import { describe, it, expect, vi, beforeEach } from 'vitest';
import { EventEmitter } from 'node:events';
import type * as net from 'node:net';
import type { Logger } from 'pino';
import type { AdapterContext, Metrics, Position } from '../src/core/types.js';
import { createTeltonikaAdapter } from '../src/adapters/teltonika/index.js';
import { CodecRegistry } from '../src/adapters/teltonika/codec/registry.js';
import type { DeviceAuthority } from '../src/adapters/teltonika/device-authority.js';
import { crc16Ibm } from '../src/adapters/teltonika/crc.js';

// ---------------------------------------------------------------------------
// Mock helpers
// ---------------------------------------------------------------------------

type MockSocket = net.Socket & {
  push(buf: Buffer): void;
  simulateClose(): void;
  getWritten(): Buffer[];
};

function makeMockSocket(): MockSocket {
  const written: Buffer[] = [];

  const emitter = new EventEmitter() as MockSocket & {
    destroyed: boolean;
    write: ReturnType<typeof vi.fn>;
    destroy: ReturnType<typeof vi.fn>;
    setNoDelay: ReturnType<typeof vi.fn>;
    setKeepAlive: ReturnType<typeof vi.fn>;
    remoteAddress: string;
    remotePort: number;
  };

  emitter.destroyed = false;
  emitter.remoteAddress = '127.0.0.1';
  emitter.remotePort = 9999;
  emitter.setNoDelay = vi.fn();
  emitter.setKeepAlive = vi.fn();
  emitter.write = vi.fn((data: Buffer | string) => {
    written.push(Buffer.isBuffer(data) ? data : Buffer.from(data));
    return true;
  });
  emitter.destroy = vi.fn(() => {
    if (!emitter.destroyed) {
      emitter.destroyed = true;
      emitter.emit('close', false);
    }
  });
  emitter.push = (buf: Buffer) => emitter.emit('data', buf);
  emitter.simulateClose = () => {
    if (!emitter.destroyed) {
      emitter.destroyed = true;
      emitter.emit('close', false);
    }
  };
  emitter.getWritten = () => written;

  return emitter;
}

function makeMockContext(): AdapterContext {
  const logger = {
    debug: vi.fn(),
    info: vi.fn(),
    warn: vi.fn(),
    error: vi.fn(),
    child: vi.fn().mockReturnThis(),
  } as unknown as Logger;

  const metrics: Metrics = {
    inc: vi.fn(),
    observe: vi.fn(),
  };

  return {
    publish: vi.fn(async (_p: Position, _codec) => {}),
    logger,
    metrics,
  };
}

/**
 * Encodes the Teltonika IMEI handshake wire format.
 */
function encodeImei(imei: string): Buffer {
  const body = Buffer.from(imei, 'ascii');
  const header = Buffer.alloc(2);
  header.writeUInt16BE(body.length, 0);
  return Buffer.concat([header, body]);
}

/**
 * Builds a complete AVL frame. Body is CodecID + N1 + empty records + N2.
 */
function buildFrame(options: { codecId: number; recordCount?: number; crcOverride?: number }): Buffer {
  const n = options.recordCount ?? 1;
  const body = Buffer.from([options.codecId, n, n]);
  const realCrc = crc16Ibm(body);
  const crc = options.crcOverride !== undefined ? options.crcOverride : realCrc;

  const preamble = Buffer.alloc(4, 0);
  const lengthBuf = Buffer.alloc(4);
  lengthBuf.writeUInt32BE(body.length, 0);
  const crcBuf = Buffer.alloc(4);
  crcBuf.writeUInt16BE(0, 0);
  crcBuf.writeUInt16BE(crc, 2);

  return Buffer.concat([preamble, lengthBuf, body, crcBuf]);
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

const IMEI = '356307042441013';

describe('Teltonika adapter — session', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  describe('unknown codec path', () => {
    it('destroys the socket without writing an ACK when codec ID is not registered', async () => {
      const socket = makeMockSocket();
      const ctx = makeMockContext();
      const registry = new CodecRegistry(); // empty — no codecs registered
      const adapter = createTeltonikaAdapter({ port: 5027, codecRegistry: registry });

      const sessionPromise = adapter.handleSession(socket, ctx);

      // Push IMEI handshake — session writes 0x01 accept
      socket.push(encodeImei(IMEI));

      // Wait until the 0x01 accept byte is written
      await vi.waitFor(
        () => {
          expect(socket.getWritten().length).toBeGreaterThan(0);
        },
        { timeout: 2000 },
      );

      // Push a frame with an unregistered codec (0x99)
      socket.push(buildFrame({ codecId: 0x99 }));

      // Session should destroy the socket after unknown codec
      await sessionPromise;

      expect(socket.destroy).toHaveBeenCalled();

      // The ONLY write must be the 0x01 accept byte — no 4-byte ACK
      const allWritten = Buffer.concat(socket.getWritten());
      expect(allWritten).toEqual(Buffer.from([0x01]));
    }, 10_000);
  });

  describe('CRC mismatch path', () => {
    it('does NOT write an ACK on CRC mismatch and keeps the socket open', async () => {
      const socket = makeMockSocket();
      const ctx = makeMockContext();
      const registry = new CodecRegistry();
      const adapter = createTeltonikaAdapter({ port: 5027, codecRegistry: registry });

      const sessionPromise = adapter.handleSession(socket, ctx);

      // Handshake
      socket.push(encodeImei(IMEI));

      // Wait for the accept byte
      await vi.waitFor(
        () => {
          expect(socket.getWritten().length).toBeGreaterThan(0);
        },
        { timeout: 2000 },
      );

      const writtenBeforeFrame = socket.getWritten().length;

      // Push a frame with a deliberately wrong CRC
      socket.push(buildFrame({ codecId: 0x08, crcOverride: 0xdead }));

      // Give the event loop time to process the frame
      await new Promise<void>((resolve) => setTimeout(resolve, 100));

      // Socket must still be open
      expect(socket.destroy).not.toHaveBeenCalled();
      expect(socket.destroyed).toBe(false);

      // No new writes after the frame (no ACK sent)
      expect(socket.getWritten().length).toBe(writtenBeforeFrame);

      // Clean up — simulate device disconnect
      socket.simulateClose();
      await sessionPromise;
    }, 10_000);
  });

  describe('STRICT_DEVICE_AUTH', () => {
    it('writes 0x00 and destroys socket for unknown device when STRICT_DEVICE_AUTH=true', async () => {
      const socket = makeMockSocket();
      const ctx = makeMockContext();

      const strictAuthority: DeviceAuthority = {
        check: vi.fn().mockResolvedValue('unknown'),
      };

      const adapter = createTeltonikaAdapter({
        port: 5027,
        deviceAuthority: strictAuthority,
        strictDeviceAuth: true,
      });

      const sessionPromise = adapter.handleSession(socket, ctx);
      socket.push(encodeImei(IMEI));

      await sessionPromise;

      const allWritten = Buffer.concat(socket.getWritten());
      expect(allWritten).toEqual(Buffer.from([0x00]));
      expect(socket.destroy).toHaveBeenCalled();
    });

    it('accepts unknown device when STRICT_DEVICE_AUTH=false (default)', async () => {
      const socket = makeMockSocket();
      const ctx = makeMockContext();

      const unknownAuthority: DeviceAuthority = {
        check: vi.fn().mockResolvedValue('unknown'),
      };

      const adapter = createTeltonikaAdapter({
        port: 5027,
        deviceAuthority: unknownAuthority,
        strictDeviceAuth: false,
      });

      const sessionPromise = adapter.handleSession(socket, ctx);
      socket.push(encodeImei(IMEI));

      // Wait for the accept byte
      await vi.waitFor(
        () => {
          expect(socket.getWritten().length).toBeGreaterThan(0);
        },
        { timeout: 2000 },
      );

      const allWritten = Buffer.concat(socket.getWritten());
      expect(allWritten[0]).toBe(0x01);

      // Not destroyed
      expect(socket.destroy).not.toHaveBeenCalled();

      socket.simulateClose();
      await sessionPromise;
    }, 10_000);
  });

  describe('known device acceptance', () => {
    it('writes 0x01 for a known device and stays connected', async () => {
      const socket = makeMockSocket();
      const ctx = makeMockContext();
      const adapter = createTeltonikaAdapter({ port: 5027 });

      const sessionPromise = adapter.handleSession(socket, ctx);
      socket.push(encodeImei(IMEI));

      // Wait for the accept byte
      await vi.waitFor(
        () => {
          expect(socket.getWritten().length).toBeGreaterThan(0);
        },
        { timeout: 2000 },
      );

      const allWritten = Buffer.concat(socket.getWritten());
      expect(allWritten[0]).toBe(0x01);

      socket.simulateClose();
      await sessionPromise;
    }, 10_000);
  });
});