning: boolean = false;

  constructor(server: FastMCP, hooks: ServerLifecycleHooks = {}) {
    this.server = server;
    this.hooks = hooks;
  }

  /**
   * Start the server with lifecycle hooks
   */
  async start(): Promise<void> {
    if (this.isRunning) {
      throw new Error('Server is already running');
    }

    try {
      if (this.hooks.onStart) {
        await this.hooks.onStart(this.server);
      }
      this.isRunning = true;
    } catch (error) {
      if (this.hooks.onError) {
        await this.hooks.onError(error as Error, this.server);
      }
      throw error;
    }
  }

  /**
   * Stop the server gracefully
   */
  async stop(): Promise<void> {
    if (!this.isRunning) {
      return;
    }

    try {
      if (this.hooks.onStop) {
        await this.hooks.onStop(this.server);
      }
      this.isRunning = false;
    } catch (error) {
      if (this.hooks.onError) {
        await this.hooks.onError(error as Error, this.server);
      }
      throw error;
    }
  }

  /**
   * Get the server instance
   */
  getServer(): FastMCP {
    return this.server;
  }

  /**
   * Check if server is running
   */
  isServerRunning(): boolean {
    return this.isRunning;
  }
}

/**
 * Setup graceful shutdown handlers for the server
 */
export function setupGracefulShutdown(
  manager: ServerLifecycleManager
): void {
  const signals: NodeJS.Signals[] = ['SIGINT', 'SIGTERM', 'SIGQUIT'];

  signals.forEach(signal => {
    process.on(signal, async () => {
      console.log(`\nReceived ${signal}, shutting down gracefully...`);
      try {
        await manager.stop();
        process.exit(0);
      } catch (error) {
        console.error('Error during shutdown:', error);
        process.exit(1);
      }
    });
  });
}