package perfectfit;

import java.io.IOException;
import java.io.InputStream;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;

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

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.exc.StreamReadException;
import com.fasterxml.jackson.databind.DatabindException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import tudelft.dialogmanager.DialogPhase;
import tudelft.dialogmanager.DialogState;
import tudelft.dialogmanager.answertypes.InvalidAnswerException;
import tudelft.dialogmanager.parameters.DoubleValue;
import tudelft.dialogmanager.parameters.Parameters;
import tudelft.dialogmanager.stimuli.Stimulus;
import tudelft.dialogmanager.stimuli.Textual;
import tudelft.mentalhealth.perfectfit.updatefuncs.CheckDeadline;
import tudelft.mentalhealth.perfectfit.updatefuncs.DateString;
import tudelft.mentalhealth.perfectfit.updatefuncs.Example;
import tudelft.mentalhealth.perfectfit.updatefuncs.StringLength;
import tudelft.mentalhealth.perfectfit.updatefuncs.Time;
import tudelft.mentalhealth.perfectfit.updatefuncs.TimeDifference;

/**
 * Servlet to handle user actions and reply with bot response.
 */
@SuppressWarnings("serial")
public class ChatServlet extends HttpServlet {
	private final static ObjectMapper jackson = new ObjectMapper();
	static {
		jackson.registerSubtypes(Example.class, Time.class, CheckDeadline.class,
				TimeDifference.class, StringLength.class, DateString.class);
	}
	InputStream stream = getClass().getClassLoader()
			.getResourceAsStream("dialog.json");

	/**
	 * This service gets the current stimulation serialized as json. replies
	 * NOT_ACCEPTABLE if chat was finished already. Replies BAD_REQUEST if the
	 * given text answer is not acceptable in current state. Replies OK if text
	 * answer was processed succesfully.
	 */
	@Override
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		DialogState state = getState(request.getSession());
		if (state.isFinal()) {
			response.sendError(HttpServletResponse.SC_NOT_ACCEPTABLE,
					"Chat is finished. Try starting a new session");
			return;
		}

		String usertext = request.getReader().lines()
				.collect(Collectors.joining(System.lineSeparator()));
		try {
			state = state.with(usertext);
		} catch (InvalidAnswerException e) {
			e.printStackTrace();
			response.sendError(HttpServletResponse.SC_BAD_REQUEST,
					e.getMessage());

		}
		// run evaluation and then prepare the next state immediately.
		state = state.withUpdate(false);
		if (!state.isFinal()) {
			state = state.withUpdate(true);
		}
		request.getSession().setAttribute("state", state);

		response.setStatus(HttpServletResponse.SC_OK);
	}

	@Override
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		DialogState state = getState(request.getSession());
		if (state == null) {
			response.sendError(HttpServletResponse.SC_PRECONDITION_FAILED,
					"Please enter the chat through the form");
			return;
		}
		if (state.isFinal()) {
			response.sendError(400,
					"Chat is finished. Try starting a new session");
			return;
		}

		DialogPhase phase = state.getCurrentPhase();
		Stimulus stimulus = phase.getStimulation()
				.substitute(state.getParameters());

		StimAnswer reply = new StimAnswer(stimulus, phase.getAnswer());
		if (!(stimulus instanceof Textual)) {
			throw new IllegalStateException(
					"The Demo App only supports Textual.");
		}

		response.setContentType("text/json;charset=UTF-8");
		response.getWriter().append(jackson.writeValueAsString(reply));
	}

	/**
	 * A OPTIONS command resets the state, using the query string in request.
	 * This can be used to restart a session, and must be used to load query
	 * arguments into the state. CONNECT seems not available , otherwise that
	 * would have been better
	 */
	@Override
	protected void doOptions(HttpServletRequest request,
			HttpServletResponse response)
			throws StreamReadException, DatabindException, IOException {
		System.out.println("Initializing session");
		InputStream stream = getClass().getClassLoader()
				.getResourceAsStream("dialog.json");

		DialogState state = jackson.readValue(stream, DialogState.class);

		state = addVariables(state, request.getParameterMap());

		// initialize the preparation so that we have the text ready.
		state = state.withUpdate(true);
		request.getSession().setAttribute("state", state);

	}

	/**
	 * @param state the current state.
	 * @param map   a querystring eg 'age=25&weight=96'
	 * @return DialogState with the parameters added.
	 * 
	 */
	private DialogState addVariables(DialogState state,
			Map<String, String[]> map) {
		Parameters params = state.getParameters();
		for (Entry<String, String[]> entry : map.entrySet()) {
			params = params.with(entry.getKey(),
					new DoubleValue(Double.valueOf(entry.getValue()[0])));
		}
		return state.with(params);

	}

	/**
	 * 
	 * @param httpSession the current session
	 * @return current {@link DialogState} for this session
	 * @throws Exception if error occurs reading the initial state. Should not
	 *                   happen
	 */
	private DialogState getState(HttpSession httpSession)
			throws JsonParseException, JsonMappingException, IOException {
		return (DialogState) httpSession.getAttribute("state");
	}
}