package com.temp.client.foundation.widget.input.support;

import com.google.gwt.event.dom.client.*;
import com.google.gwt.event.shared.*;
import com.google.gwt.user.client.Timer;
import com.temp.shared.utils.*;

import java.util.*;

public class TextBoxBaseChangeListenableHelper {
    public interface Participant {
        public HandlerRegistration addFocusHandler(FocusHandler handler);

        public HandlerRegistration addBlurHandler(BlurHandler handler);

        String getText();

        void fireChangeListeners();
    }

    public static final TextBoxBaseChangeListenableHelper INSTANCE = new TextBoxBaseChangeListenableHelper();

    private TextBoxBaseChangeListenableHelper() {
    }

    private class Control implements FocusHandler, BlurHandler {
        private final Participant participant;
        private final HandlerRegistration focus, blur;
        private boolean participantIsFocused = false;
        private String currentText = "";

        public Control(Participant participant) {
            this.participant = participant;
            focus = participant.addFocusHandler(this);
            blur = participant.addBlurHandler(this);
        }

        private void detach() {
            remove(focus);
            remove(blur);
        }

        private void remove(HandlerRegistration handler) {
            if (handler != null) {
                handler.removeHandler();
            }
        }

        @Override
        public void onFocus(FocusEvent event) {
            participantIsFocused = true;
            currentText = getCurrentText();
            setCurrentControl(this); // Enable polling
        }

        @Override
        public void onBlur(BlurEvent event) {
            clearCurrentControl(this); // Disable polling
            if (participantIsFocused) {
                checkForChange();
                participantIsFocused = false;
                currentText = "";
            }
        }

        private boolean participantTextChanged() {
            String value = getCurrentText();
            if (!currentText.equals(value)) {
                currentText = value;
                return true;
            }
            return false;
        }

        private String getCurrentText() {
            return StringUtils.deNull(participant.getText());
        }

        private void checkForChange() {
            if (participantIsFocused && participantTextChanged()) {
                participant.fireChangeListeners();
            }
        }
    }

    private Map<Participant, Control> participantControl = new IdentityHashMap<Participant, Control>();
    private Timer timer = null;
    private Control currentControl;

    public void attach(Participant participant) {
        boolean wasEmpty = participantControl.isEmpty();
        participantControl.put(participant, new Control(participant));
        if (wasEmpty) {
            startTimer();
        }
    }

    public void detach(Participant participant) {
        Control control = participantControl.remove(participant);
        if (control != null) {
            control.detach();
            if (participantControl.isEmpty()) {
                stopTimer();
            }
        }
    }

    private void setCurrentControl(Control control) {
        currentControl = control;
    }

    private void clearCurrentControl(Control control) {
        if (control == currentControl) {
            setCurrentControl(null);
        }
    }

    private void startTimer() {
        stopTimer();
        timer = new Timer() {
            @Override
            public void run() {
                Control control = currentControl;
                if (control != null) {
                    control.checkForChange();
                }
            }
        };
        timer.scheduleRepeating(250);
    }

    private void stopTimer() {
        if (timer != null) {
            timer.cancel();
            timer = null;
        }
    }
}