/**
 * Message Framing Test Suite
 * Tests length-prefix-4be framing for ISO 20022 messages
 */

import { LengthPrefixFramer } from '@/transport/framing/length-prefix';
import { readFileSync } from 'fs';
import { join } from 'path';

describe('Message Framing Tests', () => {
  const pacs008Template = readFileSync(
    join(__dirname, '../../../docs/examples/pacs008-template-a.xml'),
    'utf-8'
  );

  describe('Length-Prefix-4BE Framing', () => {
    it('should frame message with 4-byte big-endian length prefix', () => {
      const message = Buffer.from('Hello, World!', 'utf-8');
      const framed = LengthPrefixFramer.frame(message);

      expect(framed.length).toBe(4 + message.length);
      expect(framed.readUInt32BE(0)).toBe(message.length);
    });

    it('should correctly frame ISO 20022 pacs.008 message', () => {
      const message = Buffer.from(pacs008Template, 'utf-8');
      const framed = LengthPrefixFramer.frame(message);

      expect(framed.length).toBe(4 + message.length);
      expect(framed.readUInt32BE(0)).toBe(message.length);
      
      // Verify message content is preserved
      const unframed = framed.slice(4);
      expect(unframed.toString('utf-8')).toBe(pacs008Template);
    });

    it('should handle empty message', () => {
      const message = Buffer.alloc(0);
      const framed = LengthPrefixFramer.frame(message);

      expect(framed.length).toBe(4);
      expect(framed.readUInt32BE(0)).toBe(0);
    });

    it('should handle large messages (up to 4GB)', () => {
      const largeMessage = Buffer.alloc(1024 * 1024); // 1MB
      largeMessage.fill('A');
      
      const framed = LengthPrefixFramer.frame(largeMessage);
      expect(framed.length).toBe(4 + largeMessage.length);
      expect(framed.readUInt32BE(0)).toBe(largeMessage.length);
    });

    it('should handle messages with maximum 32-bit length', () => {
      const maxLength = 0xFFFFFFFF; // Max 32-bit unsigned int
      const lengthBuffer = Buffer.allocUnsafe(4);
      lengthBuffer.writeUInt32BE(maxLength, 0);
      
      expect(lengthBuffer.readUInt32BE(0)).toBe(maxLength);
    });
  });

  describe('Length-Prefix Unframing', () => {
    it('should unframe message correctly', () => {
      const original = Buffer.from('Test message', 'utf-8');
      const framed = LengthPrefixFramer.frame(original);
      
      const { message, remaining } = LengthPrefixFramer.unframe(framed);
      
      expect(message).not.toBeNull();
      expect(message!.toString('utf-8')).toBe('Test message');
      expect(remaining.length).toBe(0);
    });

    it('should handle partial frames (need more data)', () => {
      const partialFrame = Buffer.alloc(2); // Only 2 bytes, need 4 for length
      partialFrame.writeUInt16BE(100, 0);
      
      const { message, remaining } = LengthPrefixFramer.unframe(partialFrame);
      
      expect(message).toBeNull();
      expect(remaining.length).toBe(2);
    });

    it('should handle incomplete message payload', () => {
      const message = Buffer.from('Hello', 'utf-8');
      const framed = LengthPrefixFramer.frame(message);
      const partial = framed.slice(0, 6); // Only length + 2 bytes of message
      
      const { message: unframed, remaining } = LengthPrefixFramer.unframe(partial);
      
      expect(unframed).toBeNull();
      expect(remaining.length).toBe(6);
    });

    it('should handle multiple messages in buffer', () => {
      const msg1 = Buffer.from('First message', 'utf-8');
      const msg2 = Buffer.from('Second message', 'utf-8');
      
      const framed1 = LengthPrefixFramer.frame(msg1);
      const framed2 = LengthPrefixFramer.frame(msg2);
      const combined = Buffer.concat([framed1, framed2]);
      
      // Unframe first message
      const { message: first, remaining: afterFirst } = LengthPrefixFramer.unframe(combined);
      expect(first!.toString('utf-8')).toBe('First message');
      
      // Unframe second message
      const { message: second, remaining: afterSecond } = LengthPrefixFramer.unframe(afterFirst);
      expect(second!.toString('utf-8')).toBe('Second message');
      expect(afterSecond.length).toBe(0);
    });

    it('should correctly unframe ISO 20022 message', () => {
      const message = Buffer.from(pacs008Template, 'utf-8');
      const framed = LengthPrefixFramer.frame(message);
      
      const { message: unframed, remaining } = LengthPrefixFramer.unframe(framed);
      
      expect(unframed).not.toBeNull();
      expect(unframed!.toString('utf-8')).toBe(pacs008Template);
      expect(remaining.length).toBe(0);
    });
  });

  describe('Expected Length Detection', () => {
    it('should get expected length from buffer', () => {
      const message = Buffer.from('Test', 'utf-8');
      const framed = LengthPrefixFramer.frame(message);
      
      const expectedLength = LengthPrefixFramer.getExpectedLength(framed);
      expect(expectedLength).toBe(message.length);
    });

    it('should return null for incomplete length prefix', () => {
      const partial = Buffer.alloc(2);
      const expectedLength = LengthPrefixFramer.getExpectedLength(partial);
      expect(expectedLength).toBeNull();
    });

    it('should handle zero-length message', () => {
      const empty = Buffer.alloc(4);
      empty.writeUInt32BE(0, 0);
      
      const expectedLength = LengthPrefixFramer.getExpectedLength(empty);
      expect(expectedLength).toBe(0);
    });
  });

  describe('Framing Edge Cases', () => {
    it('should handle Unicode characters correctly', () => {
      const unicodeMessage = Buffer.from('测试消息 🚀', 'utf-8');
      const framed = LengthPrefixFramer.frame(unicodeMessage);
      
      const { message } = LengthPrefixFramer.unframe(framed);
      expect(message!.toString('utf-8')).toBe('测试消息 🚀');
    });

    it('should handle binary data', () => {
      const binaryData = Buffer.from([0x00, 0x01, 0x02, 0xFF, 0xFE, 0xFD]);
      const framed = LengthPrefixFramer.frame(binaryData);
      
      const { message } = LengthPrefixFramer.unframe(framed);
      expect(Buffer.compare(message!, binaryData)).toBe(0);
    });

    it('should maintain message integrity through frame/unframe cycle', () => {
      const testCases = [
        'Simple message',
        pacs008Template,
        'A'.repeat(1000),
        'Multi\nline\nmessage',
        'Message with special chars: !@#$%^&*()',
      ];

      for (const testCase of testCases) {
        const original = Buffer.from(testCase, 'utf-8');
        const framed = LengthPrefixFramer.frame(original);
        const { message } = LengthPrefixFramer.unframe(framed);
        
        expect(message!.toString('utf-8')).toBe(testCase);
      }
    });
  });
});