/**
 * Mock TLS Receiver Server
 * Simulates receiver for testing without external dependencies
 */

import * as tls from 'tls';
import * as fs from 'fs';
import * as path from 'path';
import { LengthPrefixFramer } from '@/transport/framing/length-prefix';

export interface MockReceiverConfig {
  port: number;
  host?: string;
  responseDelay?: number; // ms
  ackResponse?: boolean; // true for ACK, false for NACK
  simulateErrors?: boolean;
  errorRate?: number; // 0-1, probability of error
}

export class MockReceiverServer {
  private server: tls.Server | null = null;
  private config: MockReceiverConfig;
  private connections: Set<tls.TLSSocket> = new Set();
  private messageCount = 0;
  private ackCount = 0;
  private nackCount = 0;

  constructor(config: MockReceiverConfig) {
    this.config = {
      host: '0.0.0.0',
      responseDelay: 0,
      ackResponse: true,
      simulateErrors: false,
      errorRate: 0,
      ...config,
    };
  }

  /**
   * Start the mock server
   */
  async start(): Promise<void> {
    return new Promise((resolve, reject) => {
      try {
        // Create self-signed certificate for testing
        const certPath = path.join(__dirname, '../../test-certs/server-cert.pem');
        const keyPath = path.join(__dirname, '../../test-certs/server-key.pem');

        // Create test certificates if they don't exist
        if (!fs.existsSync(certPath) || !fs.existsSync(keyPath)) {
          this.createTestCertificates(certPath, keyPath);
        }

        const options: tls.TlsOptions = {
          cert: fs.readFileSync(certPath),
          key: fs.readFileSync(keyPath),
          rejectUnauthorized: false, // For testing only
        };

        this.server = tls.createServer(options, (socket) => {
          this.connections.add(socket);
          let buffer = Buffer.alloc(0);

          socket.on('data', async (data) => {
            buffer = Buffer.concat([buffer, data]);

            // Try to unframe messages
            while (buffer.length >= 4) {
              // Create a proper Buffer to avoid ArrayBufferLike type issue
              const bufferCopy = Buffer.from(buffer);
              const { message, remaining } = LengthPrefixFramer.unframe(bufferCopy);

              if (!message) {
                // Need more data
                break;
              }

              // Process message
              await this.handleMessage(socket, message.toString('utf-8'));
              // Create new Buffer from remaining to avoid type issues
              buffer = Buffer.from(remaining);
            }
          });

          socket.on('error', (error) => {
            console.error('Mock server socket error:', error);
          });

          socket.on('close', () => {
            this.connections.delete(socket);
          });
        });

        this.server.listen(this.config.port, this.config.host, () => {
          console.log(`Mock receiver server listening on ${this.config.host}:${this.config.port}`);
          resolve();
        });

        this.server.on('error', (error) => {
          reject(error);
        });
      } catch (error) {
        reject(error);
      }
    });
  }

  /**
   * Stop the mock server
   */
  async stop(): Promise<void> {
    return new Promise((resolve) => {
      if (this.server) {
        // Close all connections
        for (const socket of this.connections) {
          socket.destroy();
        }
        this.connections.clear();

        this.server.close(() => {
          this.server = null;
          resolve();
        });
      } else {
        resolve();
      }
    });
  }

  /**
   * Handle incoming message
   */
  private async handleMessage(socket: tls.TLSSocket, xmlContent: string): Promise<void> {
    this.messageCount++;

    // Simulate response delay
    if (this.config.responseDelay && this.config.responseDelay > 0) {
      await new Promise((resolve) => setTimeout(resolve, this.config.responseDelay));
    }

    // Simulate errors
    if (this.config.simulateErrors && Math.random() < this.config.errorRate!) {
      socket.destroy();
      return;
    }

    // Generate response
    const response = this.generateResponse(xmlContent);
    const responseBuffer = Buffer.from(response, 'utf-8');
    // Create new Buffer to avoid ArrayBufferLike type issue
    const responseBufferCopy = Buffer.allocUnsafe(responseBuffer.length);
    responseBuffer.copy(responseBufferCopy);
    const framedResponse = LengthPrefixFramer.frame(responseBufferCopy);

    socket.write(framedResponse);
  }

  /**
   * Generate ACK/NACK response
   */
  private generateResponse(xmlContent: string): string {
    // Extract UETR and MsgId from incoming message
    const uetrMatch = xmlContent.match(/<UETR>([^<]+)<\/UETR>/);
    const msgIdMatch = xmlContent.match(/<MsgId>([^<]+)<\/MsgId>/);

    const uetr = uetrMatch ? uetrMatch[1] : '00000000-0000-0000-0000-000000000000';
    const msgId = msgIdMatch ? msgIdMatch[1] : 'TEST-MSG-ID';

    if (this.config.ackResponse) {
      this.ackCount++;
      return `<?xml version="1.0" encoding="UTF-8"?>
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:pacs.002.001.10">
  <Ack>
    <UETR>${uetr}</UETR>
    <MsgId>${msgId}</MsgId>
    <Status>ACCEPTED</Status>
  </Ack>
</Document>`;
    } else {
      this.nackCount++;
      return `<?xml version="1.0" encoding="UTF-8"?>
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:pacs.002.001.10">
  <Nack>
    <UETR>${uetr}</UETR>
    <MsgId>${msgId}</MsgId>
    <Reason>Test NACK response</Reason>
  </Nack>
</Document>`;
    }
  }

  /**
   * Create test certificates (simplified - in production use proper certs)
   */
  private createTestCertificates(certPath: string, keyPath: string): void {
    const certDir = path.dirname(certPath);
    if (!fs.existsSync(certDir)) {
      fs.mkdirSync(certDir, { recursive: true });
    }

    // Note: In a real implementation, use openssl or a proper certificate generator
    // This is a placeholder - actual certificates should be generated properly
    const { execSync } = require('child_process');
    
    try {
      // Generate self-signed certificate for testing
      execSync(
        `openssl req -x509 -newkey rsa:2048 -keyout "${keyPath}" -out "${certPath}" -days 365 -nodes -subj "/CN=test-receiver"`,
        { stdio: 'ignore' }
      );
    } catch (error) {
      console.warn('Could not generate test certificates. Using placeholder.');
      // Create placeholder files
      fs.writeFileSync(certPath, 'PLACEHOLDER_CERT');
      fs.writeFileSync(keyPath, 'PLACEHOLDER_KEY');
    }
  }

  /**
   * Get server statistics
   */
  getStats() {
    return {
      messageCount: this.messageCount,
      ackCount: this.ackCount,
      nackCount: this.nackCount,
      activeConnections: this.connections.size,
    };
  }

  /**
   * Reset statistics
   */
  resetStats(): void {
    this.messageCount = 0;
    this.ackCount = 0;
    this.nackCount = 0;
  }

  /**
   * Configure response behavior
   */
  configure(config: Partial<MockReceiverConfig>): void {
    this.config = { ...this.config, ...config };
  }
}