import http from 'http'; 
import { jest } from '@jest/globals';
import { SSEServerTransport } from './sse.js'; 

const createMockResponse = () => {
  const res = {
    writeHead: jest.fn<http.ServerResponse['writeHead']>(),
    write: jest.fn<http.ServerResponse['write']>().mockReturnValue(true),
    on: jest.fn<http.ServerResponse['on']>(),
  };
  res.writeHead.mockReturnThis();
  res.on.mockReturnThis();
  
  return res as unknown as http.ServerResponse;
};

describe('SSEServerTransport', () => {
  describe('start method', () => { 
    it('should correctly append sessionId to a simple relative endpoint', async () => { 
      const mockRes = createMockResponse();
      const endpoint = '/messages';
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /messages?sessionId=${expectedSessionId}\n\n`
      );
    });

    it('should correctly append sessionId to an endpoint with existing query parameters', async () => { 
      const mockRes = createMockResponse();
      const endpoint = '/messages?foo=bar&baz=qux';
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /messages?foo=bar&baz=qux&sessionId=${expectedSessionId}\n\n`
      );
    });

    it('should correctly append sessionId to an endpoint with a hash fragment', async () => { 
      const mockRes = createMockResponse();
      const endpoint = '/messages#section1';
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /messages?sessionId=${expectedSessionId}#section1\n\n`
      );
    });

    it('should correctly append sessionId to an endpoint with query parameters and a hash fragment', async () => { 
      const mockRes = createMockResponse();
      const endpoint = '/messages?key=value#section2';
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /messages?key=value&sessionId=${expectedSessionId}#section2\n\n`
      );
    });

    it('should correctly handle the root path endpoint "/"', async () => { 
      const mockRes = createMockResponse();
      const endpoint = '/';
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /?sessionId=${expectedSessionId}\n\n`
      );
    });

    it('should correctly handle an empty string endpoint ""', async () => { 
      const mockRes = createMockResponse();
      const endpoint = ''; 
      const transport = new SSEServerTransport(endpoint, mockRes);
      const expectedSessionId = transport.sessionId;

      await transport.start();

      expect(mockRes.writeHead).toHaveBeenCalledWith(200, expect.any(Object));
      expect(mockRes.write).toHaveBeenCalledTimes(1);
      expect(mockRes.write).toHaveBeenCalledWith(
        `event: endpoint\ndata: /?sessionId=${expectedSessionId}\n\n`
      );
    });
  });
});