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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.search.pagetemplates.model;
import java.util.*;
/**
* A choice between some alternative lists of page elements.
*
* @author bratseth
*/
public final class Choice extends AbstractChoice {
private List<List<PageElement>> alternatives=new ArrayList<>(3);
/** Creates an empty choice */
public Choice() { }
/** Creates a choice having a single alternative having a single page element */
public static Choice createSingleton(PageElement singletonAlternative) {
Choice choice=new Choice();
choice.alternatives().add(createSingletonList(singletonAlternative));
return choice;
}
/** Creates a choice in which each alternative consists of a single element */
public static Choice createSingletons(List<PageElement> alternatives) {
Choice choice=new Choice();
for (PageElement alternative : alternatives)
choice.alternatives().add(createSingletonList(alternative));
return choice;
}
private static List<PageElement> createSingletonList(PageElement member) {
List<PageElement> list=new ArrayList<>();
list.add(member);
return list;
}
/**
* Creates a choice between some alternatives. This method takes a copy of the given lists.
*/
public Choice(List<List<PageElement>> alternatives) {
for (List<PageElement> alternative : alternatives)
this.alternatives.add(new ArrayList<>(alternative));
}
/**
* Returns the alternatives of this as a live reference to the alternatives of this.
* The list and elements may be modified unless this is frozen. This is never null.
*/
public List<List<PageElement>> alternatives() { return alternatives; }
/** Convenience shorthand of <code>return alternatives().get(index)</code> */
public List<PageElement> get(int index) {
return alternatives.get(index);
}
/** Convenience shorthand for <code>if (alternative!=null) alternatives().add(alternative)</code> */
public void add(List<PageElement> alternative) {
if (alternative!=null)
alternatives.add(new ArrayList<>(alternative));
}
/** Returns true only if there are no alternatives in this */
public boolean isEmpty() { return alternatives.size()==0; }
/** Answers true if this is either a choice between the given class, or between Lists of the given class */
@SuppressWarnings({ "rawtypes", "unchecked" })
@Override
public boolean isChoiceBetween(Class pageTemplateModelElementClass) {
List firstNonEmpty=null;
for (List<PageElement> value : alternatives) {
if (pageTemplateModelElementClass.isAssignableFrom(value.getClass())) return true;
if (value instanceof List) {
List listValue=(List)value;
if (listValue.size()>0)
firstNonEmpty=listValue;
}
}
if (firstNonEmpty==null) return false;
return (pageTemplateModelElementClass.isAssignableFrom(firstNonEmpty.get(0).getClass()));
}
@Override
public void freeze() {
if (isFrozen()) return;
super.freeze();
for (ListIterator<List<PageElement>> i=alternatives.listIterator(); i.hasNext(); ) {
List<PageElement> alternative=i.next();
for (PageElement alternativeElement : alternative)
alternativeElement.freeze();
i.set(Collections.unmodifiableList(alternative));
}
alternatives= Collections.unmodifiableList(alternatives);
}
/** Accepts a visitor to this structure */
@Override
public void accept(PageTemplateVisitor visitor) {
visitor.visit(this);
for (List<PageElement> alternative : alternatives) {
for (PageElement alternativeElement : alternative)
alternativeElement.accept(visitor);
}
}
@Override
public String toString() {
if (alternatives.isEmpty()) return "(empty choice)";
if (alternatives.size()==1) return alternatives.get(0).toString();
return "a choice between " + alternatives;
}
}
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