package dk.thoerup.circuitbreaker.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * This is a web interface for viewing and controlling the CircuitBreakers currently registered in CircuitBreakerManager
 * <p> 
 * To use this servlet in you .war module just create a simple servlet that extends this class (instead of HttpServlet)
 * The new custom servlet doesn't need to implement any of the standard servlet methods - its all done in this implementation.
 *  
 * <p>
 * Example:
 * <pre>
 * public class CircuitBreakerServlet extends CircuitBreakerServletBase {
 *   private static final long serialVersionUID = 1L;
 * }
 * </pre>
 * 
 * If you add a servlet init pameter to your deployment descriptor with the name 'readonly' and a integer value > 0,  you can disable the 
 * control buttons:
 * <p>
 *   &lt;init-param>&lt;param-name>readonly&lt;/param-name>&lt;param-value>1&lt;/param-value>&lt;/init-param>
 *   <!-- <init-param><param-name>readonly</param-name><param-value>1</param-value></init-param> -->
 *   
 *  You could also configure it dynamically from a ContextListener:
 *  ServletRegistration.Dynamic dynconf = sce.getServletContext().addServlet("circuitbreaker", dk.thoerup.circuitbreaker.web.CircuitBreakerServletBase.class );
 *  dynconf.addMapping("/CircuitBreakerServlet");
 *  dynconf.setInitParameter("readonly", "1");
 * 
 */

public class CircuitBreakerServletBase  extends javax.servlet.http.HttpServlet  {
	
	private static final long serialVersionUID = 1L;
	
	private boolean readOnly = false;
	
	
	
	@Override
	public void init() throws ServletException {
		super.init();
		
		String readOnlyStr = getInitParameter("readonly");
		if (readOnlyStr != null && readOnlyStr.trim().length() >0) {
			int readOnlyInt = Integer.parseInt(readOnlyStr.trim());
			readOnly = (readOnlyInt > 0);
		}
	}

	private Command getCommand(String command) throws ServletException {
		if (command == null || command.equals("list"))
			return new ListCircuitBreakers();
		
		if (command.equals("view"))
			return new ViewCircuitBreaker(readOnly);
		if (command.equals("action"))
			return new ActionCommand(readOnly);
		if (command.equals("log"))
			return new LogViewCommand();
		
		throw new ServletException("No such command:" + command);
	}

	@Override
	public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		Command cmd = getCommand( req.getParameter("command"));
		
		String response = cmd.execute(req,resp);
		
		resp.setDateHeader("Expires", 0);
		resp.setHeader("Pragma", "no-cache");
		resp.setHeader("Cache-Control", "no-cache");
		resp.setContentType("text/html");
		
		resp.getWriter().print(response);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}

}