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

import com.google.gwt.event.dom.client.*;
import com.google.gwt.event.shared.*;
import com.temp.client.foundation.widget.input.support.*;
import com.temp.client.foundation.widget.input.support.events.*;
import com.temp.shared.utils.*;

public class InputWidgetChangeFilter<T> implements InputWidgetValueAdapter<T>
{
    protected final NonDomHandlerManager<ChangeHandler> handlerManager;
    protected final InputWidgetValueAdapter<T> delegateTo;
    protected T baseNotChangedValue;
    protected boolean isChanged;

    public InputWidgetChangeFilter(InputWidgetValueAdapter<T> delegateTo) {
        handlerManager = new NonDomHandlerManager<ChangeHandler>(this);
        this.delegateTo = delegateTo;
        baseNotChangedValue = delegateTo.getValue();
        delegateTo.addChangeHandler(new ChangeHandler() {
            @Override
            public void onChange(ChangeEvent event) {
                checkForChange();
            }
        });
    }

    public HandlerRegistration addFilteredChangeHandler(ChangeHandler handler) {
        return handler == null ? null : registerChangeHandler(handler);
    }

    @Override
    public HandlerRegistration addChangeHandler(ChangeHandler handler) {
        return delegateTo.addChangeHandler(handler);
    }

    @Override
    public T getValue() {
        return checkForChange();
    }

    @Override
    public void setValue(T value) {
        delegateTo.setValue(value);
        baseNotChangedValue = delegateTo.getValue();
        setChanged(false);
    }

    public T getBaseValue() {
        return baseNotChangedValue;
    }

    public void setValueAsUser(T value) {
        delegateTo.setValue(value);
        checkForChange();
    }

    public boolean isChanged() {
        return isChanged;
    }

    protected T checkForChange() {
        T curValue = delegateTo.getValue();
        setChanged(!ObjectUtils.areEqual(baseNotChangedValue, curValue));
        return curValue;
    }

    protected void setChanged(boolean newChangedState) {
        boolean curChangedState = isChanged;
        isChanged = newChangedState;
        if (curChangedState != newChangedState) {
            notifyChangeHandlers();
        }
    }

    protected void notifyChangeHandlers() {
        handlerManager.fireEvent(new NonDomChangeEvent());
    }

    protected HandlerRegistration registerChangeHandler(ChangeHandler handler) {
        return handlerManager.addHandler(handler);
    }
}