WhenIsSetValueBinder.java

package org.tessell.model.dsl;

import org.tessell.model.properties.Property;

import com.google.gwt.user.client.TakesValue;
import com.google.gwt.user.client.ui.HasValue;

public class WhenIsSetValueBinder<P, Q> {

  private final Binder b;
  private final Property<P> property;
  private final WhenCondition<P> condition;
  private final TakesValue<Q> value;

  WhenIsSetValueBinder(final Binder b, final Property<P> property, final WhenCondition<P> condition, final TakesValue<Q> value) {
    this.b = b;
    this.property = property;
    this.condition = condition;
    this.value = value;
  }

  public void to(final Q newValue) {
    b.add(property.addPropertyChangedHandler(e -> {
      if (condition.evaluate(property)) {
        value.setValue(newValue);
      }
    }));
    if (condition.evaluate(property)) {
      if (value instanceof Property) {
        ((Property<Q>) value).setInitialValue(newValue);
      } else {
        value.setValue(newValue); // set initial
      }
    }
  }

  public void to(final HasValue<Q> newValue) {
    b.add(property.addPropertyChangedHandler(e -> {
      if (condition.evaluate(property)) {
        value.setValue(newValue.getValue());
      }
    }));
    if (condition.evaluate(property)) {
      value.setValue(newValue.getValue()); // set initial
    }
  }

  public void toOrElse(final Q ifTrue, final Q ifFalse) {
    b.add(property.addPropertyChangedHandler(e -> update(ifTrue, ifFalse)));
    update(ifTrue, ifFalse); // set initial value
  }

  private void update(final Q ifTrue, final Q ifFalse) {
    if (condition.evaluate(property)) {
      value.setValue(ifTrue);
    } else {
      value.setValue(ifFalse);
    }
  }

}