package mcp.server;

import jakarta.servlet.ReadListener;
import jakarta.servlet.ServletInputStream;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import mcp.registry.ToolRegistry;
import mcp.tools.McpTool;
import mcp.util.Err;
import mcp.util.Ok;
import mcp.util.Result;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;

import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.mockito.Mockito.*;

public class ToolRegistrationServletTest {

    private ToolRegistry toolRegistry;
    private HttpServletRequest request;
    private HttpServletResponse response;
    private StringWriter responseWriter;

    @BeforeEach
    void setUp() throws IOException {
        toolRegistry = new ToolRegistry(java.util.Set.of());
        request = mock(HttpServletRequest.class);
        response = mock(HttpServletResponse.class);
        responseWriter = new StringWriter();
        when(response.getWriter()).thenReturn(new PrintWriter(responseWriter));
    }

    @Test
    void testDoPostSuccess() throws Exception {
        McpTool mockTool = mock(McpTool.class);
        when(mockTool.name()).thenReturn("EchoTool");

        // Use anonymous subclass instead of spy to avoid instrumentation issues on Java 25
        ToolRegistrationServlet servlet = new ToolRegistrationServlet(toolRegistry) {
            @Override
            public Result<McpTool, Exception> registerTool(String jarPath, String className) {
                toolRegistry.register(mockTool);
                return new Ok<McpTool, Exception>(mockTool);
            }
        };

        String json = "{\"jarPath\": \"/tmp/test.jar\", \"className\": \"com.example.EchoTool\"}";
        mockRequestInput(json);

        servlet.doPost(request, response);

        verify(response).setStatus(HttpServletResponse.SC_OK);
        assertTrue(responseWriter.toString().contains("Tool registered successfully: EchoTool"));
        assertTrue(toolRegistry.get("EchoTool") != null);
    }

    @Test
    void testDoPostMissingParams() throws Exception {
        ToolRegistrationServlet servlet = new ToolRegistrationServlet(toolRegistry);
        String json = "{\"jarPath\": \"/tmp/test.jar\"}"; // missing className
        mockRequestInput(json);

        servlet.doPost(request, response);

        verify(response).setStatus(HttpServletResponse.SC_BAD_REQUEST);
        assertTrue(responseWriter.toString().contains("Missing jarPath or className"));
    }

    @Test
    void testDoPostRegistrationError() throws Exception {
        ToolRegistrationServlet servlet = new ToolRegistrationServlet(toolRegistry) {
            @Override
            public Result<McpTool, Exception> registerTool(String jarPath, String className) {
                return new Err<McpTool, Exception>(new Exception("Loading failed"));
            }
        };

        String json = "{\"jarPath\": \"/tmp/test.jar\", \"className\": \"com.example.FailTool\"}";
        mockRequestInput(json);

        servlet.doPost(request, response);

        verify(response).setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        assertTrue(responseWriter.toString().contains("Error registering tool: Loading failed"));
    }

    private void mockRequestInput(String json) throws IOException {
        ByteArrayInputStream bais = new ByteArrayInputStream(json.getBytes());
        ServletInputStream sis = new ServletInputStream() {
            @Override
            public int read() throws IOException {
                return bais.read();
            }

            @Override
            public boolean isFinished() {
                return bais.available() == 0;
            }

            @Override
            public boolean isReady() {
                return true;
            }

            @Override
            public void setReadListener(ReadListener readListener) {
            }
        };
        when(request.getInputStream()).thenReturn(sis);
    }
}