import { describe, it, expect } from 'vitest';
import { encodeTPKT, parseTPKTHeader, isValidTPKTHeader } from '../../src/protocol/tpkt.js';
import { TPKT_VERSION, TPKT_HEADER_LEN } from '../../src/protocol/constants.js';

describe('TPKT', () => {
  describe('encodeTPKT', () => {
    it('should encode empty payload', () => {
      const payload = Buffer.alloc(0);
      const frame = encodeTPKT(payload);
      expect(frame.length).toBe(4);
      expect(frame[0]).toBe(TPKT_VERSION);
      expect(frame[1]).toBe(0x00);
      expect(frame.readUInt16BE(2)).toBe(4); // length = header + empty payload
    });

    it('should encode payload with data', () => {
      const payload = Buffer.from([0x01, 0x02, 0x03, 0x04, 0x05]);
      const frame = encodeTPKT(payload);
      expect(frame.length).toBe(9);
      expect(frame[0]).toBe(TPKT_VERSION);
      expect(frame[1]).toBe(0x00);
      expect(frame.readUInt16BE(2)).toBe(9);
      expect(frame.subarray(4)).toEqual(payload);
    });

    it('should encode large payload', () => {
      const payload = Buffer.alloc(1000, 0xAB);
      const frame = encodeTPKT(payload);
      expect(frame.length).toBe(1004);
      expect(frame.readUInt16BE(2)).toBe(1004);
      expect(frame.subarray(4).length).toBe(1000);
    });
  });

  describe('parseTPKTHeader', () => {
    it('should parse valid header', () => {
      const header = Buffer.from([0x03, 0x00, 0x00, 0x08]);
      const result = parseTPKTHeader(header);
      expect(result.version).toBe(TPKT_VERSION);
      expect(result.length).toBe(8);
    });

    it('should parse maximum length', () => {
      const header = Buffer.from([0x03, 0x00, 0xFF, 0xFF]);
      const result = parseTPKTHeader(header);
      expect(result.length).toBe(65535);
    });
  });

  describe('isValidTPKTHeader', () => {
    it('should return true for valid header', () => {
      const header = Buffer.from([0x03, 0x00, 0x00, 0x08]);
      expect(isValidTPKTHeader(header)).toBe(true);
    });

    it('should return false for wrong version', () => {
      const header = Buffer.from([0x02, 0x00, 0x00, 0x08]);
      expect(isValidTPKTHeader(header)).toBe(false);
    });

    it('should return false for too short buffer', () => {
      const header = Buffer.from([0x03, 0x00]);
      expect(isValidTPKTHeader(header)).toBe(false);
    });
  });

  describe('roundtrip', () => {
    it('should roundtrip encode and parse', () => {
      const payload = Buffer.from([0xE0, 0x01, 0x02]);
      const frame = encodeTPKT(payload);
      const parsed = parseTPKTHeader(frame);
      expect(parsed.version).toBe(TPKT_VERSION);
      expect(parsed.length).toBe(frame.length);
      expect(frame.subarray(TPKT_HEADER_LEN)).toEqual(payload);
    });
  });
});